Intermittent connection on field only
 

We're competing at the LA regional this weekend, and are having nothing but trouble when competing on the field. We lose communication at completely random times (moving, not moving, before match, during match, etc), and for random durations (for anywhere between a few seconds to almost the entire match). However, this only occurs when we are on the competition field with FMS, but has happened in every single match. When we run tethered in the pit, tethered on the practice field, and wireless on the practice field (with the practice field radio), it works perfectly, no hiccups.

We've replaced the following components, with no effect: cRIO, radio, ethernet cable, driver station computer, and radio 12-5v power converter. It occurs with the default LabVIEW code as well as our own code. We pulled every single circuit breaker, so that the only items powered were the cRIO and the radio, and it still occurred. We've had multiple people from our team, other teams, and event staff check our wiring, and wiggle the wires looking for shorts or loose connections, but haven't found anything. Our chassis is open to ground. cRIO is mounted to wood, and the camera is mounted to plastic. Our radio is mounted pretty high, and not overly surrounded by metal. The closest motor is around 12 inches away. We are not using any of the banebots 775 motors.

About the only control system component that we haven't replaced is PD board. I've used a DMM to look at the 24v and 12v power supplies, and both seemed fine. 24v supply was at 23.9v and 12v was at the battery voltage (12.5). I didn't see any change when communications dropped. While everything seems good with the PD board, since it's the only thing we haven't changed, I'm worried it's our only choice tomorrow. The PD board is brand new from the kit this year.

Any ideas or additional troubleshooting steps?

Re: Intermittent connection on field only
 

Joe,
sorry to hear of your issues as I can only imagine the frustrations.
I didnt get to watch you folks today, but members of our team clearly saw what was happening to both you and 1717 today.

The only hiccups our team had during the end part of build season was our laptop/driver station blanking out or blue screening at times. Randy found the issue to be with our bluetooth mouse interfering when we ran Labview. We bought brand new i7 core laptops this season due to the kinect.

I hope you find the culprit.
You are usually the source for finding solutions vs. vice versa.

Re: Intermittent connection on field only
 

A few more data points.

This does happen while setting up prior to a match also, while the robot is disabled. We set the robot out on the field, it links up, and then it will randomly lose connection while other robots are being set up.

We are using the camera connected directly to radio. All the code to access the camera on the robot is disabled.

We have customized the dashboard, and our using our own laptop. However the issue occurs on two different laptops. Driver Station CPU utilization is low. We are not using the kinect or the cypress board. cRIO CPU utilization is around 50%, but this happens with the default LabVIEW code also.

We've had two CSA's, the Field Supervisor, and the FTA all look at both the robot and the field logs, without any obvious answers, the robot just loses communication.

There is no correlation with battery voltage as seen in the FMS logs or the DS charts tab. (unless something is happening too fast to see). It happens with multiple batteries.

Re: Intermittent connection on field only
 

In addition to wiggling the wires, have you tightened down the connections (particularly on the PD board)? That bit us one year through an entire regional; one of the wires from the battery to the board was not tightened down really hard. If we wiggled the wire it seemed good, but it wasn't until we tried replacing the wires that we found they weren't tightened properly.

Re: Intermittent connection on field only
 

It looks like this problem happens to the best of em.
We had this same problem in Breakaway, we would lose connection randomly and for a random period of time.

I wish I knew the solution, have you considered changing both CRio and Driver Station computer?
Edit: Nevermind, i see that you have.

Re: Intermittent connection on field only
 

It seems that 364 is having similar issues at the Bayou regional. In that thread, Greg asked for cRIO and radio info. Adding it here for completeness.

We've tried 3 radios, all rev A. Two with firmware version 1.21 (one was ours and one from spare parts) and one with firmware version 1.4 (purchased last month). We've tried 2 cRios, both have been 4 slot cRios (no room for 8 slot).

Re: Intermittent connection on field only
 

If you unplug the camera from the Wireless Gaming adapter, does the problem go away? Can the FTA tell if your robot is more bandwidth hungry than the others at the event?

We had a situation with the symptoms you describe happen at the Chestnut Hill District Event, and the FTA ultimately traced the problem down to a pair of particularly bandwidth hungry robots. After they changed their camera settings (lowered resolution, lowered framerate, increased compression), I believe the problems went away.

I know that there is no worse feeling in FRC than watching your robot die in the middle of the field with no discernible cause.

Re: Intermittent connection on field only
 

3193 was having very similar issues to what you were describing in Pittsburgh. For some reason, the staff was reluctant to let them program a new radio at the kiosk - they brought a brand new one with them from home (not sure of the firmware/rev level on that). Ultimately, the staff relented - they programmed the new radio at the kiosk and then had no issues with on-field robot comms the rest of the competition. The team was also making other repairs to the bot inside the base at the time that might have affected wiring connections, etc., so this might have been a coincidence.

It sounds like you've swapped radios many times already, though.

Re: Intermittent connection on field only
 

We're still at a loss. We're going back to the classmate, eliminating CAN, eliminating the camera. That's the last of the niceties of our robot. We're back to basic framework.

Re: Intermittent connection on field only
 

At Alamo during week 1, the Robonauts had similar problems in a couple matches on Friday. In one match we never started autonomous, and in another we lost connection with 30 seconds remaining.

Changing out the classmate stopped the symptoms. Although I'm not fully convinced the classmate was the root cause, we didn't have any problems afterward. Prior to changing it out, we were seeing delays off the chart (> 100 msec) and approaching 50 lost packets per unit time, even when tethered. This went away after we swapped the classmate.

Re: Intermittent connection on field only
 

No go still. This is sickening. We're at the point where the only variable left is the FMS, and they're not budging. It's not code, it's not electrical, it's not us.

We also moved the router to an unpopulated part of the robot because of interference worries. I don't know what's left.

Frankly, I'm pissed off because of this. FTA has given little support so far.

Our problem still occurred even with the camera unplugged and unpowered. At one point we pulled all breakers so only the radio and crio had power.

This morning, we swapped the PD board and it ran perfectly in our first match. 2 more qualification matches to go.

Sent from my BlackBerry 9650 using Tapatalk

Re: Intermittent connection on field only
 

Murphy says it's always the part that can't be causing the problem, that is the problem....

Hope it stays fixed!

Re: Intermittent connection on field only
 

Joe,
The 12 volt output for the radio should be 12 volts +/- 0.1 volts. It should not read the same as the battery. Since you replace the PD already, I am going to guess that the 12 volt supply has a problem. However, none of this explains the action on the field vs all other trials. If the radio resets due to a power dump it takes about 50 seconds. The new FMS dashboard also reports lost packets. Were you told that there were cluster of lost packets on your data stream? They also have the ability to check emissions on your channel, have they looked at that? Normally they only check prior to the event and not during the event. It really sounds like something is interfering with your radio. I know it's not supposed to happen but it obviously is. What is the possibility that your WPA key is corrupt in the kiosk? Have you always configured at the same kiosk or did you try the second one?

Re: Intermittent connection on field only
 

My understanding is that it tracks battery voltage at >12 volts. That may be wrong.

Re: Intermittent connection on field only
 

Joe,

This sounds very similar to what was happening to us at Chesapeake. We, too, thought it had to be the FMS, since we were only having the issues when we connected to the field. The FTA said, that in his experience, the type of connection issues we were having were usually due to hardware issues. We replaced several wires, swapped out our cameras, removed the cameras, etc... All approaches I see above. We re-checked every connection, taped down everything that might move, did a very thourough shock and vibe set of tests on the bot in the pits, and then, at least, everything seemed to work in our first quarterfinal, and thought we had found the issue. The next match, we were playing blind again, our cameras had dropped the frames, and the lag times between the camera and the dashboard were killing us. we asked the FTA if the logs showed any connection issues, and he said no. He then said, "You do have, however, a lot of latency showing up. A lot more than I would expect."

We decided to bring the cameras home and run tests with our practice bot to see if we could re-create the issues, but were generally unable to do so. A post here on CD, regarding the 3-13 update had a post from a member of the Killer Bees (33) talking about issues he had found in some of the LabView code, and he posted a sample code he had written that had helped with some of the latency issues they were having.
http://www.chiefdelphi.com/forums/sh...=104580&page=2
It sounded familiar to our problems, so I forwarded the info to our programmers. Other than some of the basic code, our team had written a lot of the code ourselves. When they reviewed the info in this post, they found some of the same issues mentioned. They have been optimizing the code as described, and finding that the code is now a lot more efficient. We are continuing to run tests to see if there are other issues, but are hopeful that when we get to DC, we will not see a repeat of the problems we had in Chesapeake.
In previous years we had build rather "simple" machines, with very little reliance in sensors and complex code, this year, we have two cameras, complex image processing, a complex set of code that keeps track of the state of each ball in the system, etc... I'm wondering if this year's general increase in the complexity of the bots teams are building is bring some of these code issues to light? If you all find anything else that is causing these problems, I would love to hear about it. Thanks!

Steve

Re: Intermittent connection on field only
 

One team at Boilermaker today had the same symptoms described here: inconsistent loss of wireless communication during a match. There didn't seem to be any pattern other than noting that it never happened on the practice field. When I was called in to help troubleshoot, I discovered the 12v-to-5v converter essentially stuck to the bottom of the D-Link. After I suggested that they move it to a less potentially interfering location, they had a string of successful matches all the way through the elimination rounds.

I remember the same problem with the same fix with another team last year.

I'm going to engage in some speculation here. The 12v radio power from the PDB comes from a boosted supply. The supply should have filtering on the output, but if something is faulty it's going to have some ripple in it from the switching. That could be causing electrical noise and RFI from the 5v converter. It might be that an insufficiently clean 5v input makes the D-Link act a bit flaky. Without taking a few hours with an oscilloscope and a collection of parts to do a careful analysis, I think that's the best theory I'm going to come up with.

Re: Intermittent connection on field only
 

Just to document other occurrences of the problem, we had this identicle trouble at Greater Kansas City in week 1. We tried all the replacements and fixes mentioned in this thread, including filtering the power from the DC adapter. To this day we do not know the problem. Just to make sure it is not the router itself, we have replaced it with a new one. One possibility is physical damage to the router PCB/components caused by shocks/jarring/vibration. This router certainly was not designed for such abuse. Our older, 2011 router which has seen more mileage and abuse exhibits the same problem but more frequently. We have mounted the new router in a location with less shock and more cushioning to try to keep it pristine. Time and another competition will tell if this solves the problem.

Re: Intermittent connection on field only
 

We had a dead robot one match in San Diego, because of a problem that we were aware of but hadn't fixed yet.

The ethernet connectors on our bridge seem to have a bad design or have been damaged or something. When the cable is plugged in and latched, it can be pulled out against the latch, and lose connection. We have tried several different cables, they all act the same, no connection if not pushed in all the way. We fixed it with some hot glue.

I doubt this is your problem, but it's worth a look.

Re: Intermittent connection on field only
 

Max,
The 12 volt radio output is exactly 12 volts from a boost/buck regulator inside the PD. It continues to work until the battery falls to about 4.5 volts at which time it quits altogether. It does not track the battery.

Re: Intermittent connection on field only
 

Can anyone confirm or deny seeing this problem during practice matches on Thursday?

Re: Intermittent connection on field only
 

On behalf of Team 1756, thank you Alan.

Re: Intermittent connection on field only
 

This may sound silly, but I haven't seen anyone with problems explicitly mentioning communications drops with their router plugged into the regulated port for the router.

Our alliance captain apparently got through two rounds of inspection and every qualification match before their communications started dropping Saturday afternoon. The problem was quickly traced to that wiring problem, and was rectified over a series of timeouts, cool-downs, and gentle, gentle driving.

Re: Intermittent connection on field only
 

We ran a total of 5 matches on Saturday with the new power distribution board, without a single problem. After removing the "bad" power supply, we did discover that there was a few pieces of metallic swarf on the outside. It's possible that a piece worked its way inside and caused problems. The mechanical team has been sufficiently reprimanded.

I'm still interested in the explanation of what the PD board could be doing to cause issues with the radio. Like Alan speculated, perhaps some noise that isn't filtered by the power converter.

That disagrees with the data sheet for the power distribution board. http://www.usfirst.org/sites/default...on%20Board.pdf It also disagrees with our experience, both the "bad" board and the "good" board output voltage above 12v when the battery is above 12v.

We had a problem in one practice match, which was initially attributed to code, but may have actually been this problem.

Our radio was properly connected through the 12-5v converter and the boosted power supply. On a side note, I'm amazed that every year I find a few teams that made it through inspection without using the boosted power supply.

Re: Intermittent connection on field only
 

Re: Intermittent connection on field only
 

You said you tried running the robot with and without the camera but I'll mention this anyway. At Knoxville we had a similar problem with the robot stopping on the competition field but never having a problem anywhere else. We had very high trip times and a lot of lost packets. We were displaying the camera vidoe on the dashboard using one of the older E09 classmates. It turned out the classmate could not handle the video stream load even though it was only 4 or 5 frames per second. Disabling the video stream brought down the trip times and lost packets and the problem seems to have gone away. Check the stats in the Dashboard Log File Viewer.

Re: Intermittent connection on field only
 

I was the CSA that checked the logs. In a couple of cases, there was a flurry of dropped packets right before the robot was disabled. In other cases, there were some lost packets, but nothing unusual. There really was no pattern we could determine in the logs. Sometimes they were disabled for 4 seconds, a couple times for 30 seconds and once for the remainder of the match (> 45 secs).

Re: Intermittent connection on field only
 

Sorry to mislead, I meant the 12 volt supply does not track the battery below 12 volts. The maximum output of the supply according to the sheet will not make more than 13 volts even with a 15 volt input.

Re: Intermittent connection on field only
 

For anyone who's interested, I've attached ds log files from our second match on Friday, where we dropped out once prior to the match and twice during the match. It appears that upon reconnecting, the DS creates a new log file, so there are 4 files in the attached zip file.

Re: Intermittent connection on field only
 

We have also been getting D-Link drop outs on the field. During our competition at Traverse City and at Western Michigan District we had several communications drop outs. Our robot was not driving hard and no major current draws on the battery. The Field controls personal said our radio reset. I am questioning this answer because I see the radio takes about 1 1/2 minutes to power-up and starts its wireless communications. We loss communications for about 40 seconds. After 40 seconds we are off and running again. My thoughts are we having a wireless network access point/network problem on the field control access point. We saw several other teams with the same problem at these two events.

We have checked the power to the 12V/5V converter. We have replaced the Ethernet cable with a shielded Ethernet cable. We added (4) 470uf 35V capacitors across the 5V power into the D-Link radio. We are running LabView and a camera on our robot network back to out DS. We process the camera image on the DS and send data back to the Robot through a UDP packet.

HELP.... We ordered a new D-Link radio and power converter today but I think there is an issue on the Field Control Access Point.

Re: Intermittent connection on field only
 

I think I've noticed a pattern in who these failures happen to.

They're ALL using LabVIEW... Has there been a single failure of this type with a C++ or Java team?

Re: Intermittent connection on field only
 

Your symptoms do point to the radio power dropping out momentarily. If you reconnect after 40 seconds then the power to the radio was interrupted.

Replacing the radio and converter are a good start, but don't overlook the Power Distribution Board. Also, check the connection to the barrel plug on the D-Link. (Many teams use hot glue, tape, etc to ensure a somewhat better connection).

I am wondering if PWBs in the radios are being damaged internally this year due to the harder shocks that robots are taking (falling off the bridge, going over the bump). The D-link radios were designed to sit on a desk, not to take high-G impacts. Might be worth it to make sure the radio isn't rigidly mounted to the frame.

Re: Intermittent connection on field only
 

While a DAP-1522's expected link-up time is 50+ seconds after a reset, 40 seconds is almost exactly right for communication to be reestablished after a cRIO reset.

I watched one D-Link DAP-1522 consistently work in less than 30 seconds after a complete power cycle of the robot. It was, to put it mildly, unexpectedly quick. This was not using wireless, but it's still faster than I generally see with a wired connection.

Re: Intermittent connection on field only
 

We're running Java and had the same problem multiple times at the Oregon Regional. Other teams were having problems as well.

Re: Intermittent connection on field only
 

I was FTAA at the regional at Utah this last week, and we were having similar problems. The FTA found that every team on the field had high trip times (>30ms) when there was a team with a D-Link running firmware version 1.4.

We has the CSA downgrade those bridges to v1.2 of the firmware and all of the trip times went back down to normal. I am not sure if this is the same problem that everyone else was having, but downgrading the firmware on any of the older bridges running 1.4 seemed to help.

-Clint

Re: Intermittent connection on field only
 

I hope FRC ensures that every robot on the field is running v1.2 going forward.

Re: Intermittent connection on field only
 

I am sure that the FTAs and FIRST staff will look into this and, hopefully, we will see a response from them at the next events.

Re: Intermittent connection on field only
 

We also had this issue at the LA regional, and were advised that there was a "general issue with the field" by the FTA. I was informed that it was causing control problems and sending reset commands to robots.

I'm not sure if this was the cause, but I think it may explain some of the problems that occurred to various teams, including 2637.

Re: Intermittent connection on field only
 

Our team at Sacramento/Davis coded in C++ and we had this problem.

The odd part was that we were only hit by dropped packets on Saturday. Team 3256 was also hit by this however they might have fixed it by halving the resolution on both of their cameras.

Re: Intermittent connection on field only
 

We had a problem at VCU where we would lose comms during the match, and the cycle time was about 40 seconds so we blamed the cRIO rebooting but couldn't figure it out. No problems showed up when tethered in the pits, and couldn't get a slot on the practice field. It turned out to be that the radio was not connected to the regulated supply on the PD board and was cycling when voltage dropped. This was noticed by our FTA who was able to watch the robot from a close vantage point and saw the radio reboot.

We had a handful of problems plauge us throughout Friday, but they were all traced to robot issues and not FMS. (bad jag, bad motor, improper wiring)

Wetzel

Re: Intermittent connection on field only
 

We had issues last year with the D-Link disconnecting. We competed in two regionals before tracing it to the barrel plug, which we purchased from Radio Shack. The ID of this Barrel plug was slightly larger than the AC adapter cord that came with the D-Link. We changed the Barrel plug, using the one that came with the D-Link and the problem went away.

Re: Intermittent connection on field only
 

I actually had an oscilloscope at the MAR Mount Olive District event and someone took the time to check the power on a teams robot that was experiencing these symptoms. This was a 25Mhz analog scope and there were no issues.

Immediately I suggested it could be the camera feed, but it seemed like the other teams who were helping them were using it with better success. I also suggested it could be the CAN bus or somehow related to an interaction with the CAN bridge in the Jaguar....not to toss any blame on the Jaguars...I was merely speculating.

They were using LabView. We don't use LabView and I am not clear on how LabView handles exotic exception situations during communications.

When they turned off their video (which was a serious handicap for them) they could reliably control their robot on the field. As soon as they started using it again they had problems again.

I would like to point out, that I was told our field was apparently configured with 802.11G and everything was sitting on channel 6. I was told that's how it was setup and we all had to deal with it (even Team 11 and we were the host). That would mean that the most you can hope for is 54Mbps. However, with distance, interference, TCP/IP loading issues (it's a reliable protocol and if you don't understand the implications do some research or this will get too complicated to follow) you don't really have 54Mbps.

If what I was told was correct, this is going to be a problem if your robot is bandwidth hungry.

Re: Intermittent connection on field only
 

Yup, our teams runs a javabot, and we had the same problem during our practice matches. Our problem was that there were a few inappropriately handled errors and too many output statements causing major peaks in our cRIO's CPU usage. Having a robot project where the loop iterates as fast as possible can also drive up that CPU usage.

Re: Intermittent connection on field only
 

It wasn't. The field setup uses 5GHz as you can see with a 5GHz NIC or by looking at your radio setup after programming.

Re: Intermittent connection on field only
 

The one field I have seen up close had all the robot networks on channel 60, not 6.

Re: Intermittent connection on field only
 

Team 846 had similar problems at New York Regional, which were resolved by swapping the power distribution board. Though it will not pass inspection, you can try mounting a spare PDB as a custom circuit off of one of the 40A breaker slots, and powering the radio off of that.

We will likely have more data on this phenomena later, as we plan to scope out the failed power distribution board under load. It is perhaps notable that we have measured large ripple voltages (up to 0.6v on a WORKING board) on the 5v supply output, and that this is likely a marginal condition for the D-Link, which expects 5v +/- 5%.

Re: Intermittent connection on field only
 

Aren't you supposed to power the D-Link AP with the DC-DC converter?

I know you can power the D-Link from that 5V source on the PDB, but you're pushing your luck as you've noticed.

I am absolutely sure this was a requirement last year because we showed up to Palmetto minus that DC-DC converter and electrical tried to get me to overnight it (luckily they found a donor).

Re: Intermittent connection on field only
 

Thanks. I was basically the only living body in spare parts and I couldn't stop long enough to test that myself. Unfortunately I normally have one of my A/B/G/N 'war driving' kits with me, but I had to move quickly to absorb spare parts and get all my tools so it ended up sitting at home on the floor.

I did have my Droid-X with WiFi Analyzer App and towards the end during eliminations (while I was moving batteries) I did see 4 networks that are not normally present and they were definitely G networks (my phone does not do A/N).

Are there G networks for field controls, or do these access points continue to transmit the G networks even when you're not using them? I don't know so I'm asking.

Re: Intermittent connection on field only
 

Yep, one and only one PD. However, ripple is not normal and the five volt output is to be used for the camera only. The correct wiring is to connect the five volt convertor to the +12 volt 'radio' output on the PD. The output of the convertor then feeds the radio.
Any idea what frequency the ripple was?

Re: Intermittent connection on field only
 

We weren't able to get a good measurement on the ripple due to difficulty getting the oscilloscope to trigger, but it was approximately 2KHz by our reckoning.

The 5v I mentioned isn't the 5v output on the PDB itself, it's the output of the DC-DC converter after the +12V radio output on the PDB. We don't use an Axis camera on our robot, and so the dedicated 5v on the PDB is disconnected (Sorry for the confusion, I'd completely forgotten that there was a 5v output on the PDB).

Re: Intermittent connection on field only
 

We had the same issue in CT. 4 out of 10 matches we were fine, 5 had intermittent, 1 had no robot control post autonomous, in now particular order. The robot ran fine on the wire and also fine on test radio's in the pit and on the practice field. After much testing (on and off the field) we discovered that our four JAG controllers on the drive were overloading. It appears there was a delay or lag in signal quality, our driver would unknowingly increase voltage through joystick position. When the signal would return the voltage position was high and the JAGS would overload. The process would repeat itself, 3 seconds off- 15 seconds on- 4 seconds off 15 seconds on, over and over. If the driver waited 20-30 seconds the robot would drive again only to suffer the same issue soon after. Very frustrating.

Re: Intermittent connection on field only
 

Mike,
What you describe is typical Jag over current trip. Once they go into fail mode, they wait about 3.5 seconds before returning to normal operation. Most teams using the Jags build in a ramp up to full throttle to help reduce current through the device when the motors are in stall.

Re: Intermittent connection on field only
 

We had a ramp up program and the jumpers on the jag moved to the appropriate position. It was definately a problem with tripping the jags, the question is what was the source of the problem. In any other drive condition the jags worked fine, on the field they failed at random intervals. If there was an overloaded bandwith issue and the controller was slow to react, would this craeate a situation where the joystick was in a full throttle position when the signal was processed ? If the bot was stationary and regained conscientiousness at full power would this overload the jag?

Re: Intermittent connection on field only
 

Mike,
Conditions for drivers on the field are rarely what they are back in the pit, back at your school or on the practice field. The drivers are pumped up for competition and adrenaline is flowing. The Jag fail state is not ported back to the Crio and therefore not through the FMS to Driver's Station. If your student is at full throttle when the Jag re-enables itself, your DS will be sending the full throttle command to your robot during a stall condition on your drives. (stall occurs anytime the motors are not moving and you apply current)

Re: Intermittent connection on field only
 

Agreed, The nagging question is root cause for the initial over current condition. Why with acceptable programming were we entering the overcurrent ? What is the protocol for recovering or re-entering normal function state?

Re: Intermittent connection on field only
 

A few possibilities I can offer that a driver might do in competition that you might not see in another environment:

1. What happens if you drive your robot forward and backwards quickly several times?

2. What happens if you push another robot with your robot (put 130lbs of bricks on something with wheels and try it)?

3. What happens if you go full throttle up the bridges?

4. What happens if you skate along a wall with the robot?

5. If your robot can turn in place, what happens if you do that then suddenly reverse rotation?

6. What happens if you run your end effector and drive train at the same time (does the battery brown out)?

Just a few instances that merely driving around might not simulate that easily crop up during matches.

Re: Intermittent connection on field only
 

Mike,
The only way to recover is to wait. The way to prevent over current fault is to limit the demand either in software or driver training under all conditions. Without watching your robot or knowing your drive train I can only speculate. Some of the more common factors are improper gear ratio choice, sticky tires, sharp turns, transmission losses, misalignment of chains and sprockets, binding drive parts, improper use of bearings or cantilevered drive shafts.

Re: Intermittent connection on field only
 

At 10,000 Lakes, our robot regularly had issues with getting connected to the FMS on-field.

The access point is mounted high in the robot, on Pleiglas at least 2" from any metal. We installed a new Ethernet cable as well. We have the DC-DC converter installed.

The solution that finally worked for us was cycling the power on the access point as we entered the field.

Has anyone had any experience using a shielded Ethernet cable? Was reading a bit about it here: http://www.l-com.com/content/FAQ.aspx?Type=FAQ&ID=4803

Re: Intermittent connection on field only
 

I am not a fan of suggesting it but I should tell you anyway.

If push comes to shove and you can't locate a reasonable resolution to your intermittent overload on the Jaguars, perhaps you could consider using Victors for at least the most likely overloaded systems.

Using the Victors won't actually stop you from overloading the system, but the Victors will just brute force until they self-destruct and if all else were to fail that might be sufficient to get you through till you can either adjust the software or the hardware to resolve this issue.

Keep in mind, what you'd be doing is not a good idea with the Victors either, but if it's rare and intermittent they'll probably survive it. If it's not a rare overload then you might literally be playing with fire (or at least smoke).

Obviously this would mean possibly adding PWM for the Victors to a robot that might not be using PWM to control the Jaguars and this might mean retuning the controls for the differences. This could also involve tinkering with some wiring. However, you could prepare for such a change in advance of competition.

Re: Intermittent connection on field only
 

I think the Victors will survive.
I actually tested this hypothesis a couple of weeks ago and the 40amp breaker on the circuit will trip before the Victor suffers harm.

The order seems to be:

• Jaguars trip first (most sensitive)
• 40 amp breakers trip second

What this means is that swapping the Jag out for Victor will help in marginal cases, but won't do any good if the problem is more than borderline.
Some gear ratios just need to be recalculated.

Re: Intermittent connection on field only
 

I generally agree. The risk is not so much the incidental overload, but the cumulative damage. The auto-reset breakers are not very fast and they often finally open the circuit at currents much higher than their ratings. The Victors are well built and we've been using them for years with very low failure rates but I can see how repeatedly banging on those MOSFETs could result in eventual failure.

Re: Intermittent connection on field only
 

Gearing and box's were mostly KOP, one issue that could have occured was misalignment under full load, potentially binding a gear. I don't think this was the issue we will test and answer that. We had four jags simultaneously overload at once. Four wheel drive, i think the bot would continue to move even if only 1 motor was active, albeit in a circle. Victors and direct drive might be the solution.

Re: Intermittent connection on field only
 

Can you clarify what you mean by direct drive?

Re: Intermittent connection on field only
 

The Victor FETs are rated at around 40 amps each with three in parallel for each leg of the bridge for about 120 amps. This figure is continuous with peaks above that but must be derated as junction temperature goes up. Remember that neither controller has any heatsink for the power devices. The 40 amp circuit breaker can withstand up to 240 amps for short durations but will likely first trip between 100 and 120 amps. The trip point is reduced for each successive trip as the breaker heats up internally. When the breaker trips repeatedly, it buzzes and gets HOT!
The stated trip for the Jag is greater than 90 amps for just under 1 second, with 100 amps stated as the maximum current through the device. Following an over current trip, the Jag will wait about 3.5 seconds before re-enable. While the series resistance for the FET is lower than the one used in the Jag, there are only two per leg.

Re: Intermittent connection on field only
 

I just want to add that this means that it's hard to repeatedly overload the Victor's in a short duration of time when the 40A auto-reset breaker is protecting the circuit because the breaker heating causes them to trip at lower and lower currents.

However, each time you let the breaker cool off you run the risk again that the next overload will get a shot at cumulatively damaging the MOSFETs in the Victors because it's back to 240A max and 100A-120A normally.

The time frame between matches can reach that point. Also if you blow cool air on the breakers you increase the risks of this happening.

Re: Intermittent connection on field only
 

Mike,
How did you couple to the wheels from the KOP transmissions? When you reached trip point were you driving straight or turning? Were you using the standard KOP frame with bolts for wheel axles?

Re: Intermittent connection on field only
 

All jags were independently powered from the distribution board, fused at 40 amps and wired with 10ga. Power consumption to each circuit should have been the max of 1 motor. Two front motors were Cim's w/ simbox and KOP gears and sprockets with #35 chain and 8" plaction wheels. Rears were the 16000 rpm AM motor coupled to a AM planetary with the simbox and KOP gears and sprockets, 8" omni wheel #35 chain. We realize there is a difference in RPM between front and back, testing under all foreseeable conditions proved it to be an acceptable setup. Our acid test was a %500 game cycle test at accelerated driving speeds. We are going to set the bot up and load test each circuit under varying conditions, this should provide us with some good data.

Re: Intermittent connection on field only
 

Mike,
I am going to bet that the 8" wheels are really the big effector here. Have you calculated your final gear ratio and motor RPM?

Re: Intermittent connection on field only
 

Good point. There's a team at Queen City this weekend having Jaguar cutouts on their drive motors, and they have CIMpleBoxes driving 8" wheels.

Re: Intermittent connection on field only
 

Team fusion did not change a single thing on their bot since the bayou regional, we went to lonestar unbagged the robot and put it on the field it connected and had no problems the entire regional

Re: Intermittent connection on field only
 

At the Central Valley Regional we had connection issues in all the matches except two. After changing all the electrical components and then some on the 9th match we started working but not at first. When our robot was brought onto the field the same connection issues were apparent (no connection dropped packets) Two FTA's went on the field and after they came off we were connected. After the match I asked the FTA what he had done and he said they connected the driver station to the robot when they saw no connectivity and it connected ok through a cable. But when he disconnected the Driver Station the radio would not connect to the field so he powered off the robot to reboot the robot. When it came back up we have connectivity for the entire match. Next match we make sure we do not connect the robot to our driver station by cable or if we do we power the robot off then on and so on our last match we ran again not perfect because of the code we had running but we ran the whole match with few lost packets. My guess is we were actually cycling power to the bridge as we entered the field as you stated above.

Re: Intermittent connection on field only
 

I am NYC right not Philly, but students from Team 11 at MAR regional are reporting to me significant connectivity issues.

Apparently they are impacting even our team and we've participated in 3 other events without any issue.

Can someone confirm these reports?

Re: Intermittent connection on field only
 

I can confirm this and they have all seem to have centered around RED Driver Station 1. I know 1712, 11, 25, 1676, and others have all had issues at Red driver station 1 and no others.

1712 has not had ANY connectivity issues in 36 of our 37 matches to date with the only failure today at the MAR championship. Our driver station laptop could not connect to the robot but as soon as we swapped out to the FTA's classmate we had no issue. This of course hurt us in the match as the drivers did not have their normal feedback for shooting but we didn't have any other issues. Returning to the pits we tethered up and had no issues at all with our normal driver station laptop and two different ethernet cords. Unfortunately the pits closed immediately after the award ceremony (huh?) and we were not allowed out to the field to work with the FTA to further troubleshoot/check the problem.

I have noticed a LOT more connectivity issues here at the MAR Championship than I saw at Hatboro-Horsham, Chestnut Hill, and Lenape all with the same MAR field (as far as I know). I'm not ready to rule out that something between our driver station laptop and FMS disagreed but the fact that this has only happened in one match, in one driver station, at one event, and to other teams in the same driver station really makes me wonder.

Re: Intermittent connection on field only
 

Thanks I'll forward the observations to them. Team 11 has communicated that this has played a role in costing them 3 losses (when I last look they've lost 4 times...so it's safe to say they aren't over-estimating the impact of this 'phantom' problem). We've sent out the spare 4 slot cRIO FRC2, they are either close to or will have swapped the DC-DC converter for the D-Link AP. They've swapped the AP. They have reflashed the cRIO. They can swap the cRIO. The logs show communication and an 11-12V battery till the communication simply stops. I know for a fact from many test runs that the robot will remain in communication down to just over 9V on that measurment. They are rebooting the entire robot when they load it onto the field as a standard process (this includes the AP and the cRIO).

I've given them some TCP/IP related suggestions to try and now that you tell me this I'm gonna ask them to dump the registry settings on that laptop to get a comparison with one that works.

I don't believe in 'phantom' problems and while I can't say for certain that the problem isn't in that robot extremely little has changed between the MORT district even we hosted and this event. We are not under funded and a bad battery is extremely unlikely because of it. Therefore there's likely something wrong in wireless and if it's going to cost a place in eliminations at a championship I should think it should be a priority to find out what.

It's quite frustrating that we've had no apparent problems up until this point. That we've done basically nothing to the robot to start the problems. That we're not even using any high-bandwidth applications (no sending video) and here we are with problems. The control system on that robot is basically using PWM and if it's not communicating, to put it bluntly, this means that essentially there is no safe design to escape this mess. It's even more frustrating that I pointed out in these forums before these competitions began that we had problems just once before (with last year's robot) like this at a field at a small off-season event and during that time the process for troubleshooting it was hopelessly ineffective because the tools to do the troubleshooting simply do not exist within the context of the FMS.

Having had access to the tools we were offered to do this troubleshooting this year I can say again that the tools we've been offered are clearly hopelessly ineffective. In each case I've seen at the MORT district event and now here the only resolutions have come from trial and error not quantitative measurement. Trial and error means you get to forfit games to test one thing after another and since this seems to mostly effect the actual playing field and not the practice fields you are forfiting games you and your sponsers paid to play to troubleshoot problems you can't replicate on your own.

I'm not sure what frustrates me more. That we can't teach the students through this adversity more about troubleshooting and that technology or that we don't get to compete in the competition.

Re: Intermittent connection on field only
 

Have you swapped the PDB yet? I know at least three teams that swapping the PDB has solved intermittent connection issues. Try to find a non-2012 PDB.

Re: Intermittent connection on field only
 

If communication is lost at 9 volts, something is wrong with the robot. The cRIO and wireless bridge power outputs on the Power Distribution Board are designed to maintain full voltage down to below 5 volts on the battery input.

Re: Intermittent connection on field only
 

I have no idea how low it can really go till it totally looses communications actually (though I understand how you could interpret that sentence like that). At 9V we don't consider that robot to be fully functional as it impacts the shooter performance quite noticeably.

If there was something terribly wrong like that the odds are it wouldn't have gotten into elimination or near elimination matches at 3 (make it 4) events.

Also, I don't think you can claim that the robot can communicate with a 5V battery despite the rating of the converter because the moment the robot starts to move any actuator that battery will cave at that level of discharge and then you will be outside the nominal voltage range of the DC-DC converter. Heck that's less than 50% so really at that point you've deep cycled the battery and you really would have something wrong if your cRIO was reading a battery voltage of just 5V even for a short period. That would be easily indicative of a very heavy load, a battery issue or a discharged battery.

We tested this design quite a bit. We don't have discharged batteries because we have plenty of them constantly tended. We don't have bad batteries because we'd have likely discovered them in the batch some time ago. We might have 1 or 2 marginal batteries suddenly but again too many matches that shouldn't happen and so far as I know we never created any bad batteries with this robot. Additionally even driven incorrectly, with all the mechanisms moving under full power (and the compressor running) the robot can easily sustain activity for longer than a match as we did that over and over (at least 50 times). It's performance will suffer but it has never...not even once...lost communications under those circumstances and we did have a field we constructed with bridges, other robots and targets to test it.

Additionally, as I've noted elsewhere, when this was happening at the MORT district event someone took my oscilloscope and put in on the effected robot in the pit (an entirely unrelated team as I was in charge of spare parts and I let anyone use my tools). The battery itself back from that failure was not having any issues that would cause the DC-DC converter to drop it's output voltage. That was the same battery, on the same robot, right after a failure. So it would seem that this can't all be battery supply related issues. Additionally, it wouldn't explain why with the same model bridge and again a well tested battery we lost communications last year several times during a single off season event (an event with countless issues with the field operations I might add).

Re: Intermittent connection on field only
 

As it stands they've swapped the DC-DC converter and for the moment they've avoided any additional issues since doing that. However, other teams are apparently still having communications problems. It might be related, or as I've already suggested it might not be related at all.

Thing is this is a terrible way to troubleshoot. Firstly, the field itself has probably been power cycled since yesterday. Secondly, we have no idea what has happened to the field since it was left overnight. Thirdly, we had (I think) another 3 matches (before eliminations) but each time you're operating in the environment in different locations.

The only good part about this is that it's not just us. Okay that's not really a good part either as we want to compete on a communications level playing field. At least it's acting as a leveling effect for the tournaments. If your robot has other issues then as long as this issue rotates it's way around the ranks the rankings should somewhat self level.

If luck holds out they'll avoid any more surprises like this. If not when that DC-DC converter gets back here I'm going to see if I can find any reason it might be contributing to issues. Being a power component it's not like we have lots of choices of how to handle it.

I will add this anecdote. Early this year with a prototype robot one mentor constructed an LED light source and put it on the 2012 PDB. It was drawing less than the PDB specifications but that PDB was literally making a whistling noise. That PDB is not on the robot they have. I chalked that up to loose magnetic components but as the load changed the pitched changed (was gonna make it play a little tune). The LEDs were not a switched load as he was simply limiting their current with a resistor. Still that was the first time I've ever seen one of those PDB do that and there as no excuse because that was a fraction of the available current.

Re: Intermittent connection on field only
 

At the end of the day after we replaced the DC-DC converter the problem did not come back, at least not for us. It looks like 1403 lost communications on our red alliance it helped cost the elimination match.

It was great fun as always, the communications issues aside, and as with the other competitions before this where we didn't have communications problems we placed highly. So as it turned out it wasn't the defining limit of our game but instead fell back to more regular issues.

Thanks to everyone for your input on the matter and for Team 11 still out at the event great job!
Additionally thanks to the field folks and MARs for the game and support!

Re: Intermittent connection on field only
 

1) When the battery voltage drops that low, the cRIO will have disabled all the robot actuators anyway in order to maintain power for communication.

2) When you say DC-DC converter, are you talking about the internal circuitry of the Power Distribution Board, or do you mean the 12v-to-5v converter for the D-Link?

Re: Intermittent connection on field only
 

Here are my final observations from the MAR Championships...

1) This was apparently one of FIRST's fields and not MAR's, possibly one of the advance/emergency fields. As a result I'm not sure what, if any, events this field was used for.

2) I saw much fewer communications issues Saturday, but didn't really watch all the qualifying matches.

3) Comms issues throughout the tournament seemed random and happen to no team specifically that I am aware of other than 1676.

4) In the elims the FTAs/1676 would allow the robot to connect to the field and then wait for some amount of time. If it didn't lose communications they'd be good for the match, otherwise they'd wait again (only happened once). While I know nothing specific, something specific to their robot/driver station was having more issues with the field than everyone else. I'd really like to hear their experiences and what they found out.

I must say, the FTAs and event staff did a great job being patient and troubleshooting in an attempt to make sure the matches started with all robots connected to the field.

Re: Intermittent connection on field only
 

Check for metal shavings in your crio bay and ports. Someone may have drilled above your board and the electronics are complaining. Also check your radio version. Make sure it is version 1.2 and not 1.41.

Md

Re: Intermittent connection on field only
 

I'm talking about the module you are supposed to connect to the D-Link.
Sorry am on my phone.

Re: Intermittent connection on field only
 

Always a good thing to check but it can't be the cause in this case.
The design would make it quite improbable.

If this was a robot issue at all replacing that DC-DC module seemed to be the fix.

Re: Intermittent connection on field only
 

You don't seem to understand the purpose of the boost-regulated 12 volt output from the Power Distribution Board. It stays high enough for the wireless bridge to function even if the battery sags to a ridiculously low voltage. If the PDB and 12v-to-5v converters aren't faulty, the system will maintain the bridge's operation while the battery is supplying only five volts.

Re: Intermittent connection on field only
 

I am confused as to how you arrived at this conclusion that I don't understand what you're trying to communicate.

1. You are saying that the D-Link will communicate down to 5V and I'm telling you that the system battery voltage was no where near that low and the logs demonstrate that. So even if you're correct...it doesn't matter to this situation with this robot. If that battery is reading below 9V nominal on the driver's station for this robot it needs to be replaced with a charged battery and there's no evidence to support the claim that it was that low. Not in the logs or in any set of measurements I've got from the team or the field personnel. It doesn't matter just how low a battery voltage the D-Link AP may, or may not, be able to operate that robot is designed to shoot baskets and that system can't function within the parameters the drivers expect with a battery anywhere near that low.

2. I've also mentioned at least 2 times that the DC-DC converter being replaced seems to have fixed it. If, and only if, the DC-DC converter connected to the D-Link AP was actually bad would that be the only problem. I still believe that's it's either the escape goat or just part of the overall problem. I will gladly bench test the suspected bad DC-DC converter when it's available to me and if you like provide the results (if you like I can probably even send it to you to test). The point being here is that we might not be talking about a properly functional DC-DC converter (see my note in the next post because there's a problem with this idea).

3. I've already explained in detail that the battery being low or damaged was (as this is now past tense) not the case.

4. I've also explained that at several previous competitions we operated in dozens of matches with zero events such as this. That doesn't include dozens of matches on our test field and some matches on the practice fields. So what I'm saying here is if that DC-DC converter is the problem it literally just went bad. That would *really* bother me if that happened because that particular part is pretty well protected from SWARF! and it's load should be predictable (again see my next post below).

So what am I not understanding here? That we have a possible bad DC-DC converter? Didn't miss that we replaced it just before the problems stopped as one of my recommendations to them.

I understand you're trying to help. However this is now literally beyond help. After the DC-DC converter to the D-link was replaced we continued our remaining matches without problems. However, other teams on our alliance failed to be able to communicate and short their ample assistance we seem to have done the best we could.

I'm not sure how what I may, or may not understand, effects the other robots on the field.
Perhaps we just all have a lot of unrelated power problems that effect the D-Link AP.
However, again, that would mean that something that defys the expectations of the specifications would be at work here.
We are all a little too far along in these competitions for really defective robot designs.

Re: Intermittent connection on field only
 

So here's the thing with these D-Link power issues. Let's assume that we can power this D-Link AP well below a battery voltage of 5V in a properly functional system. I respect you Alan and I haven't tried to push this limit myself so let's take this as gospel.

It really does not explain why these problems are so hard to troubleshoot off the competition field seemingly regardless of the number of tests run or the equipment. It's not just me and especially not just me since I have only attended exactly one competition this year and I spent that as the spare parts volunteer. We've had MARs folks, FIRST folks, trained engineers and teams struggling with this (and my heartfelt thanks to each and every one of you).

1. If we had the ability to measure the voltage feeding the AP on the robot at all times that would help, I have a circuit that could perform this function, but because it touches those power leads it's probably illegal on the field. So we can't really test the power to that D-Link AP either from the PDB or the DC-DC converter connected to the D-Link during a competition match. It's not a feature we have in our current system and the rules prohibit the inclusion of circuits that would add the capability.

2. I wonder what the FIRST configuration of the D-Link AP does to the power requirements of the D-Link AP. I can easily test the power requirements of the D-Link AP when it's communicating with a B/G network or N network, but not so easily with the competition field because of issue one above. Perhaps the reason these problems tend to favor the competition field is because the field settings for the D-Link AP somehow increase it's power requirements unlike other environments. That change might not even be the sort of thing you can test with a voltmeter or ammeter when the robot is stationary. If that's the case then we have an issue that makes it hard to test elements of the system unless we just hard load the power where it would feed the D-Link to it's maximum rating as a test.

If this was the case this might explain a great number of things and would mean the field itself isn't the issue. It would even touch on the reason that some teams get nailed by the PDB and some teams get nailed by the DC-DC converter connected to the D-Link (assuming they have decent power supply from the battery). Perhaps an overload situation is created beyond the specifications of the systems or perhaps those specifications are not being met in production for these parts.

In any case, did anyone that actually had problems fully load test the system at the point where the D-Link AP is connected? Can anyone confirm that actually tested this regardless? I will confirm that to my knowledge we did not fully load that D-Link power supply. We tested it anecdotally by simply using it without issue...till we had an issue on this particular competition field after many successful previous uses. Perhaps this thing is a bit of a ticking time bomb.

Re: Intermittent connection on field only
 

We also had communications issues all season but what happened at the MAR championship was interesting. We would connect to the field when we were setting up for a match. When all the robots were connected, about a minute later we would disconnect. After a reboot we would connect and run through the match with no issues. The FTA and NI engineer were as puzzled as we were. Fortunatley since we had a workaround with the reboot we were allowed to run through that sequence for each match.

Just as a side note I want to thank the FTAs and NI engineers at the event. They really went above and beyond to help.

Re: Intermittent connection on field only
 

At the MAR Mount Olive Disctrict event a team sending video back to their driver's station only seemed to have issues when they sent that video stream. If they turned off the video the robot worked fine but was at a big disadvantage beacuse a key feature was turned off.

Here's something I've been thinking about:

In my post above I proposed that perhaps the field settings for the D-Link AP raise their power requirements to a marginal or overload situation. A situation that only exists on a competition field when that particular situation is created and can't easily be measured with robots moving.

I would think that there's a non-linear but generally increasing relationship between the D-Link AP's use of power and it's attempts to communicate. I would propose that if the AP's general power requirements are generally increased that sending additional payload would be the equivalent of fuel on a fire. Sending that transit might push what is otherwise a not very good power situation (that eventually might damange the power components) into a situation where the odds are the D-Link AP power is insufficent and it'll misbehave. A situation that might leave the D-Link AP powered fully up when the robots stop moving and therefore can't be observed easily after the fact.

This possibility fits a few situations. Sending video streams from the cameras over TCP/IP to the driver's station should and does work on the none competition field and on no field at all. N wireless has more than enough bandwidth for that application. However this proposal would apply here and create this issue only on the competition field (on the robot side).

Additionally, when you first enable the D-Link AP as things normalize you're prone to have a burst of very busy transactions. Again, another shot of high traffic that could raise the D-Link AP power requirements so it could also apply in this case. You then reboot the D-Link AP as described in the post immediately above and you clear the immediate consequences of the overload you induced in that short period. Which would mean that all it would take is a good hard shot of communications to cause malfunction again.

Did anyone fully load test the D-Link AP power system?

Did anyone measure the D-Link AP power requirements when the robot was running and moving on a competition field (using 2 multimeters, one as a voltmeter and one as an ammeter on MAX/MIN would be a good start...be aware that's not a perfect test)?

Re: Intermittent connection on field only
 

Was talking with 846 at SVR and they made the comment about the radio increasing power requirement when it started to detect dropped packets. They supposed that was part of their issued with dropped communications. The ncreased power requirement was causing a a marginal compnent (PDB in their case) to fail

Re: Intermittent connection on field only
 

It would only get worse with packet loss. TCP is a reliable protocol so it'll keep trying until it times out to deliver the packets you've asked to be sent. So basically if something starts to cause issues it'll try again, causing congestion, then it'll try some more. Eventually it's a storm.

One of the things I suggested to Team 11 was to change the timing behavior of the driver's station TCP stack so that it would either wait longer or give up sooner for a successful delivery. They could also do that on their robot mounted laptop if they were using it. This would help reduce the load on the network but with so little time to test might have cause unpredictable control issues for them. Course in their case the damage to the DC-DC converter could already have been done so it might have helped before that damage happened but in this case possibly not.

A camera using TCP would also set up this situation. It's really not the best protocol for streaming live video content (if you loose live video data...give up and get more). So if the D-Link AP does draw more power when packets are lost then this would be a great way to cause a problem.

I'm gonna leave my questions on the floor for other input:

Did anyone fully load test the D-Link AP power system?

Did anyone measure the D-Link AP power requirements when the robot was running and moving on a competition field (using 2 multimeters, one as a voltmeter and one as an ammeter on MAX/MIN would be a good start...be aware that's not a perfect test)?

Re: Intermittent connection on field only
 

Expanding on the potential of an increased load on the D-Link power circuit...

We know that teams have had a hard time duplicating this issue at their own facilities. We also know that some events have not had as many reported issues (FiM and MAR district events for example).

Looking at the events where issues have occurred they seem to all be the traditional regional-type event in an arena/larger type venue, perhaps largely taking place in a city. In contrast, smaller events are taking place in high schools and other such venues where the environment is much more controlled.

Are we looking at a situation in which the D-Link AP is exceeding it's published power specifications due to it dealing with "normal" interference from various sources such as campus/venue WiFi, large number of teams with their router on in bridge mode, other devices such as bluetooth? As a result of this increased load are we damaging or pushing the DC-DC converter or PDB out of spec or degrading to out of spec over time? Are we or specific teams (for whatever reason) hitting some issue in the firmware/baseband of the D-Link? I doubt anyone could argue that we aren't exactly using the D-Link in its designed environment...

I'm going to see if I can get one of our DC-DC converters and one of our "not for competition use" PDB and attempt to load them down to their specification and beyond.

Re: Intermittent connection on field only
 

Two things you said gave me that impression. You challenged the claim that communication can be maintained at a battery voltage of 5 volts, and you responded to a mention of the PDB's boost-regulated 12 volt output with a reference instead to violating the input specification of the 12v-to-5v converter.

I only brought up the low-voltage capabilities of the system because it looked like you said the robot was losing communication at slightly above 9 volts, and that would be a symptom of either a faulty PDB or incorrect wiring.

I haven't had the opportunity to test things using a known-faulty setup, but I have seen hints that the wireless portion of the D-Link quits working if the power drops even a little below 5 volts, while the wired portion continues to function through the sag. If that's indeed the case, then a bad PDB or CPR360 (or incorrect wiring) could result in loss of communication on the field but perfectly good operation in the pit. It's also true that a robot is rarely working as hard when it's up on blocks than when it's trying to turn on a carpeted surface, so a marginal power system is much more likely to reveal itself while the robot is actually running a match.

What rule would keep you from doing this on a competition robot?

Re: Intermittent connection on field only
 

Well aware of that Alan. I can't speak for others, but low voltage was not a factor for us.
See my post in some other related thread, and jteadore's post above.
I can't speak for others, but this was not an issue for us, absolutely positively.

As I mentioned in my other post, we are heck-bent on duplicating this at home - after CMP though.

Re: Intermittent connection on field only
 

Well the Team 11 robot is >not< loosing communication at slightly above 9 volts norminal on the drivers station. Our robot just isn't a useful system when the driver's station nominally gets that low so it doesn't really matter if you can communicate to a robot that won't perform. Again that voltage was never that low. I respect you and the point you thought you were making so let's move on.

Wouldn't be applicable to Team 11. As I've stated we've driven both our robots (we have 2) around on our regulation carperted test field, on other competition fields and other practice fields for full tests of opreration more than 50 times. Sometimes quite aggressively. If the carpet induced load was the prime factor we'd have seen it quite long ago. We did not see this problem before this event and that's a whole lot of hard driving by a wide variety of drivers with a wide variety of experience driving our robots (and cars I hope).

Though I absolutely agree that if the loading of the system were the factor not testing on the regulation surface would be a bad idea. I can assure you, at least with our design on Team 11, it's been tested very well. So this isn't the hidden cause for us and I personally know it's also not the issue for several other effected teams.

Additionally when my oscilloscope was used to test another team's robot at the MAR Mount Olive event they did try loading the wheels while the robot was off the floor along with powering up other devices in different ways. The power from the battery did not sag anywhere into the terrority you're describing from what I was told.

Please see rule R42, part B:

"The wireless bridge power feed must be supplied by the 5V converter (model # TBJ12DK025Z) connected to the marked 12 Vdc supply terminals located at the end of the PD Board (i.e. the terminals located between the indicator LEDs, and not the main WAGO connectors along the sides of the PD Board). No other electrical load can be connected to these terminals (please reference any 2012 Robot Power Distribution Diagram posted on the Kit of Parts site for wireless bridge wiring information."

If you only look at that rule you'd be breaking it if you insert a current sense resistor into the path of the wireless bridge's power or put a high impedance circuit in parallel with it's input. However, I'm aware of this:

Rule R47:

"Custom circuits shall not directly alter the power pathways between the battery, PD Board, speed controllers, relays, motors, or other elements of the Robot control system (including the power pathways to other sensors or circuits). Custom high impedance voltage monitoring or low impedance current monitoring circuitry connected to the Robot’s electrical system is acceptable, if the effect on the Robot outputs is inconsequential."

Problem is, if you're a real stickler it doesn't actually call out the wireless bridge.

If you disagree with my interpretation of this then we are back to my original question as you'd interepret it as an allowed thing to do:

Did anyone measure the D-Link AP power requirements when the robot was running and moving on a competition field (using 2 multimeters, one as a voltmeter and one as an ammeter on MAX/MIN would be a good start...be aware that's not a perfect test)?

So if you think that rule will allow you to measure that information, you can add putting a custom circuit on the D-Link AP power and logging the data (probably into the control system).

Now additionally let me point this out if you create this custom monitoring circuit before build season...like I did...you're dancing with Rule R18 because I don't sell it yet:

"Please note that this means that Fabricated items from Robots entered in previous FIRST competitions may not be used on Robots in the 2012 FRC. Before the formal start of the Robot Build Season, teams are encouraged to think as much as they please about their Robots. They may develop prototypes, create proof-of-concept models, and conduct design exercises. Teams may gather all the raw stock materials and COTS Components they want."

The open source exclusion might not apply because I never fully put up the schematics either:

"Example: A different team develops a similar solution during the fall, and plans to use the developed software on their competition Robot. After completing the software, they post it in a generally accessible public forum and make the code available to all teams. Because they have made their software generally available (per the definition of COTS, it is considered COTS software and they can use it on their Robot)."

Then there's the whole it was built by a mentor not a student that bothers me but isn't against the rules.

If you use commercial multimeters then you avoid this. However, then you have loose test equipment you've put on your robot. Could get it reinspected...but again...had anyone done this? Oh and by the way, the multimeters reading DC aren't the best choice entirely because they will check very infrequently compared to say an oscilloscope so a short surge or drop might slip right past. Can't say how fast the cRIO can monitor that information depends on a lot of factors.

Re: Intermittent connection on field only
 

Double post (lost Internet access sorry).

Re: Intermittent connection on field only
 

If you would like to add such a monitoring device, you may be able to get an exception with the consent of the LRI and the FTA. They will need to contact FRC HQ, so ask well in advance.

Re: Intermittent connection on field only
 

Thank you. I'm also hoping to get someone's attention at FIRST in the near future to discuss making something like I am describing clearly acceptable in a general sense without the exception.

It might mean I have to make some more and give them away to achieve that but first I need to be clear on the process involved. I'm always happy to help but I'd rather not just blow money and time into the breeze. I have, I hope, already started this process.

Re: Intermittent connection on field only
 

Guys,
A few thoughts here. The radio boost/buck +12 volt regulator on the PD is capable of a few amps. There is a failure mode on the external 5 volt regulator that effectively turns it into a big resistor making about 7 volts when the battery is at a normal level and then drawing enough current to drag the +12 volt regulator down with varying battery. (I do not have accurate data on this phenomena since a replacement 5 volt regulator fixes the problem.) When connected to a battery instead of the regulated +12 volt output, the failed +5 volt regulator will actually follow the battery voltage when it falls below 7 volts.
The radio is designed to operate at 1.5 amps (less on the newest model) which both the PD and the 5 volt regulator are designed to supply. To my knowledge the bridge does not dynamically adjust power output but does have a power setting in one of the setup screens. (see manual for details) I am under the impression that the return to factory defaults and the WPA encryption routine sets the power output to a normal value. There is a feature of this device that adjusts power delivered to the ethernet ports and that might be where the confusion lies with varying output power. I could not find any reference to RF output power on this device.

Re: Intermittent connection on field only
 

I just wanted to update this topic as I successfully made contact with U.S. FIRST regarding what I was proposing as a 'custom test circuit' and I now have a bearing on how to get it into at least the approved parts.

Basically I need to get a sample as close to production as possible to the US FIRST KOP team before the end of August. They'll check it over a couple of weeks and once it's been rung out along with all the business details (how it's getting made, in what quantity, how can teams get it, what's the cost, etc...) They'll issue an approval if it's warranted to be included in the list of approved hardware they finalize in September.

If somehow it ends up in the KOP I would need to deliver product to them by October for distribution purposes. Otherwise I could sell or give away product without being able to declare it approved by FIRST for competition usage. Obviously the NDA for the approval of the hardware would prohibit any discussion before January of whether it's approved or not.

My appreciation to FIRST for providing me a great place to start working from.

In the mean time I'm considering making a few simple test versions to send out for testing on real fields. Obviously per Eric's post since these aren't approved you'll probably need some approval from US FIRST if you want to try something like this on a live competition field.