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