Chief Delphi

Chief Delphi (http://www.chiefdelphi.com/forums/index.php)
-   Electrical (http://www.chiefdelphi.com/forums/forumdisplay.php?f=53)
-   -   Intermittent connection on field only (http://www.chiefdelphi.com/forums/showthread.php?t=104713)

EricVanWyk 16-04-2012 19:15

Re: Intermittent connection on field only
 
Quote:

Originally Posted by DonRotolo (Post 1158764)

But adding a big honkin' capacitor on the power input to the radio should filter out any millisecond transients. I need to verify that the rules permit this. I'm thinking several dozens to a hundred microfarads (whatever's in the junk box)

Depending on the control mode of the regulator, adding a large amount of load capacitance might cause the control loop to go unstable and create additional noise. Proceed with an Oscilloscope.

techhelpbb 17-04-2012 05:13

Re: Intermittent connection on field only
 
I'm going to put a website to collect measurements from the D-Link AP robot power supplies so we can perform a statiscal analysis. I'll put some direction on the website so people understand what the process to get the measurements should be so we get them to provide us the most practical data when they enter it into the website.

When I'm done I'll put the link in here. This way everyone with a 2011 or 2012 robot can help with the testing. That could net us a few thousand points of data while more evenly distributing the work load.

There will obviously be some issues with test instrument calibration but odds are the issues from that will be statistically small.

Al Skierkiewicz 17-04-2012 08:00

Re: Intermittent connection on field only
 
Tech,
I think we need to slow down here. Most of the problems are not pointing to a power supply problem with the radio. It has been our experience that power supply problems with this radio manifest themselves by total radio reset which by most accounts lasts nearly 50 seconds. With the thousands of PD's in use thus far, only a handful have ever had a real +12 volt power supply issue and of those some were from mishandling of the PD. Those power supplies are very well designed and do more than they were originally intended to do. Remember that this power supply is designed to source a lot more current than the demand from the regulator and radio combined. When the supply faults it doesn't brown out, it just goes away. As to the 5 volt regulator, this is a 25 amp device if memory serves, and it won't brown out either. What ripple might be present on the PD power supply is high frequency and easily shunted by the high frequency impedance of the input cap(s) on the DLink.
The fixes I discussed earlier come from the knowledge that teams using the long power wiring that comes with the radio may run it near some high noise sources that are generating some very high frequencies. This noise can and does couple into wiring and in some cases, will actually travel on the outside of the wire and right into the radio bypassing everything you are suggesting.
At this point, the really offensive failures are either repetitive (and seemingly regular) losses in packets or complete loss of communications for no other obvious reason. I have seen a few robots where all of the data tell us that the robot is working, there simply isn't any robot commands. Remember that the FMS this year is watching far more things that ever before. They know what the robot battery is doing, what packets are being transferred, when the robot is communicating with the field, even if the robot is doing nothing.
If you want to look at power supply issues, you must first rule out, bent contacts in the radio, poor solder jobs on the wiring (if soldered at all), poor wire restraint and poor mounting of the radio. More than half of all radio complaints that are brought to inspectors are obvious problems with the coaxial connector supplying power to the radio. It is either loose, the wrong size, not secured, improperly insulated, the radio connector has pulled away from the board, or there is an improper termination to the 5 volt regulator. In the majority of the remaining issues (when pressed), the team had failed to use the regulator for some period of time. While in many cases the radio continues to function, the power supply has been stressed or damaged. Without doing some physical inspection of these radios, all statistical data becomes flawed.
As to the application of devices between the PD and radio, the answer is there is no rule that allows anything in this path when used on the robot. I know that there are people working on the problem and that bench testing will reveal issues if they exist.

FrankJ 17-04-2012 08:16

Re: Intermittent connection on field only
 
Has anybody considered that the in question DAP has a cracked pc board? Cracked boards manifest all kinds of strange behavior. Since the DAPs really were not designed for the robot environment, maybe they are more fragile than anybody thought.

Gdeaver 17-04-2012 08:46

Re: Intermittent connection on field only
 
We have a DC to DC switching power supply feeding a DC to DC switching power supply feeding most likely another switching power supply inside the D-link. I believe that this sets up a strong possibility that under high load a instability develops and a transient of very short duration gets through to the digital parts in the D-link. Any part that is out of spec in the chain would greatly increase the chance of this happening. Probably the only way to catch this is with a very high speed circuit or a scope. Caps are a prime source of this. That's why mother board manufactures boast about Japanese caps in their power supplies. I may be wrong but don't most N stuff have gain scheduling based on background RF levels? Why shout if its quiet. This could explain why the problems are seen on the field. Phily was a very loud rf environment based on the behavior of my I-phone while down on the floor. There are 6 robots all shouting in a loud rf environment. The D-links most likely were at max gain and highest current draw. If the power supplies do turn out to be a point of failure then there are automotive power supplies that are designed to handle the nasty automotive environment. (load dump, static, ect.)

MaxMax161 17-04-2012 09:04

Re: Intermittent connection on field only
 
This has gotten to be a very long thread so I'd like to try and summarize the important points for anyone new who comes along. If any of this is inaccurate, incomplete, or over complete please tell me so I can edit this post.

Thread Summary

Main Symptom: On the field, after the auton bell rings and before teleop ends, robots loose communication with the driver station.

Main Cause 1: Camera stressing bandwidth. Manifests in many lost packets and high trip times. Very rare when getting a 320x240 image at 30fps and 30 compression. The un-updated smart dashboard defaults to the settings on the camera which default to a 640x480 image, the default dashboard defaults (say that three times fast) to 320x240 settings.
Fix: Smartdash- reconfigure the settings on your camera. Stockdash- make sure you don't ask the camera for anything specific unless it's less then the default.

Main Cause 2: Power problem to the radio. Manifests by taking around 40s-50s for communication to come back while radio lights turn off and then go solid while rebooting. Most often a problem with the 5v-12v converter or the PDB.
Fix: Replace the 5v-12v converter and/or the PDB.

Other causes: ?


Other Symptom 1: Robot connects to field, robot comm dies, we reboot robot, everything is fine indefinitely.

Causes: ?


Other Ideas Currently Floating Around:

Idea 1: ?

techhelpbb 17-04-2012 09:34

Re: Intermittent connection on field only
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1159027)
Tech,
I think we need to slow down here. Most of the problems are not pointing to a power supply problem with the radio. It has been our experience that power supply problems with this radio manifest themselves by total radio reset which by most accounts lasts nearly 50 seconds. With the thousands of PD's in use thus far, only a handful have ever had a real +12 volt power supply issue and of those some were from mishandling of the PD. Those power supplies are very well designed and do more than they were originally intended to do. Remember that this power supply is designed to source a lot more current than the demand from the regulator and radio combined. When the supply faults it doesn't brown out, it just goes away. As to the 5 volt regulator, this is a 25 amp device if memory serves, and it won't brown out either. What ripple might be present on the PD power supply is high frequency and easily shunted by the high frequency impedance of the input cap(s) on the DLink.
The fixes I discussed earlier come from the knowledge that teams using the long power wiring that comes with the radio may run it near some high noise sources that are generating some very high frequencies. This noise can and does couple into wiring and in some cases, will actually travel on the outside of the wire and right into the radio bypassing everything you are suggesting.
At this point, the really offensive failures are either repetitive (and seemingly regular) losses in packets or complete loss of communications for no other obvious reason. I have seen a few robots where all of the data tell us that the robot is working, there simply isn't any robot commands. Remember that the FMS this year is watching far more things that ever before. They know what the robot battery is doing, what packets are being transferred, when the robot is communicating with the field, even if the robot is doing nothing.
If you want to look at power supply issues, you must first rule out, bent contacts in the radio, poor solder jobs on the wiring (if soldered at all), poor wire restraint and poor mounting of the radio. More than half of all radio complaints that are brought to inspectors are obvious problems with the coaxial connector supplying power to the radio. It is either loose, the wrong size, not secured, improperly insulated, the radio connector has pulled away from the board, or there is an improper termination to the 5 volt regulator. In the majority of the remaining issues (when pressed), the team had failed to use the regulator for some period of time. While in many cases the radio continues to function, the power supply has been stressed or damaged. Without doing some physical inspection of these radios, all statistical data becomes flawed.
As to the application of devices between the PD and radio, the answer is there is no rule that allows anything in this path when used on the robot. I know that there are people working on the problem and that bench testing will reveal issues if they exist.

Why is it a problem to create a trivial 20-30 minute exercise (per participant) to get an idea of this value?

If I had the voltage that was too low we could easily test virtually all supply issues up to the radio with those little LED modules I have. Actually come to think of it, I don't know how you can test that voltage at all if you don't know what the requirement actually is.

It wouldn't tell you exactly where the problem was (you could further isolate with more of those little modules) but it would eliminate that issue or indicate it's presence just by looking at it.

So given how small the effort why not? Certainly there's no reason I can't make the site.

To be clear I'm not saying your wrong, I'm just asking why not be sure there's no problem hidden there?

As it stands I having been watching the current method of troubleshooting and it is dramatically extended as we hunt through that great big list you offered dancing back and forth between things that effect power quality to the D-Link AP and may be intermittent and things that could additionally be wrong.

If we knew we had a power quality issue during the match that's probably half the effort right there and it's entirely possible you could have a power quality issue during the match but not any other place you can measure it during a competition.

(I've sent a question about rule R47 and the legality of using a circuit to measure that D-Link AP supply voltage to someone at FIRST. Let's see what they say.)

Al Skierkiewicz 17-04-2012 12:27

Re: Intermittent connection on field only
 
I just don't want people to get the impression that there is a power supply issue when we are quite sure that this is not the case. The issue may not even be with the radio.

techhelpbb 17-04-2012 12:58

Re: Intermittent connection on field only
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1159116)
I just don't want people to get the impression that there is a power supply issue when we are quite sure that this is not the case. The issue may not even be with the radio.

There are really two ways you can look at checking the D-Link AP power supply. Looking because you think it's the problem or looking because you don't think it's the problem.

If the voltage is too low it could still be an indicator of a wiring issue not a power supply module issue (a module being the PDB or DC-DC converter). However, first you have to know that there's a problem or not there.

It's that ambiguity that lets the imagination roam. I'm not looking to offload blame just find a process that's tangible and quantitative.

EricVanWyk 17-04-2012 15:43

Re: Intermittent connection on field only
 
Quote:

Originally Posted by Al Skierkiewicz (Post 1159116)
I just don't want people to get the impression that there is a power supply issue when we are quite sure that this is not the case. The issue may not even be with the radio.

I agree. I'm much more interested in things like firmware versions, rogue windows update services, and proximity to noise sources. Now its a matter of finding why some `bots are more sensitive than others.

The power supply issue you (Tech) are tracking, transient undervoltage, has a known fault signature that does not match reported issues. It is possible that a transient spike could affect things, but I'd expect more of a buzz than a spike in this situation. Gdeaver might be on the right track with his "switching cacophony" theory. Please confirm with your own measurements - we'd love to see the numbers. But please, no more back-to-back-to-back posts!

dcherba 17-04-2012 15:53

Re: Intermittent connection on field only
 
For three years we have been running c++ code build from the default program offered by FIRST. In match 10 at the Michigan championship we moved in hybrid and came to a complete stop with loss of packet from the FMS. The only change was an added camera at low FPS rate. Turns out the CRIO was throwing away the FMS control packet because it was overloaded with the empty code stubs for the continious teleop. This was a totally unexpected consequence of adding a camera that had nothing to do with the control program except the CRIO would see those packets and throw them away. That was enough. After reading this set of symptoms I wonder if the same continous blocks are also in labview not being used and are having the same intermittent effect.

Considering how many years I have been doing programming it was a sobering revelation to see something so simple cause the problem.

Every program I help the students write have performance timers in them and according to our data the code was being executed every 20-100millisec but not the TCP packet handler..

When everything has been ruled out look at the impossible..

jteadore 18-04-2012 08:47

Re: Intermittent connection on field only
 
Dave,
How is your camera connected? Do you connect it through the crio or direct to the radio?

dcherba 18-04-2012 11:02

Re: Intermittent connection on field only
 
our cameras were connected to the wireless and not through the crio.
It was only when we added the second camera that the problem really appeared.

MaxMax161 20-04-2012 09:08

Re: Intermittent connection on field only
 
Was your 2nd camera connected to your c-rio or did you configure it as something like 10.32.34.12 and also get it through the dashboard?

Steve Warner 21-04-2012 16:02

Re: Intermittent connection on field only
 
This subject has been covered pretty thoroughly but just to make sure I understand: Can a Dlink restart be caused by ANYTHING other than loss of voltage or low voltage at the DC input to the Dlink?


All times are GMT -5. The time now is 17:53.

Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi