COMM lost way to many times

[Al Skierkiewicz]

Bruce,
I know that this doesn't help you at this point but there doesn't seem to be any strain relief on the power plug for the radio. The barrel connector depends on the "spring force" of the outside contact to hold everything in place. I highly recommend using an adhesive backed wire tie point on the top of the radio. Loop the power wire up to the tie point and then secure with a a small wire tie. This small step keeps the connector from bouncing around and prevents pullout. Tape over the connector to the radio body also works. The antennas for this radio are on the sides of the radio, inside the vents. It doesn't help to have the stainless pneumatic tanks on that side of the radio but shouldn't be a big problem.
There is also the possibility that severe vibration has caused the power plug to pull out of the circuit board. This is easily repaired if the circuit board has not been damaged. The connector is a part of the circuit board that a good hit on the connector could cause a crack in the board. This has the same effect as broken wires. It may work most of the time, but vibration will make it lose the power.
Tinning wires is not recommended for Weidmuller terminals. They depend on the deformation of the strands to give maximum surface area for current to flow. With tinned wire, only the extreme outside surface of the wire touches the contact producing a connection equivalent to a #36 or smaller wire.

[AllenGregoryIV]

One of the other things that hasn't been metioned is the use of ferrules with the weildmuller connectors. We used them on nearly all of our competition robot connections and have had zero issues.

Here is the white paper from Weildmuller recommending their use with stranded wires.

We import ours from China using Aliexpress but you can also get them from US electronics vendors, ebay, or Amazon.

Make sure you are using the right crimp tool and gauge ferrules. Also get 8mm long ones.

[AllenGregoryIV]

This thread inspired me to write up this document. Anyone have any more suggestions to include.

https://docs.google.com/document/d/1...XrCy1gzk/edit#

[Monochron]

Originally Posted by AllenGregoryIV

One of the other things that hasn't been metioned is the use of ferrules with the weildmuller connectors. We used them on nearly all of our competition robot connections and have had zero issues.
...
Make sure you are using the right crimp tool and gauge ferrules. Also get 8mm long ones.

We used ferrules on almost all of our weidmuller connections and found that the crimps eventually work their way out after heavy competition. We are using the correct tool (ratcheting style) and gauge for our wires but getting consistent crimps never seemed possible. We are considering moving to mostly solidcore wire to avoid troubles in the future.

If you have gotten consistent crimps that hold up to this year's game, do you think that our crimping tool might be bad? I'm not sure where the failure is, but right now we aren't able to rely on ferrules.

[AllenGregoryIV]

Originally Posted by Monochron

We used ferrules on almost all of our weidmuller connections and found that the crimps eventually work their way out after heavy competition. We are using the correct tool (ratcheting style) and gauge for our wires but getting consistent crimps never seemed possible. We are considering moving to mostly solidcore wire to avoid troubles in the future.

If you have gotten consistent crimps that hold up to this year's game, do you think that our crimping tool might be bad? I'm not sure where the failure is, but right now we aren't able to rely on ferrules.

We are currently using 20 AWG ferrules for everything (we haven't purchased a full set yet). We had to adjust the tension on our crimper to get a tight hold and we crimp the insulation in addition to the terminal. We tug test every wire and didn't have any failures at Bayou. We are using generic cheap crimps and a crimper from china.

[Monochron]

Originally Posted by AllenGregoryIV

We are currently using 20 AWG ferrules for everything (we haven't purchased a full set yet). We had to adjust the tension on our crimper to get a tight hold and we crimp the insulation in addition to the terminal. We tug test every wire and didn't have any failures at Bayou. We are using generic cheap crimps and a crimper from china.

Hhm, adjusting the tension and crimping the insulation as well could make a difference for us. Thanks for the tips, I'll look into it.

[Al Skierkiewicz]

Originally Posted by Monochron

We are considering moving to mostly solidcore wire to avoid troubles in the future.

Please don't do this. Solid wire is not for use on moving objects. It has a real tendency to fatigue and break just when you need it the most. (Al's Murphy's law corollary...If it can go wrong, it will on Einstein.) Most of the contacts on the components are designed for stranded wire so that the wire can conform to the internal shape of the contact. The ferrules are specifically designed to be used with a certain product so be sure to buy the type for your application. The ferrules for use with the PDP are not round.
Be careful what you use for static discharge, any damage to the field (carpet or other) will irk the field supervisor who will then tell the Head Ref. More importantly for those who suspect static issues is to look where your wiring is running through the robot. If it is near the wheels, or other moving parts, what static might build up will rapidly jump to that wiring. While most of the components are designed to survive that discharge, that doesn't mean they will continue to function during the match. It is entirely possible that a power reboot is the only way to correct the condition. Power wiring that receives the static discharge will pass that along to other wiring that might run in parallel. Most wiring teams use only has a 300 volt rating for the insulation.

[Road Rash]

Originally Posted by Al Skierkiewicz

Be careful what you use for static discharge, any damage to the field (carpet or other) will irk the field supervisor who will then tell the Head Ref.

Good advice. The tinsel breaks easily leaving pieces of copper behind and is the reason we don't use it anymore where I work. I envision snagging issues with chains. Static string is the best bet. It's expensive, but it's lightweight, very durable and works as intended in the environment we use it in. However, even with the cost, a 72' roll of it will last for years considering you only need to use a few inches at a time. It's basically some stranded copper wire with a durable conductive sheathing.

I also agree, it's best to engineer the static issues out of the build altogether. If you cannot do this, then use the string.

[sgeckler]

Originally Posted by Al Skierkiewicz

The ferrules for use with the PDP are not round.

Al, I don't see any mention of ferrules in the 2016 control system wiring documentation I can find. Not the basic and not in the PDP user guide from CTR. Is there something more specific for the PDP that describes the "proper" shape of ferrules you could use? I assume all Wiedmuller would take round? - Sam

Ferrules not mentioned here:
http://www.ctr-electronics.com/PDP%2...7s%20Guide.pdf

Or here:
https://wpilib.screenstepslive.com/s...control-system

[Alan Anderson]

Originally Posted by sgeckler

Al, I don't see any mention of ferrules in the 2016 control system wiring documentation I can find. Not the basic and not in the PDP user guide from CTR. Is there something more specific for the PDP that describes the "proper" shape of ferrules you could use? I assume all Wiedmuller would take round? - Sam

Ferrules are not recommended. It's expected that teams will use the Wago connectors as designed, with stranded wire.

Ferrules are not actually discouraged, but you should do your research to see what Wago and Weidmuller have to say about them. The "proper shape" of a ferrule almost always includes flat sides. You must use an appropriate ferrule crimper to make them. Square shapes are probably going to work best for the connectors we use, because they provide a large connection surface and you won't have to worry about accidentally getting them in the wrong orientation.

[Greg McKaskle]

As a CSA, the most common category of comms failures are power related. It stinks for a robot to lose power or reboot in a match, but if I'm able to show them the cause of the failure and discuss solutions, I consider that a good outcome. My favorite is when I narrow it down and the students actually find the issue and identify a solution. Many of these are simply loose nuts on the battery or breaker, -- sometimes the PDP. Sometimes it is a bad crimp on the same connections. Loose fuses on the PDP are another source of failure.

I have less familiarity with it, but I have occasionally recommended replacing the circuit breaker/switch because it seemed like the softest touch would cause a loss of power.

I have not seen that many issues with radio power, but I'm certainly not a fan of the barrel connectors and generally encourage some form of positive retention, at least a strip of electrical tape stretched front to back across the jack. In previous years, it was quite common to see a bad DLink at an event. Whether this was damaged through mechanical shock or vibration, static discharge, or was bad from the factory wasn't ever clear, but some DLinks simply had high loss that went away with a radio change. I have yet to see that with OpenMesh.

I would really like to see the OP logs. The cursors, messages, and timings give very good evidence of what happened on the robot. When the disconnect happens, several things take place. The DS starts to ping each element in the chain to identify what it can still see, and the roboRIO, if it is still up, will also ping the radio from its side and post-inject messages into the log.

Key things to look for:
If the comms disconnect is only a few seconds long, I generally find that the ethernet cable was not snapped in or wiggling/tugging will cause link lights to go out.

If the roboRIO reboots but the radio is still up, the FTA can easily see this and will often tell the CSA or team. The second tab of the DS also shows the ping status of each device. Also, the results of the pings are printed to the log file as messages. As the robot comes back up you will also see a code start message.

If the radio reboots and not the roboRIO, there will be a green vertical cursor between the orange and yellow ones. Hovering over pretty much anything on the graph displays a descriptor in the lower left. The green cursors are the roboRIO telling the DS when it saw what radio go away and return. This is also in the event messages.

If the radio went out and there is no green cursor and no code start message, both devices lost power.

If the code restarts and the outage is five to ten seconds, it is more likely a code crash and restart rather than a power issue. This also looks different because the radio and roboRIO are still present and the CPU trace will sometimes help indicate the type of crash.

I hope to be able to make the log or even DS make a diagnosis to categorize the issues, but it just hasn't happened yet. As for logging while the robot sits still. Some teams do this, and it is a fine thing to do with your team. I'm pretty comfortable with the diagnostic capabilities of the existing log files and I'm not sure that RIO logs will actually be that much more effective at diagnosing problems.

Several times as CSA, I've intended to keep details about each failure and keep stats of what was found. But it quickly becomes more important to help teams than to keep count. And some teams don't ask for help and you don't find out until second-day afternoon that they have had multiple issues and you were not at the field to observe them.

Greg McKaskle

[philso]

Originally Posted by AllenGregoryIV

One of the other things that hasn't been metioned is the use of ferrules with the weildmuller connectors. We used them on nearly all of our competition robot connections and have had zero issues.

Here is the white paper from Weildmuller recommending their use with stranded wires.

We import ours from China using Aliexpress but you can also get them from US electronics vendors, ebay, or Amazon.

Make sure you are using the right crimp tool and gauge ferrules. Also get 8mm long ones.

We got our ferrules from www.ferrulesdirect.com and our crimper from amazon. We found that installing ferrules on our 16AWG wires (i.e. from the compressor) made them too large to work with the Weidmuller connectors.

The cable that came in our KOP had a right-angle plug on it. Once it was plugged in, wrapping a long cable-tie around the radio and the plug worked well to keep it plugged in very securely. We were able to pass the cable-tie under the radio, between it's "feet", so it could not slip off.

[Bruceb]

Originally Posted by Al Skierkiewicz

Bruce,
I know that this doesn't help you at this point but there doesn't seem to be any strain relief on the power plug for the radio. The barrel connector depends on the "spring force" of the outside contact to hold everything in place. I highly recommend using an adhesive backed wire tie point on the top of the radio. Loop the power wire up to the tie point and then secure with a a small wire tie. This small step keeps the connector from bouncing around and prevents pullout. Tape over the connector to the radio body also works. The antennas for this radio are on the sides of the radio, inside the vents. It doesn't help to have the stainless pneumatic tanks on that side of the radio but shouldn't be a big problem.
There is also the possibility that severe vibration has caused the power plug to pull out of the circuit board. This is easily repaired if the circuit board has not been damaged. The connector is a part of the circuit board that a good hit on the connector could cause a crack in the board. This has the same effect as broken wires. It may work most of the time, but vibration will make it lose the power.
Tinning wires is not recommended for Weidmuller terminals. They depend on the deformation of the strands to give maximum surface area for current to flow. With tinned wire, only the extreme outside surface of the wire touches the contact producing a connection equivalent to a #36 or smaller wire.

Al that was an old pic just to show the location of the radio. At the time of our latest comm losses during elims we had a new tighter barrel jack taped in place AND we were running POE. so we had two power sources.
this bot had been gone over by nearly every orange and yellow hat at both Cleveland and Milwaukee. After replacing the barrel jack and installing POE in Milwaukee we had no issues until the last match of quals then it started all over again. Had Pete Thomas doing everything he could think of during elims but he found nothing.

is it just the 706 curse? 6 time finalist in the last 4 years.

Thanks

[Bruceb]

one other thing
we NEVER lost comms during extreme contact with another robot or flying over defenses. It always happened when just starting to cross the defense and even happened when crossing the low bar once.
I am beginning to think a static discharge may be part of the problem as we noticed a static discharge when crossing defenses on the practice field.

[JDNovak]

Originally Posted by Bruceb

one other thing
we NEVER lost comms during extreme contact with another robot or flying over defenses. It always happened when just starting to cross the defense and even happened when crossing the low bar once.
I am beginning to think a static discharge may be part of the problem as we noticed a static discharge when crossing defenses on the practice field.

I believe you are on to something. Static problems can be so elusive because changes in humidity and surface contact materials are so difficult to track.I can relate one situation where static buildup definitely was the culprit and why it may relate to your problems.

We have used dozens of UsDigital MA3 absolute encoders for steering feedback over years so we know their characteristics pretty well. We have also used aluminum AM Performance wheels that contact the carpet even with tread attached. One off season we decided to replace the performance wheels with AM Plaction wheels for a demonstration robot. Within a couple of hours of run time, we had two encoder failures. The outputs would start to jitter and eventually get too bad to use. After realizing the wheels were Polycarbonate and probably isolating the chassis to allow static buildup, I attached a chain to drag the ground and never had another problem.

Many people are running pneumatic wheels this year without problems but most tires have additives that are conductive. Looking at the beach tires, they don't appear to have additives that other tires have. Is it possible that they are insulating enough to allow a charge to build on your robot? We have also had more static problems when running belts. They tend to create static like a Van De Graaff generator.

I'm not sure if a chain is the best idea this year with the defenses but something to reduce the potential between the carpet and the frame might avoid the big discharge when you touch the metal defense. If you can find a static gun some of this can be more scientifically proven.

For those that might say that the control system is immune to static, after working with plastic extrusion for 30+ years I have seen enough electronic equipment affected and destroyed from static buildup to believe that nothing is immune. Some designs are more tolerant but at some point a large enough discharge will cause damage. Also, many devices will continue to operate after being zapped but are degraded and prone to erratic performance and failure until replaced.