Re: COMM lost way to many times
 

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.

Re: COMM lost way to many times
 

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.

Re: COMM lost way to many times
 

The ESD theory is interesting. Our driver asked how he could keep from getting shocked when he was shutting off the robot at the Kansas City Regional.

Re: COMM lost way to many times
 

Were they shocked previously?

I am interested in this ESD theory. It sounds very plausible.

Re: COMM lost way to many times
 

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.

Re: COMM lost way to many times
 

I told him to have the sophomore turn off the robot that way he wouldn't get shocked. He did not say anything about getting shocked at the Colorado Regional. This may have been due to being on the floor with insulation over the ice arena.
We had one reboot during the Colorado Regional. It was in in our last qualification match. The problem was due to a loose battery connection.

I was the one of the CSAs in Colorado. Most of the issues with radios and roboRIOs were due to loose connections or components.

One robot had too much strain relief on the Ethernet cable and when the robot frame twisted, it pulled the RJ-45 all the way to one side and disconnected.

One robot had a battery cable move and unplug the Ethernet cable on the radio when going over a defense

Re: COMM lost way to many times
 

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.

Re: COMM lost way to many times
 

I guess I need to complete my theory on how static might create radio problems. The static voltage buildup doesn't cause the problem, it is the sudden discharge of that voltage (ESD) as Greg stated that can create problems.

Years before RFID was mainstream technology I bought and installed a series of antennas to read tags tied to material conveying hoses. They were used to identify where the hoses were plugged. Almost immediately I had lockups and failures. I finally determined that static discharges were being received by the antennas and were actually damaging the receivers. They wouldn't fail immediately but damage the inputs progressively. I was able to tell the damage by measuring input resistance and predict the failures. The problem was totally eliminated by creating paths for the charges to dissipate farther away from the antennas.

We are dealing with a router with antennas here also. The higher the gain the more possibility that the input can be overdriven by large magnetic pulses. The technology has advanced drastically over recent years but theoretically the radio would be the most vulnerable device unless the discharge were to the actual control system. Since it is supposed to be isolated from the frame that is less likely.

This is all just speculation and not based on anything tested with this equipment. Consumer electronic devices are tested for these kinds of events but at some reasonable level. I have seen many fail with the levels of discharge easily produced in plastics handling. The trick is to reduce the potential to an acceptable level.

We need to watch for signs of affects caused by discharges.

Re: COMM lost way to many times
 

Ah, yes.... like the old lightning straps we used to have on our cars.... We need to find those old rubber straps. lol

What's next? Rockers? :yikes:

Re: COMM lost way to many times
 

wish I had another regional to go to to test this theory.
I can see where these beach tires may have uses in other games and I sure dont want these issues again.
We are running a belt drive on AM plastic belt sprockets. Is that what is creating the charge? And the polyurethane wheels are insulating it so it can build up?
What would the best way to prevent the discharge be?

Re: COMM lost way to many times
 

Maybe one of these...

Gates 90330 Static Strap https://www.amazon.com/dp/B000CRBR8U..._iJy.wb6T3YNQP

And maybe have drive team next year wear tin foil hats?

Re: COMM lost way to many times
 

Static was not an issue for us this year. Both events we attended had relatively high (for our area) humidity.
In the past we would attach a short piece of chain to the frame and let it drag on the carpet. Only a couple links on the floor were enough.
You should see the looks we would get from inspectors and judges. But, once we explained the logic, they never questioned our approach.
This year we felt that dragging chain was a much higher risk than static build up might cause.
After being FTAA at two separate events, one thing I can say with 100% certainty. The field this year will find and expose any fault your robot has.

Re: COMM lost way to many times
 

I'm not an electrical engineer but I have hands on experience with switching material lines in the dry air of a Wisconsin winter at the sheet extrusion plant I'm employed at. I have felt those static discharges and I can see where it could affect sensitive electronic equipment.

Our forklifts all have short chains making a connection to the ground. Some of our product is corona treated to improve ink adhesion for our customers in the graphics arts industry. Naturally, this makes our finished product contain a charge in spite of our efforts to reduce this with static bar systems further downstream. The chains are there so our forklift operators aren't the ones completing the circuit when exiting the vehicle after lifting the finished product off the end of the sheet stacker.

This is a great thread with a lot of good information to absorb. Our team is weak on electrical and I'm just trying to help them out any way I can.

EDIT: Those of you looking to reduce ESD using a small chain dragging on the ground may want to look into using Static String instead. We also utilize this string to reduce static buildup on our extrusion lines. Copper tinsel works as well and both items should have fewer issues with snagging on obstacles than a chain would.

Re: COMM lost way to many times
 

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.

Re: COMM lost way to many times
 

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.