COMM lost way to many times

[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.

[G_rupp]

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.

[protoserge]

Originally Posted by G_rupp

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.

Were they shocked previously?

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

[G_rupp]

Originally Posted by protoserge

Were they shocked previously?

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

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

[JDNovak]

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.

[Zagar]

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?

[Bruceb]

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?

[olapmonkey]

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?

[billbo911]

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.

[Road Rash]

Originally Posted by JDNovak

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.

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.

[waialua359]

Originally Posted by JDNovak

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.

Mr. Novak,
thank you for your expert opinion.
I think we definitely need to look into this.
We lost COM way too many times at only our Hawaii regional.
It never happened after a hard bump or hard defense where we would suspect cables being loose. We are quite certain it is not our connections.
Hawaii has VERY high humidity.
The thing that caught my attention is getting shocked by static electricity when touching the robot this past weekend.

[philso]

Originally Posted by waialua359

Hawaii has VERY high humidity.
The thing that caught my attention is getting shocked by static electricity when touching the robot this past weekend.

High humidity and static electricity are usually mutually exclusive. One method used in industry to control static electricity is to humidify the air. I have not had static problems at work since moving from Eastern Canada to Houston but then our equipment does not have so many rotating parts. It is possible that the pneumatic tires used by many teams this year may generate much more static charge than other types of wheels used more commonly in previous years.

Try wiping some fabric softener sheets all over the tires. They leave a mildly conductive film that will help dissipate the static charge that accumulates on the tires. You would want to wipe all the way to the shafts or metal hubs that are in contact with the shafts. Hopefully, this will dissipate and equalize the charge over the whole robot so there cannot be an electro-static discharge from one part of the robot to another. It may be necessary to re-apply the fabric softener periodically since it may rub off. Alternatively, there are industrial anti-static coatings and sprays such as Staticide, but they are probably harder to get than the fabric softener. I also just found these instructions on how to make your own anti-static spray.

Perhaps CTRE can add some clamping devices such as TVS' across the inputs and outputs of the PDP and VRM. They would add only a dollar, or less, to the part costs though they would need some board space. The wiring in our robots is short enough that a TVS in the PDP would probably limit the voltages in the whole circuit running to the radio quite effectively.

[waialua359]

Originally Posted by philso

High humidity and static electricity are usually mutually exclusive. One method used in industry to control static electricity is to humidify the air. I have not had static problems at work since moving from Eastern Canada to Houston but then our equipment does not have so many rotating parts. It is possible that the pneumatic tires used by many teams this year may generate much more static charge than other types of wheels used more commonly in previous years.

Try wiping some fabric softener sheets all over the tires. They leave a mildly conductive film that will help dissipate the static charge that accumulates on the tires. You would want to wipe all the way to the shafts or metal hubs that are in contact with the shafts. Hopefully, this will dissipate and equalize the charge over the whole robot so there cannot be an electro-static discharge from one part of the robot to another. It may be necessary to re-apply the fabric softener periodically since it may rub off. Alternatively, there are industrial anti-static coatings and sprays such as Staticide, but they are probably harder to get than the fabric softener. I also just found these instructions on how to make your own anti-static spray.

Perhaps CTRE can add some clamping devices such as TVS' across the inputs and outputs of the PDP and VRM. They would add only a dollar, or less, to the part costs though they would need some board space. The wiring in our robots is short enough that a TVS in the PDP would probably limit the voltages in the whole circuit running to the radio quite effectively.

Thanks for the insight and links. We will definitely look into this for Championships.

[spacepenguine]

This is a great discussion on static electricity. Supposedly the robot frame is isolated from the electronics, but that doesn't mean it can't cause problems.

I only saw a small mention of VRM wiring, but suspect some teams may be hurting themselves by pairing up the radio and LEDs/lights on the 12v/2a bus of the VRM. There is a rule and checkbox on the inspection form to prevent this, but I'm not sure it was consistently applied across districts and regionals. We're all volunteers, after all.

From non-FIRST experience I would hot glue or permanently fix in anything with a barrel connector. They like to work their way out with vibration. We've seen this a lot with CMU's RoboBuggy.