possible solution to the static problem

[Doctorwho]

As seen in last weekend's regional competitions the electro-static discharge caused by the rover wheels and the floor can fry speed controllers, driver stations, and even knock the field systems out of whack.

It could be possible that anti-static spray could be used on your drive wheels and control board to prevent any catastrophic discharge. Plus the spray is pretty cheap and can be picked up at almost any office supply store for around $3-4, you can also buy industrial-strength spray from McMaster-Carr for $11.57 for a 11.5oz can (part # 6038T11)

Any thoughts?

[EricH]

Thought #1: If that spray affects traction, don't even think about it.
Thought #2: Might be worth it for a team with a practice robot and field to try it out.
Thought #3: Why not just put a wire hanging from your frame almost to the ground? You've got plenty of wire, I'm assuming. Can't be that hard to attach it to the frame...

[Tom Bottiglieri]

Originally Posted by EricH

Thought #3: Why not just put a wire hanging from your frame almost to the ground? You've got plenty of wire, I'm assuming. Can't be that hard to attach it to the frame...

The FRP is non conducting, so there is no path from the robot to the ground while it is driving around. If you are driving full speed into a wall or airlock, there may not be enough contact with the carpet to discharge the build up into the ground before it contacts the field frame.

[EricH]

Originally Posted by Tom Bottiglieri

The FRP is non conducting, so there is no path from the robot to the ground while it is driving around. If you are driving full speed into a wall or airlock, there may not be enough contact with the carpet to discharge the build up into the ground before it contacts the field frame.

Ah. That complicates matters.

How about grounding the airlocks? Teams can't do that, but if FIRST figures out how to do it, then the issue won't exist anymore. At least, not as much.

[GaryVoshol]

Originally Posted by Tom Bottiglieri

The FRP is non conducting, so there is no path from the robot to the ground while it is driving around. If you are driving full speed into a wall or airlock, there may not be enough contact with the carpet to discharge the build up into the ground before it contacts the field frame.

My thoughts as well. People were not reporting getting shocks when the robots were touched at the ends of the rounds. So any electrostatic charge that had built up was still there until grounded. The people on the FRP weren't grounded either.

[Steve Compton]

Hey folks,

Not sure if all your static issues are wheels and airlocks; our (1391) experience at Jersey was something else altogether. Almost all of us are spinning some sort of insulator (rubber, plastic, urethane, etc.) around - quite often - another insulator (PVC or ABS rollers) and when they aren't enough alike .... whoops. We have created VanderGraf generators that send spike charges from the rollers into someplace or another that finds its way to where we don't want it to be.

During practice rounds, we watched our robot run for 25 seconds, then stop as the CRIO rebooted, then run another 10 seconds, reboot, etc. This was early on and no one else had run into this, so we began from ground (no pun intended) up back in the pits. Curiously, static wasn't considered early - we looked at current draws, 24V supply, voltage differentials, code, etc - anything that we thought might stop he processor cold. Eventually, at 7:45 in the evening, I disconnected everything, including motors, ancillary code, and hand manipulated our belt collector - bam! same behavior as all day. We could shut off the CRIO with me as the motive force.

By next morning we had: 1. rubberized our PVC rollers with DipIt spray paint (to make the roller more similar to our belt); 2. put a 3/8" aluminum rod across the frame that touched the roller (to dissipate charge rather than having it build up and spike), and 3. begun to spray our belt prior to each round with Static-Guard (yep, the grocery store solution.)

No more problems. Ends up the static spikes were traveling through PWM cable connections - can't expect any processor to handle that, other than to reboot. We built the static generator, after all. All the ideas mentioned previously won't deal with the delivery of an internal spike to the processor, so think through your observations carefully. I really don;t think frame charge is the issue - you did insulate your processor board after all, right? The processor was just doing what it was designed to do to avoid damage. The clue we finally had that it was PWM was that even when the camera was turned off, and we had disconnected the wires to the Victors (but not the PWMs), the camera's servos were 'twitching' the camera for a couple spikes before the CRIO cut out.

Hope this helps.

[Daniel_LaFleur]

Originally Posted by Steve Compton

Hey folks,

Not sure if all your static issues are wheels and airlocks; our (1391) experience at Jersey was something else altogether. Almost all of us are spinning some sort of insulator (rubber, plastic, urethane, etc.) around - quite often - another insulator (PVC or ABS rollers) and when they aren't enough alike .... whoops. We have created VanderGraf generators that send spike charges from the rollers into someplace or another that finds its way to where we don't want it to be.

During practice rounds, we watched our robot run for 25 seconds, then stop as the CRIO rebooted, then run another 10 seconds, reboot, etc. This was early on and no one else had run into this, so we began from ground (no pun intended) up back in the pits. Curiously, static wasn't considered early - we looked at current draws, 24V supply, voltage differentials, code, etc - anything that we thought might stop he processor cold. Eventually, at 7:45 in the evening, I disconnected everything, including motors, ancillary code, and hand manipulated our belt collector - bam! same behavior as all day. We could shut off the CRIO with me as the motive force.

By next morning we had: 1. rubberized our PVC rollers with DipIt spray paint (to make the roller more similar to our belt); 2. put a 3/8" aluminum rod across the frame that touched the roller (to dissipate charge rather than having it build up and spike), and 3. begun to spray our belt prior to each round with Static-Guard (yep, the grocery store solution.)

No more problems. Ends up the static spikes were traveling through PWM cable connections - can't expect any processor to handle that, other than to reboot. We built the static generator, after all. All the ideas mentioned previously won't deal with the delivery of an internal spike to the processor, so think through your observations carefully. I really don;t think frame charge is the issue - you did insulate your processor board after all, right? The processor was just doing what it was designed to do to avoid damage. The clue we finally had that it was PWM was that even when the camera was turned off, and we had disconnected the wires to the Victors (but not the PWMs), the camera's servos were 'twitching' the camera for a couple spikes before the CRIO cut out.

Hope this helps.

Just as an anecdote to this:

While we didn't have any shutdowns or 'no comm' failures during our regional we did have 2 opponents robots shut down while we were in contact with them.

Our robot, with it's propellers, generates a large static charge. Both robots that shut down had just intruded into our ball pickup section (we were in the act of pinning them ... niether robots were near the airlock). Niether team ever figured out why they shut down ... but I suspect static discharge. Our electronics system is completely isolated from our chassis.

[writchie]

Originally Posted by Tom Bottiglieri

The FRP is non conducting, so there is no path from the robot to the ground while it is driving around. If you are driving full speed into a wall or airlock, there may not be enough contact with the carpet to discharge the build up into the ground before it contacts the field frame.

Yes the FRP is non-conducting but the use of a few static discharge wicks in light contact with the FRP floor may equalize the potential between the floor and the robot. This is common practice in aircraft design where static discharge wicks attached to control surfaces and trailing edges help prevent buildup by discharging to the air. It is also good practice to bond any metal parts that may be floating from the main chassis, except of course for the camera and cRIO.

In Florida, we usually have such high humidity that static is rarely a problem. But this year, with the unusual cold, many days here remind me more of the static environment of the Northeast or Canada. Our students have been getting zapped left and right, much to their surprise. We haven't had any resulting electrical problems (yet).

Depending on the exact mechanism involved in the static related resets, it could be that a static drain resistor of 100K - 1Meg between chassis ground and electrical ground might afford some protection. This would at least prevent very high static voltages from building up between the chassis ground and the electrical system without interfering with the safety aspects of the electrical isolation. In fact, it would be pretty easy to have a jumper with a resistor that could be installed (or not) to see if it makes a difference. Testing in a low humidity environment is certainly needed and perhaps this could be done in practice matches next week.

We had ESD problem a few decades ago with a communication device that output to line printers. The issue only cropped up in a few locations in the winter and IIRC we solved it with a drain wire on the paper basket and a couple of discharge wicks in the paper path. Although the technology was older (Z80's), the problems were similar - mysterious unexplained resets.

I think FIRST need a "Tiger Team" on this to get control of the issue by next week. Just my $0.02

[DonRotolo]

Originally Posted by Tom Bottiglieri

The FRP is non conducting, so there is no path from the robot to the ground while it is driving around.

Perhaps, but as writchie notes, a grounding tail will allow static to discharge readily. We used some finely-stranded #10 wire, about 3 inches long, one end into a ring terminal and the other end fanned out into a good imitation of a paintbrush.

This was purely precautionary, as we have not experienced any issues where we might suspect ESD or static.

Originally Posted by Wayne C.

We wear Static Guard like cologne.

Ah, that explains that

Folks should also note that just the spark of an ESD event is not the only chance for damage - the spark creates an electromagnetic field which can cause damaging voltages to be induced into near-by conductors. So it's not enough to control when & where it sparks; you need to control the sparks themselves. Team 25, with their anti-static wrist straps and mats, are on the right track, This isn't rocket science people.

Originally Posted by David Brinza

One of the tricky issues with ESD is that it can cause "latent" damage. A piece of equipment might continue to work after a "zap", but in reality some internal damage may have occurred. The next zap - even a tiny one, can cause a permanent failure.

Such latently damaged items are also called "walking wounded" and are especially problematic - the wound may also cause unintended operations, but it will be so intermittent it becomes difficult to find. And, in a high-reliability application (such as a spacecraft) it is a disaster.

I will ask our coach to ask Q&A to 'approve' a 1 MOhm resistor between components (frame, power, and cRio) for ESD bleed.

Don

[nuggetsyl]

Originally Posted by EricH

Thought #1: If that spray affects traction, don't even think about it.
Thought #2: Might be worth it for a team with a practice robot and field to try it out.
Thought #3: Why not just put a wire hanging from your frame almost to the ground? You've got plenty of wire, I'm assuming. Can't be that hard to attach it to the frame...

Your first though scares me that you are more worried about a team getting traction then a team frying their driver station.

[MrForbes]

Eric might have been thinking about the rules....

[nuggetsyl]

Originally Posted by squirrel

Eric might have been thinking about the rules....

My first thoughts are about the teams. What fun is it going to be if a team blows their driver station or power blocks and cant run.

[EricH]

Originally Posted by nuggetsyl

My first thoughts are about the teams. What fun is it going to be if a team blows their driver station or power blocks and cant run.

What fun is it going to be if the team finds that they can't run because they're in violation of a rule? Remember, violation of the robot rules not only keeps you from competing, but if it happens on the field, it's grounds for a disable and a card.

[Raging Min Pin]

I didn't see anything at the mini-regional I was at, but if this is a problem with the field, FIRST needs to be contacted.

[Vikesrock]

Originally Posted by Raging Min Pin

I didn't see anything at the mini-regional I was at, but if this is a problem with the field, FIRST needs to be contacted.

FIRST is well aware of the problem. Dean and Woodie were both at BAE and there is even a video around here somewhere of Dean spraying parts of the field down with water.