Static on the HDPE

[DanL]

Originally posted by D.J. Fluck
THIS IS A VERY SERIOUS ISSUE!!!!!

almost everytime I picked up the bot off of the HDPE at SLR, I got a nice discharge into my body. Several times over the weekend, we believe we were zapped and killed because of static.

We were actually talking about your team's design today. We figured that a tread system made of Linotex (or some other bright red non-slip material) pretty much is a Vandergraf generator - as the tread moves along the surface, it picks up electrons that are dropped off into the frame as the tread moves back across the top.

Anyways, it sounds like some teams have more problems with this than others, so my advice to everyone is to put your freshmen in charge of collecting the bot after a match ;-)

[Lloyd Burns]

If you have a problem, try this: attatch some sharp nails to the frame of your robot, sticking into the air (but not inside the bot), or hang a conductive fringe (metallized foil decoration) from it. This will allow the charge to dissipate without building up a large charge, which lowers the voltage = length of arc. Remember, for a robot of fixed capacitance, V varies as Q (Q=CV)

Don't have the points hanging down toward the HDPE, though, like the combs on a Wimshurst machine. That would only aid in transferring charge.

If they remain insulated, your crew can approach with a math protractor pointed at the robot (as they close from min 4 feet). Once they touch the point to the 'bot, they can pick the 'bot up, and point the protractor at the end-of-field diamond plate (as the approach and touch it.

This suggestion won't help the on-board electronics, but the points on the 'bot might.

I've played with Van de Graafs and Wimshursts; they can be a real pain. Maybe the venues are way too dry at this time of year.
Are your shoes synthetic-rubber-soled ?

=-=-=-=-=-=-

BTW, There is little difference in specie between ESD and lightning, only in magnitude of charge (them's cool ohms !) and voltage. The lightning storm just "builds" charge continuously, whereas our puny efforts with fur and bakelite have limits. If we had capacitors as big as the Earth / Cloud / Air dielectric thing, and enough time !

And, in another vein, many of the accidents with electricity aren't because the heart has stopped, but because the sudden jolt gets a reaction - somebody jerks, or drops sometihing, or loses his grip. This would apply to many static shocks !

[Al Skierkiewicz]

It matters not as to what type of drive systems is in use and humidity seems to have little to do with the problem. (It reached into the seventies for outside temperature on Saturday in St. Louis and the venue was on the Missouri River so I am sure that the humidity was much higher than here in Chicago) Several robots at SLR went dead at certain intervals, many when approaching the top of the ramp or when rubbing against the walls of the ramp. Although it was not possible to interview all of the teams, we did observe both partial and full control losses during the competition for many robots.
We are still looking for input from teams that competed over the weekend. Did you experience any control loss when traversing from ramp or HDPE to the opposite material? Please give specifics such as description of loss, (full control and/or loss of colored light, radio modem, error lights, etc.) and did another robot contact yours at the point of loss of control?
Thanks for your input.

[Manoel]

Originally posted by Lloyd Burns
If you have a problem, try this: attatch some sharp nails to the frame of your robot, sticking into the air (but not inside the bot), or hang a conductive fringe (metallized foil decoration) from it. This will allow the charge to dissipate without building up a large charge, which lowers the voltage = length of arc. Remember, for a robot of fixed capacitance, V varies as Q (Q=CV)

Wouldn't that violate that rule about no sharp edges on the robot?
I'm also guessing that adding a chain to the robot to discharge itself on the mesh (like trucks transporting flammable compounds) would violate the "no metal on carpet" rule.
I'm getting concerned about this, because we have a similar setup to the TechnoKats, with rubber treads...

[Madison]

Originally posted by Manoel
Wouldn't that violate that rule about no sharp edges on the robot?
I'm also guessing that adding a chain to the robot to discharge itself on the mesh (like trucks transporting flammable compounds) would violate the "no metal on carpet" rule.
I'm getting concerned about this, because we have a similar setup to the TechnoKats, with rubber treads...

The chain, however, wouldn't be a 'traction device' and ought to be legal.

Right now, though, my biggest fear is that the inspectors (made up of students and other volunteers) won't be clear on the rules and give teams an undue hard time. I know that, just from reading these boards, many, many teams simply don't know the rules.

This concerns me as well, as I'm fairly certain we're using the same materials as 45 on our wheels, though in smaller quantity.

[Manoel]

Originally posted by M. Krass
The chain, however, wouldn't be a 'traction device' and ought to be legal.

Ok, that solution is back to the top of the list.
What about these, any chance it would work?
- Wrapping the robot controller in those plastic bags that computer hardware come in... They're supposed to protect them from ESD
- Build a Faraday cage around the RC

[EDIT]: Actually, just realized that those plastic bags are Faraday cages, in a way. [/EDIT]

The crazy ideas are up, now for the engineers to say if they're worth anything.

[Lloyd Burns]

Sharp edges on a piece of metallized mylar ?

To answer Al's question, we made a ramp, and had generic "carpet" on the floor, in an unheated school cafeteria (60 degF +, Outside Air Temp at single digits degF). We too have 'rubber' tread, but on wooden wheels, and have NOT encountered the 'static cling' that is troubling others. We have had a few hours of practice on this ramp.

Could conductive wheels clad in a thin insulator be charging better than our non-conductive aluminum-painted wheels ? The capacitance to the hdpe might be higher, and the resistance between the frame and just inside the rubber might affect it.

Maybe the wire ramp is being charged by induction, leading to higher robot charge on top of the hill. A dragged chain might change this situation, but it could also tangle on the mesh fasteners, or even on the welds in the mesh. Perhaps some limp wire...

[Al Skierkiewicz]

To add some more data...
We can carry our prototype to the top of the ramp and leave it there. Run it a few minutes on top and it will arc as soon as any part of it gets over the ramp. We have tried anchors, (pieces of RF gasketing made of woven wire and they did not help. As to the faraday cage, we suspect that the problem is not the controller itself but the wiring connected to the controller picking up the induced pulse that is causing the problem. Of course we are having problems with our custom circuit board as well. "Still needing more data...must have data!"

[petek]

So, now that we've got some regionals under our belts, were static electric charges a problem on the ramps? Any spontaneous robot controller brain fades? Or can we put this one to bed?

[Dave Flowerday]

Originally posted by petek
Or can we put this one to bed?

Did you read any of the above posts? There are literally dozens of unexplained robot resets and loss of signal conditions being reported from this weekend's competitions. We at team 111 believe at least some of these are probably due to static discharge. When we originally asked FIRST about this they basically brushed us off. Perhaps now that more teams are seeing similar problems they will reconsider.

By the way, there are products out there that could be used to treat the HDPE to lessen the static buildup. It's called staticide and it could be used to clean the HDPE periodically. So (in my mind) there is something that could be done about this by FIRST.

[Austin]

In its static-charging characteristics, how does natural rubber compare to synthetic rubber?

[Manoel]

Originally posted by Lloyd Burns
Could conductive wheels clad in a thin insulator be charging better than our non-conductive aluminum-painted wheels ? The capacitance to the hdpe might be higher, and the resistance between the frame and just inside the rubber might affect it.

Well, at least on the pictures on the site, the TechnoKats robot have nylon (or some material like that) pulleys. So I'm guessing that even if metal does make a difference, the event is not exclusive to it.

[Austin]

Originally posted by Manoel
Well, at least on the pictures on the site, the TechnoKats robot have nylon (or some material like that) pulleys. So I'm guessing that even if metal does make a difference, the event is not exclusive to it.

we use delrin pullies, w/ natural rubber treads w/ a polyurethane backing

[ChrisA]

It does not make a great difference as to what is touching the rubber. Whether that is conductive or not makes no difference. When the rubber of the wheel rubs against the HDPE the HDPE is given a charge. When a material that is at a different potential than that of the HDPE the electrons will naturally want to jump from one to the other to even it out which causes an arc. This is the static that is being seen and felt from the HDPE.

I would have thought everyone would have figured this out by now, but I guess that this is not the case.

[R Bohannan]

We had problems at the Granite State Regional, as did several other teams. During our first practice rounds, we were losing our drive system. We added a dangling wire (12 ga) to the bot and didn't see anymore problems on Thursday.

On Friday, we started having problems again. In fact, we were re-inspected because at the end of a match, when our drive system was dead, our light DIDN'T go off! It was then that we found out that our "dangling wire" had been pulled off.

After installing about a 1/2 dozen new dangling wires, we still had one more occurrence - during our elimination round arggh.

BTW, the inspectors told us that we should hang the wires off of the robot. It will be interesting to see if that is consistent at all the regionals.