Hello Everybody, My Team hooked up a control system today on the kit base with the new plastic Lunacy wheels, and we noticed that if you drive the wheels on carpet and let them spin in place, the robot becomes a van de graff generator. If you touch it it will shock you! Several people tried to move the robot only to be shocked. I wonder if that will be an issue on the competition floor, or from the carpet on the field?
The amount of potential energy (static electricity) stored in your robot’s chassis will vary, but I do not believe that during a match of Lunacy you will generate any sort of harmful charges in your robot… this does mean that Dave was right when he said mounting your cRIO on your chassis is bad. So in other words…
Listen to Dave, don’t mount the cRIO without proper insulation
This may pose a problem, if the polymer in the floor and wheels do, in fact, cause a build up of static electricity. I can see robots and, especially, trailers falling to that problem a lot from sliding.
I have seen the comment about not mounting the cRIO or Camera directly to the chasis, or make sure it is isolated, and other such comments.
Could someone give a brief explanation about how to isolate these devices?
Does isolation mean to have some sort of insulating material between the device and the chasis suffice? For example, mount the cRIO on plexiglass, or rubber, or wood rather than directly to the chasis.
Simply mounting the components to a plastic or wood board is sufficient (as long as the fasteners don’t also contact your robot’s chassis). The goal is to keep any single wiring fault from allowing current transfer through non-wiring metal within your robot.
If your chassis is isolated and then 1 wiring fault occurs, there won’t be any problems. For example, let’s start with a camera chassis that is mistakenly connected to the robot chassis. If a 12V line then contacts the chassis with a grounded camera chassis, let the fun (aka welding) begin…
When driving last years robot with KOP wheels on the waxed hall way floor the static build up was tremendous. The discharge into a finger was very painful. We may make the worse behaved team member be the robot retriever.
When driving the robot around at school, especially on carpet, you may want to hang a short length of chain from the chassis to drag on the floor. Don’t use #35 roller chain, use something like you would use on a swingset
I don’t know if this will be allowed at the competitions, but hope that it will be.
This will help prevent the chassis from building up a charge as the wheels spin on the carpet.
The use of drag chains is standard practice in industry on carts used to move static sensitive items, since the rubber wheels on a metal cart will do the same thing when it is being moved around.
That reminds me of the rule a few years ago where the robot had to be touching the field in a loading zone to pick up a game piece and everyone put wire ties on the center of the frame that touched the point of the triangular area.
Yeah, tonight we put a little pigtail wire on our robot because we ran out of people to “help” us move the robot that didn’t know it would shock them (I know, I’m evil). Once we did that, you could barely hear a slight tick when you touch the frame, and you can’t feel anything. A grounding brush eliminates most of the static electricity, but since there still is some, it’s a potential worry. Static like this sits around a few thousand volts, and although it’s very low current, it’s enough to take out a single microchip. On our robot, everything is insulated from the frame except for the motors, which feed through the TB’s. If you insulate the TB’s, all of your electronics should be fine. However, I think the Jaguars’ capacitors will take up the static if you happen to have something touching the frame. Just make sure more than ever that this year, YOUR FRAME IS NOT AT GROUND POTENTIAL. Last year, we had several wiring problems, and our frame was grounded, so every time someone got a little careless with a PWM cable and the +5 touched the frame, you got a pretty little fireworks show. This year, those pops could happen even without a short because of this static.
If they do not allow us to use grounding brushes (or even if they do, to lessen movement resistance), you might consider putting grounding brushes on the wheels themselves. It’s the dielectrics that store charge (like the wheels and the floor), and the metal frame only conducts it. If you conduct it back into a closed circuit, it should eliminate the static electricity. I will test this tomorrow and report back its effectiveness. For right now, act as if this static electricity WILL damage your electronics and take the appropriate precautions. Just remember, nylon spacers are your friend!