Quote:
Originally Posted by Scott_4140
You're correct that you can no longer drag a wire. FIRST determined that the benefit was minimal. Not sure why they banned it.
The next best suggestion is to use the USB Surge Protector listed on page 17 of the FTC Robot Wiring Guide. If you haven't looked at this guide, it's available on the Team Resources page.
http://www.usfirst.org/roboticsprogr...team-resources |
I can offer some explanations here. Dragging a wire was found to offer minimal benefit, but it caused problems when a team without a grounding wire touched a metal surface on an ungrounded robot, as this created a sudden, large static discharge event which often locked up one or both robots involved. Consequently, banning or requiring such a strap are the main potential solutions, and given the lack of observed benefit, the GDC went with banning it.
The USB surge protector is not the next best solution-it is the best solution. I am not aware of any teams using the devices at the events I have FTA'd at locking up. A ferrite bead is the next best (and cheaper) solution, and seems to greatly reduce the incidence of lockups. The cause of lockups appears to be ESD discharge entering the NXT through the USB cable, which a surge protector prevents. (Ideally the NXT itself would have better ESD protection on its USB cable, but we are using the NXT in a way it was never really originally designed to be used-a mostly plastic, slow moving, TECHNIC-based robot will generate much less ESD, and normally will not be run with the USB cable plugged in while running. I believe that the sensor and motor ports have better ESD protection, probably because they were inteded to be used while the robot is driving.)
By the way, talk to your state FTA's/affiliate partners and ask if they are using any sort of anti-static spray-it is currently recommended but not required by FIRST, but it definitely seems to help. Anti-static spray on your robot may help, but a USB surge protector is more helpful.
If you have any questions/concerns, ask!