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Originally Posted by Sparks333
Al,
That sounds reasonable. My only point here is that some teams really gear their motors down, so it is sorta kinda maybe possible that by backdriving they are spinning the motors much faster than the wheels. I'm drawing at straws here, aren't I. What I saw was a team pushing their robot in a parking lot, then complaining of a burning smell. On closer examination, the victors wouldn't turn on. Since it was another team's, I couldn't get a close look at the vics, but a couple mentors blamed it on backdriving. I have avoided it ever since.
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On our robot, driving the arm at any decent speed, (its powered by a geared down Van Door Motor) will provide enough juice to turn on the RC, and our LEDs will continue to blink running off the 7.2v battery after the motor stops providing power. I've even seen the fans on the victors spin up from pushing the bot on the floor. Not the big fans though... I think the major source of problems is if there is somewhere for the current generated to go or not. Because if the current cant flow, the voltage generated increases. That is what could possibly cause problems.
If this were the problem, it would be very possible to provide something to sink the current and keep voltage spikes down. A 120mm fan or two would do the job, or maybe some sort of lighting. Just make sure that the load is wired so that it is on when the main breaker is on. Can I say for sure that this is the problem? No. Is it a possibility? yes. Look at the schematic symbol for some FETs and you see a reverse biased diode, with the H-bridge, that would act as a rectifier, and power up the bot.