Hi everyone, fond this site while googling things for a project and though I could get some help here. Here's a little bit of background stuff: I did the whole iraq thing instead of college, so now that i'm back in the swing of things school wise I've found I can't remember simple things from high school tinkering(both electronics and robotics classes). I'm in an introductory engineering class and our first design competition is a cable car drag racer jousting thing of sorts. Say that 5 times fast. There are 4 cables (2 for us 2 for the other guys) maybe 40ft long, with a ring in the middle. Whoever gets the ring wins. Weight limit is 600grams(1.32lbs), so that means I need to harvest 20ft of raw cable traveling power from something the size of my boot. Drive can be spring/rubber bands/whatever but electronics are limited to common AA's in no more than 6V setups. I'm leaning towards electric drive for the sustained power over the distance it's got to go, but we're not allowed to do any controlling other than releasing the thing. I'd rather not just have someone catch it at the other end or let it slam into the cable anchors
Is there a simple circuit I could build that just cuts power after x amounts of seconds? Maybe with a potentiometer to adjust it to the performance of the machine. That'd give me a coasting chance before blowing the gearhead motor apart when someone catches the thing on the other end. Once again, I'm restricted to 6V of AA's, so within the weight limit at most I'll have 10 AA's, 2 sets of 5 in series linked in parallel.
It's either this or a small egg timer/clockwork motor that physically trips a kill switch:P
Thanks for any help and suggestions.