Power, Motors, and Control Geeks
No costume is complete without an electric motor and the subsequent risk of fire, electrocution, noxious smoke, and/or embarrassing failure.
In my Snow Globe costume from last year I discovered the importance of power and power management. I didn’t fully test my costume and ran out of batteries about half way through the contest. Fortunately the judges were sufficiently impressed that I still won, but had they died mid performance the results would have been much less lucrative.
I’m taking a couple lessons away from last year. The first is that D batteries, even 12 of them, do not provide enough power to drive a few DC blowers for more than about half an hour. Second, a switch isn’t a convenient or efficient way to throttle a blower motor.
This year will see me bouncing up on stage with a couple 12V cordless drill batteries in a backpack and a PWM motor controller mounted on the shoulder strap. My goal is at least an hour at full power and two or more hours at reduced power. Two fully charged drill batteries should provide enough amp hours.
Since I haven’t tried much in the way of etching circuits I opted for the easy way out and purchased a ready to solder kit from Carl’s Electronics. I was very pleased with the price, quality, and delivery speed. Not that speed mattered when I left the bag on my desk for a month.
Assembly was very simple, and required just a little head scratching when attempting to discern the color bands on the resistors. I don’t know if it’s old age, or pad paint, but in either case it sucks. I finally gave up trying to discern red and orange from violet and just grabbed the ohm meter.
I’ve tested it with some gator clips and my 12V leaf blower (8 amps) and my newly acquired (just for this costume) 12V bilge vent fan (4 amps). While the everything held together at 8 amps, the heat sink got a warm enough that I’d put a fan on it if I were going to run for more than a few minutes. At 4 amps it was just warm to the touch. In the next motor controller article , I will post better pictures, some ideas on connecting the batteries and motor, and generally wrap up the installation so it won’t be so unsafe as to cause fires or noxious smoke.
