Power requirements of an unmarked electrical motor?

March 9, 2005 8:12 AM

I picked up a whole box of unmarked motors at a garage sale for three dollars. How can I figure out how much electricity I need to use to power them?

Each motor is slightly higher than the height of a 35mm film canister, and about a centimeter bigger in diameter. They have pretty powerful magnets inside, as they stick together in the box. Only two electrical leads.

It'd be fun to make a little autonomous robot or two, but before I construct my army of minions I need to know what types of batteries they could run on.

posted by the_W to sports, hobbies, & recreation (3 comments total)

well, you only need to choose voltage - at a particular voltage they'll draw whatever current they need. and you think they're battery powered, so they're probably not mains. so connect a 1.5V battery (A,AA,C,D whatever - doesn't matter) and see if it makes one go. if not, try two batteries in series (so wire - battery 1 - battery 2 - wire). then three, then four. it should go by four, with some luck. whatever it works with, that's what it needs.

using bigger batteries at the same voltage just makes it last longer (sorry if that's obvious).
posted by andrew cooke at 8:50 AM on March 9, 2005

Thanks. I was able to get it running slowly on one battery, and it was whizzing away like mad on two. Now I just have to figure out how to attach these wheels to the shaft.
posted by the_W at 9:30 AM on March 9, 2005

You can probably use a potentiometer to control the speed. A potentiometer is basically a variable resistor controlled by a small knob. Radio shack, etc, would carry them. Wire it in series with the batteries. The resistor will lower the voltage that the battery gets. The higher the resistance, the less voltage, and I'm thinking, the slower your motor will go.

You can probably also run it off, say, a DC power adaptor or a computer power supply. You can often find DC power adaptor adaptors (for lack of a better word). These are little things that the adaptor will plug into that you can solder or sometimes wire-wrap into your circuit. This is useful if you need a removable adaptor. If you don't, just cut the end off a DC adaptor and wire it into the circuit. I'd recommend a lower amperage model, something like a phone charger, an old discman power adaptor, something like that. You probably have a dozen old ones sitting around or you can buy a new one from somewhere like radio shack. If you're buying new you can usually get them in an adjustable range of voltages. Then, in combination with the potentiometers you'd have a stepped range of speeds, each of which could be adjusted with the variable resisitor.
posted by RustyBrooks at 10:01 AM on March 9, 2005