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This question is very basic, but I'd like to ask it anyway.

I need to drive a small motor. I'm thinking about connecting it directly to 4 AA batteries and using a simple switch. Is there anything else needed?

Also, it its datasheet unit gcm is mentioned. What is it? I thought that torque is measured in N*m or similar units.

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I remember pulling a DC motor from a toy when I was young and hooking it up to the speaker output on my dad's stereo - It didn't drive (obviously in retrospect) but you could hear the Beatles playing through oscillations in the motor :) – Peter Gibson Oct 10 '10 at 23:17
@Peter Gibson I am sooo going to try that! – AndrejaKo Oct 10 '10 at 23:48
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make sure you use your Dad's stereo then! – Peter Gibson Oct 11 '10 at 0:27

2 Answers

up vote 7 down vote accepted

gcm is gram * centimeters. The stall torque is listed as 340 gcm. This means that if you stuck a pulley with a radius of 1 cm on the shaft, wrapped a string around it, and tied it to some weights, it would fail to lift more than 340 grams.

Your strategy of 4 AA batteries and a switch will probably work. If the system involved digital electronics, you'd want to add a diode in parallel with the motor to prevent voltage spikes when you opened the switch. (Google "flyback diode.") You'd also want a capacitor in parallel with the motor to filter out high-frequency electrical noise, which would scramble the rest of your circuitry. But for a small motor and a mechanical switch, you'll be fine.

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If you are planning to control the motor with a microcontroller (e.g. Arduino) you may need to have a look at using MOSFETs to switch the motor on and off.

A good introductory description, including a video, of motor control can be found here.

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