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I am building a robot that sports 2 motors ripped from an old RC car. After many attempts to find the data sheets, nothing of use turned up. So, I ran some test and found this out about the motors.

  • Operating Amps(No load): 130 mA
  • Max Eff: 500 mA
  • Stall: 2.5 A

My question is, How many amps does my motor driver circuit need to be able to handle? Could I get away with a 1A driver, or should my circuit need to be able to handle the full stall amperage?

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The easy answer is that it should be able to handle up to 2.5A. Since that's the max the motor can draw, the driver's limit won't be exceeded.

Another approach is to use a weaker driver and then actively limit the current somehow. This is not so good for two reasons. First, at a lower current like 1A you will have lower torque. If the motor is presented with some mechanical resistance, it might not be able to overcome it at the limited current. Second, it makes the control electronics more complicated.

A H bridge or low side FET drive isn't much harder to make for 2.5A than 1A at your low voltages. I wouldn't try to play games cutting corners on the driver. That's the most likely component to fail since it would be the most stressed, especially if it can't really handle the full current.

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