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I have been given this arm:

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It consists of 4 servos, which need to be controlled individually.

Can I control them using Gertboard? Gertboard has only one motor driver, but it also has several open collector ports and buffered outputs.

I know Raspberry Pi itself can control a servo through a PWM pin and that you can emulate PWM on any additional pins. How do I do it safely via Gertboard? Should I use buffered pins? Won't servos blow my Pi or Gertboard up?

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You can connect a servo control wire direct to a Pi gpio and use hardware timed PWM to control the servo position. You could have an in-line resistor if you prefer (say 1K-10K).

I don't know if you can generate reliable PWM on a Gertboard. Software timed PWM is unlikely to give satisfactory control of servos. That said, there is little harm in trying, at worse you will shorten the servo's life a little.

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  • So a servo can't damage the computer like DC motors can? Will the resistor prevent any damage?
    – katspaugh
    Commented Dec 5, 2014 at 13:15
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    A resistor may help prevent damage if you wire it incorrectly, i.e. connect to 5V when you meant to connect to the control wire. I don't use them myself. Frankly they might cause more problems then they solve as far as the servo control wire is concerned. Servos have in-built motor driver boards. Motors don't. You should always control motors via a motor driver board or motor driver chip. Again, I don't use resistors between the gpios and the motor driver board.
    – joan
    Commented Dec 5, 2014 at 13:24

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