I am working on a hobby circuit. And got a quick question.

I am using regular mini DC Motor as DC Generator. If the motor is rotated one side it generates few volts. If the motor is rotated in opposite direction the output polarity is switched. Which is normal.

I would like to know how/what circuit to connect to output of Motor, such that if the motor was rotated in any direction, the polarity of the output after the circuit is same.

  • 2
    \$\begingroup\$ You could use a full wave rectifier (4 diodes). \$\endgroup\$
    – Matthijs
    May 12, 2014 at 12:09

2 Answers 2


You can use a simple bridge rectifier to get what you want. This requires that you must rotate the motors with a minimum speed so that the diodes are forward biased and the output is available.enter image description here

  • 4
    \$\begingroup\$ Right idea, but for this application you really want Schottky diodes to minimize the voltage drop of the full wave bridge. \$\endgroup\$ May 12, 2014 at 12:23
  • 1
    \$\begingroup\$ Thanks @OlinLathrop I forgot that. This will also help reduce the minimum rmp required to get voltage on the output side. \$\endgroup\$
    – Damon
    May 12, 2014 at 12:27
  • \$\begingroup\$ Yes, 1N5817 would work just fine given that your motor doesn't produce a current more than 1A. \$\endgroup\$
    – Damon
    May 12, 2014 at 13:07

What you want is called a full wave rectifier. An explanation can be found here http://www.eecs.tufts.edu/~dsculley/tutorial/diodes/diodes3.html. You can build them up out of 4 diodes, or you can buy modules with all 4 ready made. Be aware, though, that in either phase your motor voltage will be reduced by ~1.4 to 2 volts due to the voltage drop across two diodes (you can reduce this by using Schottky diodes, but they cost more).


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