View Full Version : Bridge rectifier for DC voltage when using motor as a generator. Quick question

04-18-2010, 03:45 AM
Hey, I have a simple question:

I am spinning the shaft of a DC motor to produce electricity (generator). Depending on the direction of shaft spin, the motor produces positive voltage in one wire Or the other. I want to apply this voltage to my basic stamp without having to worry about which direction the motor shaft is spinning...

Thus, can I use a bridge rectifier for this situation? I know a bridge rectifier is normally used to convert AC voltage into DC. But can it also be used to make sure I'm not flipping the voltage to my basic stamp from my DC generator if I turn it the wrong way?

As for ratings on the bridge rectifier, do I pick one that has voltage and current ratings that I know I will never exceed?

I'm pretty sure I know the answers to these questions, but just wanted a second opinion.


Mike Green
04-18-2010, 04:00 AM
A bridge rectifier is exactly what you want when you might have AC or DC of either polarity. You will also want a filter capacitor on the output side of the bridge rectifier. If you're just going to be powering a Stamp and some little things (like LEDs) or even a couple of servo motors, you could use a rectifier with a 5A current rating and at a 50V rating for the rectifier, maybe a 35V rating for the filter capacitor. RadioShack has a 1000uF 35V electrolytic capacitor that would work fine as well as a 4A 50V bridge rectifier.

04-18-2010, 04:01 AM
Yes a bridge rectifier will work. The four diodes work together to convert the direction of current to one constant direction. And yes, you should always allow margins in the ratings so that the ratings are never exceeded. Even when you think the ratings cannot be exceeded, they will be if you don't allow for extra margins.

"The man who smiles when things go wrong has thought of someone to blame it on."


04-18-2010, 04:02 AM
Thanks Mike and Lucky, I appreciate the advice. Just what I needed.