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Spinning the wheels: interfacing PMDC motors to a microcontroller

Bill Marshall
Engineer, PhD, lecturer, freelance technical writer, blogger & tweeter interested in robots, AI, planetary explorers and all things electronic. STEM ambassador. Designed, built and programmed my first microcomputer in 1976. Still learning, still building, still coding today.


September 30, 2019 07:13

Thank you Dr for the information... Does the PMDC appropriates to be a wind turbine generator?

0 Votes

October 1, 2019 07:46

@Eng.Ali In principle, yes. A brushed motor will give you a DC voltage, a brushless type (BLDC) can even provide AC! But if you want to build a practical, efficient generator then you will need to be careful about your motor selection. A generation device will have different characteristics to a motor. This link to an article by motor manufacturers Maxon Motor should tell you all you need to know: For Makers, it is possible to rewind a BLDC motor to make a slow-speed generator - if you can dismantle one without damage.

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January 14, 2019 16:15

Hi Bill,
Re: "The beauty of the PMDC is its simplicity and the linearity of its operation (Fig.1). Notice all the straight lines on the graphs!"
I agree that voltage control is simple to use, but it may well be worthwhile adding the associated Power/Speed ‘curve’. This will show that caution is required If you need to use laws of motion in your design.

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January 16, 2019 08:39

@Martin_C You're right I should include the power/speed curve as part of the practical design exercise involving motor selection. I'll make it the subject of my next post.

January 10, 2019 08:31

Thanks, Bill. This is just what I needed to start my child's project!

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January 9, 2019 08:58

Another nice article - thanks.
My first H-Bridge circuit used change-over relays which worked very well!
I was intrigued at the time with the last two options in your truth table "coast/stop" and "brake/stop" which as described allows you to coast and then effectively put the 'hand brake' on! The motor (plus gearbox) can be a surprisingly effective brake in this latter state.

0 Votes

January 9, 2019 08:58

@Boss You're absolutely right about the braking effect of a gearbox - especially if it contains a worm gear!

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