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A guide to H-bridge design and motor interfacing?

I'm going to need a pair of H-bridges for The Heavy soon.

Each needs to control a 180Watt motor at 12v, but (ideally) be able to run 24v to the same motors at a later point in development. So looking at 15Amps per controller. 20 for safety?

I want to run them with PWM, and be able to change direction quickly, as well as lock the motor and set it to freewheel.

I intend to use a small automotive fuse box for safety (blade fuses), and would like to get opto-isolation on the control lines if they'll work at the frequencies needed (partly for safety, partly for a little more flexibility with control levels).

H-bridge layout seems fairly standard, but I'd like advice on speccing the parts to use. What do you need to look for when selecting which bits to use?

Also what would be advisable to have on it to provide EMI filtering? Is it really nessesary or just good practice?

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Hi

It would proberly be best to find some darlington effekt transistors, that can handle the effekt you need. They should also be easy to use with PWM. And they come in a big varyation. Havent tried to make any ting that big, but right now i am working on a controller for my little 9v DC motor. But in general it is the same,  you just need some components that can handle more effekt.