# Commanding a 12V DC motor with high power (~20A)

I'd like to control a 12V DC motor but it has very high power, around 20A.

I was looking for H-bridges but they all support only low power (around 1A)

Do I have to build my own H-bridge with high power MOSFETs?

I just need a high power H-bridge.

• The off-the-shelf product closest to your goal may be a speed controller for an R/C vehicle - something intended for a brushed motor in a large vehicle with 3 LiPo cells would be about right. If you decide to make your own, the many online writeups of R/C speed control designs may be quite practically informative. (It's also possible to adapt a brushless controller circuit with a firmware change, and some current de-rating since the load will not be shared with a third phase). – Chris Stratton Oct 8 '14 at 17:37
• You link a P-channel FET, which tends not to perform as well as an N-channel device. For bidirectional control, you do need a high side switch, but the highest performance devices will employ a flying gate driver to permit using a better-performing N-channel device on the high side as well as low. – Chris Stratton Oct 8 '14 at 17:42

It might be fun to implement your own H bridge with external MOSFETS, such as the P channel FET that you linked to, plus N channel FETs for low-side with similar parameters.

You would have to implement a lot of protection measures though with discrete components that it might be better to find and implement a circuit which external switches but based mainly on a H bridge controller IC. The controller IC will have push/pull or charge pump MOSFET gate drivers for hard and fast control of the external MOSFETs, meaning you will waste less heat, and some have the option for current sense resistor feedback for over-current protection and other nice features.

Make sure you include clamping diodes to deal with back EMF.

Of course if you have little experience, it might be better to first make some simpler lower power H bridges first, and then work up to a nice big fully controlled high power one.

You may also buy motor controllers (for quite a lot of money) and save yourself some time and issues with testing. You show Sparkfun as a website in your link, perhaps check out the products available at Pololu's website, there are some nice motor driver solutions there.

You may also consider trying to change the motor you are using, to a 24V or 48V motor, to half or quarter the amount of current used for the same approximate 'power' output. Current is the killer, in terms of heat and nice explosions, so trying to reduce the amount of current to something less crazy would be something to look into for your project/design/thing.

• I have 8 motors to command so if I buy motor controllers for each it would cost me a LOT – user2591935 Oct 8 '14 at 16:26
• Shop around - I just saw a "30A" (take that with a healthy suspicion, at least if you don't add additional heatsinking) brushed ESC listed for $8. – Chris Stratton Oct 8 '14 at 17:39 • I am not sure if ESC would work. The engines are not brushless ( they only have 2 wires at exit + and - ), and the battery is lead-acid battery – user2591935 Oct 8 '14 at 17:48 • @user2591935 Brushed means a normal DC motor. Brushless are more exciting. Also you can make some seriously high power stuff for very cheap, some fairly uber MOSFETs for$1 each and you can do 50A+ per motor. Of course, the connectors are always horribly expensive hehe. Anyway you should find some reference designs for H bridges, and I really do encourage you to get an H bridge controller IC and use their reference examples to design your drivers. Then just make 8 of these modules, one for each motor. – KyranF Oct 8 '14 at 18:03
• Okey then. But I think that I am not enough experienced to make my own H Bridge Controller. ESC would be better is it possible to command ESC with a microcontroller ? – user2591935 Oct 8 '14 at 18:16