brake with a H-bridge

I want to brake a DC-motor with a H-bridge build with MOSFETS but I don't know how to do that. can anyone help me?

You need independent control of all 4 transistors. Just switch both terminals of the motor to the same voltage (either +V or GND).

This may not be enough, using a geared DC motor will give you prefect results.

Reduction gear boxes are made to increase the torke on the load side while decreasing speed. if you try to move the output shaft you will feel like it is stuck and locked, i don't want to go into mechanical details, but this is the best locking system ever used for robotics applications.

if you don't need a powerfull locking, dknguyen idea is way to go.

Actually you can try it by simply by making a shor-circuit on the motor wires and see for yourself if it is enough...

Are you referring to one-way worm gears where the gearbox cannot be back driven? Or the friction losses involved in any gearbox helping braking?

But when I make a short-curcuit by switching both terminals to the GND, I will get a high current, doen't that kill the MOSFETS?

JCD said:

But when I make a short-curcuit by switching both terminals to the GND, I will get a high current, doen't that kill the MOSFETS?

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No, there's no no current being supplied by the battery, the top two MOSFETS are turned OFF (or they better be!).

JCD said:

But when I make a short-curcuit by switching both terminals to the GND, I will get a high current, doen't that kill the MOSFETS?

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switching both terminals to the GND is not a short-circuit, a short circuit is to connect the 2 wires of the motor together.

I was telling you to make a short cuircuit so that you make a test with your motor, before building the Hbridge to see if it will be enough to brake the motor according to the load attached to it. sure if you short-circut the motor while it is connected to the bridge, you will kill the mosfets!

Then, if the short circuit on the motor is enough, then to do the same effect with an H-bridge, just do what dknguyen said.

dknguyen said:

Are you referring to one-way worm gears where the gearbox cannot be back driven? Or the friction losses involved in any gearbox helping braking?

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Yes, that is the optimum bracking, but also any reduction gear box with a high ratio like (90 to 1) or something, will have a perfect bracking effect.

So, this means that the best way to brake the motor is to open the lower 2 MOSFETS and close the top 2.

ikalogic said:

switching both terminals to the GND is not a short-circuit, a short circuit is to connect the 2 wires of the motor together.

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It's just the same thing! - except that's it's not a 'perfect' S/C, it's the 'resistance' of the two FET's in series across the motor (which will be very low).