Is there anyone out there that has tried Richard Valentine's circuit "Driving a high current DC motor using an H-bridge" ?
Or does anyone have a circuit that they know works.
24V dc and up to 40amps (peak).

 

Is there anyone out there that has tried Richard Valentine's circuit "Driving a high current DC motor using an H-bridge" ?
Or does anyone have a circuit that they know works.
24V dc and up to 40amps (peak).

Where might we see Mr Valentine's circuit?

 

Here

http://hades.mech.northwestern.edu/index.php/Driving_a_high_current_DC_Motor_using_an_H-bridge

 

Here

http://hades.mech.northwestern.edu/index.php/Driving_a_high_current_DC_Motor_using_an_H-bridge

Thanks @be80be. Rather difficult to get more generic than that circuit.

 

Thanks @be80be. Rather difficult to get more generic than that circuit.

Thanks for your comment. I should have been more specific. I can't see a way to reverse motor diection.The text (which comes with the cct) states the stop position is when the pwm markspace ratio is 50%.

 

Thanks for your comment. I should have been more specific. I can't see a way to reverse motor diection.The text (which comes with the cct) states the stop position is when the pwm markspace ratio is 50%.

Here's a simplified schematic. When the duty-cycle of the PWM signal is 100%, the + motor terminal will be driven high (100% of time) and the - terminal low (100% of time). When the duty-cycle of the signal is 0%, the + motor terminal will be driven low and the - terminal will be driven high. That is, the motor will reverse directions. When the PWM signal is 50%, each motor terminal is high 50% of the time, with the average voltage across the motor then being 0V; the motor is not driven in either direction.

 

Here's a simplified schematic. When the duty-cycle of the PWM signal is 100%, the + motor terminal will be driven high (100% of time) and the - terminal low (100% of time). When the duty-cycle of the signal is 0%, the + motor terminal will be driven low and the - terminal will be driven high. That is, the motor will reverse directions. When the PWM signal is 50%, each motor terminal is high 50% of the time, with the average voltage across the motor then being 0V; the motor is not driven in either direction.View attachment 198468

Thanks for your continued interest. That's my problem. I'm trying to find a driver that will give full PWM control in a selected ( input) direction, in addition to stop. Don't like the idea of both sides of the bridge "competing with each other. IR have a unit ( IFR40PBF ) which has the functionality, but it is suface mount, which I can't handle at prototype stage, but hasn't the drive capability for the 50 amp n-mosfets I intend to use.
Supply is 24v dc.
I have tentatively thought of using four drivers and to switch the PWM input between the pairs. But I'm not competant to know if this will work

 

Thanks for your continued interest. That's my problem. I'm trying to find a driver that will give full PWM control in a selected ( input) direction, in addition to stop. Don't like the idea of both sides of the bridge "competing with each other. IR have a unit ( IFR40PBF ) which has the functionality, but it is suface mount, which I can't handle at prototype stage, but hasn't the drive capability for the 50 amp n-mosfets I intend to use.
Supply is 24v dc.
I have tentatively thought of using four drivers and to switch the PWM input between the pairs. But I'm not competant to know if this will work

Select a driver that allows independent drive for each half of the H-bridge. For stop, set each half-drive to the same state, either high or low. That will drive each side of the motor with the same voltage; i.e. it will no longer be driven. Of course, there is no positive brake in such situations, simply a status of "no drive."

 

Use a couple of inputs from your processor, one for direction, and one for PWM.
Something like this...

If the PWM signal is low, no FETs are on. This could be just an enable signal if you do not want speed control.
You could just do it all with logic gates but it is too early in the morning to work that out

EDIT: I forgot to add on the 74HC139, there is an enable pin input that needs to be connected to 0V.

 

Have a look at this old thread of mine. Things get interesting after post #182

 

Select a driver that allows independent drive for each half of the H-bridge. For stop, set each half-drive to the same state, either high or low. That will drive each side of the motor with the same voltage; i.e. it will no longer be driven. Of course, there is no positive brake in such situations, simply a status of "no drive."

Yes, you can use independent drivers (2 hi-side, 2 lo-side, or 2 lo and hi-side, or 2 half-bridge) with various logic schemes to drive them. Requiring thru-hole parts does considerably reduce your choices.

 

Thanks for your quick response. Unfortunately I am hesitant to put my schematic in a public forum as it is company property, and I would need to get legal approval before doing so. This is frustrating for me as I know everyone who is trying to help will ask for it.

 

Something to consider, the Opto-Isolator in most cases will have a Miller Capacitance issue meaning that the output PWM will be skewed from the input PWM. Other variables will be input voltage to the Opto that will translate to current variations. IOW you can't go from 5V to 3,3V and expect the same results ... that goes for the tolerance of the current limiting resistor as well into the Opto.

The higher the PWM frequency the more noticable the effect will be throiugh the Opto