High current H-brigde for 12v, 40000 rpm, 15A(with load) DC Motor

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Anirban Raha

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Hi all,
I want to control the speed of a DC motor(40000 rpm, 12V) that is taking about 15A of current when loaded. To generate PWM signals, i am using a 8051 micro-controller(AT89s52). However i am really having trouble finding a H-bridge driver IC(like L293d or l298 etc) because the current rating is way above their ratings. So i have decided to make a h-bridge myself. But what i really want is to control 4 similar motors separately using a single H-bridge. Is it possible if I use 4 pwm signals? If yes, then please post a circuit based on the above requirements. It would be very helpful. If not, then could you just post a circuit that can control a single motor? Any suggestions, circuits, links will be greatly appreciated...Thanks a lot in advance...
 
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What? You want to control 4 motors separately with ONE circuit? 4 PWM signals into one H-Bridge??? This violates just about every law of electronics and common sense.

And you, just as well as I, can search the web for information on circuits to do what you want. Look at MOSFET manufacturers sites e.g., International Rectifier.
 

Thnx for replying...that means i need to make 4 seperate h bridges to control 4 motors? Nd also could you tell me what other things i would need for this circuit...? for e.g. a heatsink etc. due to the high current rating? Nd also would the circuit be small or a massive one?
P.S. i really don't know anything about H-bridges
 

Wow.

How do you define "small" and "massive"? Your circuit will probably be bigger than an atom and smaller than an asteroid.

What do you mean by 'other things' you would need? A microprocessor? A power supply? A book on motor control? I don't mean to sound arrogant, but it sounds like you're going into this project with very little knowledge of what you need to control a motor. There is lots of information on the web about what you are trying to do. I suggest you educate yourself about motor control, H-Bridges, MOSFETs, etc.
 


I am generating the PWM signal using a 8051 microprocessor...And yes i guess i will need a power supply...nd yes I am also aware that the size of the circuit would be somewhat between that of an asteroid and an atom...what i meant by other things are heat-sinks and other such devices to keep the temperature in check...I have already said that I don't know much about H-bridges...It only H-bridge that i am concerned about...Nd yes you do sound arrogant...because you are...C'mon man...i was just seeking help...if you did not want to help...then why bother with the replies?
 

In general you shouldn't expect exact answers to vague questions...

If you want to control four motors independently you need four separate driver circuits, each with its own PWM signals. Keep in mind if you only need to drive the motor in one direction you could get away with a simpler DC chopper instead of a full H bridge.

As for size, I'd imagine a ~200W driver would be less than 3"x3"x1" just for the power circuitry and heatsink, depending on how well it's engineered.
 

The H-bridge shown below has a rating of 10A current. Will this work? Can the same circuit be used for 20A by using transistors of higher current rating? And also are there any other kind of modifications required if I use this circuit to drive the 15A motor?
 
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Please could you explain how I can use a DC Chopper to control the speed of a single motor in one direction with a circuit?
 

That's a really poor design for a motor driver. Darlington transistors will be very lossy at low drive voltages, and the gate drive will be very slow, not suitable for high frequency PWM.

Anirban Raha said:
Please could you explain how I can use a DC Chopper to control the speed of a single motor in one direction with a circuit?
Click to expand...
Information is easy to find if you search for it
 

mtwieg said:
That's a really poor design for a motor driver. Darlington transistors will be very lossy at low drive voltages, and the gate drive will be very slow, not suitable for high frequency PWM.


Information is easy to find if you search for it
Click to expand...

Ok...looks pretty simple...except that I don't understand where I should apply the PWM signal in the given circuit(referring to the link that you have suggested)...And could you also suggest what transistors would be suitable for this circuit keeping in mind that it will be handling 15A of current(max)...?
 

For a DC chopper, the PWM is applied to the gate/base of the switching transistor. N channel MOSFETs are best for this sort of circuit, look for something with a Vds rating of at least 30V, and a Rdson of <20mohm.
 
mtwieg said:
For a DC chopper, the PWM is applied to the gate/base of the switching transistor. N channel MOSFETs are best for this sort of circuit, look for something with a Vds rating of at least 30V, and a Rdson of <20mohm.
Click to expand...

Will this do? - https://www.adafruit.com/products/355. And also do I need a MOSFET driver? Or will it be sufficient just to replace the transistor with a MOSFET in the chopper circuit that you have suggested?
 


Will this circuit work? Do i need to use any resistors to limit the gate source current due to the pwm signal? The pwm signal is output from the 8051...
 

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