can somebody helpme in this problem
i use PIC16f84A to control a DC motor directly .........but it does not work.....i dont know why ???????????????

when i'm use a varilable supply, DC motor work at 0.7 volt
can any body solve this problem to me........

 

You can't feed a motor directly from a PIC, it won't supply anywhere near enough current!.

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u'll need an H-bridge , or atleast a power transistor (eg-3055) to drive a motor

 

thanx..................
But my main problem that i have 8-10 DC motors so haw can control them seperatly...............
if i want to use a H-bridge, ineed 4-transistors for each motor.
so 4 by 8 motors = 32 transitors.....................
it's impossible to use it in small area

 

Use H bridge ICs. The twin H bridge IC is prety popular.

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Do you need to reverse the motors?, if so you need H-bridges (either IC or discrete), or a DPCO relay - either way, if you haven't got room you can't do it!.

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I've got a similar question. For controlling multiple motors, that is.

Is there any kind of PWM control IC that will -say- take a digital input and latch the pulse width? That way it would continue its PWM until the next digital input arrived? It seems excessive to have a seperate µcontroller generating PWM for each motor.

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You might consider using a PIC as a dedicated PWM controller?, something like the 16F628 has a single PWM channel, some others have two. I don't know if any of the 8 pin PIC's have PWM, but if not you could do it in software?.

Don't be scared of using more than one PIC - it's only a component like anything else, the 8 pin ones are useful for replacing 555 timers, and are FAR more useful!.

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thanx for you.......................but still i have one question..
i saw many robots like 'robosapien' and i check it's internal structure.i'm noy found any tibe of H-bridge..........i'm amazing that they are conect microprocessor directly to the motor................
any body can answer my quetion????????????????????????

 

Yes - the microprocessor ISN'T connected directly to the motor, you are mistaken!. I would suggest there are four possible reasons:

1) You haven't recognised the motor drivers.
2) They are surface mount and extremely small, and possibly on the other side of the PCB.
3) The motor has the driver built inside (like servos do).
4) There's an H-bridge actually inside the same encapsulation as the micro-controller (although I think this unlikely).

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