PWM

How can i regulate the pwm when i have different loads?

Thanks

noname said:

How can i regulate the pwm when i have different loads?

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It's rather a vague question, and doesn't actually ask what you want to know?.

I'm presuming you want to keep the speed of the motor constant?, to do so you need a feedback signal that alters the PWM in response to motor speed changes.

or to do eactly like Nigel said but with current feedback

Bascially is sounds like you will need a control-loop

1) voltage-loop
2) current-loop
3) speed-loop

depending on what you want (as nigel said vague) you will need 1,2 or all of the above.

Bascially you will have a demanded voltage/current/speed. you wll also need a voltage/current/speed feedback (ie what the system is actually doing).

using an OPAMP in a diff-amp arrangement you can then get the difference between the two - the error. It is this error that is used to generate the PWM (via comparason with a triangle wave).

Ans as you can see as the error gets closer to zero (ie the output is the demand) then the PWM will go to 50% (if that is how you set it up)

Basic priciple:
This is a voltage-control loop. It will maintain the voltage even if the load changes (ie it draws more or less current)

The level can be control by the input pin "V-Demand".

This is just an overview and is missing alot but the priciple can be seen