Control DC Motor Speed using Astable - Mike's Project

[madmike159]

I am making a project to control the speed of a DC motor using an astable. I need to be able to change the speed of an astable (555, or one made from gate) using about 8 different voltages.

The only way I can think to do this is with a MOSFET was a voltage controlled resistor, but no one can ever get these to work.

Can anyone think of another way of varing the astable's speed or a way to implement the MOSFET?

Thanks
Mike

 

[Topher925]

Call me stupid but what's an "astable"?

 

[madmike159]

Its also known as an oscillator, it creates continuous pulses at a set speed. It is often used in timing circuits.

 

[MATLABdude]

Call me stupid but what's an "astable"?

That means that you're getting a periodic waveform (e.g. a square wave for a clock) instead of a single pulse (monostable) or toggling the state (bistable)

As for the original post, if you're using a microcontroller for this, you're better off using the PWM generation feature. You can also use a digital potentiometer, but these are usually digitally controlled. Unless you want to start cascading comparators to control a parallel-input digital pot.

 

[madmike159]

No I think I'll stick with my VCR. I will look into the other ideas though, thanks for the help.

If anyone has any more ideas it would be much appreciated.