electric motor rpm control

jellywerker · Post by **jellywerker** » Sun Dec 11, 2005 10:35 pm

Does anyone have a link to a circuit for controlling the rpm sspeed of small electric motors. I would like to build something that lets me change between 30, 60, 80 (or 90), and 120 rpm. SInce most small motors rotate quickly (1700 rpm+) I figure I would gear it down a bit, but I still need some control over the motor itself.

Any help?

Edit: after little searching, and some common sense, since a dc motor's speed is controlled by it's current, would making a swith/circuit that switched between the currents needed to make the motor run at the speeds needed work? Or does it need to be more complex?

Edit2: I'm starting to feel stupid. all I need to do is hook up a pot connected to a knob right? Then I get variable speed...

Post by **marshallh** » Sun Dec 11, 2005 11:09 pm

Either a pot or a PWM switchmode controller. Google it if you don't know what that is.

jellywerker · Post by **jellywerker** » Sun Dec 11, 2005 11:37 pm

I know.

Edit: I'll go with the pot, it's simpler.

nos_slived · Post by **nos_slived** » Mon Dec 12, 2005 12:12 am

I think DC motors are dependant on voltage, not current, because I can hook a motor up to 6V battery with no other load, and it will go slower than when I attach a 9V source.

timmeh87 · Post by **timmeh87** » Mon Dec 12, 2005 12:50 am

pwm is where its at

jellywerker · Post by **jellywerker** » Mon Dec 12, 2005 12:43 pm

Care to explain why?

timmeh87 · Post by **timmeh87** » Mon Dec 12, 2005 1:05 pm

lol. im just a fan (pun) of the unnesecarily complicated.

im my portable im [planning] to have a microcontroller with a temp. sensor that can turn the fan on and off as its needed. and ill probably find other things it can dofor me as well. i dont think my battery protection chip has led outputs, so i might be able to get them to communicate, and have the microcontroller drive the leds. it depends if microchip supports the dalass/maxim 1-wire protocol...