How to control a small DC motor

[dixonjk]

Could anyone please tell me of a device that would allow me to control the speed of a small (12-24v) DC motor (not a stpper motor)? Its for a small pump, I would like to be able to control it using Visual Basic.

[CJL5585]

http://www.pololu.com/products/pololu/0705/

Should work for you.

[Davidh]

How about a darlington pair transistor control.

Darlington Pair

Variants can drive up to 3 amps, even more I'd expect but am not qualified to advise, I recently constructed the linked circut to drive the wire feed motor on a MIG welder. Drawing less than 1 amp. Turn the knob to the right it goes faster, to the left it goes slower. Needs a decent heat sink on the big transistor. I have the blister to prove it!

[NC Cams]

Davigh: the darlington pair works if you want to use a totally analog congtrol system. Please note that the intent was to control it via VB which implies the use of a PC or uC.

Untill or unless you do a D-A conversion somehow, the darlington circuit won't suffice.

The circuit posted in reply #2 is a clever solution to the inquiry...

I didn't readily see what sort of software or how it interfaced to the uC but surely a perusal of the linked website should address that part of the inquiry.

[Al_The_Man]

Dare I mention it But the LM2907 app sheet shows three motor control circuits, using Darlington output drive.
Instead of the Feed back tach, just use a frequency into pin 1. This should give you the frequency to analogue control you may be looking for.
Al.