PWM controller for DC servo motor?

[space-cake]

This might be a little off-forum... I'm looking for a simple way to drive a 6v 1.5W servo motor in very constant speed (it's a high rev. engine with a gear box). I know some of you guys had build drivers for TT motors so maybe someone has some helpful info? Thanks!

 

[qwertyadam]

http://www.bakatronics.com/shop/item.aspx?itemid=383

 

[rayfutrell]

National Semiconductor application note AN-292 describes a DC motor controller using a PWM IC designed for power supply use.
The speed is controled by measuring the motor back EMF during the pass transistor off period. No tachometer is needed.

Regards,
Ray

 

[SaSi]

Of course, one should also consider that speed variation of the motor is reduced by the same ratio as the one provided by the gearbox. For large reduction ratios, with the gearbox driving some sort of flywheel, even a plain DC motor should be adequate.