Controlling motor speed through a SN754410

[Steve Joblin]

I'm looking to control speed and direction of two motors for my next project. The motors are rated at 4.5 volts drawing 175mA. Here is a link to the specific motor (http://www.phenostream.com/products/igm.aspx). I'm thinking of using the PICAXE 14M and a SN754410 which is pin compatible to the L293D. I understand how to control motor on/off and direction... how about speed? Do I just use the PMW command?

 

[jodicalhon]

PWM is the best way to implement speed control although, having had no need to, I haven't looked into how you do this with a 14M. Shouldn't be too hard. Not sure about two motors.

Gee, I'm not too sure about a lot of things, aren't I!

 

[Wrenow]

Steve,

One thing to keep in mind when controlling motors is not just their "regular" draw, but their stall draw, which can be multiples of an order of magnitude higher. For instance many hobby motors which normally draw 1-2A go to over 90A at stall.

There are literally tons of R/C hobby ESC's 9electronic speed controllers) which do this job, and all you have to feed them from the Picaxe is a servo pulse stream as if it were a servo.

Some are relatively inexpensive (especially the forwards only ones - some of which are under 5 quid), while high amperage ones with reversing and which are waterproof can be a bit dear (100 quid or more).

Good luck,

Wreno

Edited by - Wrenow on 19/06/2007 14:03:44