At 03:53 AM 1/7/03 +0000, you wrote:
>Some comments on this one if you please ...
>
>I am using the PWM facility of a pic to drive an H bridge for a DC motor
>in which I need both forward and reverse.
>
>However, I now have an application where I only want to drive a motor
>forward but still vary its speed.
>
>Can I simply use a single transistor  sufficiently rated for current and
>just
>turn it on off at the base ??

Yes, but you need either a diode or another transistor to deal with
the energy in the motor inductance.

>If I can, could I also parallel the transistors
>to spread the current sharing ??

MOSFETs can be paralleled with few problems due to the positive tempco
of Rds(on) under normal operating conditions; BJTs require ballast
resistors to get them to share current nicely.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu