DC potentiometer

George, This is a basic group. The circuit you presented shows some understanding of the problem and a way to address it. It's not the best way to solve this but there was a time when someone would show you how to make it better without resorting to name calling and insults. Check into Darlington's, power MOSFET's, and PWM and see if you can find a better circuit.

Best Regards, Tom

Well, I was the one posting the original circuit and yes, it was meant to be simple to understand. :)

I may have made an error on the bias current because I thought the motor load was spec'd as 500ma., it could have been 5000ma :) in any case the idea was 500ma in mind and that very simple circuit would do it just fine.. The zener is there to suppress EMF so not to destroy the emitter in the transistor.. The motor in that application only goes one way..

The request was for a simple circuit, that is what they got and I am sure if 500 ma was the spec, that will work just fine..

I think some just react to soon and take it over the top.

Jamie

Sorry Jamie, I talked to George because I was responding to his comment. I should have addressed you. Most of us know that you are a beginner trying to learn and will not hesitate to ask questions. I just don't like rude responses when they are not warranted. I think there are many here that will help you and not rip you a new one when you make a mistake. Just keep doing what you are doing.

Tom

cation,

Thanks Tom, I'd use a Darlington too...(as Sjouke suggested.. I should have addded that to my post) Sorry, Sjouke

Or that National 'darlington' with thermal protection. (I can't recall the part number)

George H.

Hey guys,

I just want to say how much I appreciate ALL your inputs on this.

You have all invested time and effort into helping me with a way to do what I wanted to.

Thank you all. It really amazes me that there are so many people out there who will take the time to reply to questions like mine with such enthusiasm and concern.

You guys rule.

Yours truly, Joe