Newbie Question Voltage Divider?

Discussion in 'General Electronics Chat' started by leveldoc, Nov 17, 2010.

1. leveldoc Thread Starter New Member

Nov 17, 2010
1
0
Hi all,

I realize that this is a really basic question, but I am trying to learn and I would appreciate any help from you. I've never done this before. I know the basics about analog DC circuits, but have never actually played around with them.

I am trying to position control a motor using DC voltage. I believe I can set the limits but the presets are -10 to 10 V. Anyways, I have 5V input voltage and a potentiometer hooked up.

The position of the linear potentiometer is supposed to match the voltage maxing out at -10V and 10V respectively. E.g., potentiometer all the way to the left -> motor goes to the left all the way.

Could someone point me into the right direction, maybe even with a link? It's hard for me to Google this since I don't even know what I am looking for.

Thanks!
Stephan

2. Audioguru New Member

Dec 20, 2007
9,411
896
I don't know your motor but usually the current of a motor is too high to send through a pot. The high current in the pot will burn out the pot.

Also, the resistance of the pot in series with the motor reduces the current which severely reduces the torque.

We use a pulse-width-modulation circuit to control the speed of a motor so the motor has plenty of torque, and we use an H-bridge circuit to reverse the motor's rotation.

Then if you use a pot to control the PWM and H-bridge circuits, the current and heating in the pot will be low.

That is how an electric golf cart or electric wheelchair work.

3. Wendy Moderator

Mar 24, 2008
20,772
2,540
A pot (which is short for potentiometer) is used to create a reference voltage that in turn will control your motor, as AG says. In and of themselves they are useless for high power applications.

555 PWM Oscillator