Power Supply Voltage Drop Help Rhino PSM12-078S

Hello,
Sorry this is a little off topic, but here is my problem.
I am using a Direct Logic DL06 plc and a Rhino PSM12-078S (12V 72W 6A) power supply.
I want to drop the voltage, to slow down the rate of a dc motor. I have tried using a pot, no success, 0V at the pot. I've measured just about every where and I get nothing as soos as I add a linear component.
Here is my question is there a way connect a pot or rheostat and keep it alive? Failing that is there anything out on the market that is DC variable (0V - 12V) in a din mounted supply?
John

You could buy a little DC drive. The one's that I use are 90VDC but you can limit them so they could work.

Google: KB, Baldor

http://www.kbelectronics.com/

http://www.baldor.com/products/dc_controls.asp

Since it is a DL06 you could use the 2 channel analog card and use a potentiometer to the input to directly vary the output OR you can vary the speed in the program.

Are you sure you wired the pot correctly? The center terminal is usually the wiper which is the varying output. A "pot" has 3 terminals and a rheostat 2 terminals. A rheostat varies current. A pot can be converted to a rheostat by combining the center leg with one of the others.

I know I wired the pot properly, I had them on hand and tried that first. Anyways am I missing something with the switching power supply? Damn this is ticking me off!
My original idea was to put a pot or rehostat in line to control the voltage, but that doesn't work. I must admit I don't want to get another card just to control a motor, that sounds like a pain in the *** (program changes I don't want to make!). I was hoping for a cheaper, easier option!
John

I am not sure what you are doing but since its 12v I assume the motor is small i.e. similar to those in remote controlled cars.

You have not fully explaind HOW you are trying to control the voltage, as I stated a pot varies voltage while a rheostat varies current, in some cases a rheostat will not work where a pot will.

IF you have the 12v for the motor connected thru an output on the DL06, hopefully a relay output in this case, then it should be no problem connecting a "pot" after the output to vary the voltage and motor speed. I would put it after the output.

THe simple method is have the 12v feed thru the output, after the output connect that wire to one of the outer terminals of the "pot" and common (-) to other outside of "pot", and the center terminal to the motor with common (-) to the other side of motor.

NOW when the output is ON 12v should be fed to the "pot" and you should be able to vary voltage which will vary speed.

This will work, and give you PWM control.
If you want to build your own, and don't mind linear, you can do it easily with an LM338. Go here, and use the typical circuit.

Thank you very much for the help.
I looked at the item keithkyll suggested. I think that will fits my needs perfectly. Using the dual Si5HyPC2-30V-2x20AI can use three outputs two control the speed on two different motors. I output for power to the board, and 1 for motor a, and 1 for motor b. Thank you for your help.
John

I even looked at the wondermotor stuff as well. That looks pretty good.
Here are the specs on my motor:
12V dc
.20 A No load
5.54 A Peak (Stall)
2.8Q Torque
2.07 EMF Constant
2.17 Ohms terminal resistance
1.54 mH Inductance
Thanks,
John