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Potentiometer Questions

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norbss

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I have a DC motor controller that has a 4.7k OEM potentiometer. The maximum voltage of the controller is 220volts DC. My Dc motor's maximum inputs is 175 volts DC (5.3 Amps)(I think, based on the motor plate). Can I change the potentiometer to another value so that the maximum voltage will be around 175 volts max ?
 

dknguyen

Well-Known Member
Most Helpful Member
I have a DC motor controller that has a 4.7k OEM potentiometer. The maximum voltage of the controller is 220volts DC. My Dc motor's maximum inputs is 175 volts DC (5.3 Amps)(I think, based on the motor plate). Can I change the potentiometer to another value so that the maximum voltage will be around 175 volts max ?
What you do is you add fixed resistors on one or both sides of the potentiometer. Together they become a variable resistive divider that can only change within a range of divider values (not from 0 all the way to 100%).

Add a fixed resistor on the lower end prevents the overall divider from being adjusted to 0%. Adding a fixed resistors on the higher end of the pot prevents the overall divider ratio from being adjusted to 100%. The fixed resistances you pick determine how far away from the end points it can be adjusted. In your case, adding 1.2K fixed resistance on the high end of the potentiometer will cause the output of the divider to only be adjustable from 0% to 80% of the divider input voltage (175V is 80% of 220V).
 

norbss

New Member
Looking at the motor controller board, there are 2 adjustable potentiometers labeled PR1 and PR2. I've ask the seller regarding this and they said it is to adjust the output of armature output but since it is factory calibrated, it is best to leave it as is.
 

Pommie

Well-Known Member
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If you connect the potentiometer as shown on the web site then as you turn it one way the voltage will increase. Place the 1.2K (1W) resistor in series with the outer connections at the high voltage end of the potentiometer and the voltage will change. If it's now adjustable from 50 to 250 then swap the resistor to the other outer lead.

Mike.
Edit, I'm assuming you will only use the M+ and M- connections.
 

norbss

New Member
Thanks mike. so the only way is to add another potentiometer of 1.2 k ohms? can you how to install diagram for me please?
 

norbss

New Member
yes . it is just to limit the voltage for M+ and M- connections( Armature ).. The L+ and L- is for the excitation winding which is fixed at 205 volts DC.
 
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