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How to reduce the max. resistance of a potentiometer?

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ericmar

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How do I reduce the maximum resistance of a Digital Potentiometer? Just parallel a resistor across the A and B?

I tried doing this on a normal potentiometer but it doesnt seem tat way!

Suppose I hv a 10kΩ potentiometer and I want to step it down to 1kΩ and use it as voltage divider mode. So when one side is 600Ω, the other side is 400Ω. How do i configure it to achieve this?

Thanks,
Eric
 

IanP

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To reduce 10kΩ to ≈1kΩ add 4.7kΩ in parallel with 10kΩ pot and 2 x 1.5kΩ between the "bottom" (GND) and the output and the "top" and the output ..
Of course, this "new" resistor won't be linear any more .. but that is moretheless all you can do about it ..

Regards,
IanP
 

    ericmar

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ericmar

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Do u mean something like this?
circuit.jpg


I did try wat u said but it doesnt seem to be working correctly.

My potentiometer is 9.22KΩ, and instead, I use 2 x 996Ω resistors. One of these 996Ω resistors connect across the A and W of the POT, another 996Ω resistor connects across B and W of the POT. The maximum resistance of the POT was reduced to 1640Ω when the wiper is at the center of the POT, which both sides r 820Ω. But then each side can actually go up to 900Ω and then the maximum resistance across the A and B will be less than 1640Ω. That means when both side hv the equal ohm value, the POT will hv its maximum resistance (1640Ω).


Thanks,
Eric
 

IanP

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Of course, this "new" resistor won't be linear any more .. but that is moretheless all you can do about it ..

Try this: use an opamp as a voltage follower connected to the 10kΩ potentiometer and, assuming that the output resistance (impedance) of an opamp is ≈0Ω, connect 1kΩ resistor to its output to ensure that the resultant output resistance will be 1kΩ ..

Regards,
IanP
 

m.mokhtar

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Hi
you can not do that without active circuit because you want when a resistance is 400 Ω you want the other part 600 Ω which means you want it linear, you can not do that with parallel or series resistors in any combinations; so I suggest using op amp as a transconductance convereter.
Regards
 

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