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Finding remaining voltage from joystick potmeter and LM258
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tru3533:
HI,
I have a joystick potmeter that I need to measure the actual voltage and the remaining voltage from.

U1A is connected as an voltage follower.

So when potmeter gives example 1.3V the OUT1 will give 1.3V
Now OUT2 will give the remaining voltage from the supply voltage = 5V - 1.3V = 3.7V

Any idea how to do this? Any help is highly appreciated  :)

Br, Tom
Zero999:
A differential amplifier with a gain of 1, with the - input going to +5V and the + input to OUT1.

The LM258 can only work to within 1.5V of the positive supply rail, so will need to be powered from a higher voltage than 5V, or use an op-amp with rail-to-rail inputs and outputs.
tru3533:
Thank you so much Zero999, I will go ahead and try the differential amplifier.
SiliconWizard:
Note that even for OUT1, you will need an RRIO opamp (or give it a wider supply) if you want to get the whole range (0/+5V).
tru3533:
OK, so far so good.
I'm not sure how to select the differential amplifier. Any suggestions?
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