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What's a simplest way to get -5v from +/-12v? (kbin.social)
submitted 1 year ago by PinkDuck@kbin.social to c/askelectronics@discuss.tchncs.de
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Hi! I'm working on an arduino project that has a -12v/0v/+12 psu. +12 is fed directly into arduinos voltage regulator, so there's also a +5v line available. I need to convert a -5v+5v signal to 0v+5v to feed it into arduinos analogue input and I've already mocked up a schematic in circuitjs based on an opamp that seems to do what I want. The only problem is that it needs -5v to shift the signal to be unipolar. I know that I can invert +5v using another opamp, but maybe there's some simpler way? I'd really like to avoid adding another opamp just for this? In this schematic I used simple voltage divider to get the needed voltage, but I guess that's not the best approach?

TLDR: I have -12v, 0v, +12v and +5v, what's the easiest way to get -5v?

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[–] grasib@lemmy.world 1 points 1 year ago* (last edited 1 year ago)

You’re right of course. Two more questions if you don’t mind:

    1. what’s the 1k || 100k doing?
    1. if you don’t want more than 5V at the output of the OpAmp, wouldn’t it be easier to just supply the OpAmp with 5V instead of adding a shottky diode which has a forward voltage of around 0.6V? As I understand the screenshot the voltage is 5.4V at that exact point and it could theoretically raise to 5.6V.

At the moment you’re also mixing up your + input. 10V AC + 5V DC result in 7.5V input in your sim.