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I was wondering if anyone knew of a simple circuit design that would output "high" only for a certain voltage (within a small degree of error).

Thanks in advance!

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2 Answers 2

up vote 7 down vote accepted

Your question is kind of vague, but a window comparator is what I'm imagining you're asking for.

http://ecelab.com/circuit-window-comp.htm

enter image description here

That outputs a low in the middle range, though.

This will give you a high output in the middle, using open-collector comparators:

http://www.aaroncake.net/forum/uploaded/audioguru/2008425111635_window%20comparator%20circuit.PNG

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This one simple circuit I could think of. You can set the pot VR1 and VR2 to the lower and upper voltage levels respectively and the output will only be high when your input is in the range.

circuit diagram

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If the required range is fairly small, it would be better to use a single resistor chain so you could be guaranteed that the ref voltage to your low comparator will be less than the other ref voltage –  Nick T Mar 8 '11 at 0:54
    
yeah you are right... :) –  Zaxx Mar 8 '11 at 14:56

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