Author Topic: [ window voltage comparator ]  (Read 32743 times)

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Offline texane

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[ window voltage comparator ]
« on: October 17, 2009, 10:25:42 am »

As a beginner, I am reading the following book: practical electronics
for inventor, from Paul Scherz.

For a light sensor project, I need a window voltage comparator. I use
one from the above book. I attached the schema.

What should happen:
Vout is +5v when 2.3v<Vin<2.7v
Vout is 0v otherwise.

However, I get the opposite...:
Vout is 0v when 2.3v<Vin<2.7v
Vout is 5v otherwise.

I use a lm339 quad comparator, so that I actually has only one
comparator. I tested the comparator inputs/outputs independently
to see if it works, and I get right measures. Maybe there is something
I didnot understand regarding the above schema...

Any idea?

Thanks for helping,



Offline texane

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Re: [ window voltage comparator ]
« Reply #1 on: October 17, 2009, 10:40:03 am »
I think I misunderstood something... the schema
actually works as expected, sorry for posting :)

Offline Simon

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Re: [ window voltage comparator ]
« Reply #2 on: October 18, 2009, 08:41:46 pm »
if you get a similar situation again (thats if it really happens) reverse the inputs on the comparators

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