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0V sensing circuit

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BOOJAN

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I want to build something, but for that “something” I need circuit that can sense when the voltage is 0V, and when the input is 0V it can trigger NE555, and that needs to trigger relay….I don’t have problem with NE555, but I have with that 0V sensing circuit…so anyone can help??
 

ccurtis

Well-Known Member
Other pertinent questions are:

  1. How much noise is on the signal?
  2. What's the tolerance on the 0V parameter. 0±?
  3. How far does the signal voltage go above and below 0?
  4. What is the minimum period of the signal?
  5. What is the rise and fall time of the signal?
  6. What power supply voltage and current is available to power the circuit?
 

MikeMl

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BOOJAN

New Member
1-substracting circuit
2-0V sensing circuit (the one I was looking for)
3-trigering circuit with NE555

The voltages V1 and V2 are from 0-0.6V-DC
The power supply voltage is ±9V-DC
I would like the tolerance to be as low as possible

I was planning to do this with subtracting circuit, so when the voltage is 0V the sensing circuit triggers the 555 and that will trigger the relay
just for you.JPG
 

MikeMl

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Note that "Out" swings from ground to ~+8V. If you want it to go to ~-8, then connect the neg supply pin of the 358 to -9V
 

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MikeMl

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How can I eliminate those other impulses expect the one when the voltage is 0V?
There is no such thing as a circuit that says a voltage is zero. You can build a detector that has a Boolean output X = V ≥ -Δ, and another Y = V ≤ Δ. Let Z=X AND Y. That means that Z is true if
-Δ < V < Δ. This is called a "window comparator", where the width of the window is 2Δ.

How small do you want Δ to be?
 
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BOOJAN

New Member
Might be helpful if you tell us exactly what that "something" is you're trying to build.
I am trying to make some current limiter for my power supply, because it doesn’t have any....I want the drop down voltage of the output resistor to compare with other voltage given from other power supply (made with resistors, and potentiometers) and when the voltage is the same, or when it will pass some limit to trigger transistor, and that transistor to trigger NE555 and it needs to trigger one relay.....or maybe I will wont make it with NE555.... You understand what I mean??
 

MikeMl

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Here is another attempt. Output "AND" is high only when A-B is near 0V.
 

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MikeMl

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