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??
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.
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??