I need to replace a physical switch with a transistor. I have a 12V supply which is always on, and i have a 12V control signal.
I need some way of generating a short pulse on both the power up of the 12V control signal and the power down of the control signal. It must be a short pulse (to replicate a short button press <1s >500ms).
I looked at 555 monostable timer circuits but they need to see high-low-high. Where as I can provide only high-low and low-high.
Can anyone provide any hints on possible ICs or circuits to achieve this please?
Best Answer
Without going into too much detail I would consider the exclusive or gate edge detector circuit: -
This can be scaled up in time by using much bigger values for the capacitor and resistor of course. See also this answer for a rising/falling edge detector - it goes into more detail.