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Momentarily switch circuit

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I need a circuit that gives momentarily contact when I close a switch and will give another momentarily contact when I open the same switch again.So when I switch a switch on there must be a circuit that acts as a push button switch and when I switch that switch off again it must act as another separate push button.I have a device that switches on with a push button and switches off with another push button. I want to switch the device on and of with a thermostat by using a circuit that connects the thermostat to those two push buttons, so that i can still use them to switch the device if I want to.

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The circuit below uses edge triggering so you get an output on the rising edge and the falling edge of a pulse. The SN74LVCIG123 is a surface mount component but there is a throw hole chip; the 74123. The 74123 is a retriggerable monostable multivibrator (one shot).  Retriggerable means  that  the output persist as long as the input is applied so if you switch closure  is longer than the output pulse it still remains high.

The 74121  is a nonretriggerable version. 

If you use a two position selector switch that would  work; selecting ground or high. Else you   may have to use retriggerable monostable to get a real pulse if you use a simple push button; as input to the circuit.


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Thank you Harry, just to be sure, for input I will close a switch (it stays closed) between 'pulse in' and ground and that will give me a momentary 5V pulse at 'pulse 1 out'. When I open my switch again, it will give me a momentary 5V pulse at 'pulse 2 out' ? Do I understand it right? I appreciate your help

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You need to create a pulse that goes from low to high and back again to low. Like the first pulse B:


If you connect a resistor ( say 10k perhaps ) from the pulse in  line to ground that will hold  it low. Then connect your switch from the pulse in line to the Vcc the supply voltage. When you switch on the switch you create the rising edge like pulse B above. See line 4 below. When you open the switch you get the trailing edge of pulse B above. That is the transition for line 5 below.  The function table may differ from this one for the one-shot you use.  Remember if your switch is closed longer than the output pulse you create be sure to use a nonretriggerable chip. Analog makes chips of this type also: the LTC6993 family of one-shots.




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