Redge Posted May 15, 2020 Report Share Posted May 15, 2020 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. Quote Link to comment Share on other sites More sharing options...
HarryA Posted May 16, 2020 Report Share Posted May 16, 2020 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. Quote Link to comment Share on other sites More sharing options...
Redge Posted May 16, 2020 Author Report Share Posted May 16, 2020 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 Quote Link to comment Share on other sites More sharing options...
HarryA Posted May 16, 2020 Report Share Posted May 16, 2020 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. . Quote Link to comment Share on other sites More sharing options...
Redge Posted May 16, 2020 Author Report Share Posted May 16, 2020 Thank you Quote Link to comment Share on other sites More sharing options...
Redge Posted May 17, 2020 Author Report Share Posted May 17, 2020 I came up with this circuit, any comments? Quote Link to comment Share on other sites More sharing options...
HarryA Posted May 19, 2020 Report Share Posted May 19, 2020 That looks good. Good use of the capacitor. If you replaced the DPDT toggle switch with a relay powered of the supply on power failure would it switch to inverter automaticlly? Quote Link to comment Share on other sites More sharing options...
Sugandhan Vazhumuni Posted May 29, 2020 Report Share Posted May 29, 2020 This sugunthan from india @HarryA u have any video about this topic and can u send me Quote Link to comment Share on other sites More sharing options...
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