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Single switch - two outputs (with delay for second)


Mar 27, 2013
Mar 27, 2013
Hi All

Came here for some more expert advice :)

I have a circuit (completed) and a power source (5V 1Amp protected with a polyfuse and TVS diode) - but now I need to manage the power state.

I have the following circuit for latching a relay on / off using two switches. Input 1 is always high. When it goes low the latch switches off after a time derived from the capacitor and resistor pair. I would like to be able to change this slightly if possible so that I can :

1. Remove the requirement for a relay (it is the only mechanical element in my project) - replace with darlington pair that can manage 5v 1Amp+? The reason I initially liked the relay is the fact it just passes power straight through from the source without affecting it.

2. Use the first switch for 2 inputs. The first time it is pressed it should latch the circuit on, the second time it is pressed (for 3 seconds? - capacitor and resistor timing pair) it should provide an output to a Output 1 - used a sensor on the circuit to perform some action.

This would allow me to have an ATX style power supply control. Press once on for latch, press again and hold for the circuit to sense a shutdown on Output 1 (this pin in monitored). When the circuit has shutdown, the Input 1 pin will go low and so all power is removed from the circuit - as I do not want it sat on standby.

Notes : the power input is an LM2596 DC DC 5v supply. There is also a switch called "latch mode" that allows the user to override the Input 1 sensing and use the circuit purely as an on / off latch.


Any help would be greatly appreciated as my electronics knowledge was GCSE - some 10 years ago.