I want to us this touch switch circuit in a project. It works fine, but I need to modify it. Currently, when power is removed and then reapplied, the circuit returns to the state it was in when power was removed. For example, I can turn the LED on and off using the two contact points, but if the LED is on and I remove power, the LED will be on when I reconnect the power. I need the LED (and relay) to always have no power to it (them) whenever power to the circuit is restored. What change(s) do I need to make?

 

I should have added. For my project, I will be using momentary push switches instead of some type of touch input.

 

Connect a capacitor from pin 13 to ground. First guess value 100pF.

 

As Albert said but I would go with closer to 10-100nF, depending upon how fast the power comes up.

Also add a 100Ω resistor in series with that switch so reduce the high peak current from the capacitor, which could otherwise damage the switch contacts.

 

If the resistors on those inputs stay at 1MΩ the time constant is getting rather long with much bigger capacitors. I could stretch to 1nF

 

I will try these suggestions over the next couple of days. I may not have any of these capacitors on hand, so I may need to make a trip to pick some up.

 

If the resistors on those inputs stay at 1MΩ the time constant is getting rather long with much bigger capacitors. I could stretch to 1nF

That time is just the recovery time until it will respond to another input after the PB is released.
For example, 1MΩ and 10nF gives a time-constant of only 10ms.

 

I had a 100nF capacitor on hand. I inserted it between pin 13 and ground, and now the circuit operates as I need it. Thanks.