As sometimes happens in life, I have figured out a better way. However, I will build and test this prototype circuit to find out why it's not working. I suspect I have a fundamental misunderstanding about the 4040. So by getting it working, I will learned something. Recently I bought an Alexa. Among the devices it supports are powered outlets. I can just tell Alexa to set a timer on the outlet. Turning the outlet on and off for the required amount of time. Problem solved. When I get the circuit working I will post the results. My parts bin grew a little bit with this experience, not a bad thing.

 

I will build and test this prototype circuit to find out why it's not working.

In the post #17 schematic, the 4040 still is holding the 555 in a permanent Reset state.

ak

 

When Q12 is low it's not. When Q12 is high the timer is finished and everything stops until until the 4040 is reset, at which point the timer ( both the 555 and the AC outlet) starts timing again. I may have screwed up on the 4040 reset.

 

When the 4040 is reset with a high on pin 11 coming from the switch, that drives Q12 low. That drives the 555 Reset input low. The Reset input is active-low, so the 555 is held in reset by the 4040 and is not making clock pulses. Without clock 2048 clock pulses, Q12 cannot go high, so the circuit sits there locked up in a permanent reset state (all 4040 outputs low, no 555 activity).

ak

 

OK, thanks.

 

"Good enough is enemy of the best." An old engineering saying, Author unknown.

"Best is the enemy of good enough." An old real-world ( production / sales / marketing / finances ) saying.

ak