Delay relay triggered by switch turning off
Here's one example.



On power-up R6 &amp; C3 ensure relay is switched off.

Sensor switch closes, relay energises and timer is held in reset.

At end of shower sensor switch opens, timer is enabled and starts to run.

At end of timing period, timer output goes high and relay is switched off.

Timer can be reset even when it's running by sensor switch closing.

Timing period is set by combination of the values of C2, R4, VR1 and also which of the outputs of the 4060 is selected.

I haven't selected the timing component values or output for any particular timing period. They would need to be calculated.

EDIT

Hi Damian,

This afternoon I have built and tested the above circuit and found it to work very well.

I have measured the run-on delays for three different IC2 outputs, with the timing components shown (VR1, C2, R4). The results are as follows.

IC2, pin 13 : 3s to 30s

IC2, pin 15 : 6s to 60s

IC2, pin 1 : 24s to 240s

EDIT

Added supply filtering.