OP

Quoted from Schwaggs:

Alright DIY'er, I finally got around to writing up the schematic and scanning it in. Sorry it took so long...
Basic operation is:
The open flipper button does not provide a path to ground for the opto LED. While the opto LED is off, the opto coupled transistor does not conduct which acts like a very high resistor. This allows C1 to slowly charge through R2. As it charges, the Gate voltage of Q1 rises to the point of saturation in about 30 seconds, turning the LED backlight on.
When the flipper button is pressed, the opto LED is lit up, the opto transistor conducts. The transistor in the opto acts like a short to ground, rapidly discharging C1 to near zero volts turning off Q1.
Hope this helps!

On-Delay Circuit.jpg 108 KB