On/Off Timer

If you need an adjustable ‘on’ or ‘off’ time for some application, then this is the circuit you have been looking for. A problem that often occurs when adjusting timers is that the individual times affect each other. This circuit completely solves this problem because the time defining elements — both R and C — are switched over. That means that there is an RC pair (P1 + R3 and C1) for the ‘off’ time and another pair (P2 + R4 and C2) for the ‘on’ time.

Resistors:
R1 = 4MOhm 7
R2 = 100kOhm 
R3,R4 = 10kOhm 
P1,P2 = 1MOhm preset
Capacitors:
C1,C2,C4 = 100nF
C3 = 100pF
C5 = 10µ F 25V radial
Miscellaneous:
D1 = 1N4001
T1 = BC517 (Darlington)
IC1 = 4053
IC2 = 4060
Re1 = E-card relay, 12V coil, V23057 B0002 A201 (Schrack)