Component List

The values shown will switch the relay with a very short turn on delay

(values given in brackets will produce a turn on delay of about 4 s).

Resistors:

R1 = 47 Ω, 2.5 W, Fusible resistor VSW 2.5-47

R2, R3 = 1 MΩ

R4 = 1 kΩ

R5 = 0 Ω or wire link (47 kΩ)

R6, R7 = 33 kΩ

Capacitors:

C1 = 0.022 µF, 250 VAC, X1/X2 (optional, see text)

C2 = 0.15 µF, 250 VAC, X1/X2, for 12 V relay with 360 Ω coil

C2 = 0.068 µF, 250 VAC, X1/X2, for 24 V relay with 1440 Ω coil

C3 = 0.022 µF, 250 VAC, X1/X2

C4 = 100 µF, 25 V (12 V relay)

C4 = 100 µF, 35 V (24 V relay)

C5 = 1 µF, 63 V (100 µF, 25 V for 12 V-Relay, 100 µF, 35 V for 24 V relay)

Semiconductors:

D1 = Zener diode rated at 15 V for 12 V relay, 30 V for 24 V relay

D2 = not fitted (1N4148)

D3 = Zener diode rated at 11 V for 12 V relay, 22 V for 24 V relay (8.2 V for 12 V relay, 16 V for 24 V relay)

D4 = 1N4148

Br1 = Bridge rectifier 1 A, >200 V, e.g. W06G

T1 = BC327

T2 = BC337

Miscellaneous:

Re1 = Relay 12 V (360 Ω coil), e.g. Schrack RT314012

Re1 = Relay 24 V (1440 Ω coil), e.g. Schrack RT314024

K1 = 2-way 7.5 mm pitch terminal block

K2 = 3-way 7.5 mm pitch terminal block