Automatic Shutdown Timer (ART373E)

The circuit shown in Figure 1 turns off a load after a time elapses from the moment its power is established. This period depends on the time constant of the RC circuit formed by the potentiometer P1, resistor R1 and the capacitor C1 which can have values of up to 2 200 uF.

Figure 1
Figure 1



At higher values, the circuit can reach timings longer than one hour.

Among the possible applications, we suggest systems of automatic shutdown or automatic timing activation of several devices.

The type of controlled load depends exclusively on the contact capacity of the relay used.

For applications where a battery is used as the power source, low power relays should be used.

The S1 pressure switch is optional as a reset and also to ensure that at the beginning we have a complete timing with the capacitor load from zero.

In Figure 2 we have a suggestion of a printed circuit board for the assembly of this timer.





This board provides the use of relays with DIL socket.

For higher current relays, the design of the board should be redone according to the arrangement of the terminals or even to be built outside the board.


CI-1 - 4093 - CMOS integrated circuit

Q1 - BC548 or equivalent - general purpose NPN transistor

D1 - 1N4148 - general purpose diode

R1 - 100 k ohm x 1/8 W - resistor - brown, black, yellow

R2 - 4.7 k ohm x 1/8 W - resistor - yellow, violet, red

P1 - 1 M ohm at 4.7 M ohm - potentiometer

C1 - 10 uF at 2 200 uF x 16 V - electrolytic capacitor

C2 - 100 uF x 16 V - electrolytic capacitor

K1 - 6 or 12 V x 50 mA or more sensitive - relay

S1 - Pressure switch - optional - see text



Printed circuit board, relay socket (optional), wires, welding, etc.