A Bedside Lamp Timer Circuit Schematic

30 minutes operation, Blinking LED signals 6 last minutes before turn-off

The purpose of this circuit is to power a lamp or other appliance
for a given time (30 minutes in this case), and then to turn it off. It
is useful when reading at bed by night, turning off the bedside lamp
automatically in case the reader falls asleep… After turn-on by P1
pushbutton, the LED illuminates for around 25
minutes, but then it starts to blink for two minutes, stops blinking for
two minutes and blinks for another two just before switching the lamp
off, thus signaling that the on-time is ending. If the user want to
prolong the reading, he/she can earn another half-hour of light by
pushing on P1. Turning-off the lamp at user’s ease is obtained by
pushing on P2.

A Bedside Lamp Timer Circuit

A Bedside Lamp Timer Circuit Diagram

Parts:

Resistors
R1 = 1K
R2 = 4K7
R3 = 10M
R4 = 1M
R5 = 10K

Capacitors
C1 = 470µF-25V
C2-C4100nF-63V

Semiconductors
C1 = 470µF-25V
C2-C4 = 100nF-63V
D1-D4 = 1N4002
D5 = 5mm. Red LED
IC1 = CD4012
IC2 = CD4060
Q1 = BC328
Q2 = BC547

Miscellaneous
P1,P2 = SPST Pushbuttons
T1 = 9+9 Volt Secondary 1VA Mains transformer
RL1 = 10.5V 470 Ohm Relay with SPDT 2A 220V switch
PL1 = Male Mains plug
SK1 = Female Mains socket

Circuit operation:

Q1 and Q2 form an ALL-ON ALLOFF
circuit that in the off state draws no significant current. P1 starts
the circuit, the relay is turned on and the two ICs are powered. The
lamp is powered by the relay switch, and IC2 is reset with a positive
voltage at pin 12. IC2 starts oscillating at a frequency set by R4 and
C4. With the values shown, pin 3 goes high after around 30 minutes,
turning off the circuit via C3. During the c6 minutes preceding
turn-off.

The LED does a blinking action by
connections of IC1 to pins 1, 2 & 15 of IC2. Blinking frequency is
provided by IC2 oscillator at pin 9. The two gates of IC1 are wired in
parallel to source more current. If required, a piezo sounder can be
connected to pins 1 & 14 of IC1. Obviously, timings can be varied
changing C4 and/or R4 values.

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