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A Timer For Ultra-Long Delays

Set It, and Forget It!

A Timer For Ultra-Long Delays
A Timer For Ultra-Long Delays
This microcontroller-based relay circuit is capable of activating devices remotely after a delay up to 255 years. The solution is ideal for applications such as triggering actions in a remote, rarely visited place.
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Materials

Component list

Component List

Resistors

All are 0.25 W unless otherwise specified

RC1 = 1.2 kΩ, 1 %

RC2 = 2.7 kΩ, 1 %

RC3, RCUP = 5.6 kΩ, 1 %

R1 = 220 Ω

R2 = 10 kΩ

R3 = 1.2 kΩ

R4 = 33 Ω, 0.5 W

R5 = 3.3 kΩ

 

Capacitors

C1, C2, C4 = 220 µF, 25 V

C3 = 100 nF, ceramic

 

Miscellaneous

U1 = PIC12F683

U2 = 78L05

Q1 = BC337

D1 = 5-mm green LED

D2 = 1N4148

D3 = LED

CMD, SET = 6-mm tactile switch

CONF = DIP Switch, 4-way

J1, J2 = Screw terminals

RL1 = Relay, 12-V coil

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