CircuitDB | 3 seconds to 2 minutes timer

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3 seconds to 2 minutes timer

Description

This timer makes a LED be on for a certain amount of time after pressing the switch.
This time is adjustable from 3 seconds to 2 minutes using the potmeter.
Instead of a LED other load can be connected to this circuit, a relay for instance.

TinyCAD file of this circuit

Partlist

R1 = 100 Ω
R2, R3 = 10 kΩ
R4 = 500 kΩ potmeter
C1 = 220 湩/16 V
D1 = LED
T1, T2 = BC 547B
S1 = Switch, normally open

Files

timer.dsn

Posted by Jospfh at Apr 22 2008 8:33

Comments

Jun 5 2008 6:23

guardianzx9

Would it be possible to modify this circuit to close the relay(light led) for 3 seconds upon connecting to 12v
and then close the relay again for 3 seconds upon removal of 12v?

Thanks

Jun 6 2008 7:55

StickManWitBallz

I keep looking at the placement of the switch! This really makes no sense to me! Even without the switch the way you have it as soon as it is connected to a power source it will begin to power the transistors before anyone even thinks about pushing the switch! Then when the switch is even pressed it will create a dead Short! I believe by adding the switch before the component labeled R4 you will have a working timer!
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