LED on 1sec after power supplied to it

Thread Starter

Faris1985

Joined Nov 29, 2011
7
I want to turn on an LED 1 sec after power is supplied to it and the LED should then be on until power is disconnected. Pls provide the schematics if possible
 

thatoneguy

Joined Feb 19, 2009
6,359
I abhor relays.

I'm thinking an RC setup on the base of the driving transistor, which will be +/- 10% on accuracy, but very simple.
 

wayneh

Joined Sep 9, 2010
16,114
I think this is more-or-less what was suggested above. I have NOT done the math on the timing, the cap and resistors, I just took a wild guess.
 

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Wendy

Joined Mar 24, 2008
21,906
With those base resistor values I doubt it will get close. In the end the transistor needs to be in saturation.

I don't know if the OP is wanting fading or not, which is the circuit I pointed to. If just a delay a 555 or other Schmitt Trigger is probably the ways to go, as it addresses the fundamental gain issue.
 
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