# Please Help -- "Power ON Delay Circuit Using 555."

Discussion in 'General Electronics Chat' started by famesethu, Nov 18, 2009.

1. ### famesethu Thread Starter New Member

Oct 25, 2009
12
0
Hey guys,

I need to make a Power ON Delay Circuit with variable delay from 1sec to 10sec using 555 and a pot(variable resistor).
That is when power is given to the circuit it must not produce an output until the delay time(say 1sec to 10sec).
Providing a schematic diagram with time delay equation will be sufficient.
Thank you.........
Its Very Urgent.........

Dec 19, 2007
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Mar 24, 2008
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4. ### famesethu Thread Starter New Member

Oct 25, 2009
12
0
Hey Bill,what's the value for the other Resistors and capacitors...?
In the T=1.1RC equation,R in ohms and C in farads or microfards.......?
i'm looking forward to your circuit......

5. ### Safiya.Jan New Member

Jun 18, 2017
2
1
What are the values of R1, C1, C2, R2?

MichaelT likes this.
6. ### Dodgydave AAC Fanatic!

Jun 22, 2012
8,106
1,399
He wants a delayed pulse, you need to change the transistor for a Pnp, that circuit will operate immediately...

7. ### Safiya.Jan New Member

Jun 18, 2017
2
1
I want the relay switch to operate another circuit which will switch on after a delay, would that still be the same case?

Jun 8, 2016
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9. ### Wendy Moderator

Mar 24, 2008
21,724
3,002
This is a standard monostablewhose trigger is the power on itself.The formula t.7Rt and=Ct applies. a 1Korm for the base resistor will likely suffice.R1=10K and C1=1uf

Wendy's Index

I have had stroke
This jusr means I am not as sharp as usual.

555 Monostable

Last edited: Jun 18, 2017
10. ### Wendy Moderator

Mar 24, 2008
21,724
3,002
Yes, The relay is to handle power

11. ### EM Fields Active Member

Jun 8, 2016
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154
That's just a semi-standard 555 one-shot and won't work as a POWER-ON delay:

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12. ### Wendy Moderator

Mar 24, 2008
21,724
3,002
But this is... *Wow this was started in the year2009

R1=10K, R2 =1K
Q1= 2N22222
C1=0.1uf

13. ### EM Fields Active Member

Jun 8, 2016
583
154
Regardless, pin 2 will be low when Vcc goes high, (t0) which will unconditionally drive pin 3 high immediately instead of delaying its rise for t0 + 1.1RtCt.