Here you go. Change R1 to 18k for 1.98 seconds (give or take for component tolerances.)

Hello

I made the circuit by this scheme.
It works fine but I have one problem.
I need a very long time, 2.5 hours. So R1 and C1 are very large, 1.8M R1 and 4700 uF. I know it's a lot over 555 documentation but it's okay, it works 2.5 hours + - 5 min and that's okay.
My problem is that my application when it comes to these 2.5 hours should work right away if I turn off the power and turn it on again. However, C1 probably has no discharge to the end so when I want to turn on the device I have to turn off the power, wait 10 to 15 seconds and then turn it on.
Is there a solution?

 

MOD, Created new Thread.

 

One sure way is to put a reset button across the timing capacitor.
You can also try a diode from the capacitor to Vcc (cathode to Vcc).
Which 555-timer are you using? What is the full part number on the IC?