Trigger 555 on power up

[grrr_arrghh]

hi.

I'm sure I know the answer to this, but I can't for the life of me think what it is. SO. If you have (as shown below) 2 555s as a monostable and astable, where the astable only pulses for the duration that the monostable's output is high, how do you trigger the monostable on power-up? It must not stay on, and it must not be triggered again, until the whole thing is turned off and on again.

Cheers,

Tim

Edit: Ignore the component values, I will work them out at a later date.

 

[k7elp60]

Put a capacitor in parallel with switch SW1. I would try a 1uf electrolytic with the + on the trigger pin and the negative to ground. The 555 will trigger on power up and each time SW1 is pressed.

 

[grrr_arrghh]

ah, yes, thankyou very much.

Tim