connecting mono 555 to astable 555

[dt]

Hey there,

I am trying to connect a 555 mono to a 555 astable, this is the easy part, the problem is that when the circuit is switched on the astable instantly starts, this is not desirable i only want the astable to start once the mono has been triggered

See attachment for current state of affairs.


Any suggestions?????

 

[Russlk]

The reason that the astable starts immediatly is that the mono output is low until the start button is pushed. The astable will stop when the mono starts timing, probably the opposite of what you want. If you use the mono output to supply the positive supply to the astable, it should work as you expect.

 

[mstechca]

If the RESET pin of a 555 (pin 4) is set to high, that timer is active. If the RESET pin is low, it wont work.

Make it so that the RESET pin of your astable is low until the button is pressed.

If the output of the monostable 555 is low when the button is pressed, then add an inverter between the mono's output and the astable's reset pin.