hi i can use any supply voltage so long as it will triger a optoisolator i would like to use 9v from a AA battery pack but could go to 12v if needed
the idea is to trigger a TIP120 transistor via the optoisolator
the timing delay i was hoping to use a pottentiometer maybe two one caurse one fine ajustment
i have had a quick look at some 555 circuites on the net and this great site but canot find any with millisecond delay
It has a range a bit wider than you specified, but that's necessary due to tolerances in resistors/capacitors.
I didn't show caps across the Vcc/GND terminals of the 555 timer; but you need an 0.1uF/100nF ceramic or poly metal film and a 1uF or larger aluminum electrolytic.
many thanks sgtwookie for your time and help i will give that a go tommorow on some breadboard
one thing i forgot to say was that it will be trigered by a microphone so a single pulse for a millisecond or so when it hears a bang
then wait the pre set time and fire a 12v dc solenoid via the tip120 transistor it would be nice too for it to only fire once untill a reset button is pressed, the mic will have a simple pre amp so the threshold can be ajusted
Oh, silly me - I thought you wanted an astable instead of a monostable. That's a different circuit, but it'll have similarities. I really don't know why I posted an astable configuration.
Do you have the preamp for the mic built already, and is it working?
i hope to make somthink that will hear the sound of a bang wait the elapsed time of the set duration in milliseconds, then fire a 12v solenoid once via a TIP120 transistor
and not fire again till re-armed and a bang is heared again to start the process off again
Just so you know; that project uses a 741 opamp which has rather poor performance and requires at least 9v to operate. You would be much better off using almost any other voltage-feedback opamp.
hi sgtwookie yes i managed to see the 741 from the pic on the supliers website,
i dont mind that it is crude and requires 9+ volts as i have 12v available from the battery pack i am going to use on the solenoid,
it does not matter as i am only looking to get a response from a microphone detecting a bang from a droped item etc so no real audio application is required,
i was hoping that someone may have a simple circuit etc as i was looking at having to use a arduino micro to do what i wanted , but did not want all the addition of the periferals to run the arduino crystals etc etc
i was hoping for same simple 2 or three chips and some capacitors resistors etc