How to put Delay feature in 555 Timer circuit

[debasisswan]

Hi,
I was looking for a simple sound or light operated switch to trigger my camera flash (For stop action photography) with certain delay between triggering sound or light impulse and final switching- in the range of around 50ms to 500 ms. I found the attached circuit to be simple enough but it cannot provide me time delay between the triggering sound and final switching.

With my limited understating of electronics, I am planning to achieve this delay with certain modification in this circuit. please guide me in this. My idea is- first ii need to keep the pulse width of the 55 very long by rearranging the values of C2 and R3. Next, I will have to make a series of variable resistor (Say R8) and capacitor(say C4). Connect the open resistor end of the series at the point in between R2 and OK1 while connecting the other open capacitor end of the series to ground.

Please guide me- am I correct in my though5t process? if yes, what could be the suggested values for R2, C3, and R8, C4 (the resistor and capacitor to be used in the new series).

Thanks in advance-
Regards-
Debasisswan

 

[BradtheRad]

From what you describe you need two stages of timers.

1: delay after initial sound begins (or ends?)

2: 'on' time for activating equipment

It may be easiest to use a second 555 IC. There's the 556 which contains two 555 in one package.

Otherwise if you are willing to experiment, you can use a simple RC combination and find the correct values to achieve the time you want.

If I follow you correctly you want to isolate it from pin 3 (output of 555), by putting in a diode. Then your RC combination downstream can work as a time delay on its own?

A good value to start with a resistor is 1000 ohms. Maybe 10k. Low ohms tends to go with high current, which may not be available. Megohms goes with tiny current, which can be drained away by a leaky capacitor, or nearby components.

---------- Post added at 17:09 ---------- Previous post was at 16:53 ----------

This simple circuit can be used to extend the 'on' time after receiving a positive pulse.

 

[allenf]

try downloding
Electronics 2000 - Hobby Electronics - Software, Calculators, Technical Data, Pin-outs, Beginners Guide, Forum, Links...

That will help you imensly in what you are trying to do which if I`m reading right is delay a monostable vibrator trigger time

 

[jbike]

See **broken link removed** the "2 stage time delay circuit" for the basis of a timer I would use in your application, where you need to set an accurate delay time for catching water drops.

 

[hasan_fneish]

see this maybe it will help https://www.electronics-project-design.com/timedelaycircuit.html