Hello all,
I think using a Micro would be of more use to me compared to a 555.
Since i think, i could have levels of precision also.
eg: (.01 sec to 1)
( 1 to 10 ) etc., by using switch arrangements.

The ideas given by Andy were very useful. I would definitely tryout with one.



Since the dispenser is being controlled by the solenoid, the air pressure is being adjusted to adjust the dispensing rate.
To make it clear, the dispensing rate can be adjusted by changing the Time or air pressure or changing the tip of the dispensing tube (or)with a combination of these three.

But, i would also like to see the functioning of a 555 for such an application and the precision that it gives.

So, i reworked on my circuit to make it error free.
The Timing components are:
1 meg ohm potentiometer and 10uF electrolytic cap (due to present non availability of mylar cap in my nearby, i have used electrolytic as a present option )
Then, i tested with an LED at o/p.
The following things happened:
1) Before trigger - LED is in OFF state
2) When trigger is applied in a state when the 1meg ohm timing potentiometer show zero resistance ( i.e.,before tuning it) - the LED glows constantly and comes to 'OFF' state only when the potentiometer is tuned to some value. else not.
3) Finally, for what ever value i select in the potentiomer(up to 1Meg ohm), the o/p state of the LED after triggering is, just one flicker. The LED is not experiencing any time delay to switch 'OFF'.

I would like to get few suggestions to overcome the problems i have mentioned in points 2 & 3.

Kndly use the Link below to see the circuit:

http://www.8052.com/users/Sur...ircuit.pdf


-suresh.