bit urgent please -timer doesnt reset its time

[sush]

retrigerable 555 timer

was trying to weork with 555 Timer. I tried this example given in Proteus. The circuit is working fine. The timer run for 5.167seconds each time i press the push button. But One probelm i get is let's say the timer is running and the time passed is 2 seconds at that time the timer dosent resets its time it runs for total of 5.167 seconds But i want it should run for 2+5.167 = 7.167 seconds. What changes do i need to make in the circuit.
This circuit is given under "C:\Program Files\Labcenter Electronics\Proteus 7 Professional\SAMPLES\Interactive Simulation\Counter Timer\Timer Mode.dsn"

else i have given the pic also.



It's bit urgent please.

 

[sau_sol]

advantage of ic74121 over 555timer

please post the circuit for making the changes or you are asking for a new circuit?

 

[sush]

555 retrigable

sorry. Now i have attache the pic & the file link in proteus.

I tried removing Pin 4 from +5v & now i have connected pin4 & pin2 together. Now when i press the button it''s working fine, but the system waits for the key to be released can this be removed (the key release wait)

 

[ravimarcus]

Re: bit urgent please

sorry. Now i have attache the pic & the file link in proteus.

I tried removing Pin 4 from +5v & now i have connected pin4 & pin2 together. Now when i press the button it''s working fine, but the system waits for the key to be released can this be removed (the key release wait)

Use this for switch interface. There will be only one pulse and for the next one, you have to release the key and press again.

Cheers

Ravi

 

[Js_Ong]

Re: bit urgent please

Hi Sush,

You are now using 555 timer as a monostable multivabrator, as I know 555 timer is can not be use for retrigable, means you have 5.167 seconds delay once push button is pressed, but within 5.167 seconds if any signal is given, 555 will not give you futher delay, it will stop at 5.167 seconds anyway. You already had the correct connection and had the correct output. If you are looking for 2+5.167 = 7.167 seconds, you need a retrigerable monostable multivabrator. Please look for IC74121.