shaiqbashir Posted July 13, 2006 Report Share Posted July 13, 2006 Hi guys!well! im using 555 IC as a monostable multivibrator. What im using values are R=690kohmsC=10ufand i have connected trigger pin i.e. pin2 to the ground. Now i think when the circuit will be on, the pin3 should give me a pulse of width around 5-7 sec and then the output on pin3 should become low. BUt here is what im getting:I get a constant output of around 5V as my Vcc is 5V. and when i connect my trigger pin to Vcc, the output becomes 0, when i connect it to GND, the output becomes 5V. But the thing is that output on pin3 doesnot get low after even a minute. WHat is this problem??PLease help me as soon as possible!i shall be thankful to u for this act of kindness!Good Bye! Quote Link to comment Share on other sites More sharing options...
audioguru Posted July 13, 2006 Report Share Posted July 13, 2006 Hi Shaiq,The datasheet tells how to use a 555.If the trigger pin is held low then the timing cycle will never end. Quote Link to comment Share on other sites More sharing options...
shaiqbashir Posted July 13, 2006 Author Report Share Posted July 13, 2006 Thank u very much audioguru!i got it now. Hope my monostable will work now!thanks once again! Quote Link to comment Share on other sites More sharing options...
audioguru Posted July 13, 2006 Report Share Posted July 13, 2006 Hi Shaiq,If the trigger goes to ground for a time period that is too long then add a 10k resistor from pin 2 to the positive supply and a coupling capacitor from the trigger source. Then it makes a short negative pulse no matter how long the trigger source is grounded. Quote Link to comment Share on other sites More sharing options...
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