| ??? 02/05/06 02:15 Read: times |
#109215 - Blown Discharge PIN Responding to: ???'s previous message |
Suresh R said:
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'. but obviously. you should have read data sheet before like every one saying here. PIN 7 is the open collector of the discharge transistor. Even though datasheets says no current limiting is required,i doubt you can connect pin 7 directly to Vcc(when your pot shows zero ohms). Use a Series 1k resistor as Kai suggested. because when ever voltage goes over the threshhold voltage PIN 7 almost shorts to ground. Whats probably happenning here is when Your pot is shorted to Vcc and you trigger the monostable output goes High momentarily and as PIN 6 is already at VCC it will turn off. when you increase the resistance letting the capacitor to charge at some rate decided by the R and C voltage AT the pin 6 takes little time to reach threshhold voltage and thats the time you acheive. finally no time delay is the sign that Steave is right you might have your discharge transitor blown off so that capacitor is always charged and no timedelay. Replace the beast. Abhishek |
