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Problem with 555 timer

Discussion in 'General Electronics Discussion' started by electrowhiz, Apr 9, 2017.

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  1. electrowhiz


    Apr 9, 2017
    I planned to operate 555 timer in monostable mode. I gave the connections correctly.
    Pin 8:Vcc
    pin1: gnd
    pin 5: 0.1 nf cap to gnd
    pin 8 to 7:47kohm
    pin 7 to 6:just a wire
    pin 6 to gnd: 100 microfarad
    pin 2 to Vcc through a resistor.
    pin4: to Vcc
    toggle switch is used to alter between gnd and Vcc for triggering the pin2
    pin 3 to gnd: resistor in series with led.
    when i gave a trigger, the led started to glow continuously. Why this happens? actually i set it to operate only for 5s.
    The Led turned off only when the supply is removed.What should i do to rectify this problem
  2. AnalogKid


    Jun 10, 2015
    First, since you are a whiz, post a schematic. Be sure to have a reference designator for each component so we can discuss them clearly.

  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Discharging the 100uF capacitor through the discharge pin could easily kill the transistor. Check you don't have continuity between pin 1 and 7 now.
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