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Way to check whether ne555 timer is working?

  1. Jan 28, 2012 #1
    is there any way to check whether ne555 timer is working?i got a project in my coll about seismic sensor and this is the circuit diagram http://1.bp.blogspot.com/_a-VJV2rj-08/TE3BFy92lAI/AAAAAAAAAFs/8Ugz6gINKJw/s1600/Untitled.png.
    when i soldered everythin perfectly,and a supply is give to it,the voltage is not getting transferred to the pins 1,2and 3 when i check them by using multimeter.do i have to set any offset voltage initially before using that in a circuit?if it is so please explain.....
  2. jcsd
  3. Jan 28, 2012 #2


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    Re: ne555

    You need to check that when you hit the seismic sensor, there is a voltage change on pin 6 of IC1 and then (if there is) check the voltage at the transistor end of R5.

    This really needs to be done with an oscilloscope.

    If these are OK, then notice that the timing circuit (R7 and C5) is set for about 100 seconds and it will also be very easily upset by leakage in C5 because R7 is so large.

    So, C5 needs to be a Tantalum type although tantalum 100 uF capacitors are probably expensive. You could get a 10 uF one to try out the circuit.

    Don't do any of this unless you have the input pulses working properly as described above.
  4. Jan 29, 2012 #3

    jim hardy

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    Re: ne555

    that's good advice from Vk6,,, (as always)

    you might briefly jumper on the 555 pins 2 and 6 (or the respective ends of R7 and R10)

    that should make it try to run in astable mode at about 1 hz

    and give you some flashes on the red LED.

    """voltage is not getting transferred to the pins 1,2and 3 """
    where exactly are you placing the + amd - meter leads?
    pin2 ought to be solid +9 volts.
    double check you pinout - good picture here

    """is there any way to check whether ne555 timer is working?"""
    have you studied the description of operation?
    Pins 2 and 6 control pin 3...

    last thing i see is, no power supply bypass capacitor.
    were it mine i'd replace R6 with a short piece of wire so C3 can stabilize the supply.
    555 takes a big gulp of current when his output switches and can upset a meek power supply.
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