I blew my 555

Discussion in 'General Electronics Chat' started by R!f@@, Apr 19, 2011.

  1. R!f@@

    Thread Starter AAC Fanatic!

    Apr 2, 2009
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    [​IMG]

    I thought I would make a PWM to test the Cybex Tread board. That to give it the speed input signal. So searched and decided the to simulate the circuit.

    Since like for ever Multisim has been giving me timestep error, I dedicated quite a few investment on to finding out the reason and all paid off. it was the XP SP3 CD that I use created the run around. Any machine with SP3 wil give u a timestep error and will not simulate any Multisim circuit.

    Oh well !! that's solved, back to the circuit.
    I simulated the circuit in V11 and see the 555's pin3 connection to the fet.

    It was not like tht before, but when I hit "RUN" , the 555 model changes to the one u are seeing above.

    Is it telling me that I blew my Timer? :eek:
     
  2. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
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    Did it also come with the little puff of smoke? I had to deal with that with students in a lab. They all thought it was funny until they couldn't stop it from happening. Turns out the resistors they simulated with were marked at 0.25 W and they were simulating a circuit with 50 A.

    Are you exceeding the allowable current from the 555?
     
  3. R!f@@

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    Ooops ! My mistake it works..
    But as not intended....
    Needed to replace the 555 Model :D
     
    Last edited: Apr 19, 2011
  4. Wendy

    Moderator

    Mar 24, 2008
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    Well, duh! There was a piece missing! :D
     
  5. R!f@@

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    Apr 2, 2009
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    DUH!!

    Kekekekekk!!!

    I got the thing working as I wanted. The 500K VR value is critical. :eek:

    I can change the frequency from 1 Hz to 500Hz by simply switching the capacitor connected to the trigger...

    Hmmm!! I can make a test pulsing thingy like this ..NO !!
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Your threshold and trigger should be connected together in the 1st circuit you posted. There is a junction missing.
     
  7. R!f@@

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    Apr 2, 2009
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    Ya....I figured that out a bit later..:D
     
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