555 circuit double-check

Discussion in 'General Electronics Chat' started by Georacer, Jul 16, 2010.

  1. Georacer

    Thread Starter Moderator

    Nov 25, 2009
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    I found this circuit posted by Bill_Marsden in a thread over at Homework Help section, thread name "pleaseee helppppppp" (very imaginative title).
    [​IMG]

    I tried to build it just for fun but it seems to give a constant low on the output, lighting only the red switch, no matter how desperately I push the pushbutton. Could someone try to test this circuit, just to find out if it's me or the design that's problematic.

    P.S. I ran the circuit on 5V Vcc and used the NE555N

    Thanks for your time.
     
    Last edited: Jul 16, 2010
  2. Wendy

    Moderator

    Mar 24, 2008
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    I'm in the process of running experiments on it (as I just finished the ebook article today).

    One thing you can try is connect pin 2 to Vcc, the output will be low and stay there. Then connect pin 2 to ground, the output will go high and stay there.

    ************************

    OK, just breadboarded it using this layout...

    [​IMG]

    It works over the entire power supply range, 4.5V to 15V. The red wire is a 2" (500cm) wire folded in half. It substitutes for a push button.

    I had a moment I doubted it though, it appears one of the kids spilled something (milk for cereal?) on the bread board. I had to work the connections to get them to make reliably.
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    Last edited: Jul 17, 2010
  3. Georacer

    Thread Starter Moderator

    Nov 25, 2009
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    I thought it was me... Thanks for your trouble!
    Back to the lab then...
     
  4. Georacer

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    Nov 25, 2009
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    Yes, it works now. I guess I 'll never find out what i did wrong. I have a question though. When I push the button very fast, the LED's don't flip. Could it be that the capacitor doesn't have time to charge? That means that there's a maximum frequency of operation. I also can't understand why this ciruit doesn't work without the capacitor? Shouldn't the Vout from pin 3 reach pin 2 through the resistance? I also noticed that if we override the resistance between pin 3 and the switch we experience a lot of bounce wich I guess is the reason you inserted the RC circuit.
     
    Last edited: Jul 17, 2010
  5. Wendy

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  6. Georacer

    Thread Starter Moderator

    Nov 25, 2009
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    Sure, I 'd like to help! Where should I post my thoughts? Here or over at your submission?
     
  7. Wendy

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    Mar 24, 2008
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    On the submission. I seem to work differently than the other guys, I prefer to write in public, sometimes we have a had a few go off and start ranting (hello, did I leave the bathroom door open... again?) but mostly it is positive.

    If I mis-spoke myself or got something flat wrong it allows it to be corrected before it winds up in the book. I'm also always looking for new and interesting ideas, thought the circuit does not have to be original.
     
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