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555 Timer LED

  1. May 1, 2009 #1
    I'm not sure if this is the right forum to put this in and I never took photos of something to put on the internet but I can't get this circuit to work and I need help. The LED is normally on. When I press the switch the LED should blink, slow down until its original condition. Maybe this should go in the homework forum. I never did this before. I don't have the switch right now but i'm using two wires instead. Will it not work without the switch?

    http://img21.imageshack.us/img21/8325/1007495.th.jpg [Broken]
    http://img510.imageshack.us/img510/7609/circuit.th.jpg [Broken]
    http://img21.imageshack.us/img21/3797/1007494.th.jpg [Broken]
    http://img21.imageshack.us/img21/4036/1007493m.th.jpg [Broken]
    http://img21.imageshack.us/img21/1492/1007492k.th.jpg [Broken]
    http://img21.imageshack.us/img21/2503/1007491.th.jpg [Broken]
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. May 1, 2009 #2

    vk6kro

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    You have posted about 15 MB of pictures. It is much better to reduce these pictures to less than 100 KB each before posting them. They have to be clear on the screen but not high resolution.

    The circuit looks OK but I haven't checked your wiring. You need to do this yourself.

    The output frequency might be a bit fast if you are hoping to see the light flash. A program I fed it into said the frequency would be about 10 Hz. This might be a bit too fast to see.
    If it is lit but not obviously flashing, it may be flashing too fast to see.

    Try making the capacitor on pin 6 a 0.47 uF if this is the case. That should give about 2 flashes a second.

    What are you seeing? Is it doing anything? Do you have a multimeter or a CRO?

    No, the switch doesn't matter as long as your wires are twisted together.
    It won't change its flash rate though, except a brief moment when the 22uF charges up but this would be very fast.
     
    Last edited: May 1, 2009
  4. May 1, 2009 #3
    Your circuit looks nearly identical to fig. 1 in :
    www.northcountryradio.com/PDFs/column009.pdf[/URL]
     
    Last edited by a moderator: Apr 24, 2017
  5. May 1, 2009 #4

    vk6kro

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    Yes, the circuit is pretty standard, but those chips are the CMOS version.

    This OP is using a standard 555 with some pretty big resistors. The CMOS chips have lower leakage values and hence can use higher value resistors. I haven't got a data sheet handy, but I suspect he might be pushing his luck with 470 K's on a normal 555.
     
  6. May 1, 2009 #5
    Thanks. I'll try putting in the .47 uF Cap. I'll also reduce the size of the pics. Should I reduce them here or just in the future?
     
  7. May 1, 2009 #6
    The LED goes on and when I connect the two wires where the switch would be the LED dims slightly. I put in a .47 Capacitor and I still had the same outcome.
     
  8. May 1, 2009 #7

    vk6kro

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    Just for the future. Nobody wants to download big pictures if they don't need to.

    You need to just follow the wires and make sure they go where they are supposed to go.

    If you still have trouble, measure the voltage at each pin of the 555 and post those voltage readings.

    If you have a spare 555, or better, a CMOS 555, you could try that as well.
     
  9. May 2, 2009 #8
    I am using a 6 volt battery and I got these voltage readings.
    Pin 1: 0V
    Pin 2: 1.9V
    Pin 3: 5V
    Pin 4: 6.4V
    Pin 5: 4.3V
    Pin 6: .1V
    Pin 7: .1V
    Pin 8: 6.4V
     
  10. May 2, 2009 #9

    vk6kro

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    .

    Pin 6 and pin 2 should be the same since they are joined together.

    Better check your wiring.
     
  11. May 2, 2009 #10
    *Fix*
    Pin 1: 0V
    Pin 2: .1V
    Pin 3: 5V
    Pin 4: 6.4V
    Pin 5: 4.3V
    Pin 6: .1V
    Pin 7: .1V
    Pin 8: 6.4V
     
  12. May 2, 2009 #11

    vk6kro

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    Is it working now?
     
  13. May 2, 2009 #12
    No It isn't
     
  14. May 2, 2009 #13

    vk6kro

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    Is the LED lighting up at all?
     
  15. May 2, 2009 #14
    Same as this
     
  16. May 2, 2009 #15

    vk6kro

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    OK.

    Just looking at your picture, it looks like the 470 Ks are really 470 ohms. Is that right?
    Can you measure them?


    BTW where are you?
     
  17. May 2, 2009 #16
    just shoot me. OMG. I can't believe I missed that. I was looking for something harder. I had the circuit on top of a cd case. Is that what you meant by where are you?
     
  18. May 2, 2009 #17
    470 K would be yellow, violet, yellow wouldn't it.
     
  19. May 2, 2009 #18

    vk6kro

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    What part of the world are you in? What country? What city?


    470 K would be yellow, violet, yellow wouldn't it...........YES
     
  20. May 2, 2009 #19
    North Bellmore, NY
     
  21. May 2, 2009 #20
    You live in Australia? I see it in your profile. cool
     
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