simple circuit ??

Discussion in 'General Electronics Chat' started by musomaniac, Jan 10, 2012.

  1. musomaniac

    Thread Starter New Member

    Jan 7, 2012
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    hi guys , i've just built this circuit , with a touch sensor , so when you put your finger on the sensor the led flashes , when you press harder the led flashes faster .
    Could any of you guys explain to me why ? And how this circuit actually works . Sorry if i'm being a pain , i have numerous books as i explained in my opening post , and i understand to a degree what each component does , apart from the ic , but if i could get a kickstart with an explanation i could go from there .



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  2. musomaniac

    Thread Starter New Member

    Jan 7, 2012
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  3. BillB3857

    Senior Member

    Feb 28, 2009
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    Look up 555 astable. It will explain it all. Do you have any initial thoughts as to what is going on? Digging for info is a great way to learn.
     
  4. musomaniac

    Thread Starter New Member

    Jan 7, 2012
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    as far as i can gather at the moment bill is , R2 is lowering the current for the LED , R1 and the resistance of your finger across the touch sensor control timing and duration of LED flashes ( but i don't know why !!) C1 controls timing and duration of flashes (but again i dont know why) and the 555 sends pulses of current to the LED
     
  5. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    The answer is given on page 4 of the attached document in the section entitled Astable Operation. Most other questions about the 555 are also answered in this document.

    The 555 is probably the most versatile IC ever built. As such, its basic operation is relatively simple, but the different ways it can be connected and used are many.
     
  6. musomaniac

    Thread Starter New Member

    Jan 7, 2012
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    ok tracecom many thanks for the help
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Radio Shack sensor kit?
     
  8. musomaniac

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    Jan 7, 2012
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    haha right on the button thatoneguy , hope its ok is it ? the only problem is that the book doesn't explain how the circuits work in any detail
     
  9. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Yeah, a kid I know has one, it looked familiar. I think they should at least try to explain what is happening in the circuits, otherwise it's not so much educational as putting circuits together.
     
  10. musomaniac

    Thread Starter New Member

    Jan 7, 2012
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    yeah thats what i thought too , i've spent the rest of the day trying to figure out how it works !!
     
  11. musomaniac

    Thread Starter New Member

    Jan 7, 2012
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    is the touch sensor in the circuit diagram a Force Sensistive Resistor ??
     
  12. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    No, it's just copper pads spaced closely together, but not connected, there's sort of a picture of how it looks in the schematic posted above.
     
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