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simple circuit won't work..

Discussion in 'General Electronics Discussion' started by CiaranM, Sep 30, 2012.

  1. CiaranM

    CiaranM

    74
    1
    May 19, 2012
    hello. I tried to make a joule thief, but it doesn't work. I've made one before which worked, so I see no reason why this one shouldn't. The picture's a bit blurred, so I'll say what I did...
    - connected LED across collector and emitter, with cathode at emitter.
    - connected resistor to base
    - connected left side black wire to the resistor (not to base terminal)
    - connected right side red wire to collector
    - connected -V to emitter
    - connected left side red wire and right side black wire to +V
    - I tested the LED on a battery and it worked
    - I tested the joule thief battery on the previous joule thief I made, and the LED lit up
    - I changed the transistor
    - I changed the resistor from 1k to 470

    Why won't the circuit work?!
     

    Attached Files:

    Last edited: Sep 30, 2012
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    The picture is too fuzzy.

    Do you have a circuit diagram?

    We need both the circuit diagram and a sharp image so we stand a chance of seeing what you did wrong. Presumably the circuit is OK -- based on your statement about building a working version previously (was it from the same circuit diagram?)
     
  3. donkey

    donkey

    1,286
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    Feb 26, 2011
    picture is fuzzy and I can't tell what your power source is.
    I can't tell if you have pushed the components all the way in.
    I can't tell if you have mistaken the breadboard pin layout.
    better picture and a schematic will be good.
     
  4. CiaranM

    CiaranM

    74
    1
    May 19, 2012
    I assumed everyone here would know the schematic.. but here it is, anyway
    http://www.kobakant.at/DIY/?p=172
    I'm afraid I couldn't take a better quality picture. Damn camera.
    everything is pushed in properly, plus I tried a different board, still no result.
    Is the toroid winding critical to circuit operation?

    -- I was trying a 'dead' 1.5V cell.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,214
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    There are many circuits for these devices.

    In your case, I would suggest swapping around the leads for one of the windings (but not both).

    This is probably the easiest mistake to make, and it is a 50/50 chance unless you're *really* paying attention (whereupon it becomes a 100% chance :D)

    edit: This assumes you have 2 windings as shown in the circuit diagram, not a tapped winding as shown in the images on the same page.
     
    Last edited: Sep 30, 2012
  6. CiaranM

    CiaranM

    74
    1
    May 19, 2012
    what does 'tapped' actually mean?
    hmm, I tried swapping wires.. no luck. I think I'll return to building oscillators and things. despite being much more complex, they somehow work better than this..? ah electronics is weird
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Tapped means you wind the coil so far, take a loop of wire to be a contact, then keep winding. You have three connections to the coil, one at each end, and a tap somewhere between them.

    The other way to make a coil like this is to wind to separate windings, joining two of them together at some point. If you join them the right way, you get something functionally the same as the above. If you connect them the wrong way you get something different that won't work.
     
  8. MrEE

    MrEE

    84
    0
    Apr 13, 2012
    I see another toroid in the background. I presume that one is not connected. Check transistor pinout against a datasheet. Sometimes the base is on the side and sometimes in the middle. If you used a 2N3904 like in the link you sent, then the pinout is EBC (looking with the flat side towards you). Also a hint for taking a better close up picture:
    1- use a macro function if your camera has it.
    2- set to your highest available pixes (common ones are 5 Mpix, 8 Mpix etc.) Take a picture from a distance that gives you a decent focus. Then use a simple photo editor that lets you crop the picture.
     
    Last edited: Oct 1, 2012
  9. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
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    May 8, 2012
    Actually, this is an oscillator. Similar to an Armstrong design.

    Chris
     
  10. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    I don't see any "turns" data in your post or in the link you posted.

    Chris
     
  11. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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  12. CiaranM

    CiaranM

    74
    1
    May 19, 2012
    ahh, so that's what 'tapped' means. so, if you're tapping a primary transformer winding for example, you would merely strip off a bit of insulation somewhere for the tap?
    thanks for the advice MrEE.

    and yeah.. I kinda forgot that the joule thief is essentially an oscillator..

    I gave up on the joule thief and I learned how to use NPN transistors for combinational logic. I looked online at a NOT circuit with a transistor, and I figured out some others.
    If you're interested, I will be happy to provide a schematic for any of the following:
    (All use NPN transistors)
    - NOT
    - AND
    - OR
    - NOR [OR > NOT]
    - NOR [NOT > AND]
    - NOR [dual path > OR]
    - NAND [dual path > AND]
    - NAND [NOT > OR]
    - NOT LED-switcher
     
    Last edited: Sep 30, 2012
  13. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    If there's a connection it escapes me.

    Chris
     
  14. CiaranM

    CiaranM

    74
    1
    May 19, 2012
    there's not supposed to be a connection... I just wanted to learn something new
     
  15. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    If you quit whenever something doesn't work as expected you'll be spinning your wheels endlessly.

    Chris
     
  16. CiaranM

    CiaranM

    74
    1
    May 19, 2012
    nahhh its not like that.. I was wasting my time anyway. there wasn't a reason for the joule thief not to work.. but it didn't work anyway, ha ha. I learned things today,so its all-OK
     
  17. BobK

    BobK

    7,645
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    Jan 5, 2010
    That looks like too few turns to me. My joule thief has about 20 turns of enameled wire on a similar sized toroid.
     
  18. CiaranM

    CiaranM

    74
    1
    May 19, 2012
    that seems reasonable. how did you manage to get 20 turns? is it OK to overlap wire?
    by the way, have you ever tried hooking up a joule thief to another joule thief?
     
  19. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    By winding, and winding, and winding (about 20 times).

    In this case, sure.

    Can you think of a reason why one might want to? And what it might achieve?
     
  20. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    By using small gauge enameled wire. It's called magnet wire.

    Chris
     
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