Can someone please help a newbie going crazy! (flashing led)

Discussion in 'General Electronics Chat' started by cfiiman, Dec 18, 2012.

  1. cfiiman

    Thread Starter New Member

    Dec 18, 2012
    6
    0
    I've been chasing this forever it seems like, I have built just a simple flashing led but for some reason the led slowly stops flashing, I'll explain further.

    I have a 3 volt blinking LED that is wired to a 2032 3V battery holder that is wired to an on/off slide switch, everything should be working perfectly and at first it does. When I first put the battery into the holder it turns on fine and blinks the problem happens after I shut it off and try to turn it back on. If I wait just a few seconds it will come back on when I turn the switch on but it takes a few seconds, the longer I wait to turn it back on the longer it takes. Originally I was using a 5 volt blinking LED and I was sure that was the problem so I switched down to a 3 volt to match the battery but it is still doing it. If I wait a few minutes and then try to turn it back on it will take forever to start working or not at all, if I remove the battery and put it back it works fine every time, it only starts the problem by using the switch, I seriously am about to go crazy I have no idea why it is doing this. The LED's are new, the battery is new so that is not the issue. I made a quick video of it so you guys could see what I"m dealing with, please if anyone can help it would be much appreciated, thanks.

    http://www.youtube.com/watch?v=ELlfmWJSbn0
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    There are only three items that can be the problem.

    1, LED
    2, Battery
    3,Switch

    Try shorting out the switch, or replacing it with another, or replace the battery ?
     
  3. Ian Rogers

    Member

    Dec 12, 2012
    158
    29
    I'd check the resistance through the switch....
     
  4. cfiiman

    Thread Starter New Member

    Dec 18, 2012
    6
    0
    Thanks for the replies guys, I figured it out, it took a video from like an 11 year old kid on youtube to show me what I was doing wrong. I needed to make the positive one long wire from the led to the battery, I had breaks in it with the switch, duh! Well this thread might help someone in the future so i'm glad I posted anyways, thanks again.
     
  5. cfiiman

    Thread Starter New Member

    Dec 18, 2012
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    0
    Thought this might help anyone having the same issue as me, I drew out what the fix was, I had the positive leg of the LED wired to the end of the switch which allowed it to work but only initially for some reason, when I wire it as shown below it works perfect:

    [​IMG]
     
  6. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    One of my personal mottos:
    "Stupid" strikes all of us from time to time.
    or,
    we learn more from our mistakes than from our successes.
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    For a even longer life add a 220µF cap across the battery. It will soak up a charge when the LED is off, and supplement the flagging battery power when the LED is on.
     
  8. cfiiman

    Thread Starter New Member

    Dec 18, 2012
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    0
    Could you explain what that means? I seriously don't know very much, I don't know what a 220 cap is or how to wire it in, thanks!
     
  9. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    Like this??
     
  10. cfiiman

    Thread Starter New Member

    Dec 18, 2012
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    0
    I feel like a fish out of water, I don't know how to read that schematic :(
     
  11. Austin Clark

    Member

    Dec 28, 2011
    409
    44
    Yes, That's what he meant (I think). If the circuit is working fine as-is, it might not be necessary. Basically, the capacitor is supposed to act like a "buffer", in case the battery wasn't able to "keep up" with the LED. When the LED is OFF, the capacitor is charging from the battery (buffering), when the LED is ON, the capacitor supplements the battery to run the LED (like watching a buffered video while at the same time still downloading more of the video on top).
     
  12. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,535
    Think of a capacitor like a small battery. It has a + lead that is marked (or the - lead is marked). Just put it across the battery in the same polarity.
     
  13. cfiiman

    Thread Starter New Member

    Dec 18, 2012
    6
    0
    Ok, I researched all I could on them, I still can't get how it "helps" my battery? Not sure what you mean by buffering, I have read that when the switch is off the capacitor is not doing anything is this incorrect? I can see the logic, say on a car's audio amp, when you hit a big bass note or something needing "extra" power the capacitor would help, but am having a hard time seeing how on a little 3 volt led? From what I read it just stores a short "full charge", after the switch is off the led will take a few seconds to shut off, and when you first turn it on the battery has to charge the cap as well as power the light, seems like it would reduce battery life :confused: I know I'm wrong in my thinking but not sure why and can't find any useful info addressing it, can you explain how it "helps" ? Thanks!
     
  14. Austin Clark

    Member

    Dec 28, 2011
    409
    44
    Well, it might NOT help, as I stated earlier. I was just explaining the concept. Batteries, especially those small ones, have internal resistance that acts like a series resistor. If this internal resistance is too high, when you try to draw too much current, the voltage will drop to a point where the battery can "keep up". This point might be too low for the LED and internal controller to operate.
     
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