Help with relay circuit

Discussion in 'The Projects Forum' started by Svpam, Oct 17, 2012.

  1. Svpam

    Thread Starter New Member

    Oct 17, 2012
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    Hi, I'm new to electronics.

    Would anyone be able to tell me why this circuit isn't working as intended?

    The intended result is that the relay oscillates and the LEDs flash when the button is pressed, however when I press the button the leftmost LED lights constantly and nothing else happens.

    I get voltage across the left LED, the resistor and the capacitor, but no voltage across the second LED and I can't hear my relay oscillating. There's no sound from it.

    The switch is over to the left connector via alligator clips and wire and I'm providing 12V DC.

    http://i.imgur.com/SIVDW.jpg
     
  2. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I'm not great at deciphering a breadboard. could you post a schematic? even hand drawn is fine
     
  3. NFA Fabrication

    Member

    Aug 12, 2012
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    Beat me to it. Too many possibilities for misinterpretation with breadboard pics.
     
  4. Svpam

    Thread Starter New Member

    Oct 17, 2012
    10
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    Here it is.

    http://i.imgur.com/SErAE.jpg

    Thanks.
     
  5. Svpam

    Thread Starter New Member

    Oct 17, 2012
    10
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    In my picture I can see that the left LED was in the wrong place but my result is the same when I change it.
     
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    The stripboard drawing is some help, but is still not a schematic. For example, the stripboard drawing doesn't show the polarities of the LEDs or the cap. Post a link to the site where you got the stripboard drawing.

    It should be easy to fix.


    ETA: I mean breadboard drawing, not stripboard drawing.
     
    Last edited: Oct 18, 2012
  7. Svpam

    Thread Starter New Member

    Oct 17, 2012
    10
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    Ah, sorry. Its here:

    http://i.imgur.com/Gq7Qt.jpg

    My resistor value is 1k since I don't have 680Ohm.
     
  8. tracecom

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    1k is fine. It's hard to tell, but it doesn't look like your +12 is ever getting to the coil of the relay.
     
  9. Svpam

    Thread Starter New Member

    Oct 17, 2012
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    Since I'm getting voltage across my capacitor which is in parallel with the coil, does this mean there's probably an issue with my relay and I should just get a new one?

    The capacitor is on the same row as the relay so I think voltage should be going to it.
     
  10. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    That's possible. If you take the relay off the breadboard and apply 12V to the contacts, does the relay operate?
     
  11. Svpam

    Thread Starter New Member

    Oct 17, 2012
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    It does actually. I can hear it clicking, although not very consistently.
     
  12. tracecom

    AAC Fanatic!

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    The relay should operate every time you apply power directly and release every time you remove power. If it does, then the coil of the relay is doing what it is supposed to. The next issue is to get the relay operating every time you press the button and releasing every time you release the button. Run the power through the NC relay contacts, add the cap and the relay should oscillate when you hold down the button and stop when you release the button. Then, you can add the LEDs and get them to flash.

    I have to leave the computer for a while. Good luck.
     
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  13. Svpam

    Thread Starter New Member

    Oct 17, 2012
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    I did the first thing you said about activating the relay with the switch and it wasn't working, so I switched the wires from my 12vDC and it started working.

    Could have sworn I had it right.

    Thanks for your help.
     
  14. Svpam

    Thread Starter New Member

    Oct 17, 2012
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    Gah. Both LEDs light up at the same time and if I try more basic circuits such as:

    [​IMG]

    The second LED always refuses to light.
     
  15. strantor

    AAC Fanatic!

    Oct 3, 2010
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    take your breadboard apart and start over. There aren't a whole lot of things that could be wrong, mostly human error. make sure your LED polarity is correct and make sure you are working with 2 good leds. make sure you are using the correct pins on the relay. when I say "make sure," I mean look at the datasheet and back at the component a few times and verify you have a correct understanding which pins are which. Also make sure that your relay is in fact a double throw model and not a single throw. You do this by comparing the model number to the model number breakdown in the datasheet. Sometimes they will make several models of relay all in the same package (look exactly the same), with the same pins, and some of the pins may not be functional.
     
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  16. panic mode

    Senior Member

    Oct 10, 2011
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    1. post relay part number, we need to verify coil voltage and pinout
    2. remove everything but relay, power source and button. if you wire button, relay NC contact and relay coil in series, relay will oscillate.
    3. your relay has DPDT contacts, use ANOTHER set of relay contacts to control LEDs.
     
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  17. Svpam

    Thread Starter New Member

    Oct 17, 2012
    10
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    Wow I looked at my data sheet and my coil was the closest to the relay, not the one in between.

    Thanks, I'll do this in the future.
     
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  18. panic mode

    Senior Member

    Oct 10, 2011
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    it should be something like this unless I got NO, NC swapped around
     
  19. Svpam

    Thread Starter New Member

    Oct 17, 2012
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    Yeh that's what it was like, everything's working now.

    I thought NC and NO were at either side of the activation.
     
  20. tracecom

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    So, you learned the best lesson of all...the one that all of us have learned and then forgotten and had to relearn, and so on.... check the simple things first!

    Glad it's working. :)
     
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