Using a 12v relay in a 4v circuit

Discussion in 'The Projects Forum' started by OigMan, Jul 30, 2014.

  1. OigMan

    Thread Starter New Member

    Jul 30, 2014
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    This might be a bit of an odd one but I am using an 18650 battery as a power source which puts out about 4.2v on a full charge and as many as 20 amps. I am trying to use a relay in my circuit but am having trouble finding a 4v relay that will support more than 1 amp. I was thinking about using 3 18650 batteries to be able to run at 12v high amp relay but I would then have to reduce the power down to 4v before it reaches the kanthal heating element. Is there any way to use a 12v relay in a 4v circuit?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Use a 3v-35v SSR.
    Max.
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    There are plenty of 5v relays.. but what exactly are you trying to do.
    A relay has a coil (that you apply voltage to and it uses a small amount of current).
    that coil switches a set of contacts magnetically to create a circuit just like flipping a manual wall switch.
    The "contact" side is isolated from the "coil" side and is commonly switching a different voltage/current level or the same.

    So are you using this 4v source to turn on the coil side and then also using the same 4v to turn on a heating element (e-smoke or dab vaporizer.. I'd guess)
    What is the "on" button?
    What is the resistance of your heating coil?

    Just because a battery could deliver 20A doesn't mean it ever will
     
  4. OigMan

    Thread Starter New Member

    Jul 30, 2014
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    Thank you for the quick reply and while this would likely do the trick I freer that it is to large as space is a limiting factor

    Mcgyvr, you are correct this is for an electronic cigarette. I have a 4v high amp current that I am trying not to run though the switch just to be safe because 20 amps is a lot of current to put though most momentary switches. Not to mention the only high amp switches I could find can only be activated with 12v of power

    I have worked with relays before but only in 12v circuits, honestly I have only worked with 12v systems period as the only time I am doing any kind of wiring its usually on my car or truck
     
    Last edited: Jul 30, 2014
  5. paulktreg

    Distinguished Member

    Jun 2, 2008
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    Do you need something like this but I presume you aren't in the UK?
     
  6. OigMan

    Thread Starter New Member

    Jul 30, 2014
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    That looks like something that would be useful to me yes and you're correct I am in the US. Awesome find though thank you, maybe I can find that here.
     
  7. inwo

    Well-Known Member

    Nov 7, 2013
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  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    and the resistance of your heating coil is....?

    If your voltage is 4V and your coil is 1 ohm..
    Then the max current you will draw from the battery is 4/1=4A
    If a 2 ohm coil 4/2=2A

    You probably don't have a .2 ohm coil so you will never have 20A..
    hopefully you aren't one of those silly cloud chasers.
     
  9. takao21203

    Distinguished Member

    Apr 28, 2012
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    you should use a MOSFET
     
  10. alfacliff

    Well-Known Member

    Dec 13, 2013
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    as max said before, use a ssr. a solid state relay with an input voltage of 3 to 35 volts at very low current. just make sure it is a DC ssr. a simple 4 connection fairly small block of eoxy.
     
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