Connecting several SMD boards to 12v

Discussion in 'The Projects Forum' started by interested amateur, Jul 30, 2013.

  1. interested amateur

    Thread Starter New Member

    Jul 29, 2013
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    Hi Guys,
    I've had an interest in electronics for many years, but have never had the gumption to take it up as a hobby. This is my first attempt at a project. :cool:
    I'd like to connect 8 SMD boards together. The boards have 48 lights on each. Two sets of 4 in a strip formation. Each board has its own power connection, so I'd have to daisy chain them together to the power
    Would I need any type of power interface between the boards and the power source?
    Originally, the boards were to replace interior lights in a vehicle, so I'd assume, I could connect them up to a 12v jack and add a dimmer module then thats should be it?

    Ideally, I'd like to add a rechargeable battery pack to the unit too.
    I'd appreciate any input as I'd like to take up electronics as a hobby. :)
     
  2. interested amateur

    Thread Starter New Member

    Jul 29, 2013
    6
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    This type of thing if anyones not too sure....

    [​IMG]
     
  3. Shagas

    Active Member

    May 13, 2013
    802
    74
    Do the LED's have any inbuilt resistors on the other side or anything?
    If not then you will have to calculate them .
    And what is the voltage rating for those things anyway? Since they are for vehicle use then they are probably 12 v or maybe 24 if we are talking about big vehicles . You should find that out first.

    You can connect all the boards in parallel to a 12v battery (assuming it's powered by 12v) if it can handle the current
     
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  4. interested amateur

    Thread Starter New Member

    Jul 29, 2013
    6
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    Hi
    Thank you for the reply.
    Yes, they have inbuilt resistors on the circuit. I wanted to connect then to a small battery pack, such as a Li-ion 1.5v 4 pack. I used these as they're very,very low voltage. Even though they can be hooked straight into a 12v system.
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,123
    3,048
    I don't think they're both low voltage and 12V. If they're truly meant for direct connection to an automotive power supply, then any voltage up to ~14V should be fine since those are common in a car.

    Just be careful that whatever power supply you use does not have peaks higher than that. For instance a wall wart rated to 12V might actually have peak voltages up to 16V or maybe even more. An old computer PSU is regulated and is a very handy thing for a hobby power supply. You can get one for free is you grab a computer on its way to the recycle dump.
     
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  6. interested amateur

    Thread Starter New Member

    Jul 29, 2013
    6
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    Hi

    Thanks for the info :)
    I want it for an automotive application. So it will feed off a 12v cigarette lighter jack or have a li-ion 4 x 1.5 battery pack to use when its of a power feed.
    It will never see mains voltage, only DC.
     
  7. cornishlad

    Member

    Jul 31, 2013
    196
    25
    Hi..I just joined to ask a question and here I am trying to answer one !
    I think you will find that those boards are wired in sub groups with three leds in series and one surface mount resistor for each set of three. I suspect that if you revisit the ad where you got them they just say 12v. They don't say for vehicles specifically.
    three leds in series require about 9.9v to light up at all. The current control resistor in each 3 set is quite low value....maybe 100 ohms. if you worked out the correct current control resistance for 14.4V ( the likely voltage while the alternator is charging the battery) you would find it would be more than double.
    LED life is shortened considerably by overcurrent. So if your lighting system is only going to be used with a battery (12.1 to 12.6v) it will be ok to parallel all the boards and go. If you plan on using while the battery is being charged then it's sensible to feed them from 1 or more regulator chips. The LM2940 low dropout one is popular and can be got online from a led shop pre built in a plastic box. up to 1 amp per chip with heat sink..

    edit if by 4 x 1.5v you mean 6v then they won't light.
     
    Last edited: Jul 31, 2013
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  8. interested amateur

    Thread Starter New Member

    Jul 29, 2013
    6
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    I've had 6 wired into a 9v battery and they lit fine. Very low consumption ;)
     
  9. interested amateur

    Thread Starter New Member

    Jul 29, 2013
    6
    0
    Does anyone know what would be most efficient method to connect these to the same power source?

    Many thanks in anticipation..... :cool:
     
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