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Thread: Non-audio LED voltage question

  1. #1
    Forum Veteran 62vauxhall's Avatar
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    No such things as bad days, just bad moments

    Non-audio LED voltage question

    I found a clamp on goose neck Ikea lamp for $1.99 that I thought would be good to use in conjunction with a turntable - sort of a spot light.

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    It uses one of those Cree LED or something visually similar.

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    No AC power adapter was with it but I thought I could cross that bridge with a little research. It took fair bit of searching using various terms before I found something, a blog actually, whereby someone wished to change the LED inside one of these things because they did not like the color of the light it emitted. It clashed against the color of their other LED room lighting don't cha know. In any case the power source was identified as being 4v.

    With that information I searched some thrift stores I know which have many, many AC adapters but found none with a 4v output. Most were 5 volts and higher. Thinking of this more of an experiment, I purchased one rated at 3v thinking that the LED would likely illuminate but at a reduced intensity.

    This afternoon i identified which terminal of the lamp's plug was + and likewise the wire from the adapter.

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    So far so good but when I measured the voltage coming out of the adapter, it was 5v not 3v. Is this one of those instances when that voltage will drop once connected to a load or am I going to burn up the LED?

    FWIW, while cruising the 2nd hand stores, I also looked for similar lamps and did find a few but they were all also without adapters. I also tried one of the area's Ikea stores. No adapters for this series of lamps were available, the lamp in question is discontinued and there were no such adapters or whole lamps in their "as is" department. They guy I asked did a pretty thorough look 'round.
    Last edited by 62vauxhall; 06-30-2018 at 11:18 PM.

  2. #2
    Forum Veteran Skywavebe's Avatar
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    Work too much
    If you are sure it uses 4 Vdc then you can make you own power supply by utilizing a chip called a LM317T. Get a DC supply that is greater than 4 V say 6 to 12Vdc and then put that into this regulator and dial in the voltage that you need. They do not need much power usually and it is good to 1.5 amp I think.
    4Vdc supplies would be rare and the one they made were for portables like 4.5 Vdc non regulated. You did not say how much current it requires.
    Best regards,

    Sam Palermo, BSEE
    Skywave Tape Deck Repair, Chicago area
    (708)334-2260, E mail- skywavebe@sbcglobal.net
    Past Teac/Tascam Lead Service Technician

  3. #3
    Forum Veteran 62vauxhall's Avatar
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    No such things as bad days, just bad moments
    Sam, thanks for responding.

    There was next to no info on this thing so I couldn't provide any particulars. Not surprising though for something that sold new for twelve or fifteen dollars.

    There was a stroke of luck, sort of, yesterday. When at a Value Village flipping through records, I found a different Ikea lamp that used a similar adaptor. I detached it, took it to the cashier saying I found it on the floor and got it for 99 cents.

    When home, I measured it's voltage to satisfy my curiosity and got about 6.5 volts.

    But the the stupid thing had a different output plug. I "MacGyver'ed" an antenna plug for a Yamaha receiver that I knew would come in handy some day and the lamp works.

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