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Illuminated Sign

Discussion in 'Power Electronics' started by dsjonesuk, Jun 24, 2020.

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  1. dsjonesuk

    dsjonesuk

    2
    0
    Jun 24, 2020
    Hi all

    I am looking to get this sign running from the mains:

    IMG_5025.jpg

    It was previously powered by three AA batteries:
    IMG_5024.jpg

    Could someone point me in the right direction please?

    Many thanks in advance!
     
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    10,025
    2,138
    Nov 17, 2011
    3 × AA batteries = 4.5 V.
    This sign probably runs pretty well from a USB charger (5 V). Just connect the corresponding '+' and '-' wires from the charger to the respective connections of the battery compartment.
    Observe the current requirements: The charger needs to be able to supply as much or more current than the sign requires. If you do not have a current rating for the sign, measure current drawn from the batteries using a multimeter.
    If the lamps or LEDs are too bright, add a diode in series with the charger, e.g. from charger '+' to battery compartment '+' to drop a few hundred millivolts.
     
  3. KMoffett

    KMoffett

    717
    71
    Jan 21, 2009
    Probable a 5V, regulated, SMPS (switch mode sower supply), wall transformer would work. Can you measure the current draw with the batteries?
     
  4. hevans1944

    hevans1944 Hop - AC8NS

    4,474
    2,085
    Jun 21, 2012
    It appears that someone has already tried to make some "improvements" over the original three AA cell arrangement. The battery compartment is trashed, spring contacts corroded, some terminals missing, wires disconnected, etc. Did you retrieve this sign from a landfill, or perform the modifications yourself?

    All of the LEDs appear to be wired in parallel, which is NOT a good way to operate LEDs. If you want good life from this sign, you should check each LED for brightness and functionality by first disconnecting the parallel wiring arrangement. Connect each LED in turn to a voltage source with a series current-limiting resistor. Replace any LED that fails to light up brightly with 20 milliamperes of current. Ask here if the selection of a voltage source (for testing) and a resistor (for current limiting) is beyond your current level of competence.

    Next, connect a pair of small-gauge wires (like the black zip-cord wire shown in your photo) to each LED, with sufficient length to allow all the wire-pairs to be brought back to a common location inside the back of the sign. There you will install a small prototyping board with a current-limiting resistor for each LED.

    At this time you may consider getting creative with your sign, instead of just connecting all those wires attached to the prototyping board to a power source. Perhaps a "chaser" effect where the LEDs illuminate in sequence, chasing each other around the sign, would be an appropriate effect. Or perhaps a simple ON-OFF-BLINK-ON-OFF sequence would be attractive. Lots of possibilities now that you have access to all the LEDs independently. Folks here at EP can help with the design if need be.

    i have seen a LOT of these cheap "artisan" thingys for sale (mostly in arts and crafts shops) lately. They all look cheaply made on the outside, but worse on the inside if anything electrical is involved. And they are invariably overpriced. However, a well-made sign like yours appears to be, does not have to suffer from inadequate electrical wiring, or limited battery operating life. Spend a few bux to get it wired up properly.
     
  5. dsjonesuk

    dsjonesuk

    2
    0
    Jun 24, 2020
    Thanks very much for all you replies! I really like the sound of the chasing effect, but well beyond my skills!! Would you know any companies that I could send it to to do this for me?
     
  6. hevans1944

    hevans1944 Hop - AC8NS

    4,474
    2,085
    Jun 21, 2012
    @dsjonesuk: ElectronicsPoint is oriented towards Do It Yourself (DIY) electronics experiences. We seldom (if ever) veer off into the commercial realm. There are plenty of individuals, and perhaps even companies, that can design and build a chaser circuit but you won't find them here. Make Google your best friend to locate things like that.

    Once you have all your LEDs individually connected to their own series current-limiting resistor, located on the prototyping board, you can add a "wall wart" power supply to make sure all the LEDs "light up" at the same time. The fancy "special effects" can be added later, either by yourself with a little help from some of us here, or by someone you hire to do the work. If this sign is for a commercial enterprise, such as a real bar, rather than a novelty sign for home use, you may want to expend the money to hire someone to create a "special effects" board to wire into your prototyping board. But do the prototyping board first. It is essential that each LED have its very own current-limiting resistor, and this should be well within your capabilities if you know how to solder.

    It is possible to wire two or more LEDs in series, so that a single current-limiting resistor will serve. But this also means the voltage requred to operate just one LED must be increased for each additional LED that is in series. EP has a resource that explains all this.
     
    Martaine2005 likes this.
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