Beginner Struggling with 1st Project

Discussion in 'General Electronics Chat' started by trogre, Jul 13, 2010.

  1. trogre

    Thread Starter New Member

    Jul 12, 2010
    2
    0
    Hello to all.
    Absolute beginner at electronics, so far I have purchased a multimeter & a solder station, as yet not used them. I was going to purchase a project but decided as a 1st project to test and hopefully fix the fault on garden solar light.
    The problem is, it does not turn off during the day. On inspection of components it has a 1.2v battery, on/off switch, 4 small solar cells, LED, & a circuit board. It does not have a light sensor, at least not a separate one.
    It is the circuit board that surprised me as it only has 2 components so I thought this will be an easy first project to test .1st component is a 220Ω resistor which I will have to take out & test but it is the 2nd component which is giving me problems as I have no idea what it is to test or buy a new one.
    At the moment really only familiar with what a resistor looks like as I am still learning how to identify other components. I have looked on the web and as yet cannot identify what the 2nd component is. Most of what I have looked at has either 2 or 3 pins (legs?) and not 4 as picture.
    [​IMG]

    Again, not as yet familiar with trying to upload a proper schematic so rather than upload a load of wiggly lines all I can say is all the other components are linked to this black 4 pin item.
    Would appreciate if anyone can point me in the right direction and if so how would I go about testing this component. If the worse comes to the worse & I fail then I will rebuild the light by downloading a different schematic.
    Thank you in advance
     
  2. trogre

    Thread Starter New Member

    Jul 12, 2010
    2
    0
    Sorry forgot to say.The component has writing on the side,SS550 and I thought this must be some sort of identifying code.However when I took another light apart the same component has the code 0116 on it so that was no help,could be a batch number instead ?
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    I think you're going to be surprised to find that what you think is a resistor, is actually a 220uH inductor. When you measure it with an Ohmmeter, it'll probably be just an Ohm or two.

    The 4-legged critter is some type of DC-DC boost switching regulator. White LEDs really need 3.4v to 3.8v in order to light up. A pair of rechargeable AA batteries will only put out about 2.4v when wired in series. In order to get the higher voltage, they used a switching regulator and an inductor to get there. This is actually quite common nowadays.

    The 4-legged critter is some proprietary circuit. They don't have the part number on it, because they don't want you to be able to reverse-engineer it and start making them yourself.

    In reality, the light might be working as it was designed. With the really long days and bright sun we're having this summer, the batteries are probably getting charged up completely by early afternoon. In order to keep them from becoming overcharged, the regulator starts running the LED to drain current.

    As long as you get at least several hours of light out of them after the sun goes down, I don't think you have a problem.

    Another possibility is that the battery connections are bad/corroded, or the battery/batteries are shot. Try cleaning any corrosion off of the terminals.

    Try measuring the current output of the battery/batteries under load. After charging them up, measure their current output by using a 300 Ohm resistor in series with a meter set to the 20mA scale. You should read 4mA current. If you can't find a 300 Ohm resistor, then get a 100 Ohm resistor; you should measure 12mA current when wired in series.

    Don't try to use an ammeter directly across the battery terminals, as a good battery can put out well over 1A current, and it will blow your meter's fuse.
     
  4. Jaguarjoe

    Active Member

    Apr 7, 2010
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  5. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Instead of using a LDR or other photo sensor, some solar lights simply use the solar cell.

    The solar cell can tell when it is dark ore not. If there is no power from the cell, a transistor can let the LED turn on.
    This is most likely inside of the IC.

    Bring your light inside for a day or two.

    Keep it in a dark place until the battery is drained. Put it back in the sunlight.

    Does the LED come back on immediately?
     
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