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OT solar garden lights

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  • OT solar garden lights

    Anybody hacked one of these? I just bought a $4 one to use the solar cell from for another application, but I wonder how it's able to take the low battery voltage and jump it high enough to run the led- I understand boost circuitry, but that requires a capacitor, and this unit doesn't have one, unless it's part of the black dot ic on the pc board. Just for experiments sake, I jumped a small capacitor, less than 1 mf, across the led. It went out, so the most I know is there's a switching frequency involved. How can there be a voltage jump without a capacitor or inductor- that's what's bugging me-

    All there is to the circuit is the black dot ic and two resistors, if you don't count the photocell, the solar cell, the single battery, and the led. Maybe one of the components that looks like a resistor is actually a capacitor- that's all I can think of that would make the circuit work.

    I'm just curious, and it's not a big deal anyway. I bought it for the solar cell to use in a remote control testing device.

    Of course, one other factor that I'm not sure of for my application is if the solar cell is actually responsive to IR. I have built one of these in the past, and the cell I used does work well, but these days the cells are not what they used to be. The one I used then could make 60 ma from about 1 sq inch- this one is about 2 sq in and is only making 15 ma in bright sun. One I took out of a calculator couldn't even budge the needle on a 1 ma full scale meter-
    Last edited by darryl; 05-19-2010, 04:41 PM.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    Well- I found that the solar cell in this garden light won't respond to remote controls- not even a flicker on the 'scope. Then I found a solar panel in a radio and it does respond. I'm not surprised- they are different types of cells. Now my task is to extricate one of the cells without damaging it so I can wire it to a meter movement and build a remote control tester. Soldering pencil is heating as we speak.

    In case anyone is interested- the little circuit from the garden light does indeed jump the voltage from the single nicad to a higher value to run the led, and the output is clean dc on the led. The component inline with the led is an inductor, and the circuit is putting an ac signal onto one end of it. That signal is around 500khz, about the same as the low end of the am broadcast band. The led itself must be integrating the high frequency pulses.

    That's this little experiment over with. Of course, it leads me to question the influx of solar energy per sq meter in bright sunlight, which has often been quoted as being 1000 watts/sg meter. How is the efficiency of a solar cell actually determined? Is it based on the spectrum it is capable of responding to, or the total spectrum that impinges on it?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-