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I have a cheap battery powered LED light strand that had a corroded and non-functional control board. The LEDs looks like they are rated for about 3.3V with up to 20mA per bulb, and the original string controller ran them at about 2.9V and 2mA per bulb.

The LEDs are wired where they are all wired in parallel, with alternating LEDs alternating in polarity. Putting DC power on the light string lights up every other light. Swapping the input polarity lights up the other lights. Apparently, reverse voltage does not hurt these LEDs. The control board must have alternated power at different rates to make the lights appear to flicker, dance, or all appear to be constantly on through persistence of vision.

I can reliably drive these LEDs with a power supply regulating voltage and current with fixed polarity. How would you recommend to automatically oscillate the voltage polarity at a rate to make use of the alternating LEDs, particularly with an adjustment to control the oscillation rate?

Thanks, H

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  • \$\begingroup\$ What I did with mine was run them from an AC output wall wart. The flicker is horrible, but they are for outdoor use, so viewers don't have to tolerate them for long. \$\endgroup\$
    – Neil_UK
    Dec 14, 2020 at 7:58
  • \$\begingroup\$ Low frequency oscillator and a polarity reversing relay. \$\endgroup\$
    – Andy aka
    Dec 14, 2020 at 10:29
  • \$\begingroup\$ Wouldn't a relay be worn out quickly by oscillating even at a few times a second? Seems more like a job for an H bridge. It would be nice to control the oscillation rate between 1 and 120 Hz. What oscillator circuit would you recommend that could switch between H bridge directions? \$\endgroup\$
    – H in OH
    Dec 31, 2020 at 14:51

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