Design a Mains Powered Solution for 5 Sets of External Solar LEDs

Confused as to why my question has been closed, when community guidelines restrict questions on consumer electronics, except when they are being modified.

"(questions are not allowed on)consumer electronics such as media players, cell phones or smart phones, EXCEPT when designing these products or MODIFYING their electronics for other uses"

Im trying modify the LEDs to work without the supplied solar panels.

Im not very experience in electrical engineering. I want to have a nice little project to see if I could make this simple modification myself (everyone has to start learning somewhere). Was really hoping this site could help me get started, even if the question is probably very easy for you guys - its not easy for me.


1 Answer 1


It is too vague to be answered in its current form. To build any form of LED driver, you will need to know their rated current, how they are connected (in this case likely parallel but that's not necessarily true) and what voltage they require. It seems likely that LEDs suiting the raw battery voltage were picked, but we can't rule out that a step-up converter was used. The existing LED driver may use PWM to drive them. You'd need to know the total current consumption.

Without knowing any/all of the above, you cannot design a LED driver. It will have to be reverse-engineered at some extent, preferably with an oscilloscope. Connectors are the least of your problems. Sure, you can very likely just smack on something that gives out 5V at x Ampere and it will very likely work, but that's DIY trial & error, not electrical engineering.

  • \$\begingroup\$ thanks. Makes sense. Any suggestion where I can get diy help? I was thinking just adding all the batteries up and using a driver that could deliver the summed up values. But have no idea if that will work. \$\endgroup\$
    – GWed
    Dec 20, 2023 at 13:16
  • \$\begingroup\$ @GWed There is diy.stackexchange.com but I doubt they will accept this question either. Basically you cannot supply something unless you know what it is you are supplying - it's common sense. The best solution is to buy new xmas lights really. I actually bought one of these solar panel ones too mostly out of curiousity, but it's far too crappy and/or it's far too dark where I live to make it work. Mine used chargeable NiMH cells so I just charge it manually. \$\endgroup\$
    – Lundin
    Dec 20, 2023 at 13:26
  • \$\begingroup\$ thanks. Not sure it is necessary to know what’s being powered if you already know the max power delivered to each (the battery) but maybe that’s why you’re an electronics engineering expert, and I’m not. \$\endgroup\$
    – GWed
    Dec 20, 2023 at 14:10
  • \$\begingroup\$ @GWed Supply LEDs with too high current and they will break. These will have a series resistance per LED which assumes that a certain supply voltage is applied. \$\endgroup\$
    – Lundin
    Dec 20, 2023 at 14:22
  • \$\begingroup\$ but battery is 3.7V. So can I not just assime that is my max supply? \$\endgroup\$
    – GWed
    Dec 20, 2023 at 14:48
  • \$\begingroup\$ @GWed Not in case there's a step-up regulator. For example suppose the manufacturer got a good deal on 3.5Vfwd LEDs. That's too high forward voltage to reliably power from a 3.7V cell, but since they got this good deal on the LEDs, it might be economic to add a step-up regulator. These are extremely price-sensitive products so the designer will take all manner of shortcuts. Someone else with a recent xmas light question found out that no series resistors were used, instead they used crappy wires and relied on that. \$\endgroup\$
    – Lundin
    Dec 20, 2023 at 14:56
  • \$\begingroup\$ TL;DR for the novice: LEDs are not light bulbs. Light bulbs are not LEDs. \$\endgroup\$
    – Lundin
    Dec 20, 2023 at 14:57
  • \$\begingroup\$ thanks. So if we assume most conservative approach I.e given we know the battery properties, and I want to power all 5 with the same driver, what’s the most sensible driver output I should look for that wouldn’t burn the leds? Let’s assume it’s a cheap crappy product, \$\endgroup\$
    – GWed
    Dec 20, 2023 at 15:00
  • \$\begingroup\$ @GWed You can't know that unless you know which LEDs that are used and what series resistance (if any) that's built in. This is all in my answer above. \$\endgroup\$
    – Lundin
    Dec 20, 2023 at 15:03
  • \$\begingroup\$ so my curiosity has got the better of me - ive dismantled the control unit with the battery in, and found a pcb. Serial number is FIY100-3VR-11R-V10-PBS. Is that any help for the resistor? 11R maybe? \$\endgroup\$
    – GWed
    Dec 20, 2023 at 18:00

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