Request for Assistance with LED Light Array

I have an motion sensing flood light that worked well for several years before taking on water and rusting out. Fortunately the LED array is fine. The rest of the light (solar panel, battery, charging board, motion senser) is a rusty pile of goo and not salvageable. I have tested each of the LEDs individually using the diode test mode on my multimeter and they all work. I can’t get the entire array to light up though, and I’ve tried applying 5v on all pins, with ground always attached to the ground pin. Since this part of the light is intact I would really like to get it working as a manually operated flood light.

I’ve attached a photo of the back side of the board and would appreciate any assistance on how to get it working.


It looks like it uses 5 leds in series. If they are white LEDs then you would need at least 16-18 volts to light it up.

The odd thing though is the presence of five wires on the board with two VCC and two FB connections. If one follows the routing on the single side board it loops between VCC, FB and GND. So… where would positive and negative be applied to? I’m afraid of guessing and checking in the case of guessing wrong.

Between ground and Vdd. The FB lines look like they were come current control feedback to the driver. There might be two Vdd lines if one controls a single row of LEDs for a high/low mode… can
t tell from the pics. Also, what are the markings on those resistors in series with the LED strings?

The resistors along the bottom row are all marked 62R0, so 62 ohms. The ones along the top are 0 ohm jumpers across a trace.

My bet is it needs 18 volts. I try cranking up the volts slowly and see what happens…

That did it, thanks texaspyro!

You were right, the two VCC pins were controlling interleaved banks of LEDs. I connected them both together with GND as ground to a 17v power supply and it lit right up. I can’t crank it up to 18v at the moment because my power supply is limited to certain discrete outputs (modified ATX computer power supply, +12v & –5v =17v).

At 17v the array draws 170mA.

18v wall adapters are cheap enough, so this is great news!

For reference, the original product was this (search ebay for “eLEDing 36 LED solar powered motion sensing”). It was nice for two years before the water ingress issue. It probably didn’t help that I mounted it with the base station aiming at the ground under a porch.

It looks like there are 45 LEDs. If you assume 20 mA per LED, you should crank the voltage up until it hits around 1 amp. You can probably do up to 30 mA per LED, so 1.5 amps might be OK. Probably needs more than 18V…

That did it!

I used a programmable power supply at work and slowly cranked up the voltage while watching the current. I had max current set to 1A.

The brightness stopped increasing at 24v at which point the array draws 0.480A, self limiting.

Thanks for your help!

Whoops, made a mistake in my current calculations. There are 9 paralleled strings of five LEDs (not 45 LEDs all connected in parallel). If each string of 5 LEDs is drawing 20 mA, you should shoot for around 200 mA. At 0.5A, you are putting 100 mA into each LED, probably too much for a decent lifetime. I would not do more than 30 mA per LED string (assuming they are standard 5mm white LEDs)

I noticed :slight_smile:

I left the array running during lunch to see how it would fare and came back to it drawing significantly less current. I had it facing downwards because it was bright and turned it over to it looking quite a bit different. It was HOT!

It looked so pretty while it lasted though!

I’m not heartbroken over it. For the cost of even repairing this I can buy one of the 10w flood lights from wallbuys, etc and it’s smaller, brighter, and proven to be more waterproof. Plus it runs on 120vac instead of around 24v.