The light housing already has 1/4" tempered glass. Wouldn't that difuse the light for me?

 

Again, no manufacturer's name and no datasheets.
How will you "solder" the LED to the aluminum heatsink holder?

 

As I suspected, looks like no current regulation on the light that started this thread. I broke one open and this is what I found.

 

How was the circuit laid out, 60 LEDs total as...
-20 parallel strings of 3 bulbs in series
-or-
-15 parallel strings with 4 bulbs in series
Other...

 

No way to tell. The pcb traces are sealed up. No way yo see them.

 

There has to be one resistor per string, or each string would act like a short and the current draw would be higher.

A horrid design. You get what you pay for.

 

For me a great design. Now I can add my own current limitation if I can only figure out what current to limit them too. Any ideas? They are advertised at 3.5W.

But I have to agree bad design. The unsuspecting person using them in their rv without regulation would drain their battery in no time.

 

Heat management looks rather non-existent, you mentioned it was "VERY Bright", so using a lab supply, limit the current to around 15mA/LED and see if that brightness is acceptable. Then connect an LM317 or current limiting scheme of choice inline.

Heat, both from the LEDs and from a linear current limiter, will be an issue after a period of time inside the enclosure if you seal it back up. If this isn't for outdoor use, you could add vent holes.

 

Current limiter will be a buck regulator. The current one is external and a 700ma buckpuck plus. I would imagine I have same heat issues with current light of around 118 LEDs . The light has a large cavity behind the light panel.

 

If the LEDs have a typical forward voltage of 3.5V then 3.5W occurs when the current is 3.5W/3.5V= 1A. But that is the absolute maximum allowed current when the LED is cooled properly.

 

But these seem to be standard 3mm leds. They would not take 1A for very long.

And isn't going to matter how they are wired? Judging by the physical configuration, would not it make sense they were all in parallel?

 

You can black box it by setting putting the 700mA buck puck on the power leads, then measuring voltages at different points. You'll then be able to tell what the internal routing and layout of the board is since all of the LEDs are roughly the same Vf, certain points will show Vin, resistors, then how many Vfs before you hit ground on various pins.

Granted, it's not fast, but short of taking it to a courthouse X-Ray machine and asking nicely, there isn't a way to see the connections. Though applying more aggressive dis-assembly of the sacrificial unit would also work if you don't want to spend that much time (or if you don't know a courthouse guard).

 

You can black box it by setting putting the 700mA buck puck on the power leads, then measuring voltages at different points. You'll then be able to tell what the internal routing and layout of the board is since all of the LEDs are roughly the same Vf, certain points will show Vin, resistors, then how many Vfs before you hit ground on various pins.

Granted, it's not fast, but short of taking it to a courthouse X-Ray machine and asking nicely, there isn't a way to see the connections. Though applying more aggressive dis-assembly of the sacrificial unit would also work if you don't want to spend that much time (or if you don't know a courthouse guard).

Not sure I am following you. What do you mean by "certain" points.

BTW I do intend to order this supply:

http://www.circuitspecialists.com/bench-power-supply-csi3303s.html which has current limiting.

 

Not sure I am following you. What do you mean by "certain" points.

BTW I do intend to order this supply:

http://www.circuitspecialists.com/bench-power-supply-csi3303s.html which has current limiting.

Power supply looks decent, a lot of features for the price!

I meant that you have a spiral of solder pads working out from the center. Put one DMM lead on GND of the supply, turn on low pass filter if needed (cap from DMM + to - if using a PWM supply and fast meter), and measure voltages at the different pads. Knowing Vf of each diode and V+, you should be able to get a good idea of what is in between the pads, assuming it's only LED Vf drops, V+, or a limiting resistor. I don't see them adding any more parts or effort into the build for the price they are selling them at (which means it was built for < $1).

 

I did a little experimenting with these lights tonight using my fancy new current limit supply. I downloaded a light meter app for my tablet PC.

At .25 amps I get 3700-4000 lux per light. Increasing the current to .3amps only gives me another 500 lux.

At 12V no load voltage reads 9.2 volts with load and limited to .25 amps. Light seems to shut down around 7.8 volts.

I might try two in parallel tomorrow. Given my findings tonight, I don't see how I could get two in series with only a 12v supply.

 

At what points on the board were you measuring the lights? Or was this testing across the supply leads?

 

Across the supply leads? I should measure voltage at the pads? What would that tell be exactly again? How many should I measure?

 

Across the supply leads? I should measure voltage at the pads? What would that tell be exactly again? How many should I measure?

I was thinking if you tested out points on the spiral PCB pads, you could find how the LEDs are actually connected. Then you could run it on a lower supply voltage by soldering in new wires where applicable.

 

That would be a monumental project. There are lots of leds and the runs are all sealed up.

 

I ordered a few of these

http://dx.com/p/gu5-3-3-5w-6500k-420-lumen-60-led-white-light-bulb-12v-131888


from Dela Extreme. I hooked them to my homemade LM317 power supply (it has no current limitation). I connected an amp meter and measured over 1 amp.

I assumed these bulbs had their own current regulation but they are advertised at 3.5W

At 3.5W I should only be drawing less than 300 ma correct?

Am I correct to assume they don't have current regulation?

YOu must ask the dealer to replace the lights. As it will cause problems in future