I recently got me a set of 4 DMX-Controllable LED Lights of ebay for 35€ including shipping.
But they are rather dimm. The article page states
Power Consumption: 15W
LED: 12 pcs * 1W LED (Red*3, Green*3, Blue*3, White*3)
When setting all LEDs to maximum (RGBW) the multimeter reads 185mA DC. At just 12V thats not barely enough. Interestingly though, setting it to AC+DC mode reveals a stunning consumption of 340mA, thats almost 4Watt.
But wait, why is there even AC voltage when everything is turned up to full brightness?
Scope to the rescue!
I put a 1Ohm resistor in series to measure current, so 1mV -> 1mA. The voltage across the LEDs is always 12V, as output by the PSU.
You can see 478us PWM-Period with a on-time of 126us. Thats a DutyCycle of 26% at 100% brightness. That explains the AC current measured earlier. The peak current is ~275mA.
- Red: 780mA, DutyCycle 17us/318us -> 0.5Watt RMS
- Green: 350mA, DutyCycle 108us/480us -> 0.95 Watt RMS
- Blue: 275mA, DutyCycle 126us/480us -> 0.86 Watt RMS
- White: 487mA, DutyCycle 98us/480us -> 1.19 Watt RMS
This roughly correlates with the 4Watts measured with the multimeter.
But what about the overall quality? I guess you get what you pay for.
- The LED PCB is made out of aluminium and is a decent heatsink. But it is rather thin. The LED-lenses are as described and work properly.
- Plastic case seems nice. No problems here
- The Control-Knobs are easy to use, the 7-Segment-Display shuts off after a few seconds. Premium feature!
- No gamma adjustment. 50% Brightness equals 50% (of max) DutyCycle.
- The DMX In- Out-Port are just connected to each other. No RS485-driver to improve signal quality
- The internal plugs are JST-XH (clones?), but they saved a few cents by just populating pins instead of complete receptables on the controller board.
- The PWM-Base-Frequency of red is different than the other colors. WTF?
- Since no DC is > 25% one would expect that the PWM-Periods are interleaved so the current does not add up. But nope, thats not the case.
- No resistors in front of the LEDs. So the 3 red LEDs which have a combined Vf lower than 9V are run at the full 12V.
- There is no sign of any PFC on the primary side of the PSU.
- The PSUs isolation between primary and secondary is garbage. The feedback-opto has all its 4 terminals pretty close to the primary side. Thats less than 1mm.
Conclusion – Next steps
So this is not as bright as I want it to be. And the PSU looks dangerous. So the next logical step is to fix that. I used a lab power-supply to check if each LED actually can handle 1Watt. The answer is yes, but then it gets hot rather quickly. So some sort of cooling is required.
I think the mod will be made with series-resistors in front of the LEDs so they can run of 12V DC. Then all 4 fixtures controlled by one KaratLight Device. Not sure about cooling yet, running this at 12Watt will be to much heat for the aluminium PCB to handle.