Cheap Small LED bar
I bought this one just to play with as it is a bit cheap. It cost me around $6 with which looks like Cree XB-D LEDs.
I saw in another store that looked the same but was cheaper by a small amount though I did not purchase it as it used Cree-lookalike LEDs and the seller was passing it off as legit Cree. The endcaps were plastic as opposed to this one which used diecast aluminum.
I measured this to take in about 10W constant power as it appears to use a DC-DC current regulator.
Packaging as it came.
This is all that is in the box.
The tiny 6 inch LED bar, some screws and brackets.
This is the LED bar itself. It is quite cute but looks decent.
Back side appears to be smooth without a heatsink but....
The other side has the fins. It can either face up or down depending on how you mount it.
It does not appear to use silicone sealant on the end caps and this side has a small gap between the front cover and the end rubber seal.
Removed the end cover. It is held in by three SS allen bolts.
A look at the light assembly.
Front screws were loosened and the transparent cover came off.
Rubber seals were stretched and is shorter than the lenght of the heatsink.
It uses a decent DC-DC regulator, Cree XB-D LEDs, Aluminum core PCB and some heatsink goop behind it all.
There are no electrolytic caps so it should work well at high temperatures without issues of drying out then failing.
The front cover is polycarbonate and has deformed from the front screws pressing against it toward the white rubber seals.
All in one LED driver chip marked AP5170 which supplies all six LEDs. The XB-D is rated at 3W so this is underdriven by almost half.
I used clamps to hold the rubber seals stretched out while tightening the front cover.
With the clamps removed, the seals pop out a bit.
Loosening the screws near the end and pushing it lightly with the screwdriver and it pulls in enough to be put back together with decent seal.
With the reflector in place, on one end, the LED is perfectly centered.
This looks suspicious. LED die looks different from real Cree XB-D.
The other side LED is not. This meant that the distance between LEDs on the PCB is not the same as the holes in the reflector!
Light working again.
Based on the datasheet and power consumption, I estimate the light output to be around 800-900lm total.
Beam is an OK spot. Color temp is a bit cold at around 6500K.
I have another pricier LED aux light (costed more than twice this) that I bought a couple years back also with six genuine XB-D LEDs but those were a more pleasant 5500-6000K tint.
Upon closer inspection, the LED does not have the "X" which is in the middle of a genuine XB-D die so this must use an imitation Cree LED. It looks like a real one at a quick glance but unfortunately, is a fake. The cheaper light I saw was a lot more obvious though with a ceramic package the size of an XT-E but with a really small die.
This is with five LEDs covered and only the one shining, which is centered on the reflector.
The halo can be seen around the spot.
And this is the one off-center.
Spot is slightly deformed and the halo is obviously off center.
I decided to use it as a reverse light. This would help me backing up in dark parking spots.
I will have to replace those incandescent reverse lights with white LED ones for a more uniform look.
I simply mounted the LED bar on the plastic trim using double sided adhesive tape and clamps made from stainless sheet.
The light also produces a ton of RF noise such that the ultrasonic parking sensors which are tapped on the same reverse light supply, goes crazy when the engine is running as the DC-DC converter regulates LED current on the higher supply voltage.
The solution is a 1000uF low ESR cap across the LED supply. A smaller value could have probably worked but this was the first one I got when I reached in the parts bin.
Turned out the cap alone was not enough when the engine is cold and the voltage is at 14.3V but was OK when it has warmed up and voltage is at 13.6V so I made this LC Pi filter using SMD inductor, ceramic and tantalum caps.
There is still an occasional blip but useable now.
Tucked it in and there you have it.
These are cheap and work OK. Not the cheapest that everything was skimped on but quality control with sealing could have been better. They would be nice as DRLs as they are bright enough in daytime to be clearly visible but could be distracting when used at night. Perfectly fine for offroad use though. The RF noise issue could be a problem for some applications.
03 Feb 2017:
I could not leave this well enough alone so I took it apart again.
There isn't as much goop as I was hoping.
Checking at the circuit, there isn't much decoupling in the B+ input. Just a single 1uF MLCC (above D3, on the right of the pic)
At about 11.6V, supply is pretty much clean as the SMPS is running at linear mode.
At 12.5V, it starts oscillating and the supply current ripple is very bad. We are seeing 880mV PP across a 0.5ohm sense resistor which means current ripple is at 1.76A peak!
At 14.4V, frequency increases and ripple slightly decreases at 1.64A peak. The sharp transistions make a lot of RF noise.
There is a space for two decoupling caps marked C5 and C6 in the upper left of the IC, I placed two 4.7uF MLCC there and placed a low ESR tantalum on the space where the previous 1uF was in.
Ripple significantly dropped and the edges are now sloped for a much lower noise level. It still messed with the reverse sensor so I put the pi filter back but no need for the extra 1000uF cap.
A closer look of the die and it looks different from the genuine XB-D chip so I have my doubts if this is indeed a Cree chip.
23 Feb 2017:
I bought another one. This is the cheap one I was talking about.
Box says "American Cree LED". okay.
At quick glance it looks the same as above. But there are no screws holding the front lens on.
LED is NOT Cree as far as I can tell. If anyone knows which LED this is, let me know and I'll add the info.
End caps are plastic but do have metal threaded inserts.
Screws that hold the end caps are self tappers and appear to be chrome plated, not stainless steel.
The front lens is held in by inserting rod/wires to compress the white sealing rubber.
aluminum clad PCB is a little thinner too.
Beam is a mess. The reflector rattles inside the light and the LEDs would not center in it.
Light tint is also bluish (I estimate it to be 6500-7000K) but not horribly blue, but still not the nice pure white genuine Cree LEDs have.
And I also bought a few of these too. They are pretty much the same as the 6 inch version and has the same parts and build quality but is half the size.
I plan on using these for the bike.
Took the 3-LED version apart.
Closeup of the LED.
The cap marked C1 is the lone decoupling for the B+ supply. It measured 3uF so I paralleled an electrolytic 25V 47uF across it, there is plenty of room to put the additional cap.
Side view of the LED.
Back of the metal core PCB. It is mounted dry so I put in grease before putting it together.
I didn't like the bluish tint of the light so I tinted the front yellow.
beam output is a little better than the 6-LED version but still worse than the first one above.
Page created and copyright R.Quan ©25 Jan 2011.