XR-E vs. XP-E

[rayman]

I just compared two Crees, one XP-E Q3-5A and one XR-E Q3-5A. Solder two wires to each an tried them shortly with a single Li-Ion-RCR123. I thought that both emitters should have about the same brightness. But the XR-E is about twice or three times brighter than the XR-E. Bought the XR-E from a CPFer so this is definitly a Q3-5A but the XP-E which I bought from KD was supposed to be also a Q3-5A. Bought two and the first one was very dim also. So could it be that it's just a very old binning?

rayman

 

[eprom]

Hi Rayman,

It is hard to compare two emitters with eye, because

1-) We must drive two at same current. In this case one can have a higher Vf so get less current and seen dimmer.

2-) XR-E has an 90 degree viewing angle vs XP-E has an 115 degree viewing angle. So this is the second problem to compare them with eye.

give a chance to KD's XP-E

Cheers,

 

[rayman]

I tried it with two 700ma drivers with the same result. The XP-E had it's chances . Glued it on a heatsink now it's going to be my testing emitter . Regarding you second point, the difference was so big that it couldn't be the optic.

rayman

 

[John_Galt]

Were you comparing hotspots? A ceiling bounce test might be better to determine brightness... Also, the XP-E might have a higher Vf, like eprom said...

 

[rayman]

Compare the overall brightness by turning off all lights and then trying both lights with a 700ma driver.

rayman

 

[uk_caver]

What are you powering the 700mA driver with, and have you checked what current is actually getting to the LEDs?

 

[znomit]

But the XR-E is about twice or three times brighter than the XR-E.

Bit of clarification needed here :thinking:

I'd put them both is series so you know they're getting the same current. 2-3x is a huge difference.

 

[Ragiska]

not if they don't have the same Vf, and they will look drasticaly different due to emission pattern. intensity over an area varies with the square of the radius of the lit area, so it does makes HUGE difference.

 

[mudman cj]

It sounds like you may have been comparing the emitters before you glued them to heatsinks. I would expect the smaller XP-E package to quickly heat up to a higher temperature than the XR-E and therefore reduce its output. This factor would of course be compounded with the emission pattern differences already mentioned as well as differences in Vf. If the XP-E has a higher Vf, then it will dissipate more heat at the same drive current, further exacerbating the thermal issue.