Question about multi-LED lights (SL 4AA LED etc.)

Has anyone opened one of these up and looked at the circuit? In particular, does each LED have its own limiting resistor? Lights of interest include SL ProPoly 4AA LED, PT Attitude, Lightwave 4000, and so forth. Reason for asking: these lights tend to overdrive their LED's and I'm wondering where the points of failure are, i.e. if a resistor or LED goes, do the rest of them keep working?

Thanks.

Re: Question about multi-LED lights (SL 4AA LED et

I have a SL 4aa LED. Each LED has their own limiting resistor. Also, I had 3 of the LEDs go out while the other 4 still work.

Re: Question about multi-LED lights (SL 4AA LED et

Sockman-

That is good news and BAD news!

Good in that the LEDs are not hooked in series causing one failure to kill all seven!

But that is horrible considering marketing is constantly saying how LED's have a 100,000 hour life. I wonder what caused the failure and how hard Streamlight is driving these LEDs?


GregR

Re: Question about multi-LED lights (SL 4AA LED et

I would imagine that heat was the main factor that caused the LEDs to fail. The light becomes hot after about 15+ minutes and the reflector's silverish coating was starting to melt. I can't measure the current, but I would assume that they were severely overdriven.

Re: Question about multi-LED lights (SL 4AA LED et

By the way, when I said that my SL 4AA LEDs "failed", I meant that they would blink until going out completely. That's still not a whole lot better than them burning out completely though. I'm glad that the LEDs were hooked up in parallel.

While where on the topic of multi-LED lights, does anyone know if there are any flashlights where the LEDs were hooked up in series?

Re: Question about multi-LED lights (SL 4AA LED et

As far I can tell, there are no lights using 5 mm LEDs that do not use limiting series resistors. The only notable exceptions are the button / coin cell powered lights, where the current limiter is the battery itself.

A bit off topic... I have used for six months a PT Attitude as night light, I mean the light turned on for 10 Hrs on off-the-charger NiMH every night. After this performance, I compared the PT Attitude with a new one off the box, and there were no dissimilarities between the two, relative to brightness and beam quality.
PT drives their Nichia at 50 mA in the Attitude, same as Inova and Streamlight in their respective 5 mm LED lights. It seems that LED life, in these conditions, is on average 10.000 hrs.

Anthony

Re: Question about multi-LED lights (SL 4AA LED et

I've heard it claimed that the CCrane/Tek-Tite lights have no resistors and consequently burn out their leds pretty fast. I've also heard the earlier SL 4aa's ran at higher current than newer ones, so the newer ones don't heat up as much.

Re: Question about multi-LED lights (SL 4AA LED et

I've never had an LED go out in a Tektite flashlight. As I understand though, the newer (2003) Tektites have a resistor in there to help limit current.