Is SSCP4 a drop-in replacement for Luxeon I?

[alexlockhart]

I have a Cateye HL-EL510 bike light. I got the older HL-EL500 when it first came out like 4 years ago, and was impressed at its brightness and long run time. The newer 510 that I've had now for about 2 years seems to have the same overall brightness, but has a tight oval beam with some spill, which is an excellent pattern for commuting (my main riding).

With the newer, more efficient LEDs available now, I've been thinking about modding my light to use one of them. The 510 uses a plain Luxeon I lambertian emitter, and from my calculations of burn time (30 hours on 4xAA) it drives it at about 150mA. Probably less, since the driver can't be perfectly efficient. Of course, that's far less than it could be driving, even the LuxI, but that's done because the battery life is a strong selling point for this light. 20 lumens or so, if it's well-focused, is enough for the cheap battery-powered LED light market.

I know the SSCP4 has the exact same physical characteristics as the LuxI, so I know I could just un-solder the LuxI and solder in the SSCP4, but it's slightly different electrically. The biggest difference that I can see is its Vf is 3.25, whereas the LuxI's Vf is 3.47. Before I do the mod, I want to know how the new LED will be driven.

That depends on the driver, of course, which in this case is basically a simple resistor. The light has a high and low beam mode, and it takes the 6V from the batteries (4.8V from my NiMHs) and transforms that to something the LED likes, so it's got other stuff besides a resistor in there, but it doesn't do any real regulating - it slowly gets dimmer and dimmer as the batteries wear down.

I took the light apart the other night, and besides a few unrecognizable components, and 2 things covered in goo (by design), there's a 510mOhm resistor in there that's big enough to be the one that's the current-limiting one. I did some electronics math ( at http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm) and figured that, if it's driving the LED at 150mA, then the input voltage (before the resistor) must be 3.5 volts.

So, I'm wondering what will happen when I drop in an LED with a lower Vf. The calculations for the resistor-based driver seem to suggest that changing the Vf to 3.25 and leaving the input voltage and resistor the same means a current draw of 500mA. That would be a welcome boost to around 120 lumens, but the chart describing Vf versus mA for the SSCP4 seems to indicate that 500mA draw happens around 3.4V, not 3.25V. So I'm not sure what would happen - the driver seems to say one thing, the LED another.

Thinking about this much higher drain on the batteries, and finding out that there are Li-Ion cells that are shaped like an AA, I thought that maybe I could upgrade the batteries in the light as well. Since the light is designed for 4xAA in series, it can certainly handle 6V, so if I rewire the battery compartment to use 4x14500 in a 2S2P configuration, I'll be giving it 7.2V. To find out what would happen if I just dropped those batteries in right now, I wired 6xAA in series (which, with NiMH, is 7.2V) and fed it to the light. It was brighter, but not a lot. I took some beamshots, but they weren't very impressive - it looks maybe 20% brighter with 6xAA vs. the original 4xAA, despite a 50% increase in voltage. I don't have a multimeter, so I couldn't measure the current draw on the batteries in either configuration, and couldn't measure actual voltage delivered to the LED either.

OK, that's what I've figured out so far. Now it's time for you to tell me the things I don't know: What current draw, and at what Vf, will the SSCP4 have if I just drop it in? How about if I use 4x14500 in 2S2P, making the supply (before the regulator) 7.2V instead of 4.8V?

Alex

 

[Gunner12]

The Seoul P4 LED is a drop-in replacement for the Luxeon. The lower Vf should not be a problem. The current draw should be similar to the Luxeon. You'll need a 0.030 inch lift for the Seoul to focus correctly in a Luxeon reflector and watch out for the positive slug. Isolate with a thin layer of Arctic Alumina. If you used 14500 batteries, it might fry the regulator. They are 4.2v off the charger so that makes it 8.4v. The 14500 battery has about the same amount of power as a good 1.2V rechargeable.

Welcome to CPF!

 

[alexlockhart]

Thanks for the welcome, and the info!

Obviously, I don't know enough about LEDs and their regulators to figure this out, which is why I posted here, but it's confusing to me how they would have the same current draw with different Vf. Is that generally true for any LEDs? Do they all have similar current draw in the same circuit? Do regulators control the voltage, or current, or both? With most devices that use electricity (incan bulbs, for example), they require a certain voltage to operate "normally", and if provided that voltage, they draw a certain current, and no more. Given unlimited current at a specific voltage, LEDs will run away, asking for more and more current, until they go , right? So does that mean that even with different Vf, a regulator will provide a capped amount of current, and the draw will be similar?

Thanks for the link to the spacer. That's a dimensional difference I had not thought significant, but it makes sense that it would be for focusing. The datasheets confirm the SSC is 0.78mm shorter from bottom of slug to top of dome than the Lux1, which is 0.030" shorter.

From the Luxeon datasheet: "Electrical insulation between the case and the board is required - slug of device is not electrically neutral. Do not electrically connect either the anode or cathode to the slug." The Cateye accomplishes this by having the emitter mounted on an aluminum heatsink disc, with the solder points going through plastic-grommeted holes and wires connecting that to the circuit board. So I think I'll be fine with the positive slug on the P4, since the Luxeon is the same.

Would using the higher voltage batteries slowly fry the regulator? 7.2V certainly didn't, for the short time I ran it with that. 8.4V might be different, but this regulator is not much more than a resistor, so that's why I had the courage to hook it up to 7.2V in the first place. 8.4V is 40% more than the 6V it was designed for, though. Anyway, it's true that 14500s have similar power as NiMH AAs, which highlights the market-driven optimization of different cell sizes. The best 4/3AF size NiMH cells have about 55% as much power as the same size 18650 Li-Ion cells, but in AA size, the power is about the same. In other words, a 14500 Li-Ion should have almost twice the power of an AA NiMH, but it doesn't. I might as well keep using my Ni-MHs.

Alex

 

[Gunner12]

Try posting/request moving this to the modding forum, you'll get more experienced/correct answers there.

I haven't modded my self, I'm just responding based on what I have read and seen on this forum and around the web.

Actually, the Luxeon has a negative slug, not positive like the Seoul. I don't know much about how LEDs operate. Here's a Chart and a Graph about the Seoul.

Seoul Semiconductor W42180 bin U (tested February 2007)

(From White LED lumen testing)

As you can see, the LED can actually run from 3-4v. Given unlimited current and a variable voltage, the LED will probably go .

The regulator should adapt to fit the LED's voltage. For example, the Elly(at Dealextreme) flashlight's regulator will provide up to 5v to whatever it is connected to, weather that be a LED or a laser module.

A regulator controls both the current and voltage. I think you could change the resistors to change the current provided by the regulator(don't try it unless you know what you are doing).

Most regulators used in Flashlights are DC-DC converters, this Wikipedia link might help.

There are three main kinds of regulator, Boost(increases voltage), Buck(Decreases voltage) and Buck/Boost(can increase and decrease voltage). Try using 1 or 2 1.2-1.5v batteries. If it still lights up brightly, then it is a Buck/Boost regulator. If not, then it haves a Buck regulator.

When a regulator is driven above what is is supposed to handle, one or more of the components will overheat and let out smoke. Once you see/smell the magic smoke, your regulator is probably fried.

From most of the LED replacement mods I have seen, the regulator did not seem to mind the change in Vf, But some regulators seemed to have changed the current a bit when changing to the new LED(variations on the same brand and model of flashlight). Your mod should be fine as long as you don't make any big mistakes.

Good luck with your mod!

 

[cave dave]

I have done three P4 mods and haven't had to fool around with reflector positioning or anything. Just replace the emitter. Do you have pics of the insides? Is it on a star board?

Also you could just measure the current while you are in there if you are currious. I doubt its regulated at all with that kind of runtime. The P4 might draw more current and have a shorter runtime but don't worry about it, it can handle it.

PS: a "drop in" mod is just that. No skills required, just like changing a bulb. Soldering required is not a "drop in" mod.

 

[alexlockhart]

Try posting/request moving this to the modding forum, you'll get more experienced/correct answers there.

Like most newbies, I'm displaying my ignorance on several levels. Mods, if you happen to be reading this, would you kindly move it to the modding forum?

That's great data in those charts, thanks. What I don't know for sure is exactly what kind of regulator is in there. There are two components potted in resin on the board, one good-sized 510mOhm resistor, and one or two other itty bitty thingies. The regulator turns battery voltage (4-6V) into LED voltage (3.4V) and provides a high and low brightness mode, so it's doing something besides just resisting, but I don't know what. Since it lets the LED dim slowly as the batteries run down, I can tell it's a simple resistor-based regulator, but I don't know how it does its high/low brightness. It's a cheap light, so it's nothing fancy that uses an IC chip.

Thanks to your help, I've got the info I need now to feel confident with doing this mod, and I should be able to go back to the Luxeon if necessary, unless I let the magic smoke out - I've done that plenty of times before. I'll be getting a multimeter from DX when I get the LED, so I'll be able to measure everything in there before and after I do the mod. Hopefully the new P4 LED will manage to draw a little more current from my regulator, but even if it draws the same, it'll still be more than twice as bright. If it draws less, I may have to figure out what resistor to swap in to change that. First I just need to try this and see.

I have very detailed pictures of the insides of the thing, but they don't seem necessary at this point, so PM me if you really want to see what's inside Cateye's best 3-year-old AA battery light. When I do the mod, I'll make a thread in the modding forum to document my work. There are a lot of these Cateye lights around, and if it's this cheap and easy to make them decently bright, I imagine people would want to know how.

Alex

 

[wintermute]

Careful of that positive slug on the SSC emitter. If you can use a SSC star (which photonfanatic will have in a week)- the bottom of the star is electrically isolated, so it will be a drop in. Also, if the heatsink is anodized, the positive slug of the emitter won't be a problem either.

 

[cave dave]

Careful of that positive slug on the SSC emitter. If you can use a SSC star (which photonfanatic will have in a week)- the bottom of the star is electrically isolated, so it will be a drop in. Also, if the heatsink is anodized, the positive slug of the emitter won't be a problem either.

Hence why a picture would be valuable!

Photon fantastic already has stars I think, but it might be worth waiting for UVOH.