Adding regulation to a light

[Velcro]

I'm using a Cateye EL-200 on my bike. I like it a lot, especially when I put fresh batteries in it. However, it amazes me (and annoys me) how quickly the output goes from full brightness to dimmer and dimmer with just two hours or so use. Cateye claims 110 hours in steady and 220 hours in blinking mode. We all know such claims are pretty inflated, but still. Anyway, I ride in traffic on a daily basis so I want my light to be as bright as possible for as long as possible. Which means I'm regularly replacing the batteries while I haven't even reached half of their lifespan, just to keep it optimal bright.

So I was thinking how much work it would be to add regulating circuitry. Something like the Opalec Newbeam is what I had in mind. A completely linear output curve. I'm not familiar with the components used for regulating circuitry, so I don't know how much room they would take. But the Opalec module is so small that it made me wonder.

As you can see, the output of the NewBeam is very steady linear (more linear than any runtime plot I've seen). It has three white LED's with 2 AA batteries and does almost 10 hours. The Cateye has three white LED's and 4 AA batteries so that would mean 20 hours of steady bright light in continues-on mode, and 40+ blinking. Has anyone tried something similar? And where can I find pics of the components used for regulation? Thanks in advance.

 

[leukos]

I'm not familiar with the Cateye EL-200 and probably some of the serious modders here could tell you how to do it. IMHO, I think it would be easier to use NiMH batteries or lithiums to give you a flatter discharge rate. Their performance in a 4 AA application would come close to the characteristics of regulated circuitry. /ubbthreads/images/graemlins/cool.gif

 

[Wolfen]

Have you looked at the Sandwiche Shoppe Forum and store? Wayne has all kinds of circuits availabe

 

[Wolfen]

Sandwiche Shoppe Forum

 

[Wolfen]

Maybe a Sandwich Shoppe Down Boy 917 MaH. Should work pretty good. Decent runtime (1.5 hours on 4 nimhs ?)and brightness.

 

[Wolfen]

Quad post. Anyway check out Waynes store and forum and head over to the modified lights section.

 

[IsaacHayes]

if it only uses 3 leds, then it only needs 60ma of current (if ran at led specs). 917ma DB would fry it...

 

[Wolfen]

Velcro,
Is the Cateye a luxeon based light or 5mm LEDs? If it 5mm leds then you can use one of the lower output circuits.

 

[Velcro]

5mm.

 

[Wolfen]

I would revisit this topic in the modified lights section or contact Dat2zip to find a suitable converter board for your light.

 

[Doug Owen]

I suggest you might want a 334 based Low Drop Out (linear) regulator. For instance, WorldTorch LDO circuit .

You could probably set it up for 90 or so mA and drive all three LEDs in parallel (I'd check the Vf match and add 10 or 20 ohms in series with each), or use a separate driver for each. You have to solder the bits together, but the kit of parts is only $4, including shipping for US folks.

Efficiencies for this application can be higher than 'any other way'. You can expect very near 'label ratings', that is a 90 mA set up (30 per LED) using 2500 mAh NiMH cells will give you (2500 mAh/90 mA) 27 hours or so of 'dead flat' output. In some cases you can even remove one cell and get nearly the same run time. Efficiency then goes from say 75% overall (nothing to scoff at) to 'mid 90s', something nearly unheard of.

Doug Owen

 

[Velcro]

Doug, that sounds great (especially the part about the price /ubbthreads/images/graemlins/smile.gif ). But the problem is that I don't use NiMH batteries (nor do I really wish to). I use alkaline batteries only, and sometimes even carbon-zinc (NiMH are pretty expensive over here, not to mention a proper charger). That's why I'm intriged about the regulation of the NewBeam. It allows the use of NiCad, NiMH, alkaline and even carbon-zinc batteries with brightness and output curve being equal regardless of which battery chemistry is used (but with shorter runtimes depending on chemistry of course).

 

[Velcro]

bump

 

[Doug Owen]

[ QUOTE ]
Velcro said:
Doug, that sounds great (especially the part about the price /ubbthreads/images/graemlins/smile.gif ). But the problem is that I don't use NiMH batteries (nor do I really wish to). I use alkaline batteries only, and sometimes even carbon-zinc (NiMH are pretty expensive over here, not to mention a proper charger). That's why I'm intriged about the regulation of the NewBeam. It allows the use of NiCad, NiMH, alkaline and even carbon-zinc batteries with brightness and output curve being equal regardless of which battery chemistry is used (but with shorter runtimes depending on chemistry of course).

[/ QUOTE ]

Not to worry, it's just fine on four alkalines, although the efficiency is not so outstanding. The performance is, of course, what you want. At the start, you'll be something like 60% efficient (3.6/6), at 'midlife' (say 12 hours of run time at 30 mA per LED) you're at 75% (3.6/4.8). At end of life for the cells, when you drop out of regulation, some 24 plus hours in, you're of course at '100%' (actually only a bit over 97%, but close enough for jazz). Overall average close to 75%, nothing to be ashamed of for sure. In fact hard, if not impossible, to beat.

Dead flat output until the bitter end.

Go ahead, give the idea a try, it's a good one....

Doug Owen

 

[Velcro]

Doug, it sounds great. I'll definately give it a try. Now how to get that kit over here. /ubbthreads/images/graemlins/thinking.gif Hmm, maybe I'll even replace the current LED's with those 26Kmcd ones. That would make it a pretty fine light. /ubbthreads/images/graemlins/grin.gif

 

[Doug Owen]

[ QUOTE ]
Velcro said:
Doug, it sounds great. I'll definately give it a try. Now how to get that kit over here. /ubbthreads/images/graemlins/thinking.gif Hmm, maybe I'll even replace the current LED's with those 26Kmcd ones. That would make it a pretty fine light. /ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

If 'spot' is what you want, then for sure swap out the one in the kit it's nothing special. In fact I often file on the end to make a very broad beam for area light.

As to getting the kit, the parts are all listed, the only 'hard to find part' is the regulator IC. If you can't sort out getting them, send me a PM......

Doug Owen

 

[Doug Owen]

[ QUOTE ]
Doug Owen said:
If 'spot' is what you want, then for sure swap out the one in the kit it's nothing special. In fact I often file on the end to make a very broad beam for area light.



[/ QUOTE ]

Sorry, that makes no sense, I'm thinking of the wrong LEDs. For sure consider replacing the ones in the bike lamp......

Brain fade.

Doug Owen