Candle Power Flashlight Forum

I hope this is the right place. I put it here as this is LED related. I know this is a forum for flashlights, but my particular need is for a dynamo (bicycle generator for those not in the know).

Now I hope one of you guys has good electrical component knowledge, because it looks like I may need it.

What I am looking at is taking a standard bicycle bottle-dynamo (make and model are not really important here, as they only really deal with amount of drag, and fitting if not using a bottle). And changing the lamps over to LED. I had thought of normal LED lights, but then I stumbled across the EverLED. For those not familiar with the EverLED, it is a drop in replacement for PR3 halogen (etc...) incandescant bulbs, but can be used for torches with between 1 & 6 cells (thats 1.5-9v alkaline or 1.2-7.2v NiMH/NiCad).

http://www.everled.com/

Now down to business... most standard dynamos are rated to 6V and 3W and are aimed at being variable voltage, but constants (or very close to constant) current.

Normal use is 1 2.4w bulb forward, and 1 0.6w bulb rearward, although the rear bulb can be sacrificed and a 3w front bulb used instead.

Because the EverLED can be used with varying voltages, it "seemed" destined to be used with dynamo's.

With a little searching I found the following site...

www.cycling.org/lists/bikecurrent/archive/2004/2004-06/1086837544000

For some reason it doesn't like loading, so the info I show has been taken using Google's cached version of the page.

[BC] EverLED data
Bruce and Tracey Ingle <inglegis.net>

Some data on the EverLED's consumption...unfortunately, I don't have a means of measuring relative output with any real accuracy (maybe a third of a stop with an old photo meter, if I dug out one that works, and it's tough to judge by eye.)

Code:

Volts      mA  VxA (Watts)

  0.5     225   0.113
  0.9     295   0.268
  1.1     330   0.356
  1.2     518   0.622
  1.5     538   0.807
  2.0     485   0.970
  2.5     429   1.073
  3.0     348   1.044
  3.5     298   1.043
  4.0     286   1.144
  4.5     269   1.211
  5.0     248   1.240
  5.5     191   1.051
  6.0     172   1.032
  6.5     160   1.040
  7.0     150   1.050
  7.5     142   1.065
  8.0     136   1.088
  8.5     141   1.199
  9.0     160   1.440
  9.5     300   2.850

So, it appears to have a fairly constant consumption between 2.5 and 8.5 Volts. Below 2.5 volts, the consumption falls off, and above 8.5 volts it gets
very inefficient. I doubt it'd tolerate 9.5 volts very long because the regulator would necessarily be burning up a lot of power. It's rated for 1-6
alkaline cells, so the extra power consumption would quickly take the edge off 6 cells above 1.5V.

I'm guessing the easiest way to dim it efficiently would be to just switch it between two different voltage batteries, e.g. a 6V 223 Li/Mn02 or Li/S02
and a 1.5V AA Li/FeS2 (or even just an alkaline AAA) for disposable apps. For Ni-based rechargeables, perhaps a switchable series/ parallel arrangement
would work. 2-3 cells in series would develop the full consumption (and presumably the full output as well.) Or, you could mix types...have a rechargeable for max output, with a small alkaline or Li/FeS2 for dimming and backup power.

At this point, it's been running off a used (1.3V open circuit) AAA for the last hour or so. The thing is very good at using the last bit of energy out of a
single cell.

Click to expand...

Re: [BC] EverLED data
Alan Braggins <armbncipher.com>

I wonder how it would do hooked up to a dynamo and bridge rectifier.

Click to expand...

Re: [BC] EverLED data
Jonathan Edelson <winnie_pubborealis.com>

Poorly without an additional _shunt_ regulator. The problem is that there is a switching regulator somewhere in the device; current consumption goes down as voltage goes up. A dyno, on the other hand is almost a constant current device; current remains constant and the voltage goes down or up (to a maximum set by speed) in order to push that current through the load.

It looks to me as though a shunt regulator set at between 2 and 2.5V in parallel with the EverLed would be a good match for a dyno.

On the other hand, simply using a 3W luxeon with a bridge rectifier and a dyno would be a good match. The constant current characteristic of the dyno looks like it would be great for running LEDs.

Click to expand...

What I would like to achieve is to replace the single headlamp with 2 headlamps. If using halogen, this is only possible with 12v generators and they are PRICEY. Buy using the EverLED, you get close to the designed optics of the original lamp, which you dont necessarily get with a pure LED setup. Looking at the current consumption, I see no reason not to use to EverLED's at the front, and some for of lighting at around 0.6w at the rear.

The one thing that is really stopping me is this "shunt regulator" I do not entirely understand what it is, nor how to wire one (3 pin T092 or similar, don't want to go 5 pin or PIC).

So could anyone give me any ideas? And could anyone comment on the fact that some of the Lumec lights have an intergral bi-directional z-diode for overvoltage protection.... Is this anything like the shunt regulator?

Many Thanks.