gna

I bought a couple of GH6 dynohubs years ago, and managed to get one good hub from the two. I finally built it up in wheel, and I thought I would use it to light some LEDs. Maybe these are better questions for the electronics forum, but I'll start here.

I want to use circuit #3 from Pilom.de. Has anyone used the old SA dynohub to power LEDs? What sort of output should I expect from the Dynohub?

JaccoW

If I recall correctly these will do just fine with most modern led lights. The quality ones at least.

As for output, Minisystem has a series of blog posts where he upgrades the magnets of one and does a ton of measurements.
GH6 stands for Generator Hub 6 volts but many will be a little less powerful than that. Apparently in a 20" wheel they produce ~2.25- 2.5W.
Modern hubs do 1.5-3W which has become possible because of LED lights offering more light using less power.

Unless I am sorely mistaken I'd say a modern LED light with limited power draw (1.5W) should work just fine.
There was a thread over at Cycling UK forum in 2012 with some good suggestions.
Though modern B+M rear lights for example can run the full 3W of a dynamo hub without blowing up.

My guess is however that most headlights will work just fine, requiring perhaps a slightly higher speed to offer the same light.

gna

Thank you. I did see Minisystem's blog several years ago; I don't want to go that far. If I can drive LEDs with an old GH6 that's good enough for me.
I should probably explain that this is something of a DIY effort--I have an old SA headlight/taillight combo, and I want to put LEDs in them:



I went ahead and followed circuit #3 , using a Cree red LED in the tailight:



I mocked it up with some UF4007 diodes (what I had), a 4700 uF cap, and a white Cree LED. It seems to work just fine, though the taillight is a bit dim and blinks at the speed I can spin the wheel by hand. I'll have to work on this some more.

gilesa

I did something similar about 7 years ago, using what seems to be the same headlamp model. It uses several small LEDs in a fake bulb, so the lamp internals were not modified. That means it probably uses less than half the potential output, but is fine around town. I would want something brighter for unlit roads. With power LEDs able to take full output, you will probably do much better.

There is a lot of flicker at low speed (my circuit has no smoothing capacitor), but I choose to consider that a feature, like blinking battery lights. You will probably get a brighter tail lamp and less flicker at low speed by wiring it in parallel with the headlamp LED, through a low-value (10 ohm?) resistor. Choice of resistor will set the front/back balance. It will to useful to know what you end up with.

Metal polish will remove most of the yellowing of the plastic headlamp lens. I also polished the reflector.

rhm

In the past I have used GH6 hubs for running home-made LED lights with pretty good results. I tried a bunch of different things, eventually deciding the best way to do it was to wire a single headlight LED and a single taillight LED in reverse polarity-- I run a wire from one hub terminal to the + of the headlight and the - of the taillight; and a wire from the other hub terminal to the - of the headlight and the + of the taillight. Each LED got the full strength of the current, but alternately. If you watched in slow motion, you'd see the two light flash alternately. At speed, you couldn't notice.

I was pretty satisfied with the light I got, but in more recent years I have got spoiled by modern LED lights designed by people who actually know what they're doing.

I have never tried using a GH6 to power something like an BuM Cyo senso-plus premium or whatever they're called. Definitely worth a try.

52telecaster

I've not used a gh6 but i have used modern 2.4 watt hubs and can say most of the smaller led headlights use nowhere near the entire available wattage. U can run 2 if u want of some models so i am guessing your gh6 could run 1. I use 30-40 lux models. Not blinding but good enough for me to commute.

gna

I experimented with the taillight in series with the headlight as well as parallel, though I didn't use a resistor. It's very bright. I imagine I would need to heat sink it, though, if it were to see full power. In this circuit it sees about 1/4 power, but I would hope that would be enough for a taillight. I think I will try wiring it up on the bike to see what it looks like.


I've tried just about everything to remove the yellowing from the headlight lens--denatured alcohol, toothpaste, baking soda--and nothing has worked. I was about to consider it a feature--it makes the white LED look more "warm white," like an old incandescent bulb--but I will try metal polish. Thanks!

Random Tandem

I was pleased to find that I could take the light components out of a cheap Harbor Freight headlight to work with my GH6 hub. It flickers at walking speed but lights well when I am pedaling. It is a less than $3 option to try.

-Will

Road Fan

How well do these light up the road?

gna

Good question. LEDs are much brighter than the old bulbs, but the reflector is designed to extract as much light as possible from the bulb. The focal point and design are not optimal for an LED. I could use a collimator for the LED, but I'm not sure how well it will work.

Velo Mule

Good post. I am saving a DynoHub for when I get a Raleigh Sport. Someday I hope. I'll keep checking in. I built a LED headlight and taillight for a Sanyo bottom bracket generator that works OK. It is probably twelve years old now. It is so crude. I used PVC Pipe for the headlight and never put a lens in. It still works. I hope to do better with the DynoHub set up.

gna

Well, I tried it on the bike. I was able to get the light on the bracket, even with a Wald basket in front. The headlight lights up once I get moving, and the taillight blinks but is plenty bright enough. I rode around just now after dark, and though it throws a lot of light, it's not really focused. I asked my wife to take pictures but she already has her nightgown on. Maybe tomorrow.

I experimented with a collimator but it just looked like a flashlight behind the glass. Maybe a better one would work.

jamesj

This is a great thread. I also have a GH6 hub on my Superbe and want to use it but always wondered if I could run something modern.

BigChief 

I'm using the Nicelite NL 432 bulb for the headlamp and the NL 437R in the tail lamp of my 1951 Rudge. They claim that a regulator in the circuit is essential, but I've been running the system without one for months without blowing out any bulbs. The red tail light is quite bright. The headlamp lights the road directly in front of the bike nicely. For night riding I also use one of those AAA battery powered headband lights that has a narrow focus that projects further out front. These work well together. The headband light lights the road well ahead of me and reflects animal eyes far away and the bike's lamp helps me see things like rocks and potholes as they come close.

gna

Hmmm. Those bulbs look like they do a better job than what I used. My taillight wasn't a screw in mount, but I'm sure it could be modified. I'm a little turned around by the discussion of a voltage regulator on their site, but it looks to be very simple to install: https://www.reflectalite.com/XGEN2_instructions.pdf.

I have used this LED in some old bicycle lights that use batteries or I converted to battery power, and it seems to work well. I could have used one (and still could) but I didn't have one handy, plus the Cree Q5 was pretty cheap.

BigChief 

The Nicelites are great. They screw right into the original holders. They claim the regulator is necessary and maybe it is, but I have maybe 4 hours of night riding on them without it and all is well. We'll see, but I have a feeling that unless I start mashing top gear down hills, I'll be fine.

gna

Here's some pics of the setup:







I had my daughter take some crappy pictures and video in the alley this evening. The phone had trouble focusing and suffers from VVS (vertical video syndrome). I'm surprised at how bright the lights are, and the blinking works for a taillight. It will work just fine for "be seen" lights for commuting and errands.





https://youtu.be/lc1YkyUlaTE