Electronics, Lighting, & Gadgets - What's the Glass Ceiling for Dynohub Lights?

Anyone have any projections as to how bright the dynohub lights will get before they plateau? Right now the Edelux and the E3 triple are the brightest production lights and supposedly put out around 500 lumens each. It's hard with the Edelux because it is rated in lux but it is apparently comparable to the E3 so I would guess it is around 500 lumens.

With LEDs becoming more and more efficient do you think it is possible to get 900 lumen dynohub lights? The theoretical maximum efficiency is 683 lumens/watt. This will not be reached. However, how close do you think we can get to that? If we got to 300 lumens/watt then that would be 900 lumens from a dynohub. Do you think that is possible?

Cree has achieved 161 lumens/watt in laboratory settings for a white LED. Things are progressing in efficiency but where will we reach a point of diminishing return?

http://www.cree.com/press/press_detail.asp?i=1227101620851

The limiting factor is that to get power out you have to put power in.

Dynohubs all seem to max out at 500mA.

Voltage however is related to the speed the hub is driven.

If you are cycling fast enough you might get 20V @ 0.5A so about 10W is achievable.

How much light you will get depends on how you use the available power, in part, how sophisticated and well designed your lighting system is.

Light outputs will continue to creep up as better LEDs are released, however for any real advancement the design of the dynohub itself could do with being dragged into the 21st century.

I've done a little reading. It seems 1000 lumens is doable from dynamo, albeit DIY, which some people have done.

E3 Triple at 500 lumen is a stretch. More like 400 lumen. Then again, DIY it and you'll spend fractions of a E3 Triple.




If you are cycling fast enough you might get 20V @ 0.5A so about 10W is achievable.


IIRC. Schmidt SON is able to generate 50V at 50km/h, Shimano's can probably do the same.

IIRC. Schmidt SON is able to generate 50V at 50km/h, Shimano's can probably do the same.

I think you'll find that is with a low load ?

You can get high voltages if the hub isn't doing much work.

During benchtesting a Shimano DH-3D71 managed to generate 55 V and 500 mA and ignite and drive a fluorescent tube - however, it was spinning at 136 km/h (about 85 mph-ish).

Unfortunately I find it difficult to maintain such speeds.

The schmidt is definitely posh and expensive and has very good bearings, build quality and looks nice, however I haven't found any evidence that the performance is any better than a shimano.

:)

I think you'll find that is with a low load ?

You can get high voltages if the hub isn't doing much work.

During benchtesting a Shimano DH-3D71 managed to generate 55 V and 500 mA and ignite and drive a fluorescent tube - however, it was spinning at 136 km/h (about 85 mph-ish).

Unfortunately I find it difficult to maintain such speeds.

The schmidt is definitely posh and expensive and has very good bearings, build quality and looks nice, however I haven't found any evidence that the performance is any better than a shimano.

:)

At least 1000 lumens is achievable, at 30km/h. My favorite dynamo circuit site: http://pilom.com/BicycleElectronics/DynamoCircuits.htm.

I do agree about the Schmidt vs Shimano debate, it isn't worth the 3x premium. Shimano is also coming out with newer dynamos.

Ktronik over on candlepowerforums has done some tests and it seems to max out around 12W so with the right setup you could see over 1300lm. Hes got a 1000lm light. I find 800lm more than enough on the road and 500lm probably as bright as anyone really needs... my next build will be around 300lm.

Ktronik over on candlepowerforums has done some tests and it seems to max out around 12W so with the right setup you could see over 1300lm. Hes got a 1000lm light. I find 800lm more than enough on the road and 500lm probably as bright as anyone really needs... my next build will be around 300lm.

Do you have link to the thread?

At least 1000 lumens is achievable, at 30km/h. My favorite dynamo circuit site: http://pilom.com/BicycleElectronics/DynamoCircuits.htm.

Mine too.

That is where I got this info: "During benchtesting a Shimano DH-3D71 managed to generate 55 V and 500 mA and ignite and drive a fluorescent tube - however, it was spinning at 136 km/h (about 85 mph-ish)."

;)

Do you have link to the thread?
Hes got some peaky power curves somewhere too using bipolar caps, getting 900mA out of the dyno.
http://www.candlepowerforums.com/vb/showthread.php?t=111773

Ktronik over on candlepowerforums has done some tests and it seems to max out around 12W so with the right setup you could see over 1300lm.

Hi,

Which LEDs will give you 1300lm from 12W ?

TIA

Cree XR-E R2?

Cree XR-E R2?

Unlikely, 4 x Cree R2 would give you less than 1000 lumens @ 12W

The R2 needs 3.7W to produce 250 lumens.

And that would be ignoring the losses from the rectifier etc.

Hi,

Which LEDs will give you 1300lm from 12W ?

TIA

Cree R2s at 250mA put out 92lm from 0.8W.
XR-E R2 data (http://www.candlepowerforums.com/vb/showpost.php?p=2412997&postcount=158)
You need 16 XP-Es running in two parallel strings of 8 leds.
A 4x4cm array of XP-Es is probably the way to go, you can get them on 1cm boards with 1cm optics.

At really low drive currents the R2s hit 150lm/W but I dont think its practical to pack any more than 16 into a light head.

You need 16 XP-Es running in two parallel strings of 8 leds.
A 4x4cm array of XP-Es is probably the way to go, you can get them on 1cm boards with 1cm optics.

Are you taking into account the voltage drop from the rectifier ?

It almost sounds more theoretical than practical !

What does your 16 LED headlight look like and what optics does it use ?

Is it a thrower ?

Cheers.

:)

Cree XP-E is 1cm wide with optics. You can fit 4 XP-E in the space of one XR-E.

This thread will give you more detail on the XP-E.
http://forums.mtbr.com/showthread.php?t=482205

Cree XP-E is 1cm wide with optics. You can fit 4 XP-E in the space of one XR-E.

This thread will give you more detail on the XP-E.
http://forums.mtbr.com/showthread.php?t=482205

:) I've got some for one of my project lights. :thumb:

It almost sounds more theoretical than practical !

What does your 16 LED headlight look like and what optics does it use ?


Well, this is the ceiling thread so we are talking theoretical maximums. I have no need for a 1300lm light. Theres a few quad MC-E builds out there and some lights with a dozen or more XR-Es using small polymer optics so 16 doesn't sound too crazy... or not much more crazy than whats already being done.

A 4cm square light head is quite practical. Most triple/quad XR-E units are around this size.

Well, this is the ceiling thread so we are talking theoretical maximums. I have no need for a 1300lm light. Theres a few quad MC-E builds out there and some lights with a dozen or more XR-Es using small polymer optics so 16 doesn't sound too crazy... or not much more crazy than whats already being done.

A 4cm square light head is quite practical. Most triple/quad XR-E units are around this size.

Good point about it being theoretical.

I'm not convinced about the efficiency of a 1cm optic though.

I suspect there is some light loss (x 16) :)

How would it perform at low speed ?

I suspect there is some light loss (x 16) :)

How would it perform at low speed ?

Typically 15% on most optics. I think cutter.com.au lists the individual specs. The guys over on MTBR who are using them give good reports and the beamshots look ok.

Of course at low speed it would suck.

Regarding losses Martin once said his driver efficiencies are 90-95%, I don't know if his power curves are before of after that.
Dyno efficiency however is around 50% so thats 24 leg-watts which is more than I have spare!