dynohub LED build advice. Component choice (UK) and Thermal management.

[TheBrick]

Hello,

I would like some advice on building a dynohub powered LED light. I done some reading around on this site but due to this being my first electronics project I 'm not sure how to work some things out. and am unsure about some component choices. I apologizse in advance for what may be some very stupid questions. I also apologise for the length of the post.

I am planing on building a dynohub powering 3 LEDs. I am using the circuit 10 from here.
http://pilom.com/BicycleElectronics/DynamoCircuits.htm

I shall be using the shimano dh3n80 dynohub. My first question relates to this. In the above philom link it states that if there is a zener diode it must be removed. Does the dh3n80 have a zener diode? I guess no otherwise it would have DC ouotput from terminals with fixed voltage I suppose?

My second question is about the capacitor values. How are capcitor value calculated? Do you just use the number of magnets in the generator, and the number of revolutions per second of the wheel at x speed which you require the boost to calculate the frequency. Use this to give the period T=1/f of the AC current then use the discharged formula ( http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capdis.html ) so find the required capacitance that has a half life of T?


I now have some questions about component choice.
I am based in the UK and have manged to find all the basic components at maplins.co.uk, however they do not seem to do a range of the really bright LEDs. I don't have a clue what LEDs to use but Luxeonstar post to the UK, would 3 of these be a good choice?
http://www.luxeonstar.com/premounted-rebel-neutral-white-led-on-a-20mm-star-base-160-lm-p-614.php

with three of these lens?
http://www.luxeonstar.com/fraen-low...th-flat-bottom-hldr-fits-rebel-leds-p-485.php
Of should I have three different lens patterns to give a good overall light pattern?

What connectors should be used to the dynohub? Is speaker cable ok to use to connect from the hub to light?


My last question is about thermal management. I am planning on making my hosing our of some aluminum box section,
http://bikeled.org/ suggests "3 square inches of exposed heat sink area per LED watt", but due to the moving airflow he gets away with much less, what is people opinion on this? Would some fins be required for my proposed setup? Is the pre-cut thermal tape linked to in with the LED worth it?

Thanks for any help.

 

[yellow]

Zehner-test (while I think no hub dyno features them):
no wires to light attached to hub, voltage meter connected to contacts, spin the wheel,
if the voltage goes over 7.5 volts (to somewhere 20-25 Volts): no zehner
Thats AC, of course, so set the meter to AC


Rebel led look ok
(to be honest, I dont like them, but ...)


cooling
use metal housing for giving heat away, then (+ because of low power and high speed at power with dynamo) that is more than adequate.


light housing
I will, once again, be VERY straight: that "guide" to light building - and all that are similar - is complete crap!
The only thing that You can expect is:
* much additional problems to be solved with any actual one solved - that has just been solved somehow "freehand".
* constant anger about silly things that "should do" but dont
* when built perfectly (which You wont be able to at Your 1st try), a light that still looks homemade
in short: nothing that might lead to the wish to do more/better ones

and, also again, the advise what to do:
purchase a cheapo flashlight (DX, kaido, local budget store, ...), one that features a head that is big enough for Your three led/optics.
Open up, use just the head, put led on aluminium disc - 3 mm think minimum. Mount optic/reflectors
Put that disc inside head, should be a tight fit in body
connections, end plate, wires inside and out at the back end, mount, ..., just like that "guide" You have.

Cheaper, + all housing parts needed come with lamp, everything one does himself lies inside, so the outside is plan great.



PS: with three led in series, that difficult (my opinion: ueseless, because of the manual switch) driver is unnecessary.
Simple Schottky diode rectifier, or - more advanced and giving light earlier, but flicker at low speeds - Mosfet Rectifier

PPS: when roadbike (few low speed driving) and hub, I would use an MC-E, connected in series.
Easier to build, less parts, smaller

 

[znomit]

I would source LEDs/optics from cutter.com.au, they have the brightest/most efficient and a good range of optics.

I believe the capacitor values were determined from measurement not calulated.

Bikeled is a very good place to start but your build likely depends on what tools and materials you have available.

Circuit 10 works very well but is complicated, you can start with a much simpler circuit and switch to 10 later.

I don't think that the dh3n80 has a zener.

:welcome:

 

[BrianMc]

Hello, I would like some advice on building a dynohub powered LED light. I done some reading around on this site but due to this being my first electronics project I 'm not sure how to work some things out. and am unsure about some component choices. I apologizse in advance for what may be some very stupid questions. I also apologise for the length of the post.

Last first. It'd be the pot calling the kettle black, in my case! :laughing:

If you have to, you must, especially if bitten by the bug like so many here, But in answer to a closely related question I had on this topic in case he doesn't want to repeat himself:

http://www.candlepowerforums.com/vb/showthread.php?t=214561&page=3postcount=87

Looking at the prices in the US, I had to agree with him that I couldn't build as good a low beam unit. Compare the beams in this thread:

http://www.candlepowerforums.com/vb/showthread.php?t=214540

or you can go to Peter White Cycle's site for more.

But I'll have a go at a high beam! If you are still 'go', welcome to the club!

:welcome:

I have designed and ordered parts, and am the earliest stages of my own battery powered light. What I share here is what I learned in these forums from more experienced folks.

I am planing on building a dynohub powering 3 LEDs. I am using the circuit 10 from here.
http://pilom.com/BicycleElectronics/DynamoCircuits.htm

This seems daunting to me at first glance, and I built a number of electronic kits before. Why not go up a level to Circuit 12, and get a circuit board all set for soldering and automatic light control, too?

http://www.candlepowerforums.com/vb/showthread.php?t=179805&page=3 Read last two posts.

So if Martin doesn't have this board apparently Ktronik has. He also has kits of his three XP-G CNC lite light for generators! I'm pretty sure he'd ship one from down under. If it's within your budget, it would get you experience and a light before you go the custom design route. Just a thought.

They say the stingy man pays the most. I am going to be spending more than some other kit and commercial routes I could have taken, but I want something that doesn't exist at this time, so I'll have to make it. Otherwise, the prebuilt and kit with the option to Mod in the future to satisfy the 'bug' would be my smarter and less expensive path.

I shall be using the shimano dh3n80 dynohub. My first question relates to this. In the above philom link it states that if there is a zener diode it must be removed. Does the dh3n80 have a zener diode? I guess no otherwise it would have DC ouotput from terminals with fixed voltage I suppose?

I like the other answers you got.

My second question is about the capacitor values. How are capcitor value calculated? Do you just use the number of magnets in the generator, and the number of revolutions per second of the wheel at x speed which you require the boost to calculate the frequency. Use this to give the period T=1/f of the AC current then use the discharged formula ( http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capdis.html ) so find the required capacitance that has a half life of T?

In the simple circuit, number 1, it seems bigger is better but more expensive, in the later designs it seems to relate more to number of LED's and there is no mention of the generator making a difference, and some of the users earlier in the 'generator circuit available' thread were running bottle generators, so I can't see the generator pole number being a factor. Another reason to go with a proven board and suggested values for now?

I now have some questions about component choice. I am based in the UK and have manged to find all the basic components at maplins.co.uk, however they do not seem to do a range of the really bright LEDs. I don't have a clue what LEDs to use but Luxeonstar post to the UK, would 3 of these be a good choice?
http://www.luxeonstar.com/premounted-rebel-neutral-white-led-on-a-20mm-star-base-160-lm-p-614.php

with three of these lens?
http://www.luxeonstar.com/fraen-low...th-flat-bottom-hldr-fits-rebel-leds-p-485.php
Of should I have three different lens patterns to give a good overall light pattern?

What connectors should be used to the dynohub? Is speaker cable ok to use to connect from the hub to light?

I wanted lumens per watt, and with a generator, I suspect you will, too. So I read the threads here on the CREE XP-G and on optics for it, especially those with beam shots. Cutter is not the cheapest source, but they stock unusual items, have timely delivery, decent service, and they stocked a brand new lens within days of it being listed here. My kinda people. If they ship here to the 'colonies', I suspect they can ship to Mother England. The optics and the MCPCB size (if LED is not used without) are influenced a lot by the body you plan on using.

There are lots of choices, from using plumbing parts, aluminum extrusions, electronic boxes, NOS halogen bike lights housings, to CNC units from Cutter, Ktronik, and Trouties's masterpieces :bow:to name a few.

My last question is about thermal management. I am planning on making my hosing our of some aluminum box section,
http://bikeled.org/ suggests "3 square inches of exposed heat sink area per LED watt", but due to the moving airflow he gets away with much less, what is people opinion on this? Would some fins be required for my proposed setup? Is the pre-cut thermal tape linked to in with the LED worth it?

Thanks for any help.

By my rough calculations the DX P7 headlight is about 9 watt (3.7 V x 2.4A) and has about 9 square inches of body ignoring the fins and the bezel which has a torturous thermal path, so maybe 1.5 inches per watt. Users do not find it too hot when riding, which may say as much about its thermal path out to the body, as how much surface is needed as a minimum in the body. Current = Watts = Heat. Size = weight. Size = more cooling. More cooling = more lumens per watt if cooler, or more watts and more lumens at same temp. No optimum, just different compromises. By wiser member's reviews of that light ('Has anyone played with ...') , I would hazard a guess from that thread's comments that it is close to the minimum for a bike light in square inches per watt at medium to higher speeds. If you cruise below 12 MPH or 20 KPH, it looks like something in the 2-3 inches per watt range might be the minimum needed. It. may depend on how long you have to sit at lights,as much as any other factor.

Good luck, and hope this helps.

 

[Bandgap]

Just use circuit 1 (accept a bit of flicker below 6-8mph)

plus 2 Cree XR-Es in series.

plus a switch between the dynamo and circuit 1.

This combination will give you an awful lot of light.

LEDs are so bright these days that you don't need complicated circuits unless you want to be seen from space.

I use Maplin for many components, except LEDs.

Cree does a simple optic that can be glued onto the LED and gives quite a good beam.

Do remember that all the optics you can easily buy will dazzle on-coming road users.

For a bright dazzle-free commercial dynamo light, try a Cyo.

Steve in Surrey

 

[Steve K]

LEDs are so bright these days that you don't need complicated circuits unless you want to be seen from space.

I use Maplin for many components, except LEDs.

Cree does a simple optic that can be glued onto the LED and gives quite a good beam.

hey Bandgap Steve... which optics do you currently prefer? and Cree does optics now? This is news to me, but I haven't paid attention for about a year, when I bought the Ledil Rocket optics (the smooth spot, I think) for my dynamo headlight.

I agree regarding how well a simple headlight will work. Not much point in adding a lot of complexity. I'd recommend just trying a very basic circuit and seeing how it works out. If it's not good enough, then try something more complex, but be aware that complexity will reduce reliability, especially if you aren't experienced in building electronics.

Steve K.,
in cold, windy, & sunny Illinois

 

[znomit]

Cree does optics now?

They have done a nice 8deg for ages. They updated I think last year and added wider angles.
http://www.cutter.com.au/proddetail.php?prod=cut680

Tight available from either Kai or DX for about a buck each.

 

[Steve K]

They have done a nice 8deg for ages. They updated I think last year and added wider angles.
http://www.cutter.com.au/proddetail.php?prod=cut680

Tight available from either Kai or DX for about a buck each.

nice! The datasheet is pretty vague about the width of the beam, unfortunately. If you were making an order anyway, it wouldn't cost much to buy one to see how the beam looks.

I think my next light will be using an MC-E, or one of the smaller LEDs from Cree, so I'll be searching for optics yet again.

thanks,
Steve K.
(wishing I was in warm New Zealand!)

 

[Bandgap]

Znomit has the right optic - that is good because I was having trouble finding a reference.

I think Cree buys it in for its demo kits - a bit like the original Luxeon/Os - so that potential users get an instant idea of brightness.

The beam is excellent for cycling - smooth, concentrated, and bright
- although it will still dazzle on-comers.

Greetings to Steve in chilly Illinois (and anyone else who cares to read).
I have the lathe sorted at last and have started making my MC-E + Ledil Iris housing.
In tests outside my house, the beam is pretty good for a 'main' beam.
However, the optic is 35mm across.
As soon as I get my current converter going, I think I will opt for a single XP-G plus a 26mm optic from Carclo or Ledil - A round optic, or I will have to admit I could do without the lathe!
I think I will get a similar beam out of this from a smaller lighter package.
Plus a Cyo for 'dip'.

Despite this last bit, my advice to TheBrick is still to go for twin XR-Es and glued-on Cree optics as this setup will give most well directed light for simple electronics and simple construction.

Steve

 

[TheBrick]

Fist of all I would like to say thank you for all of the excellent replies, I've been a bit slow on this due to being distracted by all the Christmas stuff.

I will take the tip of trying to find a cheap torch and using the housing off of that, I do have access to a small lathe but am no expert so one step at a time I think, get the light working then maybe think about improving the housing further down the line. Also I guess I'll give the simple circet ago too.

@BrianMc thanks for all the links, I'll have a good read through all of them. I have not digested them all yet so can not comment.

Thanks for the cree XR E tip Znomit, I'll take a look at those from the cutter.au web site. I presume you just use a single LED of this one?

Interesting point from Bandgap about dazzling on coming drivers, not something I can considered with a dynomo type light. I will have to be careful of that one. Maybe some kind of hood / peak on the light to reflect the wasted light down?

I definitely want to have a go at building something myself though, I always need to have a go. I'm sure I'll be back with some questions as this continues, and I'll post some photos when finished.

T

 

[znomit]

Thanks for the cree XR E tip Znomit, I'll take a look at those from the cutter.au web site. I presume you just use a single LED of this one?

For XREs on a triple the best road light is perhaps the MR11 optic and board combo from cutter. I see they do an XPG now too.

My current recommendation would be for an XPE and XPG with RS CXP/LXP optics. 2 leds light from a low speed and this combo gives a good spot/spill and a few less leg watts.

Thermal management is not too much of a problem with dynamo lights as you're only running 500mA and you should always have a breeze. As long as you have a reasonable thermal path from LED to metal housing you're ok.

Re torches, either DX or Kai do some without the leds/drivers, perfect for modding.

 

[TheBrick]

Thats for the optic tip. With two LEDs would you go for two different optic angle, one narrow powerful one for further down the road (7.5 deg) and a nice wide 23 deg one for up close?

Thanks again

T

 

[TheBrick]

Also apologies for more questions but I've just been looking at the cutter website and there seem to be many options on the XPE and XPG LEDs, could someone offer up some guidance on that front please.

Also the first lot of luxeonstar LEDs I looked at were pre mounted onto a MCPCB, the PCBs only seems to excist to make the LED easier to work with, are and PCBs needed with these XPE/Gs?/

Thank you.

T

 

[TheBrick]

Hello again. I'm just putting together my shopping list from cutter could someone please cast an eye over this please and see if it seem reasonable / if I'm missing anything in the excitement.

20 mm MCPCB Star in Series http://www.cutter.com.au/proddetail.php?prod=cut834


20 mm Carclo 20mm Triple Optics for XPE Frosted medium http://www.cutter.com.au/proddetail.php?prod=cut861

3 x Carclo 20mm Triple Optics for XPE http://www.cutter.com.au/proddetail.php?prod=cut937

Bin 5 looks best from the bin code sheet (if I understand it correctly), but currently out of stock.

Other components (diodes, switches thermal glue e.t.c) I will get from a local electronics store (maplins).

Thanks for the help and advice.

T

 

[znomit]

Brick
The triple optic is 16 degrees with an XPE and probably around 20-25 with an XPG. Both are too wide for a road light(16 is marginal). You are actually better off going with a single led and a tight optic.

ps if you are ordering a triple you order the leds loaded onto the board already, don't order them separately!

 

[TheBrick]

Brick
The triple optic is 16 degrees with an XPE and probably around 20-25 with an XPG. Both are too wide for a road light(16 is marginal). You are actually better off going with a single led and a tight optic.

Good point, taking 22.5 degrees then @ 20 Meters we have 8 m beam width which is going to be pretty wasteful on a road.

This seems better to me. 1 x oval at 20 meters 4 meters wide with a xpe and 1 x 7.5 degree 2.6 meters wide @ 20 m so I can concentrate some more light further up the road as the gets spread out.

CXP Ledil Optics
http://www.cutter.com.au/proddetail.php?prod=cut941

ps if you are ordering a triple you order the leds loaded onto the board already, don't order them separately!

Thanks this is exactly type of ordering mistake I want to avoid, I was imagining some very tricky soldiering butting three on one of those little boards! Pre loaded makes life a lot easier.

I see the link now with the pre loaded boards offered I presume with the above optics I would need a single square 10 mm MCPCB. I missed them earlier.

I can't really see any difference between the XPG and XPE other than size.

 

[znomit]

I see the link now with the pre loaded boards offered I presume with the above optics I would need a single square 10 mm MCPCB. I missed them earlier.

I can't really see any difference between the XPG and XPE other than size.

You need the 20mm MCPCB to seat the cxp optic properly. My advice for a dual led setup would be to use the tightest CXP optic and one XPE and one XPG. The G gives a wider beam (~10deg) but the E (~6deg) throws further. This is a good road combo.
If going to three or four LEDs also consider the MR11 optic range with XPE.

XPG vs XPE... the G has a larger light emitting area which helps to make it more efficient(more lumens) but means it puts out a wider beam. For small spot optics the extra lumens don't make up for the wider beam.

 

[TheBrick]

After sitting half done on my desk for two months it's finally done, not done a popper test ride yet but it seem bright playing with it in the living room.

The electronics and soldering where easy despite being my first project since making a radio years ago. The housing fabrication was a diffrent story. I could not find a suitable housing to reuse so had to fabricate one on my mini vice with minimal tools, hence it's a bit rustic! I defiantly have plans for more electronics plans, I'd really like to control something from my computer, use some of my programming skill in the real world!

Anyway I've learnt a lot so thanks for your help. I think I will make a MRK11 at some point when I have figured out the improvements that will be needed. I'd also like to build up a off road dynamo setup too. I may add more pictures from a ride at some point.

Thanks for your help again.

Tommy