# Simple light



## arnea (Feb 21, 2010)

I'm building lights for our adventure racing team "Mõlaväntjalg!". The lights must run all night (nine hours is ok), must be watertight (for canoeing) and must be cheap and easy to make, because I need lights for whole team.

After looking at other people's designs in this great forum, I came up with my own.


























I use aluminum stock and plastic for the light body, so it is easy to build using only hacksaw, file and drill. Main design driver was the thermal management: I wanted to come up with a solution where the LED is mounted directly to the main heatsink in order to allow it to run as cool as possible.


































The driver compartment is made from a stack of plastic sheets. Middle sheets have cutouts that form the hole for driver. The back panel is from aluminum to provide cooling for driver. On the front panel are holes for two push-buttons that turn the lamp on and off.

I decided to go with single Cree XP-G R5 running at 1.4A. This offers me 400 theoretical lumens. I think this will be enough: in this years night race I survived using Primus PE headlamp that is labeled for 40 lumens. More light would be nice, but then the nine-hour battery pack would be a real brick.

The lens is from Ledil: LXP diffuser. I wanted to get LXP-G or even better - CXP-G, but unfortunately www.led-tech.de only carried LXP and I was unable to find a cheaper place for LEDs and lenses.

Initially I planned to use Taskled bFlex driver. It had everything I wanted. But it was little bit too expensive for my budget. I looked at drivers in Dealextreme, but they all lacked the low voltage protection. I wanted to have reliable low voltage protection that really protects the battery, not just avoids the fire, as do the built-in protection circuits with their 2.5V cut-off voltage.

Finally I went with the simplest Dealextreme driver that has four AMC7135 linear regulators in parallel, each pumping 350mA. I added Maxim 811 low voltage protection circuit that shuts off the regulators when the voltage drops below 3,08V. There are two pushbuttons for on/off control.










The Maxim 811 has extra input for master reset. There is a feedback resistor from output to master reset input that keeps the state of the light: on or off. The output is high only when the voltage is over 3,08V and the lamp was switched on. When the voltage drops below 3,08V the lamp turns off. When battery recovers and voltage rises, the lamp stays off, because the master reset input is low. You can force the master reset input high or low (lamp on or off) using two pushbuttons.

I removed the diode from Dealextreme board and wired the 811 instead to drive the regulators.

The combination of the low forward voltage LED (I measured [email protected]) and single Lion cell (nominal voltage 3.7V) make the linear regulators relatively efficient - the calculated average efficiency of the driver is 86% (this includes losses in wires). The light stays regulated for >90% of time.

When I tested the lamp on the bench it got quite hot after one hour, but it was still possible to hold it in hand, so the temperature was probably around 50-55C. XP-G has thermal resistance 6C/W from junction to base. MCPCB might add 1C/W. So, at [email protected] the junction was probably at 80-85C. I think this is safe temperature. The LED efficiency was around 86%. Reduced efficiency is not a problem, because the light will be cooled down when driving.

I did some test shots. Wall shot shows the lightning pattern. I like it: big enough and very smooth.










I also compared the light with Magicshine and with my old 40 lm headlamp. The bottle is about 25 meters away from light.

Simple light









Macgicshine









Primus PE (40 lm)









Magicshine is yellower and seems to be little bit more powerful.

I had a chance to test the light in the optical laboratory at my workplace. They have a nice computerized stand that can rotate the light, alter the supply voltage, measure the light intensity, temperature, spectrum of light and then make a nice report.

First I did the temperature test. The light was running until the rise of the temperature was reduced to certain percentage. It took 20 minutes for the light to reach temperature of 17.5C over the ambient. The maximum luminous intensity was 3270 cd.

Below are the temperature vs time and luminous intensity vs temperature graphs:










Looks like the temperature would stabilize around 37-38C.










The slope of the graph matches quite well with the graph in Cree specification. The sudden drop in the beginning is interesting - it looks like a very fast rise of the temperature. Is this the initial warming of the MCPCB or LED itself?

Then I did the rotational test to measure the beam pattern. The FWHM was 14.75 degrees, which is little bit strange, because it matches the LXP-G lens, but I'm supposed to have LXP lens.










Now I need to complete the waterproofing of the lamp and battery, build the helmet mount and do some testing.

Arne


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## klynk (Apr 18, 2010)

Cheap, simple, multi-moded:
http://forums.mtbr.com/showthread.php?t=661593


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## rlouder (Jun 26, 2007)

Nice design. I like the flashlight conversion, too. Lot's of great ideas here.


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## odtexas (Oct 2, 2008)

Nice work there. Love when new people build new lights. 
That rotation test chart is something I can't remember being done here before. Interesting.


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## ThinkBike (Jun 16, 2010)

Very nice and simple industrial type design. I do like the whiter color of your XPG versus the MagicShine's yellowish cast. The MS is brighter, but for a single low power light, your design throws a nice balance between spill and distance.

Is there a cover over the lens that makes this waterproof? If there is I just can't see it in the picture. How is this mounted? Bar or Helmet?

One of the most complete posts I've seen done all at once with pictures, graphs, stats and detailed explanation of the process. Thanks for posting your work.


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## arnea (Feb 21, 2010)

Thank you for your kind words.

There is no lens cover yet. Initially I planned to use some silicone to seal the lens. But now I got some thin polycarbonate (replacement lens for welders mask) and plan to cut small square from it and epoxy it inside the lens cover tube, so that it also helps to hold the lens in place (right now it is attached to the MCPCB with adhesive only).

Regarding the mount: my first idea was to put it on the helmet. Glue some velcro on the underside of the mount and stick it to the velcro strip that is going through the vent holes of the helmet.

But since I will have more than one light I might also do handlebar mount. I'm thinking about using Bontrager bottle mount:

http://bontrager.com/model/04087

I just drill the hole through the underside plate of the lamp and bolt it on. The mount will also work as and additional heatsink.

Arne


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## arnea (Feb 21, 2010)

I calculated the lumious flux from intensity data. It was 303 lm. According to Cree specification the LED should emit 418 lm at given current and temperature. Ledil says that lens has optical effiency at least 90%. The calculated result is therefore 376 lm. Perhaps the 90% figure applies only to clear spot lens and not to the diffusor? It's also possible that small numerical errors added up during the integration.

Arne


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## arnea (Feb 21, 2010)

Mounting the light on the handlebar was easy. Mounting the light on the helmet was very cumbersome. So I did a more stable and tiltable light using more traditional construction:


















There is sled from 4mm U-profile inside the tube that acts as LED carrier and back panel of the light. The sled is pulled against one side of the tube using three screws. There is thermal paste between sled and tube to facilitate thermal transfer.

Small pushbuttons and voltage controller chip are soldered on the small PCB that is potted on epoxy and glued on the outside of the back panel. The LED driver is inside the tube.

The cooling area of the new light is almost same as the area of the old one!

During the experimentation with first light I burned down two voltage controller chips. I found another datasheet for AMC 7135 that required two capacitors: 1uF on the input line and 0,1uF in parallel with output of the regulator.

Arne


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## odtexas (Oct 2, 2008)

Looks like two adjustments points on the helmet bracket/light body interface. Neat....:thumbsup: 
Could we get a picture of the side where the bracket mounts?


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## arnea (Feb 21, 2010)

Added couple of pictures:


























There is only one mount point - other scews are just pressing the sled against the tube.

Arne


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## odtexas (Oct 2, 2008)

Thanks. still a cool mount. That picture really helped. 
Must be blinding on the snow with that light.


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## arnea (Feb 21, 2010)

Little update.

I just completed two new lights. My first lights used XP-G. I loaned the light to a friend, who used it in a canoe marathon. He commented that the light was "nothing special" 

So, for the new lights I bought XM-Ls, together with Laura RS lenses. It is really good combination. So much more light compared to XP-G!

Now I had thermal issues. After some testing and thinking about attaching a big heatsink to the light I decided to abandon the cheap Dealextreme drivers and use Lflex. I like it!

I just completed two new lights. Some small improvements in design and building process:

Sanding the slot in the helmet mount for velcro:










Sled after sanding, drilling, tapping and glueing the nuts. I bought some 5cm wide U-stock and cut it down to pieces that fit exactly into 1" square aluminium tube. It is 5mm thick, so the thermal path is good. There is plenty of room inside the light body. I tapped the holes that will hold the LED, but used nuts for bolts that will keep the light together. For some reason (perhaps I got the aluminium that is too soft) my taps are not very good and it is easy to strip the threads:










Sled after soldering. The small pushbutton is IP67 rated. It will be sunk in silicon in the back of the light:










New lights:










I used the Serious Glue to make the lenses watertight.

All four lights built so far:










Arne


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## uncle_bob (Jul 26, 2010)

Nice lights, I especially like the way you have done the helmet mount, there's no patent on it is there?


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## Ofroad'bent (Jul 10, 2010)

Great update on the sled light. I think your U-profile sled is the best yet.
I assume your L-flex is bonded on the sled with the thermal tape provided, just in case anyone doesn't get that from the pic.

I found some heatsink that works well on these lights, if you need more sinking. 
http://cgi.ebay.ca/ws/eBayISAPI.dll?...RK:MESINDXX:IT
It can be cut to width and bonded on the outside with the thermal tape included. You could add some on the top and/ or the bottom.

I also swiss-cheesed my mounting bracket to help with heat sinking as well. I have a small space between bracket and light body to allow air flow, with an aluminum spacer in there and lots of thermal paste.


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## con10der8 (May 31, 2011)

nice work


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## arnea (Feb 21, 2010)

No patents!  

Yes, the Lflex is attached with thermal tape - it is not hanging freely in the light body.

Today I had a chance to do a small 2 hour test ride on singletracks. Couple of observations:

1) the lamp feels heavy. The weight is only 90 grams, but I could feel it all the time. The helmet banged around noticeably more. I'm glad that I did not add any extra heatsinks.

2) the temperature at night was around 22 degrees and the light stayed very cool during riding.

3) I needed to tilt the light up much more than I thougth. I had to reposition the mount in order to be able to orient the beam correctly.

4) Laura RS has too tight beam for my taste. I will order some other lenses with wider beam for the third lamp. 

After first ride I tried other lamps - alone and together with my headlamp. I put my first lamp (XP-G with LXP diffuser) on the handlebars and it had much nicer beam. Also, the lower position of the lamp created the shadows for obstacles on the track and made them very noticable. But it was little bit too dark just alone. 

I think that for pure bike riding XM-L with not-so-spotty lens on the handlebars is better than my current lamp - smoother beam, no extra weight in the helmet, plenty of light, lower position. But for adventure racing I need headlamp. Of course - I could have too lamps  

Arne


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## emu26 (Jun 23, 2008)

Arnea, your helmet shouldn't be moving around because of a 90gm light on it. If that is the case then it is not adjusted to your head properly. Not sure what helmet you are using but most of the newer ones have the adjustment at the back of the head, I always tighten mine more for night rides than I do during the day and whilst I do get slight movement it isn't as noticeable as you make out and I can assure you, my helmet lights are considerably heavier than 90gms.

You might also benefit from mounting the light on the centre of the helmet rather than towards the front, this helps balance things out nicely


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## yetibetty (Dec 24, 2007)

arnea,
I understand fully what you mean about the weight of a helmet light. I made one a while back @ around 50 gr and I must say that it gets on my nerves when on my helmet. It is fine however when used on a head band when walking due to the tight fit of the elastic strap.

I have put this down to helmet fit as I can never get a helmet that fits really well and I’m sure that if I could then I wouldn’t notice a helmet light. What do you think?

You have made some nice lights, very precise straight lines, not as easy to do as it looks.

Sorry emu I type so slow that you had posted while I was typing.


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## emu26 (Jun 23, 2008)

No need to apologise. I'm fortunate in that I have a fairly "standard" melon so getting helmets to fit and adjust properly hasn't really been an issue. I'm also on my way to sporting a solar panel for the sex organ so helmets generally don't slide around that much, it's like having velcro permanently fixed in place


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## Ofroad'bent (Jul 10, 2010)

I use my lights for adventure racing too.

The system I have with the 3M Dual lock tape on the bottom of the mount and a wrap of velcro around the top is rock solid. I think my lights are more like 55-60g including mount, and I don't even notice them. Mind you, it's counterbalanced by a small battery on the back of the helmet too. Something's wrong with your mount I suspect.

Incidentally, I like a tighter centre spot with side flood for AR. For night MTB racing I like a really narrow helmet beam and a floodier handlebar light.


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## yetibetty (Dec 24, 2007)

emu26 said:


> No need to apologise. I'm fortunate in that I have a fairly "standard" melon so getting helmets to fit and adjust properly hasn't really been an issue. I'm also on my way to sporting a solar panel for the sex organ so helmets generally don't slide around that much, it's like having velcro permanently fixed in place


Solar panel on the sex organ? Got to be the best way to guarantee a nice good fit.


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## El34 (Jan 11, 2009)

I'm in the same boat as Yetibetty

Helmets do not fit my head shape either.
All the adjustments on the helmet is not enough to compensate for a weird skull shape.

I have to keep the weights very small on my helmet lights and I have to wear one of those biker type, skull-cap, do-rags to keep the helmet from moving around too much. (which works great BTW)


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## arnea (Feb 21, 2010)

I think that the problem is the distance of the light from head. The moment inertia of the object is product of its mass and distance from the center of rotation. The helmet weights ~280gr, but the mass is close to the head. The 90gr of the light as much further - I would say that the inertia of the lamp might be even bigger than the inertia of the helmet.

Anyway. I completed all three lights and battery packs. They are programmed and charged and ready for the competition tomorrow night.

Found old Shimano Dual Control shifters box:










They all fitted nicely inside:










Lights are programmed for 2000mA to get the six hour run time.

Arne


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## Ofroad'bent (Jul 10, 2010)

arnea said:


> I think that the problem is the distance of the light from head. The moment inertia of the object is product of its mass and distance from the center of rotation. The helmet weights ~280gr, but the mass is close to the head. The 90gr of the light as much further - I would say that the inertia of the lamp might be even bigger than the inertia of the helmet.
> 
> Anyway. I completed all three lights and battery packs. They are programmed and charged and ready for the competition tomorrow night.
> 
> ...


Good luck!

I use my lights on various brightness during AR- full blast for fast biking sections, 25% power for less technical riding and running (seems like 50% as bright) , 5% for map reading and hiking sections. For multi-day races there's no way I could carry enough batteries for full power all the time. That's my beef with lights like the Ay-ups and their limited power options.


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## labyrinth248 (Sep 15, 2009)

cool build


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## mattthemuppet (Jul 16, 2004)

uncle_bob said:


> there's no patent on it is there?


I'd hope not, otherwise all the people that made ones like it before hand would be a bit cheesed off...


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## ballsofcottonwool (Jun 4, 2009)

liking your minimalist helmet mount bracket


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## arnea (Feb 21, 2010)

*New mount*

The winter is coming and the helmets are going out of fashion, so I built a mount for headband do use the light for skiing and night orienteering.










The mount is made from the base of the old CPU cooler.










This is the Marvi headband from El34 store.

Arne


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## El34 (Jan 11, 2009)

I have to ask
Where are helmets going out of fashion?
I guess smashed heads are coming back into fashion?



Glad you found a good use for the Marwi headshot


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## yetibetty (Dec 24, 2007)

Forget fashion keep a brain protector on. You say winter is coming so a helmet is a good way to keep your head warm.

I like the head band and almost bought some but made my own. It's nice to use lights that you have made both on and off the bike.


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## arnea (Feb 21, 2010)

Here in Estonia  But only temporarily, until the spring! I hope we get as much snow as we had last winter, so I can enjoy cross-country skiing. Not all the tracks are lighted and some of the best ones require headlight.

Arne


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## Shkoder (Apr 15, 2010)

whole thing does not look extremely reliable (bit heavy and unbalanced) but I am sure it worth trying. as person who using to ride all night for years I want to say that even extra 100 gram feels bad on top of helmet after several hours. especially when not well balanced. so you will need to choose between extra light and headache..


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## arnea (Feb 21, 2010)

I'm building another batch of lights.

The old lights were easy to build, but too long for using with headband. I changed the design, so that I can make the light much shorter. The downside is that the construction is more complex and in order to make it watertight I will use epoxy to seal all the parts, so that I cannot open the light later.

Here are the first pics:


















I will build smaller batteries (2 cells) and attach them at the back of the headband. It should be more comfortable this way. I haven't decided yet what will be the setup for adventure racing where I must wear helmet most of the time.

Arne


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## arnea (Feb 21, 2010)

First light is almost ready. Only helmet mount is missing and battery needs to be waterproofed.

The idea was to bring the center of gravity close to the head in order to stop the lamp wobbling. Now it is as close as possible  Inside the lamp I have Lflex and neutral XM-L with Cree Rose Soft Spot lens.










Battery contains two 2800mAh cells in parallel and is mounted using velcro. The running time at 3A is about two hours. It is quite easy to swap the batterys, so I plan to carry 3-4 spares with me during longer competitions.










Single bolt keeps all the main components together. The housing is from 25mm aluminium and headband mount is from 20mm aluminium. The protector around the lens is glued in place using epoxy. All the cracks are also sealed with thin epoxy that will wick into cracks. The switch is rated IP67 so I hope that my lamp is waterproof.










Overall weight (headband, lamp and battery) is 266gr.

Arne


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## Ofroad'bent (Jul 10, 2010)

Now that's a cool solution. I also had issues with the Marwi headband holding the light too far forward, and cut it down.


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## emu26 (Jun 23, 2008)

nice build arnea and very neat workmanship, well done


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## mrradlos (Sep 3, 2010)

*double simple light*

My simple light (double XM-L, LFlex, Ledil Tina3-S)


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## mrradlos (Sep 3, 2010)

I'm not pleased with my helmet mount yet!


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## mattthemuppet (Jul 16, 2004)

is it me mrradlos or do you have those optics on backwards? It's hard to tell from the pics. Good job on the wiring though!


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## mrradlos (Sep 3, 2010)

mattthemuppet said:


> is it me mrradlos or do you have those optics on backwards? It's hard to tell from the pics. Good job on the wiring though!


You might have to turn them around for a back light 

The Tina3 optics are the smallest aspheric lenses I could find. They throw a very clear square of the XM-L. I had to move the two LEDs a bit appart (see last picture) so that the dark lines (bond wires?) of the two LEDs are not on top of each other, I also used the "filter" to blure the lines (last picture left)- of course I could have moved the optic a bit further away from the LED.
The square is much bigger and less bright than with the bigger aspherics that troutie uses in the spidereyes (ahortons aspheric lenses).


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## Ofroad'bent (Jul 10, 2010)

I'd never heard of these aspherics. Interested to hear how they fit the XM-L.

Any beam shots?


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## mrradlos (Sep 3, 2010)

Ofroad'bent said:


> I'd never heard of these aspherics. Interested to hear how they fit the XM-L.
> 
> Any beam shots?


Well, that's the best my compact camera could manage - about 1800 lumens on the white wall was a bit too much.

















Small square is XM-L T6, 3A with ahortons aspheric lens (troutie uses these in his spyder eyes and sells them I think), the big square is two XM-L T6 3A each with Tina3 optic and "diffusor-filter" shown in the picture before. The Tina3 projects a square that is about four times bigger and four times less bright?

Notice the square light comming out of the square light!!!


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## rschultz101 (Oct 5, 2009)

thanks for the lens shots !
got some squares too.
but still working on my mount. your are not alone 
those minor details take forever... running low on steam
got there a Hella of a Licht 
thought Troutie wins the styling


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## jaragon (Jun 25, 2012)

Interesting


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## emu26 (Jun 23, 2008)

Kingdavid, we are a friendly tolerant bunch on this particular forum but generally speaking we don't like blatant spam. MTBR have some fairly strict guidelines as far as advertising is concerned and digging up old threads and posting in them, as you have done elsewhere, just so that you can link websites that you sell from is against those guidelines.

Feel free to take out an add and link the add in your signature, it would be a shame to see you loose your posting access so soon after getting it.


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## arnea (Feb 21, 2010)

*Simple handlebar mount*










Small piece of plastic with two holes in it, attached to handlebar using cable tie. I used Oogoo to make the rubber-like fillet that will not allow the plate to rotate freely around the handlebar but I with sufficient force I can rotate the plate around the handlebar and adjust where the light is directed.










I used small pieces of 3M Dual Lock fastener to attach lamp to the holder. The connection is quite strong, but it is still easy to remove the light from the handlebar.










The battery is mounted between the top tube and down tube using velcro. There white stuff is made from Oogoo - it creates a bed for battery that does not allow it to slip.


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