Bison light (sort of Ay-Up clone)- Mtbr.com
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  1. #1

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    Bison light (sort of Ay-Up clone)

    Finally managed to put this together. First up, the final product



    (Sorry about the poor image quality -- this was done with an iSight camera on a Mac, as the ones I took with my digital camera were all out of focus .. )

    Parts list:

    Geocaching Micro Container aka Bison Tube 2
    Cree Q5-WC LED Emitter with 16mm Base
    23.36mm Optics/Light Diffusers for Cree Emitters
    DC extension cable
    Battery Holder 3 Way "AA" Switch Enclosed Box On/Off Switch*

    * These are now no longer available, but Kaidomain have almost the same thing which I have ordered and will report back as to their quality.

    The emitter is directly driven from 3xNiMH cells. This reduces complexity (I won't be near to fix any problems) and increases run-time.

    The name "Bison" comes from bison design who first made these kinds of tubes. Initially they were for keyrings, and maybe pill canisters. Now the geocache crowd use them.

    With this tube the rounded top (where I want to put the emitter) has the smaller internal diameter (16.5mm) compared to the rest of the tube (17.5mm). You can see it in this shot:



    The depth of the cavity is 18.32mm, which is a fair bit more than the height of the optic and emitter. Here is a schematic of those DX optics:



    Not all of the optic fits in as it is too wide. I counted on the optic sitting on the lip that would normally clip into the holder (so about 10mm depth) and then trimming the holder to fit, like so:



    And here is a shot of the holder, before and after:



    I actually ended up taking off more than is shown in this photo as the holder just would not fit in otherwise. At this point I'm not sure it is doing that much as I think the top of the holder actually holds the optic away from the sides of the holder. But what is left of the optic holder is white, so at least it will reflect out some of the light that is scattered backwards.

    So optic (sitting on the lip) and emitter is about 12mm. Depth of cavity is 18mm. So a 6mm high spacer is needed. I used these lovely little aluminium disks with a hole in the middle that were almost perfectly sized (complete luck, scavenged from work). You can see it here, with the emitter mounted on the other side and the wiring going up the middle (sorry about the crappy focus -- I don't know how to use macro mode properly):



    I had to sand down the outside of the disk as it was a little too big (shoved a bolt in their and then stuck that in my electric drill). It was also a little too tall, so I took of some height by rubbing it on sandpaper until the lip of the optic was just sitting nicely on the rim of the tube.

    In that badly focussed shot you can also almost see the cut out I had to make so the power cable can fit past the inside edge of the disk after emerging through the hole I drilled in the back. The hole in the back has to be off-centre as there is a lug on the back that I want to use to mount the light. I tried to drill the hole on angle so it emerged in the middle inside the tube but it didn't work out.

    I used artic silver to glue the emitter to the heatsink/spacer.

    To hold it all in there I had to cut the end off the rest of the tube (with the larger diameter). The magic distance is 12mm from the (open) threaded end of the larger diameter tube. This allows for the width of the cutting blade and some after-cut filing to even up the edge. Note that I have also removed the rubber o-ring so this "collar" that I have made will sit lower than with the o-ring in place. I did consider flipping the collar over so that the exposed edge was a nice anodised purple, but the thread stops before the end of the collar so that can't be done without using tools I don't have. Looks ok with the silver front edge I think.

    I did the cut with a coping saw, with fine-toothed blade. I marked where I wanted to cut with tape, made smallish cuts and kept rotating the tube. I found when I tried to do one cut all the way through it was always horrible skewed. I also used alot of
    WD-40/CRC/lube (whatever you call it in your country) which I found helped enormously to make the cutting easier.

    I couldn't have done this without my bodged up cyliner clamp:



    At this point I had to trim more off the edge of the optic as the collar would not fit over it. I used a dremmel with a grinder wheel (very difficult to do this without a dremmel I should think) and ended up taking almost all of that lip off so that it was flush with the front of the optic. There is still a bit protruding for it to sit on the rim of the tube, as the rest of the optic shapes inwards. You do have to be a little careful not to take too much off, as it is good for the optic to fit very snugly in the threaded collar as there is no rim to stop the optic falling out the front. I have used silicon to help to keep it in there, but clearly it is helpful if there is some mechanical resistance to it popping out.

    I arctic silver'd the heatsink to the bottom of the cavity (helpfully the bottom is flat).

    Here you can see the finished product with the optic slightly recessed to keep it from getting scratched and also to aid with applying some silicon to keep it in there. I also put a little silicon on the at the base of the thread to keep water from creeping inside and to keep it shut tight. I don't ever want to open this puppy up. I also put silicon in the hole in the back of the heatsink and then when I glued it up I put silicon around the cable entry to make sure it won't leak (the light will be used in Brisbane, and recent events have graphically demonstrated that it can get very very very wet up there).



    This is so out of focus ... (I'll try and take a better ones later and replace these pics)




    For me, this is the money shot:



    No point making a nice small light unless it is super light eh? (Yes that is 20g)

    Here is is with the 3xAA battery pack (with NiMH cells inside) and leads:



    I will mount this using a hose clamp. I have experimented with this and it works, but I don't have a photo yet. Basically you just drill a hole in the hose clamp, put the protruding bit from the back through it, lock it in with a straight bit of metal (cut off nail works for me) and then tighten up the clamp. It is super tight and there is even some heat transfer to the bars. You could even file an angle on the protruding bit to "toe" the light in or out a little.

    I'm pretty happy with the result. I made this for a mate's 40th birthday as a commuter light. Hope he likes it.
    Last edited by glowinthedark; 05-21-2009 at 08:37 PM.

  2. #2
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    Nice work glowinthedark.

    Where did you buy the canister from if they don't ship outside of the US?

    I am in Aust also and would love to get hold of a couple of these canisters.

  3. #3

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    Quote Originally Posted by bendyclickr
    Nice work glowinthedark.
    Thanks. I've had those containers since forever (September last year!) so it is good to have finally built them up.

    Quote Originally Posted by bendyclickr
    Where did you buy the canister from if they don't ship outside of the US?

    I am in Aust also and would love to get hold of a couple of these canisters.
    I just emailed [email protected] and Curt Schryver, the guy who runs South Mountain Traders, got back to me and said no worries about posting to Aus. He charged me US$7 shipping. Since they weight stuff all the bigger the order the less it costs. I am thinking about getting some more myself .. maybe I could order one or two for you too and send them on?

    I am planning on making a light out of the rest of the canister left over from making this light, just not got around to it yet. I also bought some of the microspheres and am in the process of working them up into a light too. In that case though I'll be using reflectors as those lenses are too deep.

  4. #4
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    I'm thinking about making 3 or 4 of these for helmet lights. They're so small you could mount them down low just over the visor where they wouldn't get caught on branches. Nice looking lights, and you match colors to your bike or gear.

  5. #5
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    Thanks for posting this, It looks like it turned out very nice (and light).

  6. #6
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    These are awesome. got me thinking now. how well will they handle the heat?
    Where did you mount the driver?

  7. #7

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    Quote Originally Posted by esXso
    I'm thinking about making 3 or 4 of these for helmet lights. They're so small you could mount them down low just over the visor where they wouldn't get caught on branches. Nice looking lights, and you match colors to your bike or gear.
    If you want really small you could go for the traditional bison tube and XPE emitters and optics, but they aren't available from DX so the cost will go up.

    Quote Originally Posted by Joshp82
    These are awesome. got me thinking now. how well will they handle the heat?
    Where did you mount the driver?
    They are light, but they are quite thick aluminium and there is a nice slug of ally in the back bit. As long as there is airflow and you're not running them at 1.4A I don't think there is a problem.

    I didn't use a driver, and there wouldn't really be space for one in the light head. You could put one inline or in the battery pack though.

    EDIT: Oh yeah, I'm off on holiday for a week, so I'm not being rude if I don't answer any more questions, but I'll check the thread when I get back.
    Last edited by glowinthedark; 05-21-2009 at 11:47 PM.

  8. #8
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    Great job glowinthedark. Exactly the thing I want to make. I am reading all the posts about leds back from 2007 trying to decide on driver, optics, and simple light body.
    I am little confused that you dont use any driver or even a resistor. So the current is determined by the internal resistance of the led(Q5), and the battery, wright?
    Do you have any measurements of the current, on full batery, 100%, 50%, 20% ...?
    If not can you make the measurement? For example 100%, 75%, 50%, 25% batery full.

    if the curent is ok this can be most eficient led light ever.

  9. #9

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    Quote Originally Posted by martinmkd2
    Great job glowinthedark. Exactly the thing I want to make. I am reading all the posts about leds back from 2007 trying to decide on driver, optics, and simple light body.
    I am little confused that you dont use any driver or even a resistor. So the current is determined by the internal resistance of the led(Q5), and the battery, wright?
    That's right. It is not generally recommended due to the possibility of thermal runaway, but in practice I haven't had an problems.

    Do you have any measurements of the current, on full batery, 100%, 50%, 20% ...?
    If not can you make the measurement? For example 100%, 75%, 50%, 25% batery full.

    if the curent is ok this can be most eficient led light ever.
    I can't make accurate measurements because I have a cheap digital voltmeter with too high an internal resistance (it drops a significant voltage across it when I put it in series and try to measure the current). I estimate it to be of the order of 700mA.

    Apart from the possibility of thermal runaway the other defect with direct driving is the output dropping as the voltage of the cells drops as they run down. Again, in practice, I don't find this to be a big deal.

    One of the reasons I went for direct drive in the Bison light was durability. I made this for a friend who lives over 1000km away and who has no ability or interest in maintaining his own LED lights. The direct drive meant it is a very simple light with almost nothing that can go wrong with it.

    Dealextreme now stock some similar pill containers. I think they have a larger internal diameter than the ones I used, but this could be a good thing. I don't know for sure until the two I have ordered are delivered to me.

    I am also in the process of making a direct drive light with a low mode using a resistor. In general resistors are not very efficient, but if the current is low enough then their efficiency can be quite high, as the losses in the resistor are related to the square of the current, e.g. a 1.2 ohm resistor in series with a 3.6V source and a 3.2 Vf LED emitter will be 89% efficient. That is not bad. Especially considering that it is a lower mode that is drawing much less current anyway, so the runtime is still extended a great deal.

  10. #10
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    Would using li-ions instead of the NiMH cause problems?

  11. #11
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    Cool, I remember starting a how tiny can we go thread a long time ago before the XP-E were released. You were considering this build all the way back then. Nice to finally see it built up. 20g is seriously light weight.

  12. #12
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    Any beam shots?

  13. #13

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    Quote Originally Posted by mojojojoaf
    Would using li-ions instead of the NiMH cause problems?
    Don't know. Sorry.

    Quote Originally Posted by bikerjay
    Cool, I remember starting a how tiny can we go thread a long time ago before the XP-E were released. You were considering this build all the way back then. Nice to finally see it built up. 20g is seriously light weight.
    Thanks. I've got to get around to making another so I can take a pic of the mounting. It is super easy and rock solid, but not very pretty (hose clamp).

    Quote Originally Posted by Leethal
    Any beam shots?
    Sorry, no. It is a single cree q5 with a DX spot lens on the front. Not too much of a mystery there. Having said that, this q5 seems to be a fair bit brighter than the R2 I also got from DX (which I also direct drive with 3 x NiMH AA). Shouldn't be the case, but certainly appeared to be.

  14. #14
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    what's the runtime w/ 3 x NiMH AA?

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