XPE/G 20mm triple helmet light..- Mtbr.com
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  1. #1
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    New question here. XPE/G 20mm triple helmet light..

    Hi gang,

    I'm designing a new small helmet light using one of the 20mm triple boards and carlco 20mm optics to compliment the MCE triple bar mounted Altair....(and a twin triple and also looking into the 7-up from cutters but more of those later....).
    As it's going to be designed for a helmet light I'd like it to be as small as possible. I'm also thinking of a smaller battery to keep weight down to a minimum. Smudge can do a 2 cell battery (7.4v 2???aH I think) that would be ideal as I wouldn't be looking for huge runtimes and could be fixed to a helmet for the miminalists out there.
    What would be the best way to drive this? I'm guessing, as the bFlex needs a greater input voltage to output voltage, I'd need a maxFlex as it is a boost regulator.
    Please correct me if I'm wrong...and any input, as always, is greatly received..

    Steve

  2. #2
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    Hi steve,

    I'm looking at doing the same thing and you can't use a maxflex and 7.4v battery pack as the vF is lower than the battery voltage when you switch to low.

  3. #3
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    Quote Originally Posted by allport
    Hi steve,

    I'm looking at doing the same thing and you can't use a maxflex and 7.4v battery pack as the vF is lower than the battery voltage when you switch to low.
    You can't say that maxFlex is not usable in this configuration. It's true that when 2S cells will be fresh out of charger, you won't be able to switch to the lowest maxFlex level (L1), as their voltage will be higher than Vf of the three XPGs. But that will only be true for the first short time period, until battery voltage stabilizes at about nominal voltage.

    And if you are uncomfortable with this, you still have the option to choose 2-level mode of Maxflex instead of 5-level mode. In UIb2 mode, even if you choose the low level to be set at maxFlex's level L2, I think your leds will be in regulation even with freshly charged battery.
    Last edited by ortelius; 11-04-2009 at 05:25 AM.

  4. #4
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    Quote Originally Posted by ortelius
    And if you are uncomfortable with this, you still have the option to choose 2-level mode of Maxflex instead of 5-level mode. In UIb2 mode, even if you choose the low level to be set at maxFlex's level L2, I think your leds will be in regulation even with freshly charged battery.
    Thanks for the repiles guys,
    I only ever tend to use L3 and L5 in 2 mode as it's easy to switch between 2 settings than 5, especially on a helmet.
    If I can use a maxFlex, it'll help to keep the size down a little.
    Steve

  5. #5
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    I'm working on the same thing right now. My main goal is to keep it small and lightweight. In particular, I want very little weight on the helmet. My current triple XPG / XRE light head based on 35mm triple optics weighs 76 grams. That's not bad, but it's still noticeable. My goal with this light is a 35-45 gram light head on the helmet and I'm hoping that will hardly be noticeable over riding w/o a helmet light.

    To accomplish that, I'm planning to include the driver PCB in the battery pack as opposed to the light head. I'm looking at two different options for how to drive this light.

    - A custom driver board and 2 cell 18650 battery configuration. The driver board would actually be 3 compact buck regulators and the 3 LEDs would be driven independently. The custom driver board would also include all the li-ion battery protection. This would give plenty of headroom for the buck converters since each one is only driving a single LED. This would also allow for controlling the brightness of each LED independently, but I can't think of any real benefit of that. I guess you could use 3 different color tint LEDs and then tune color electronically.....but I doubt that would really be useful in the real world and I doubt I'll even implement the function. But it can always be done later with firmware updates. I would also do remote temperature sensing of the light head with this option.

    - A 3 cell 18650 battery pack, bflex, and the LEDs wired in series. The bflex will be in the battery pack. This option is certainly less work. It means there will be both a protection PCB and the bflex in the battery pack. The Vf of the XPG is low enough that this will be in regulation most of the time except for extremes of low temp and battery discharge. The main disadvantage of this option is the larger battery pack and no temperature sensing for the light head.

    My plan at the moment is to finish the CNC work for the light head over the next couple of weeks and get it up and running using the bflex / 3 cell pack initially. I hope to finish the custom driver board and get PCBs made between the thanksgiving and xmas holidays.

  6. #6
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    You guys are not alone! I was just thinking about something like this myself. My plan was to put 3 XPGs in series and run them with only a High and low option. High would be 700 or 500 ma. Like you guys have said, keep the light head really small by only putting the LEDs and optics in there. My idea was to put the driver and switch in an inline box that would be clipped to my camelback shoulder strap. That way I could easily change brightness levels and also incorporate an LED for low battery warning. I was planning a Maxflex and 2 cell 7.4V pack.

    What do you guys think?

    I would love to see what you guys are working on for the light head! I will post mine when I get a good model.

    Mark

  7. #7
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    Wow... you guys are describing the lights that I just built, except I put the driver and switch in the light head (I have many batteries and did not want to deal with adding switches and drivers to all the batteries) Weight is 65 grams... but I am using ghetto mount of Zip tie to the helmet (I never take the light off). I am running the light with 3xpg, 7.4v battery, fatman at 800 mah and get about 1.3 hours with a 2200mah battery (which is not even a usable runtime... I need to get at least 4 hours to make it usable... so running a bigger battery...

    With that said... it is not a good helmet light... the XPG and 20mm narrow triple is way too floody and I actually prefer the same light with XPE's run at 500ma... the beam is a lot better than the XPG in the same optic, even though it is half as many lumens.

    Can't wait for a the optics or reflectors to start rolling in for the XPG

  8. #8
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    Steve: You'll get full dimming capabilities using a Maxflex off two cells as long as your 2-cell pack is wired in parallel (3.6V nominal).

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    Here is a quick model. Outside diameter is 28mm and length is 30mm (without strain relief). To get an idea how small this is, a quarter is 24mm diameter. I would probably add some cooling fins and can shorted it some too.
    Attached Thumbnails Attached Thumbnails XPE/G 20mm triple helmet light..-xpg-triple-helmet-light.jpg  


  10. #10
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    Placed an order for a 3x XPG and the 20mm Carclo kit last night with cutter for my first build. Excited for the parts to show up.

    bikeny your drawing is wicked.

  11. #11
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    Quote Originally Posted by cosmoworks
    Steve: You'll get full dimming capabilities using a Maxflex off two cells as long as your 2-cell pack is wired in parallel (3.6V nominal).
    Yes, but that way maxFlex would be pushed quite hard as the voltage difference is pretty high. It would need to dissipate at least 2 W of heat from the driver. I would rather stick with 2S battery configuration, even if it would mean loosing lowest (L1) level of five for a short time with freshly charged batteries. But on the other hand, you would have a bit less trouble at keeping it cool and you would also get a bit longer runtime.
    Last edited by ortelius; 11-05-2009 at 07:07 AM.

  12. #12
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    I am just finishing up a light for a co-worker that is a 3 up xp-g, carclo round 20mm with a b-flex in the head. Its basically a DIY dinotte style light. I am using a very tiny and simple switch, the one that came with the b-flex, in side a 1/2" round recess in the tail cap that will get a glow in the dark rubber boot silicone glued in. My light was rather simple to build, I work in a bike shop so I used an adjustable reamer to open up the inside of an old 1 1/8" steer tube so a copper 3/4" pipe cap fit. Next time I think I will use a 1" aluminum slug with a tight press fit. DX even has 24.5mm glass lens and o-rings that are perfect. The I.D. of steer tubes varies some but eventually I found the perfect one with a slight taper. I even "machined" some shallow fins in the outside of the light by using a park tools steer tube cutting guide - essentially a miter for round tubing, I just rotate the tube after every couple passes with the hack saw. This light actually runs on high for 5min before thermal cut back at 70c. I may bump it up to 80c.

    I wish we could get new mixed boards from cutter 1 xp-g r5, 1 xp-e warm, and 1 xp-e r2 in a warmer tint and then wire them so the 2xp-e get 500ma and the xp-g gets 1000ma and the electronics only see the vf of 2led in series, making a 3cell battery and a buck regulator ideal.

    That said I will also soon be trying a single xp-g at 1100ma with a 20mm round ledil optic that should make a very nice tight beam. Still waiting on delivery of this part from cutter, but that is no stab at cutter since they shipped the rest of my order already and will ship the ledil lens when ever they get it. Much improved service from them. They used to hold entire orders for back ordered parts.

  13. #13
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    Quote Originally Posted by bikerjay
    That said I will also soon be trying a single xp-g at 1100ma with a 20mm round ledil optic that should make a very nice tight beam. Still waiting on delivery of this part from cutter, but that is no stab at cutter since they shipped the rest of my order already and will ship the ledil lens when ever they get it. Much improved service from them. They used to hold entire orders for back ordered parts.
    I'd love to get some feedback from you on that bikerjay as soon as you finish it. I am looking to build something along those lines as a helmet mounted spotlight.

    Regards,

    OTH

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    hey steve, sounds like you're looking at doing roughly what I am (but on an even more minimalist scale)

    I'm going for a double-triple XPG on the 20mm optics. should come out to pretty small on the light end (definitely under 100g light head).

    I'm planning on running the LEDs at 3s2p, and pushing 1A into the whole system with a maxflex. figure that'll give me around a 12W high beam. there's the option of a 1s or 2s lithium pack, and both will work.

    here's a little table I was working on when I got bored. packs are made of standard lithium 18650 cells (around 55g each)

    pack hi beam runtime lowbeam runtime rough pack weight
    2s1p ~1hr ~4.5 hr 120g
    2s2p ~2hr ~9 hr 215g
    1s1p ~.5hr ~2.1 hr 60g

    i think, for a minimalist, that 1s1p is looking pretty tasty. those runtimes are using conservative guesses on efficiency from the maxflex. I think it would make for a dynamite 24hr racer setup. 2hr burn time, around 400 lumens, and probably around 150g weight. you could even move the high beam to 700mA and get more light for about an hour.

  15. #15
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    Looks good... what about just doing 2XPG series at 1000 mah with narrow 10mm optics... should get about 600 lumens and you could make the housing roughly 50 grams with driver and switch and run a 2200 mah 11.1v battery in jersey pocket. Total system weight would be around 200-220 grams, with most of the weight in your jersey pocket, and you would get over 3 hours.

    Or, same light, boost driver (maxflex, fatman), 1 2200mah 18650 battery 600+lumens, 1 hour runtime, and would weigh 100-120 grams... cut it back to 800 ma, still over 450 lumens, and have 1:20 runtime.

  16. #16
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    Quote Originally Posted by bikerjay
    That said I will also soon be trying a single xp-g at 1100ma with a 20mm round ledil optic that should make a very nice tight beam. Still waiting on delivery of this part from cutter, but that is no stab at cutter since they shipped the rest of my order already and will ship the ledil lens when ever they get it. Much improved service from them. They used to hold entire orders for back ordered parts.
    That does sound interesting. You could make it even smaller! Use 1 XPG on a 10mm round MCPCB, and Cutter lists a 10mm optic for the XP series. That would make a truly tiny light head, although you would have to watch the temperature. If run at 1000ma, the current R5 bin would put out between 350 and 370 lumens, and the S2 bin when released would be 370 to 390 lumens (those numbers are without taking optics effiencies into consideration). That is probably enough light for most people, and it would run for 4 1/2 hours on a 2 cell 2400mah lithium battery (batteries in series and using a bFlex effiecency of 88%). I may go in this direction, as that is still more light than I currently have, and light head will be smaller and lighter. Back to the CAD software!

    Mark

  17. #17
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    Quote Originally Posted by bikerjay

    That said I will also soon be trying a single xp-g at 1100ma with a 20mm round ledil optic that should make a very nice tight beam. Still waiting on delivery of this part from cutter, but that is no stab at cutter since they shipped the rest of my order already and will ship the ledil lens when ever they get it. Much improved service from them. They used to hold entire orders for back ordered parts.
    I considered that as well and went as far as to build a simple prototype using a single XPG. But, the weight and size difference between a single XPG with a 10mm optic and a triple with a 20mm optic is pretty minimal once you build a housing and mount around it.

    The single XPG does provide enough light, but I suspect you'll end up running it at 1000ma all the time where it's least efficient. With the triple, I think running at 500ma will be plenty of light and it'll be very efficient at that current and you'll still have the full power available when you need it.

  18. #18
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    Toying with the idea of mounthing 1 of these into a torch body and direct driving it, the battery should output ~1800ma's tops so thats 600ma's per LED and no driver ineffiency to worry about, still run over over 1 hour on full ( well only ) power.

    Run a 2nd torch XP-G on my head on full time and save the triple for faster technical sections in burst mode.


    What do you all reckon ?? Possible ??

  19. #19
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    why not use the 4up XPG Board?? not much bigger and you will have no problems with a maxflex and a 7.4v battery!

  20. #20
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    Quote Originally Posted by Whitedog1
    why not use the 4up XPG Board?? not much bigger and you will have no problems with a maxflex and a 7.4v battery!
    Ooh, that's a good idea

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    Thats what i've been doing and it works really well. see link, I've just been reworking this one to take XP-G's and run at 1A. I'll post some pic's of the revised one over the weekend as i've got 65 to sell now.

    http://forums.mtbr.com/showthread.php?t=557893

  22. #22
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    Quote Originally Posted by allport
    Thats what i've been doing and it works really well. see link, I've just been reworking this one to take XP-G's and run at 1A. I'll post some pic's of the revised one over the weekend as i've got 65 to sell now.

    http://forums.mtbr.com/showthread.php?t=557893
    I wonder if 2XP-Es and 2XP-Gs would work well too. The Es are available in warmer tints and throw better.

  23. #23
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    Quote Originally Posted by MtbMacgyver
    I considered that as well and went as far as to build a simple prototype using a single XPG. But, the weight and size difference between a single XPG with a 10mm optic and a triple with a 20mm optic is pretty minimal once you build a housing and mount around it.

    The single XPG does provide enough light, but I suspect you'll end up running it at 1000ma all the time where it's least efficient. With the triple, I think running at 500ma will be plenty of light and it'll be very efficient at that current and you'll still have the full power available when you need it.
    Some good points. The size of the light head with a single XPG and single 10mm optic would be truly tiny ONLY if you mount the driver elsewhere. Otherwise I think you are correct about the size. Below are a couple of drawings of a single 10mm XPG light head, with a quarter for scale. It is tiny! I am thinking of going in thie direction, as my plan is to mount the driver and switch in a seperate box which will be clipped to my camelback shoulder strap for easier access.

    You are also correct about the efficiency being better at 500ma, but with the XPG, the difference is not as much as with previous LEDs. According to Cree's datasheets, the XPG will put out 250% of it's intesity at 1000mA, whereas with the XRE, it was about 220%. That is compared to the output at 350mA. That means that for the XPG increasing the current 285% will result in 250% more light, that's pretty good!
    Attached Thumbnails Attached Thumbnails XPE/G 20mm triple helmet light..-xpg-10mm-helmet-light-1.jpg  

    XPE/G 20mm triple helmet light..-xpg-10mm-helmet-light-2.jpg  


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