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    Flashaholic Tobias Bossert's Avatar
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    Default Replacement of carbide lamps by LED lamps

    Replacement of cavers carbide lamp by LED lamps

    1.Purpose of this treat
    2.Development of a headlamp optimized for caving
    3.Amount of light required
    4.Color temperature and beam pattern
    5.Batteries and electronics
    6.Optics and housing

    1.Purpose of this treat

    Candlepowerforums is substantial work, sometimes too extensive to find exactly what you need. The purpose of this treat is to bring together all those information required to develop an optimized headlamp for utilization in caves.

    I start this treat with a lot of additional information and hope, that I can learn from feedback and proposals the members of Candlepowerforums can give me.

    I’m member of a cavers club in Austria. We plan to build our own headlamps for our club but not to sell them: we have NO commercial interest. But we think the ‘high tech’ products from www.lupine.de and www.scurion.ch are much too expensive for hobby cavers, so one aim is to develop cheep but never the less optimized alternatives.

    2.Development of a headlamp optimized for caving

    When I started my first expedition into a big alpine cave in 1965 I used a carbide hand lamp, as usual at that time. In those days it was impossible to achieve sufficient light output with battery flashlights for expeditions of several days. In the early 1970s cavers changed to carbide headlamps. Up to now most cavers still use carbide lamps, since these are extremely reliable, easy to maintain and provide sufficient light even for large rooms in big caves. Duration of expedition doesn’t matter, its a question of amount of carbide you take along (about 400g per day).

    Since some years, many manufacturers provide battery headlamps based on white LED. Unfortunately none of them really comply with what is required during a several days cave expedition. But indeed the technology is advanced enough to develop a headlamp satisfying these requirements.

    3.Amount of light output required

    The old lamps e.g. combine up to 250g of carbide with about 140g of water to produce an amount of 100g acetylene (~ 100 liters). Four sizes of burners are used commonly, consuming 7, 10, 14 or 21 l/h of acetylene. The flame delivers about 67, 92, 133 or 200 lm at a color temperature of about 2300K. The burner alone would throw a nearly isotropic pattern, only downwards a cone of about 60 degree is shaded by the burner itself. The burner is mounted in front of the helmet and uses a small reflector. During normal use, this reflector gets blackened quickly, so about 60% of the light can be used only. Most cavers in Europe use burners with 14 or 21 l/h providing a total luminous flux of about 80 to 120 lm. These lamps consume about 33 to 50 g/h of carbide. But the carbide lamp itself has an overall weight (carbide/water-container plus tube plus head lamp) of another 1000 g too.

    It would be nice to get the same total luminous flux from the new technique too.

    Actual white LEDs are promoted to deliver 100 lm/W. That’s not true. The following table demonstrates the achievable luminous output of four actual types off SSC P4.


    Table 1 – Achievable luminous output with actual white SSC P4 LEDs

    The electrical power required to replace the good old carbide lamp depends. Carbide lamps deliver a rather uniform spatial pattern, thus you have to compare with bare LED covered by plain glass only. In the worst case using the S_42182_S_SS0_I to replace a burner with 21l/h you will need 3,2 W drawn from the battery and in the best case using the W_42182_U_SVN_I to replace a burner with 14 l/h you will need 1,3W.

    So ‘paulr’ http://www.candlepowerforums.com/vb/...79&postcount=2 was right with his estimations!

    First thought: take SSC U bins, they are brightest! Really?

    4.Color temperature and spatial pattern

    We are not interested in the physiological sensation looking directly into the light source but rather in the amount of light being reflected from the objects we want to see. SSC U bin covers equivalent temperatures from 4500 to 7000K, quite different from our used carbide flame having 2300K. The reflection factor of typical materials found in caves depends on wavelength. Bluish materials are rare, e.g. loam is rather beige. Therefore it might be possible, that the “bright” U bins with 6700K subjectively will be less bright inside a cave than an objectively less bright S2 bin with 3000K.

    Color temperature

    First I tested those five LED types given in table 1 at home. Against a pure white wall indeed all U bins are the brightest subjectively. Against a wall colored with ‘apricot white’ the S bin with 4000K subjectively seems to be at least as bright as the best U bin, in this case 5300K. Against a pine wood ceiling, the S2 bin with 3000K appears brightest.

    Studies are carried out in alpine caves at the moment to determine the subjectively brightest LED type amongst those of table one. The tests cover both, plain LED (uniform spatial pattern) and narrow beam (10 deg), because it is not determined in advance, that the findings will be the same. I will supplement the results when finished!

    >> Questions to everyone:
    Are there better LEDs out for 3000 to 4000K than SSC P4 bin S and S2?
    Where can I buy W_42182_U_SUN_.. or ...SUM..., that’s 4500 to 5000K and nevertheless U bin?

    Spatial pattern

    The carbide lamp didn’t allow realizing a narrow beam. This is one significant improvement using LED technique, now you can look down into deep pits too. But during walking and climbing inside a cave, you rather would prefer uniform spatial pattern than any beam. Everyone who ever tried to make a night walk with a beam lamp knows what I mean: You either risk stumbling or you will get a stiff neck! Therefore the new electric headlamp should provide both, all-round light (covering hemisphere in front of you) and spotlight (as narrow as achievable), switched alternatively.

    5.Batteries and electronics

    In October 2007 I started the project and asked the members of candlepowerforums for applicable converter boards for my project. But this was on the wrong forum I think (flashlight electronics – batteries included). Now I can demonstrate three practical solutions, cheep, efficient and optimized for cavers headlamps. But the optimum solution depends upon the battery type to be used.

    Batteries

    Professional ‘high tech’ headlamps use Li-Ion rechargeable batteries. This is the best solution technically: Li-Ion provide the highest energy density (more than twice of alkaline and Ni-MH) and are able to deliver high drain currents even at low temperatures. But the problem arises from cavers negligence: They use the lamp until it gets dark and after the trip all the stuff ends up in the cellar, neither being cleaned nor recharged – this normally will be made up for 15 minutes before starting to the next expedition. Therefore I decided not to propose them to use Li-Ion rechargeable batteries.

    The second-best solution would be Li-FeS2 primary batteries. But if you start remembering your stuff just some hours in front of leaving to the trip and have not enough batteries at home, you will fail, because there is no shop providing these strange batteries on the way to the cave.

    Alkaline batteries would be the most practical solution in my mind. They are extremely cheep and available everywhere. But the characteristic of alkaline cells depends strongly upon the cell size! As you can derive from the studies of ‘Silver Fox’ http://www.candlepowerforums.com/vb/...ad.php?t=64660 the realistically achievable energy density of alkaline cells drained with low to medium currents is nearly independent of the cell size (50 to 90 Wh/kg depending on brand). This doesn’t surprise because the chemistry is the same for small and large cells. But the realistically achievable power per weight is much higher with smaller cells (AA-size above 20 W/kg but D-size below 8 W/kg only). Thus it makes more sense to use 6 AA cells than 1 D cells having the same weight.

    The achievable energy depends upon the power drained: the heavier the load, the smaller the drainable energy content. I made two tests in my household refrigerator: two battery packs (6 AA and 8 AA in series) were discharged with 1,5 W continuously down to 3,5V. This means, the first pack is loaded by 0,25 W and discharged to 0,6 V each cell and the second pack by 0,188 W and to 0,45 V. The weight of the second pack is 133% of first one, but delivers 142% of total energy. My conclusion is that these additional two cells could be carried much more comfortable in the backpack than in battery belt at the helmet or worn in the chest pocket!

    At the end I decided to propose using batteries of AA size. Most cavers I know will use alkaline types which you can purchase at every supermarket. But the electronics will also accept Li-FeS2 primary and Ni-MH rechargeable batteries of AA size too.

    As estimated above, at least 1,3 W will be required continuously to get an equivalent luminous flax as a carbide lamp. Inside alpine caves temperatures are about 0 to 6°C. Under such circumstances alkaline AA cells deliver about 1,5 to 2,2 Wh when drained with less than 250 mW continuously and if the converter board allows to unload the cells completely. Rough estimation: average cell consumption will be 0,7 to 1 cell per hour when using at least 6 cells in a battery pack. For a 9 hours trip with continuous light you will waste 6 ‘good’ or 9 ‘cheep’ AA alkaline batteries. The consumption expressed in weight is about 18 to 25 g/h. Remember: this will replace 33 to 50 g/h of carbide consumption, a reduction of 50%! And the device itself is much lighter than the carbide lamp too. Additionally we can hope LED efficiency still will increase in future ...

    Electronics

    We need thee levels of output current:
    Working light, about 350 mA, used continuously all over the day
    Pause light, below 35 mA, used during breaks
    Spot light, amara (as much as realistically achievable) used only for short term

    First I tested some of those multi mode buck converter boards from Kaidomain and DealExtreme. But I came back to the single mode types, because these are more flexible for my own modifications. At the end three boards are shortlisted: Taskled CC1W, Kaidomain sku.2982 and Dealextreme sku.3256. All three easily can be modified to match the requirements of cavers headlamps.

    Taskled CC1W

    By far this is the best board tested, but also the most expensive too ($15 + shipping). It has excellent manufacturing quality and George gives extensive support, answering your questions spontaneously! This board also provides the best efficiency. The output current can be varied by paralleling resistors to R2 or R3 labeled on the board.

    I provide you with measured curves for three modes, each of them with shortened polarity protection diode:
    Blue – original board (no resistors in parallel) => I = 350 mA, average efficiency 88%
    Green – dimmed down with R2 || 560 ohm => 35 mA, average efficiency 72%
    Red – boosted with R3 || 180 kohm => up to 620 mA, average efficiency 87%


    Figure 1 – Characteristics of Taskled CC1W

    Original and dimmed current is regulated constant. Boosted current would calculate to 670 mA, but the internal current limiter supersedes and the output current depends upon supply voltage. This is no disadvantage because it makes no sense to demand a boosted current from nearly discharged alkaline batteries. This board accepts supply voltages up to 20V.

    Kaidomain sku.2982

    This medium priced board ($ 3,10, free shipping) also has a good manufacturing quality but its efficiency suffers at higher current levels. This board accepts supply voltages up to 18V. Fortunately this board is now available again.

    Originally the board delivers 750 mA, always o.k. for our boost mode. To reduce output current you will have to unsolder pin 8 (FB) of the integrated circuit PT4105 and insert a resistor (I took 1,8 kohm). With an additional resistor of 56 kohm from FB to LED+ you will get about 350 mA output current, and with about 25 kohm (depends upon Vf of LED) you achieve 35 mA.


    Figure 2 – Characteristics of Kaidomain sku.2982


    Figure 3 – Application of Kaidomain sku.2982 for cavers headlamp


    DealExtreme sku.3256

    This low priced board ($ 1,61, free shipping) has poor manufacturing quality only but its efficiency is good. This board is specified for 1 A output current, but the current is unregulated and depends upon supply voltage and Vf of LED.

    Before you start modifying the output current of this board, you should solder ceramic SMD capacitors in parallel to these strange aluminium electrolytic capacitors, this will increase the efficiency by about 3% (I tried 2,2 or 4,7µF 16V).

    To reduce output current you will have to unsolder pin 4 (ISENSE) of the integrated circuit C300 and insert a resistor. This resistor should range below 100 ohm, because it is in the rf path (I took 39 ohm SMD type and soldered it on empty place “R2” after having cut the lower connection of it to IN-).

    With an additional resistor from ISENSE to ground (IN-) you can divide the sensed voltage and thus increase the output current. With an additional resistor from ISENSE to supply voltage (IN+) you can decrease the output current. But the effect of this manipulation depends upon supply voltage and therefore rotates the output current curve over input voltage clockwise. If you connect the resistor to LED- instead, this rotation will be even stronger. Choosing the optimum relation between resistors to IN- and to IN+ or LED- you can achieve a nearly flat response.

    With resistors of 27 kohm from ISENSE to LED- and of 220 ohm to IN- you will get about 1 A output current almost constant over an input voltage from 4 to 9V.


    Figure 4 – Characteristics of DealExtreme sku.3256 for high current level

    The current spikes in these curves occur when the device transfers from direct mode to switching mode and vice versa. The arrows show the different dynamic behavior for increasing and decreasing supply voltage. The arrows would be vertical with zero source impedance and horizontal with a pure current supply. During use with alkaline batteries you will not encounter these peaks, because the impedance of nearly discharged batteries is too high.

    1 A is not of interest for our project since we require lower currents. It is impossible to decrease the output current much below 100 mA using the original current measurement resistor of 0,020 ohms. You need to unsolder it and replace it by a higher value (I used 0,150 ohm). With this you can achieve flattened curve at 350 mA and 35 mA as demonstrated in the application. In this application the boost level intentionally is not flattened.


    Figure 5 – Application of DealExtreme sku.3265 for cavers headlamp


    Figure 6 – Characteristics of DealExtreme sku.3256 used for cavers headlamp

    The disadvantage of this board is the limited input voltage. Therefore the battery pack is limited to 6 alkaline cells in series or to 7 Ni-MH.

    6.Optics and housing

    Mechanical manufacturing seems to provide more problems than electronics!

    Optics

    Most actual white LED provide a dome with a week spatial concentrating. This is fine for working and pause light and needs no additional optics which would cost 15 to 25% of light anyhow. But at least you will need a plane of glass to protect the LED and the starboard. Even this will cost about 10% of emitted light and restrict the spatial pattern to about 150° (original is 180°). It would be preferable to use a transparent spherical cap, comparable to http://www.khatod.eu/pdf/pljt20_test_report.pdf but not opalescent.

    >> Questions to everyone:
    Where can I buy such transparent caps?

    For spot light we need a reflector or lens optic with low losses, narrow beam and low stray light around the spot. Most of all miniature plastic optics don’t comply with this. The best results so far were achieved with Gaggione LL3 http://www.lednlight.com/LL3.htm, in German forums sometimes called ‘Mobdar’ but as far as I can see, these are from different sources. Unfortunately this collimator needs small modification to allow optimum placement of SSC P4 LED.

    >> Questions to everyone:
    Is there any better optics for SSC P4 LED on the market?

    Housing

    The headlamp mounted at the helmet contains two parts, one for spot light and another one for working light. Spotlight will be similar to http://default.nueb.de/fahrrad/licht/mueller/ but with smaller heat sink. The other one may be a short aluminium tube (diameter 25 mm) covered by a plane of glass at front side and by a small heat sink in the back.

    At the moment four arrangements are under discussion:


    Figure 7 – Four alternative arrangements of battery box and headlamp

    Arrangement a)
    Electronics, both switches and spot light mounted in the battery box; headlamp contains all-round light only; minimum weight and size mounted at helmet.
    Headlamp diameter 25mm, length 15 mm
    Cable with two wires only
    Battery box in the chest pocket 140 x 60 x 20/25 mm; spot light with diameter 40 mm protruding 5 mm out of the flat side; switches and cable outlet flush mounted at the smallest side
    Problem: How to protect spot during crawling?

    Arrangement b)
    Electronics and both switches mounted in the battery box; headlamp contains all-round light and spot light; all switches still safe in the pocket; spot light follows movement of head.
    Headlamp diameter 25mm, length 25 mm plus diameter 40mm, length 25.
    Cable with three wires.
    Battery box in the chest pocket 120 x 60 x 20 mm; both switches and cable outlet flush mounted at the smallest side; alternatively one rotary switch instead of two toggle switches.

    Arrangement c)
    Electronics and only main switch mounted in the battery box; headlamp contains all-round light, spot light and switch to choosing amongst all-round and spot light.
    Headlamp diameter 25mm, length 25 mm plus diameter 40mm, length 25.
    Cable with three wires.
    Battery box in the chest pocket 120 x 60 x 20 mm; main switch (work-off-pause) and cable outlet flush mounted at the smallest side.

    Arrangement d)
    Only batteries in the battery box; headlamp contains all-round light, spot light, electronics and both switches.
    Headlamp diameter 25mm, length 25 mm plus diameter 40mm, length 25 plus diameter 25mm, length 25 mm (containing electronics).
    Cable with two wires only.
    Battery box in the chest pocket 100 x 60 x 20 mm; if desired, battery could be changed together with battery box.

    In any case the battery box is required to be solid enough to accept the barer rests on it at a stony subgrade. The headlamp is required to be solid enough to accept knocking one’s head against the roof. Both parts are required to be waterproof.

    At the moment nothing mechanical is realized; I’m happy not to be the one having to develop this!
    Last edited by Tobias Bossert; 08-19-2009 at 10:03 PM. Reason: we have NO commercial interests - not 'now'! Thank you FriBo for the hint.

  2. #2
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    Default Re: Replacement of carbide lamps by LED lamps

    Hello Tobias,

    Welcome to CPF.

    This looks like quite a project...

    If I may comment on your selection of batteries.

    In the conditions you are going to be using the light, the optimum, in my opinion, power supply to use would be the CR123 primary lithium battery. I don't know how many are in your club, but you could put in a bulk order and have ample cells to power your light.

    I would suggest you explore using 2 of the CR123 cells in series. Back up power could be supplied by a 9 volt battery, if your circuit would allow that, and you could also utilize a 4 AA battery holder for those who like to carry extra weight... or for the use of the Energizer L91 battery.

    Alkaline AA cells work well in the 5 - 10 C temperature range, but it has been my experience that once the temperature drops below 5 C, you need to make provisions to warm your batteries, including your spares.

    Good luck on your project.

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

  3. #3
    Flashaholic*
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    Default Re: Replacement of carbide lamps by LED lamps

    your pictures are over the size limit
    Light is the activity of what is transparent - Aristotle

  4. #4
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    Default

    please, first of all !!!
    make the pics smaller, so that one does not have to scroll sideways to read that whole post
    (I came to 2/3 till got bored and only answer to that parts)



    several points to consider:
    * try to find the TINT of the led You like, not the BIN, thats of prime importance.
    * forget the Seouls and use Crees
    * being picky on normal prices for circuits (15,-- being expensive ) is no use for Your applications.
    * I have seen carbides in caves - there will never be a more appealing short distance area light
    (possibly try sunny white 5mm leds for this)
    * working light @ 350 mA - thats the power my headlamp runs on --> for running and biking. WAY too powerful and unnecessary for normal caveing use imho

    the best TINT-showing tread on CPF: http://www.candlepowerforums.com/vb/...d.php?t=156772


    wenn Euch das interessiert (because Austrian cavers club), kann ich Euch ja mal ein paar meiner gemoddeten Lämpchen zeigen, damit Ihr nen Eindruck bekommt - wenn Ihr Euch in Wiennähe trefft (befinde mich selbst in Baden),
    oder kommt mal zu einem Nightride (gepostet auf bikeboard.at)
    Last edited by yellow; 01-05-2008 at 11:59 AM.

  5. #5
    Flashaholic Tobias Bossert's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    Quote Originally Posted by yellow View Post
    PLEASE, FIRST OF ALL !!!
    make the pics smaller, so that one does not have to scroll sideways to read that whole post

    Uups!
    I sized the pics to 1200 pix maximum width. This works fine on a screen with 1280 pix width and with browser settings not consuming more than 80 pix on left and right.

    Now I have reduced the pics to a width of 950 pix, this should be visible completely even with a screen width of 1024!

    Please don't forget to empty your browsers cach befor reloading the page, because otherwise you will not see any difference.

    This is no good solution, that there is no autoscaling managing this: So all users have to restrict to the reader with the most narrow screen...

  6. #6
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    Default Re: Replacement of carbide lamps by LED lamps

    Quote Originally Posted by Tobias Bossert View Post
    Are there better LEDs out for 3000 to 4000K than SSC P4 bin S and S2?
    Here are warm white Q2-bin Cree leds that produce at least 87.4lm with 350mA
    http://www.led-tech.de/en/High-Power...64_120_77.html
    At that site you can also find Seoul and Lumileds leds. For maximum light output but with high color temperature i would recommend to use Q5 bin Cree XR-E leds instead of the Seoul leds.

  7. #7
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    Default Re: Replacement of carbide lamps by LED lamps

    Hello Tobias,

    I need to point out that the forum rules state that the maximum picture size is restricted to 800 X 800. You are close, but you need to shrink them down just a little more.

    Thanks.

    Tom
    Behind every Great man there's always a woman rolling her eyes...

    Most batteries don't die - they are tortured to near death, then murdered...

  8. #8
    Flashaholic Tobias Bossert's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    Quote Originally Posted by Jarzaa View Post
    Here are warm white Q2-bin Cree leds that produce at least 87.4lm with 350mA
    Thank you very much!
    Indeed this warm white Cree XRE WHT-L1 5C Q2 is really "warm" (5C = 3700 to 4000K) and much brighter (87 to 93lm @350ma) than everything from SSC in warm or natural white. I'll try them out immediately!
    The other LEDs XRE WHT-L1 WG Q5 you mentioned are too "cool" (WG = 5700 to 6200K), but you are right, they are brighter than the comparable SSC P4 with U luminance.
    I'm still looking for SSC USUM or USUN (4500 to 5000K), but may be your warm white Cree will be the winner!
    Kind regards
    Tobias

  9. #9
    Flashaholic Tobias Bossert's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    Quote Originally Posted by yellow View Post
    * working light @ 350 mA - thats the power my headlamp runs on --> for running and biking. WAY too powerful and unnecessary for normal caveing use imho

    Hi yellow,
    i'm used to caving since more than 40 years now! Let me say, there are many halls in caves where you blow water into your carbide lamp to increase the flame, but nevertheless it's still too week.
    But even with the normal pressure produced by the water in the tank above the carbide the lamp gives about 80 to 120 lumens all the time. To output 100 lumens from a LED lamp you need more than 350 mA at present, don't forget the losses in the headlamp (glass).
    In caves I frequently pass along tunnels more than 10 m broad, and you realy mean that 350 mA is WAY too powerfull? - It isn't!
    And last but not least: I'm used to have this amount of light in caves for many years and will not reduce my demands now.
    Kind regards
    Tobias

  10. #10
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    Default

    phuaa, now got the whole post - good luck on the project, it sure has arleady given You quite some thoughts, right?

    I read all the usual bad things (what I consider as bad) where ppl make themselves unnecesary probs and new ones with every problem solved (starts with wanting to produce ones own light head, ...)
    Better find Yourself a flashlight that can do what You want except of runtime, then use just its head and make someting to connect the batts with it.
    Or find a cheap light You like from its looks on DX (You know the site already), put the led You like inside, circuit behind, add end plate and method of mounting to housing, connect to batt pack --> ready, including a nice housing, front glass, rubber O-rings, ..., with less work a homemade housing will give


    the part I can totally not understand is how the lights, possibly the whole equipment, is cared and prepared for after and before the uses. Anyway, there is Li-Ion only for You, a pack made from 4 pc. of 18650 will cover at least 20 hours of the 350 mAh draw.
    read more here
    (I would still mod it a bit, f.e. this protection circuit instead of that large Bratbeck, but ...

    or get a light that is meant for 2 pc. CR123a, use just its head and have it run with 7.2 V Camcorder batts - which should ease recharging as most ppl have one.

    ... You main problem will be that most light are aimed on brightness - I see no chance You can do with without modding something
    PS: did I already mention to use Crees instead of the blue Seouls?


    [edit]
    Question: how hard is that temperature problem? Thought cavers wear the batts strapped to the body under the outer clothing? Isnt that a higher temp then?
    Anyone of You uses the common Petzl led models or other commercial led headlamps? Do You all agree on to change to led? (even when only knowing the Petzls?) [/edit]
    Last edited by yellow; 01-05-2008 at 12:03 PM.

  11. #11

    Default Re: Replacement of carbide lamps by LED lamps

    Hi Tobias, I'm quite surprised that no one has mentioned the Stenlight S7 in this thread (http://www.stenlight.com/) -- it's a purpose-built caving lamp that is rapidly growing in popularity among USA cavers. I don't own one but many of my caving friends do, and it's really an impressive piece of work in terms of construction, light output, and efficiency. It's not cheap -- a basic setup of light + custom Lithium-Ion battery sells for about US$300 or so -- but all the cavers I know who have them have been extraordinarily pleased with them.

    There are discussions about it both on this board and at cavechat.org (the US NSS discussion board), eg

    http://www.forums.caves.org/viewtopi...06387cb3516203

    If you are looking for a caving-specific LED headlamp, I'd highly recommend you check out the Stenlight if possible. (I'm assuming it's available in Europe...)

  12. #12
    Flashaholic* uk_caver's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    Doesn't the Stenlight run both LEDs in series?
    If so, it's not great for people looking for a smooth (non-spot) beam unless they lose the optics on both LEDs and then get another light for spot use.

  13. #13
    Flashaholic Tobias Bossert's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    Quote Originally Posted by Beaker View Post
    If you are looking for a caving-specific LED headlamp, I'd highly recommend you check out the Stenlight if possible. (I'm assuming it's available in Europe...)
    Yes, I read the thread upon Stenlight headlamp and I looked at the page of the manufacturer. It seams to be a good and robust headlamp indeed. But it still doesn't comply with our requirements as I posted in the beginning of my thread.
    There are two LEDs in series, always used together. Each using its own optics. Consequently the only possibility to change the spacial pattern under use would be to attach and remove an additional diffuser, not very handsome in caves...
    The beam is a compromice between throw and flood: It neither meets one of both requrements. We need flood working light all over the day and for short term usage only super narrow beam (without spill).
    On the other hand it provides 70 lumens output for 3 to 5 hours only (consuming 4 to 5W, not quite good nowadays). So you will need 2 or 3 battery packs (up to 6 pieces of 18650 cells) per day...

    There is indeed a much more suitable headlamp on the market, www.scurion.ch, but I would like to surpass it technically and nevertheless avoid its high price (about $ 500).

  14. #14
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    Default Re: Replacement of carbide lamps by LED lamps

    Leaving aside the underground practicalities, how easy would it be to fully diffuse a spot beam without losing a deal of light in the process?
    Wouldn't a diffuser tend to cause backscatter?

  15. #15
    Flashaholic Tobias Bossert's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    After some month of experimenting I come back to this treat. We tested all kinds of optics – now I can demonstrate some reasonable solutions.

    1) Normal light for walking and climbing

    Neither TIR with narrow, medium or wide beam nor plain LED satisfied our requirements. On the one hand all TIR are not wide enough for walking (you tent to stumble) but on the other hand, plain LED without any optics is to fade (you can’t see where to go).
    We tested many combinations of two simultaneous LED and find one combination satisfying us in real cave tests: Combination of a medium beam with FWHM of about 16° and a very wide beam with FWHM of about 80°.
    I realized this with XR-E Q5 using Carclo ripple medium (10210 & 10205) and with SSC P4 U using Carclo wide angle reflector (10170 & 10363). The axis of the medium optics is horizontal (when you stand upright) and the wide reflector is declined downwards 20 to 30°, as shown in Figure 1.


    This free mounting without case was for photo documentation only.

    It is not easy to demonstrate the feeling of the combined beam in a picture. I put the LEDs 50cm apart from a vertical white wall while the photo was taken from about 150cm from the wall – otherwise I would need a fisheye photo lens losing the orientation. The medium beam is horizontal and the pattern therefore is circular. The wide beam is declined downwards and therefore projects elliptical; it just reaches the area immediately in front of your feet. In reality you will not realize the sharp boundary of the beam, this is due to the photo taken from thee times the distance from the wall.



    Both LED were driven by different current levels. The XR-E Q5 for the medium beam needs about 30% of the current of SSC P4 U in the wide angle reflector to achieve the impression of the figure above. We plan to provide two levels: 40m + 130mA and 90 + 300mA, so we can hold this level for about 24 or 10h with 6 alkaline AA.

    2) Pause light

    We plan to use the above mentioned medium beam with a current level of about 20mA.

    3) Spot to explore deep pits or high shafts

    At the beginning I was sure we should use Gaggione Mobdar or Gaggione LL3 because so many users mentioned them positive. But these TIR are relatively big and provide a lot of side spill too. There exist completely different TIR (‘catadioptric reflector optics’ using total reflection on the front plain and being metalized on the backside, e.g. Carclo 10144) with extremely narrow beam, but these beams are too narrow for us (at the ground of a deep pit you will see one big stone only instead of the floor of the pit completely). We tested almost all TIR and reflectors from Kaidomain and Dealextreme and others and found nothing satisfactory.
    Cree XR-E has its own internal optics narrowing the beam a little bit, so it is possible to gather almost all of its flux with a thick aspheric collimator lens. We also tested almost all acrylic lenses we found. One very cheep lens with 23mm diameter was suitable and performs quite good. This lens is sold with different holders (DX 4614, DX 4628) which do not fit for XR-E. Therefore we cut the bottom of the holder away and inserted a Carclo holder for Cree (10205). With this combination you can adjust the lens. Both holders form something like a telescope.



    This device is much smaller than Mobdar or LL3 as you can see in the following picture.



    The combination of the two holders allows adjustin the beam. The beam is narrowest when the lens forms an image of the die on the wall:



    The rectangular shape of the die is about 40x40cm at a distance of 5m. As you approach the LED to the lens, the beam gets broader, round but weaker too; the left beam is about 150cm in diameter at 5m.



    I also compared the single lens with Mobdar. The beam of the lens is set to about 70cm at 5m (rounded but not jet round). The peak intensity of illumination in the center of the beam of Mobdar is about 70% of this, but it seams that the overall flux of the Mobdar is higher and the beam is much more “beautiful”. On the other hand the beam of the lens is “without” spill, that’s what we need.

    We plan to use the single aspheric lens with XR-E Q5 at about 1A. This is for short term use only. It works fine with 6 fresh alkaline AA, but when they got discharged they will limit the current rather than the regulator. With NiMH AA cells this is no matter.

    4) As much light as possible for big halls

    We tested the SSC P7 for this. We found no compact TIR (< 30mm). Since P7 has no internal lens the original beam is too wide to gather all flux with an aspheric collimator lens. Smooth reflectors throw donuts or beams with a dark cross in the center. So you must use orange peel reflectors. But – as I know now – orange is not orange. The roughness should be high enough with respect to the focal length. Most OP reflectors I found at Kaidomain and Dealextreme were not rough enough. Only two of the smaller types can be used with P7 avoiding severe donut effects:
    DX 5951 (similar to KD 3317) has diameter of 18mm only. The hole for the emitter must be opened to fit over the dome of P7 (9mm). This gives a relatively wide beam with only a week donut.
    DX 3257 has diameter of 26,5mm. You must cut the holder side so that surface on the backside of the hole for the emitter is plain. Additionally you must open the hole to fit over the dome of P7. This gives a medium beam with a week donut.
    If you don’t like this week donut, use a diffuser from L2Optics or Polymere. But this will cost at least 15% of the flux! If we could find a stronger orange peeled reflector, the donut should be avoidable without diffuser. I just ordered KD 5405 (23mm), KD 3318 (24mm) and KD 5151 (25mm) to try these too. For the moment I prefer the DX 3257. You can see the beam of modified DX 3257 with P7 in the picture below.



    We plan to drive this P7 with about 3A. This is for short term use only. It works fine with 6 NiMH AA cells, but with alkaline AA the current will be limited to their strength naturally.

    5) Put all together

    At the moment we plan to build a headlamp with 4 LEDs and optics as described above. This should get not to big for a caving helmet, as you can see on the following picture:



    But what is about the housing?
    No idea at the moment – I still hope that some manufacturer takes my ideas and starts its own development on that base.
    But at the moment, there is no such manufacturer. Therefore I have to continue...
    For this I assembled the circuitry for such a headlamp using cheep drivers from far east:



    Next I will construct a prototype and lend out to my caving friends to optimize it. This will consume some time...

    P.S.: Moderator please help!
    The links to my pictures work well, but I can't insert images. After saving changes, they were gone. Why? Please, can anyone tell me what I'm doing wrong:
    I push the button 'insert image' than the window for the URL appears with default 'http://'. When I overwrite it by the link and accept, than the text window shows an icon at the place of insertion. After 'save changes' no pictures appear but all icons are gone too...
    P.S.: Problem solved now:
    I used Firefox 2.0.0.16 with add-in Control de Scripts 1.03 and add-in AVG Save Search 8.0, which do not insert images correctly. With older versions of Firefox or with MS IE there is no such problem.

    Last edited by Tobias Bossert; 09-25-2008 at 11:26 PM. Reason: Insert images instead of links (MS-IE works, new Firefox not!)

  16. #16

    Default Re: Replacement of carbide lamps by LED lamps

    Tobias,

    I applaud your effort and thoroughness. As a fellow caver, I am always searching for the ultimate caving headlamp and will look forward to seeing what you end up with.

  17. #17
    Flashaholic* uk_caver's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    A four-LED light? That does seem a fairly serious project.

    Might it not be easier as a general 2-led caving light, and a more 'specialist' room-lighting and shaft-spotting light?

    I imagine there might be some kind of market for a specialist light among the large numbers of people who already have some other kind of caving light that they're happy with (Duo LED, etc)
    Possibly a specialist light would be better as a handheld unit, since for shaft-examining (at least when looking upwards), a helmet mounted spot beam can literally be a pain in the neck.
    When I was playing with some P7s, the main use I found for a very bright flood beam was for photography, which is also a use where a lamp is more useful in the hand than on the helmet.

    Also for the P7 room-light, have you tried using a conical reflector? If you don't want any kind of beam, just a rather more forward-biased light than you get from a naked LED, it's definitely worth trying.

    With your FWHM of 80° using reflectors - looking at the datasheet, a naked Cree has a FWHM of only about 90°.
    How different is the reflectored Seoul to a naked Cree?
    Is it just a case of the Seoul+reflector eliminating 'wasted' extreme-wide light?

  18. #18
    Flashaholic MiniLux's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    Quote Originally Posted by Tobias Bossert View Post
    P.S.: Moderator please help!
    The links to my pictures work well, but I can't insert images. After saving changes, they were gone. Why? Please, can anyone tell me what I'm doing wrong:
    You may simply use http://www.postimage.org/, it works very well for that purpose
    P1D, LD01, T1/TK10/11/20/40, E01, HP10, P10Ti, DBS R5, CL1H V3 R2/V4 MC-E, Jet M, H30/31/50/51/501/60/SC30/60, Spear, NDI, NEX, D10, EX10, EZ AA/CR2, M20, S20, S2, L2, LF2X/2XT/3XT/5XT, ED-P71/P72, L-Mini 2/PLI/P-Rocket/X-Thrower, Q RGB, Mini 123/CR2/CR2Ti, Turbo 2AA/CR123, AA Tactical, VX Ultra, T100C2, DeCree-XPG

  19. #19
    Flashaholic gillestugan's Avatar
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    Default Re: Replacement of carbide lamps by LED lamps

    Great work Tobias!
    Thank you so much for showing how to wire multiple PT4105 in parallel using one switch for regulating output to all of them.

    My plan is to build a lamp for caving and general outdoor using two MC-Es. One very wide flood and one narrow.
    I'm probably going to use 4 X PT4105 and the dies wired 2 in series with each pair individually driven.
    This will give me a very wide input range of about 8-18V.

    Regarding the housing:
    I've used an aluminium box for a 3X XR-E setup which works very well. It handles the heat well, is waterproof (if o-ring or other seal is used) and is quite cheap. EUR 4.40. Just not as good looking as I wanted. I would prefer an oval housing. Anodised in gold, red or black. :P
    Here is the box: http://www.conrad.de/goto.php?artikel=522369

    Regards /Gille

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