LED nirvana

[AndyF]

Potholer has summed it up technically very well...

The battery case does look flimsy, but I've use one for a week in the Dent de Crolles, and on about 15 digging trips, and it hasn't shattered. We call them "Biro" lights because of the plastic...

The weak point is the belt clip. It's a "hook" rather than "thread" type and keeps coming off, so I carry mine in a £4 belt fitting digital camera case. This also gives it extra padding...

The "Gelert" version is the same basic headset, but with rear mount 4 "AA" cell battery box.

The NiMh version is great, but with a 5W bulb gives only 2 hours. O.k. for an evening trip, but not much else. The LED lasts much longer though..

What I want is the NiMh version with a 1 watt Luxeon, that would be really useful!!

 

[potholer]

Since the Gelert version does use a lower-power bulb, I guess that could be an option for someone wanting more life on a NiMH version, if they can find somewhere selling the 0.5A bulb.

An LED conversion should be possible even leaving in the original reflector - having a zoom function does mean that alignment shouldn't be much of a problem if using a side-emitter.
Heat removal might need a bit of thought if running at ~1Watt - I find my rather more radical conversion getting fairly warm if running at full power indoors, and there is a fair bit more room for circulation in mine than there would be in one that was basically a bulb-replacement.

Alternatively, if someone wanted to throw away the zoom reflector and use a Luxeon collimator to make a beam, there's a load of space inside just waiting to be used, and heat spreading may be rather easier.

 

[AndyF]

Hi Potholer,

Do you know what type of bulb the Gelert version uses? Most of these use the 5W "bi-pin" halagon... does the Gelert use an MES or similar, or is it still bi-pin?

I've never seen a bi-pin 2.5w halagon, I'd be keen to get one if they exist...!

Could you say why heat is a problem with Luxeons.. do they stop working? I'm ignorant on this issue...

 

[potholer]

The Gelert uses a bi-pin halogen, marked '4.8V 0.5A' on the base.

With Luxeons, the problem is basically that all the electrical power not converted to light ends up as heat which needs to be conducted away from the LED, which shouldn't be allowed to get much hotter than about 100C (on the circuit board of a Star). Running hot does reduce the device lifetime, and the efficiency also drops as the temperature rises.
The lifetime figures quoted by Lumileds are based on running the device at a junction temperature of 90C or less (equivalent to a circuit board temperature on a Star of ~70C)
Despite the efficiency of LEDs, as a rule of thumb you can count on having to remove almost as much energy as heat from the device as you put in in electricity.

Though a small halogen bulb is less efficient at generating light, most of *its* waste heat is in the near-infrared, and is radiated away along with the light, plus the bulb itself can run at high temperature without damage.

*Very roughly*, even comparing LEDs with halogens based on *light output* (where the LED's greater efficeincy gives it some assistance), an LED will possibly still leave you needing to dispose of twice the heat.
For a given electrical power *input*, the heat to be dealt with may be 4x that of a bulb consuming the same power (but making 1/2 the light).
So, maybe a 1W LED has nearly as much waste heat to be dealt with as a 5W halogen, yet also needs to be kept rather cooler.

 

[cucc Paul]

In english..... The hotter an led get the shorter its life span... The hotter your head gets.... The less efficent it works... Also alot of components are only rated up to 60C so if you have a circuit board in there you can cook it

 

[AndyF]

The Gelert uses a bi-pin halogen, marked '4.8V 0.5A' on the base.

Thanks. Thats great.

I'll buy a Gelert just to get the bulb, and then pop it into my NiMH and see how long it lasts. Should be 4 hours= I reckon.

 

[potholer]

I see what you mean about the original version of the lights:
http://www.peli.com/hu_2660.html
http://www.peli.com/hu_2640.html

Though they don't have an over-the-head strap, the reflector seems to be faceted, and the LED is a 3-LED setup, there's a lot of similarity.

The Peli lamps use *nominal* 3.5 and 5.8W bulbs, respectively, but it *looks* like they use a different fitting:
http://www.cezine.net/catalog/product_info.php?name=2644%20Headup%20Lite%20Halogen%20Bulb&products_id=192&language=en
and aren't cheap either.

Gelert don't seem to even list the 2-in-1 light on their own website, let alone spare bulbs.

At
http://www.reflectalite.com/halogenpage.html
A 4V8/0A5 G4 base bulb (which appears to be the right one for the gelert) seems to be £4-00

 

[AndyF]

http://www.reflectalite.com/halogenpage.html
A 4V8/0A5 G4 base bulb (which appears to be the right one for the gelert) seems to be £4-00

I can buy the whole Gelert lamp for £9.99 from Bakewell, so I think I'll buy one, I can always use the spare headset...!


The maplin lamp is a copy, rather than the Peli lamp being a "badged" product (I think!). The LED in the Maplin lamp is quite good, I tend to use it for travelling to a dig, then use the halogen while working..

I also use the Maplin lamp for France. Zero weight as you buy batteries there, and no nasty carbide to upset customs people, and no charging problems on campsites.

I get 13 hours out of a set of alkalines on 5 watts. Mixing with the LED I get typically 20 hours. If you buy TDK batteries from Aldi they are 79p each, or VARTA batteries from Ikea for 98p each thats quite cheap hassle free lighting....

 

[potholer]

Well, if you need any spare 4D-cell boxes, drop me a line. I definitely have 1 around, (and should have another somewhere) I expect never to use, and they're yours for the postage (or a similar donation in your local CRO collecting tin). You can have a couple of 5W bulbs and spare reflectors as well, if you have any use for them.

 

[diggerdog adam]

Sorry to go off thred a bit , but the other day we pased a group under ground and one of the guys in the group had a "*ankers torch" on the side of his helmit (of the type that have no batterys fully water tight) but the only prob it that you have to keep shaking them to keep a charge quite entertaining watching him going up the 30ft pitch moving his head like a nodding dog on the back shelf of a 1990 ford escort any thoughts? guess there cheep !

 

[Dave H]

Had a chat with an electronics disty the other day - well actually I only went for the free food
But he was showing off some 5W Luxeons that were impossible to look at even in a brightly lit room - he said that it was all down to the driving, and then clammed up :x (But in the demonstration they were not on continuously, so presumably not getting too hot)
What he did say though, was that he had seen in Luxeons lab some 15W devices that could be in car headlights in a couple of years.

1W, 5W and 15W lighting - normal, pitches and 'oh my god, look at the spot on the moon'

 

[potholer]

I haven't *yet* seen anything that would make me think that the light output of an LED could be significantly altered by the way it is driven - LEDs pretty much convert current to light with a basically constant efficiency across a wide current range, and pulsing an LED on and off at high frequency gives a light output which is subjectively the same as an LED driven constantly at the average current of the pulsed LED.

 

[Dave H]

Yes, that's what I thought. Maybe the salesman knew that he'd been caught out and that's why he clammed up.

One of my more eagle-eyed collegues says that it was a Semtech IC doing the driving, whilst another says that it was an ON Semi part. (They could possibly have had both on the board [driving seperate LEDs] as they are a disty for both companies)

Either way, the design they were demonstrating would not fit into an Oldham headset as the inductor was possibly the largest SMT one I've ever seen!

Maybe these Luxeons were 'golden samples'. I remember that you have said in the past that they are sorted by output.

 

[potholer]

In practice, they're so *&^%ing bright that I'd guess that even a factor of 2 difference in output might not be noticable to the eye - the only difference might be just how wide your blind spot ends up being after looking at one.

 

[AndyF]

At last I've Found it!!

http://www.ledhome.net/htm/lm-02.htm

 

[potholer]

I'm not sure I understand the figures - the table of information for the LM02 looks to be almost a straight copy from the table for the LM01. despite the seeming differences in batteries and LED numbers.

Interesting, but puzzling.

 

[Mike W]

I'm sure LM02 is an old Motorola mobile phone with lots of 5mm LEDs stuck over the keypad !!

I think I saw somewhere that for the ultimate in LED efficiency, you take a Luxeon V, 'burn it in' by running it for 12 hrs, then underrun it at 3 watts. ( For super brightness, of course, all you do is mount a load together on a very good heat sink !! )

 

[potholer]

I was *about* to say that according to the current datasheet figures, 1W Luxeons seem to be the most efficient - typically 45lm/Watt, compared to ~30lm/Watt for 3Ws at the same power.

However, when I did a quick check on the lumileds site, I found there's a new device - the 'K2' - which has a variant giving a typical 60lm/W at 350mA ('1W') and 50lm/W at 700mA ('2W').
http://www.lumileds.com/products/line.cfm?lineId=18

When they're available in quantity, they could be pretty impressive devices - I'd love to try some in my lights - running at 1W, close to twice the light of a 3W (at the same power) for the same battery life, or twice the battery life for the same brightness.

 

[AndyF]

I'm sure LM02 is an old Motorola mobile phone with lots of 5mm LEDs stuck over the keypad !!

I think you are right - with a reflector of some tin foil!

(My post about this was a bit tongue-in-cheek BTW.... :shock: )

 

[AndyF]

At last, a 20 watt headset, this one from http://www.mica.fi/

Battery life is 40 minutes..