A couple of pictures of my new home made caving light.  At it's heart is a Taskled MaxFlex2 driver and three Cree R2 LEDs.  The case is a chopped up heatsink.  It uses Canon BP511 (?5 from 7dayshop, 7.4v, 1500mAH), with a cut up charger adapter to hold it in the battery box.


Front view:  two diffuse LEDs and one with a collimator to give a beam.  Front glass is polycarbonate that'll probably scratch easily but can be easily replaced.



Small waterproof switch is used for turning on/off.



The battery box with chopped up charger converter.

[Geeky gobbeldygook]
The driver can drive the LEDs up to 1A, when the LEDs should give out >600 lumens of light (although I don't actually have the means of measuring this - but believe me it's bright).  Running at 1A the LED mounting hexagon gets to about 50C which gives a LED junction temperature of 90C.  At 1A the converter efficiency drops off to ~82%.  With the current battery the battery life is ~45 minutes.

Running at more sensible currents and brightnesses the converter has an efficiency of up to 92%.  The LED mounting tile stays <30C until the drive current rises above 500mA.  At the lowest current setting (80 lumens?) the battery lasts for 15 hours.  The light can be programmed to give various different maximum drive currents (350, 500, 700 and 1000 mA) with the 5 in between settings scaling from a fixed minimum of ~60 mA up to the maximum.

The LEDs are connected in series (to give a forward voltage greater than the battery voltage) so cannot be dimmed individually.

[/Geeky gobbeldygook]

Iam in

So your'e not the Glaswegian bloke who never backs anything??

I'm interested - was the choice of having 2 unfocussed LEDs the result of experimentation (getting a balance of spot and flood), or for some other reason (like needing to have 3 LEDs to keep your total Vf above the battery voltage)?

Yer looks good, very similar to another design i've seen somewhere...  :-\
I like the 1 spot/2 wide combo, bet it's good to cave with. 

Am i wrong in thinking there's no waterproofing between the Polycarbonate and the Al behind? A thin sheet of silicon would not be an expensive addition.
Also, i'd be suprised if you get 80 lumens at 60mA. 

Nice photos.



bark bark bark bark bark bark bark bark bark bark bark bark bark bark bark etc

the important question is
Is it brighter than a Scurion?

Rob said:

Also, i'd be suprised if you get 80 lumens at 60mA.

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It's probably not too far off.
Looking at the output vs. current graphs, while keeping fingers crossed regarding the accuracy at the low-current end, if running at constant current, 60mA could give something like 20-25% of the output compared to the the nominal output at 350mA.
80lm is 2/3 of the nominal ~120lm output of an R2, and is pretty much in the ballpark of what 3xR2s might give at 60mA each.

On the issue of 'Scurion copies', I'm not sure I've seen any homebuilds so far with independent LED controls, so being pedantic, most really seem to be closer to Stenlights

potholer said:

I'm not sure I've seen any homebuilds so far with independent LED controls,

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www.bisun.co.uk ??
Looking at it it seems to have more settings than the scurion...is this what you mean, or i am flying of on some wild tangent...(which is quite likely) 

potholer said:

I'm interested - was the choice of having 2 unfocussed LEDs the result of experimentation (getting a balance of spot and flood), or for some other reason (like needing to have 3 LEDs to keep your total Vf above the battery voltage)?

Click to expand...

I played around with some old 'high output' LEDs that I have but never built into a light and decided that I liked that configuration best, because it gives the best balance seeing as the LEDs can't be individually controlled.  Does also have the advantage of keeping the forward voltage up!

menacer said:

Looking at it it seems to have more settings than the scurion...is this what you mean, or i am flying of on some wild tangent...(which is quite likely) 

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I was thinking more of the latest generation of homebuilt one-offs or prototypes.

Besides, something approaching its 4th birthday couldn't really count as a Scurion copy.

Cave_Troll said:

the important question is
Is it brighter than a Scurion?

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Certainly in wide spread it will be! My homebuild has 2 non-opticed R2s at 700mAs and it is brighter than a Scurion P7  , so this will definately kick a normal Scurion's ass on pure flood power.

The advantage that the Scurion has is that the optics are very good, so their spot is v powerful. I'd be suprised if the "Biffa Light" has a much better throw, if at all. Also the Scurion's beam can be separated from the wide LED, alowing you to "see" much further. Oh, and also the Scurion looks lovely

Nice light Biffa!  I bet it's cheaper than a Scurion aswell.  Maybe we need a lumens per ? table for various caving lights (although I suspect candles might win there).
Lurker

I'd love to see a table of lumens per ? as my 10yr old FX3 is starting to look a little candle like and I've been considering a replacement - though I've just scrubbed the connections and it's doing pretty well again.

What *is* the deal with the Scurion spot?

From what I've seen, it doesn't look obviously much tighter than the beam from any of the 20-25mm narrow-angle optics I've tried on Seouls or Crees.
Is it meant to be more even, or to have a softer (or harder) edge, or more/less spill, or something?

Lurker said:

Nice light Biffa!  I bet it's cheaper than a Scurion aswell.  Maybe we need a lumens per ? table for various caving lights (although I suspect candles might win there).
Lurker

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LEDs and Maxflex cost ?55 from cutter.  Reckon the total cost including the three batteries is about ?90.  If however you cost my time then it costs much, much more than a Scurion; luckily I don't because I quite enjoy tinkering like this.  600lms/?90 = 6.66666 Lumens/?.  How do others compare?

Rob said:

Oh, and also the Scurion looks lovely

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And mine looks like something only its parent could love?

biffa said:

And mine looks like something only its parent could love?

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As does mine at the moment!

biffa said:

And mine looks like something only its parent could love?

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I know that feeling.
I just knocked together a twin P7 plaything, for use as a brighter extra light rather than a regular caving light - a spot for shining up avens, and a flood for photography, and while it's functional, (should be something like 640lm for either LED at 2.3A) it's not exactly pretty.



It was intended to be multi-level, but the cheap driver crapped out after a couple of minutes, so it's currently single-power until/unless I can be bothered to buy/build a better one.
Unfortunately, it had an unintended runtime test in a car boot on Sunday, and had basically flattened the batteries before it was noticed, which meant I haven't yet been able to  try it properly underground, so I'll have to wait for this weekend.
Still, it was a good test of heat issues - as it turned out, the 4xAA cells ended up getting hotter than the case.

I reckon the various bits for mine cost about ?100 (if I only count one battery pack and don't include the cost of power tools/soldering iron etc).  2 Cree r2s running at full whack should give ~500lms (I think?) so that's 5 lumens per pound.  According to wikipedia a candle produces 13 lumens and costs about 10p which is 130 lumens per pound but I know which I'd rather have stuck on my helmet!
Lurker