Yet another Oldham conversion...

[Lurker]

Hi all,
I've finally finished my Oldham conversion.  Details of how I built it are here:
http://edvin.freeweb7.com/CavingLog/LogFiles/light.html
It's a basically an Oldham headset with 2 Cree R2 LEDs, a driver circuit, lithium ion batteries and a bit of heatsinking.  I decided against putting the UV LED in it in the end - it was getting quite crowded just with 2 LEDs in the heatset!  It will get it's first underground test hopefully down Gingling this weekend Many thanks to all the people who have posted in other lamp-making threads and whose ideas I stole!
I'd be glad to hear any comments/suggestions for improvements - no doubt in a year or two I'll decide that it just isn't bright enough and the batteries don't last long enough so I'll have to build another one
Now that I have a spare UV LED, my next project will be to put it in a little 'backup light'-style torch so I can take it caving.
Lurker

 

[potholer]

A really interesting project.

I think you'll find that running a pair of R2s at your lowest power level of 40mA will give plenty enough light to cave on in emergencies and/or in confined spaces.
Once your eyes have adjusted, it's surprising how far a low-power spot will reach if there aren't other people around with anything brighter.

When trying it out, I'd suggest that you try it both with and without other lights around.
Without a base for comparision, it can be surprising how little apparent difference there is between quite different brightness levels, especially if you briefly close your eyes when switching levels.

 

[francis]

Nice mod!

I can see you have used a similar backplate as I used for mine I would also like to modify mine further, like you have done to get the heat out of the headset. I think I'll get on with it when I'm done with my exams.
Which charger (and from where) did you get for your cells? I got myself a cheap charger from dealextreme, but that only charges single cells, not packs. Did you order the LED's from cutter? If so - how much did the LED's and the postage cost?

Regards

Francis

 

[potholer]

Without a reflector to stiffen the O-ring, does it seal OK?

Personally, I avoid grease on Oldham headset bezels. It seems to make it too easy to tighten them up a bit too far, then the grease seems to get squeezed out and/or some other binding-up happens and they can be a real pig to open. It also attracts dust/mud if opened anywhere dirty though I suppose an LED headset shouldn't need to be opened often, and rarely underground since there's nothing fixable (apart from possibly the switch).

Shiny crisp-packet material is also good for small conical reflectors for wide-angle LEDS, and seems to be quite durable.

 

[Lurker]

Which charger (and from where) did you get for your cells? I got myself a cheap charger from dealextreme, but that only charges single cells, not packs. Did you order the LED's from cutter? If so - how much did the LED's and the postage cost?

I got a lithium ion battery pack charger from batteryjunction.com http://www.batteryjunction.com/unsmchforlib.html which is also where I got my cells from.  Unfortunately I couldn't find anywhere in the UK that sold the charger I needed but there must be somewhere I look hard enough.  I think there is still a fair bit about lithium ion batteries that I don't understand: when making the battery packs I made sure that each cell was charged to approximately the same voltage before they were soldered together and now when I charge them I just leave them in series rather than connecting each cell independently.  As I understand it, the ideal situation is to connect the cells independently to ensure they are all evenly charged...but feel free to correct me on this...

My LEDs (and the lens) did indeed come from cutter - it still seems to be the only place to get R2s from.  Shipping + handling came to about 15 australian dollars (or whatever that is in pounds!)

Some interesting points rasied by potholer 

ithout a reflector to stiffen the O-ring, does it seal OK?

I forgot to mention that I cut off the very top section of reflector and put it in the o ring for that very reason - I thought i tmight get deformed otherwise.

Personally, I avoid grease on Oldham headset bezels. It seems to make it too easy to tighten them up a bit too far, then the grease seems to get squeezed out and/or some other binding-up happens and they can be a real pig to open. It also attracts dust/mud if opened anywhere dirty though I suppose an LED headset shouldn't need to be opened often, and rarely underground since there's nothing fixable (apart from possibly the switch).

Good point - hadn't thought of that. I guess time will tell and the worst case is that I end up removing the bezel (if I can ) and degreasing everything.

Shiny crisp-packet material is also good for small conical reflectors for wide-angle LEDS, and seems to be quite durable.

Great idea! Am I right in thinking this is what happens in the bisun (that's where my idea came from)?  Is there ever a problem with the crisp packet material melting?

Cheers!
Lurker

 

[potholer]

Shiny crisp-packet material is also good for small conical reflectors for wide-angle LEDS, and seems to be quite durable.

Great idea! Am I right in thinking this is what happens in the bisun (that's where my idea came from)?  Is there ever a problem with the crisp packet material melting?

It's what I use for the small reflectors and filling the hole in the main reflector.
I certainly haven't seen any small reflectors suffering from heat, but my heat levels are relatively low, due to the power levels.
I'm not sure what kind of thermal failure would be expected even if a light could get hot enough - would the superglue holding the cone in shape fail before the material itself?

About all I can say is that even in damp headsets that get *fairly* warm on a regular basis, the material seems to hold up perfectly.

I have looked at really reflective commercial materials, but I think they'd tend to give too good a reflection, and be more likely to give 'lumpy' beam artifacts if a reflector is at all imperfect in shape or alignment, compared to the very slightly textured/matte effect from crisp packet material which largely smooths out minor imperfections.
Also, the commercial films I've seen tend to be either self-adhesive, or extremely thin films which wouldn't hold a shape easily. The really shiny films also seem rather to be fingerprint magnets.

(Seabrooks material seems slightly better than Walkers, and I prefer the crisps as well.)

 

[paul]

Shiny crisp-packet material is also good for small conical reflectors for wide-angle LEDS, and seems to be quite durable.

Great idea! Am I right in thinking this is what happens in the bisun (that's where my idea came from)?  Is there ever a problem with the crisp packet material melting?

It's what I use for the small reflectors and filling the hole in the main reflector.
I certainly haven't seen any small reflectors suffering from heat, but my heat levels are relatively low, due to the power levels.
I'm not sure what kind of thermal failure would be expected even if a light could get hot enough - would the superglue holding the cone in shape fail before the material itself?

About all I can say is that even in damp headsets that get *fairly* warm on a regular basis, the material seems to hold up perfectly.

I have looked at really reflective commercial materials, but I think they'd tend to give too good a reflection, and be more likely to give 'lumpy' beam artifacts if a reflector is at all imperfect in shape or alignment, compared to the very slightly textured/matte effect from crisp packet material which largely smooths out minor imperfections.
Also, the commercial films I've seen tend to be either self-adhesive, or extremely thin films which wouldn't hold a shape easily. The really shiny films also seem rather to be fingerprint magnets.

(Seabrooks material seems slightly better than Walkers, and I prefer the crisps as well.)

I bet that if you make a lot of "Bisun" conversions (which I can vouch for as very good indeed) you tend to put on a bit of weight! 

 

[potholer]

Well, I was hoping to find a use for beer cans, but haven't had any luck there so far.

 

[paul]

Well, I was hoping to find a use for beer cans, but haven't had any luck there so far.

Make portable stoves like This - looks like a good excuse to me! 

 

[Lurker]

The best possible use for beer cans is holding beer; what possible other excuse could be needed for their purchase   

The light performed really well down Gingling yesterday.  Potholer was right: the lowest 40mA setting is absolutely fine for almost all the caving and I only turned it up in the larger caverns and when I wanted to annoy my fellow cavers.  I didn't run it at 1A for very long at a time so didn't really properly test the heatsinking, but I didn't notice any problems and it was like a miniature sun on the highest setting!  The only drawback I noticed was that the throw of light from the reflector wasn't quite as close to my feet as I would want. I guess this is also partly due to having a bezel.  I might try making a wider reflector.

I was hoping to head down Gaping Gill today and pass off a photo of the floodlit main chamber as the work of my light alone but unfortunately was feeling far too lazy after yesterdays exertions!

Lurker

 

[potholer]

Regarding the reflector on the spread LED, I haven't noticed a lack of down-lighting, though there are 4 things that spring to mind.

First, using a regular Petzl lamp bracket (with a natural down-twist) on an Ecrin, the headset is angled somewhat downwards. Using a flatter bracket (like the old flat-plate-with-4-rivet design and-or a helmet with a less-vertical front might give the headset less of a natural down-cast.

Secondly, I have the LED close to the glass, and so I use small conical reflectors, somewhere around 8mm in depth. Even with a 90 degree angle, that doesn't result in a pure 90 degree beam, since the width of the emitting area combined with the small reflector means that the LED is visible for more than 45 degrees from the LED axis.

Thirdly, I tend to use Seoul P4s. Though they use the same basic chip inside as the Crees, the Seouls give more off-axis light than the Crees.

Fourthly, running the LEDs in series means that there may be a case of an otherwise adequate floor-light being somewhat overwhelmed by the presence of a bright spot, especially with an optic-based spot which might itself have limited spread.

I'd wonder if moving the LED forwards might help, using a lump of aluminium as a spacer, and a smaller reflector.
If doing that, I guess you could try filing the aluminium into a slight wedge shape to direct the LED more downwards.

 

[Lurker]

Thanks for those ideas.  Given that I have a spare Petzl lamp bracket lying around (I currently have an old style one on an Ecrin) I think I will try that first as it seems like the least destructive change to make.  Now that I have a fully working light I'm a bit scared to unscrew the headset ever again!
Lurker

 

[Lurker]

Unfortunately, at the weekend my new light took a considerable disliking to the duck/sump in Dowbergill Passage  It seems Oldham headsets aren't all that waterproof afterall!  My suspiscion is that it leaked through the switch so my new plan, once I've dried everything out and worked out if anything needs replacing, is to use a waterproof switch.  I've had a look online but without much success - I'd be interested to hear any suggestions for waterproof switches of an appropriate size to fit in and Oldham headset, or failing that any other way of making it more waterproof (potting compound perhaps...)?
Cheers
Lurker

 

[potholer]

How is your Oldham switch sealed?
Older headsets used some sort of fibre washer, but more recent ones use o-rings.
Both seem reasonably good if kept greased, especially since a greased switch can be pulled a bit tighter without getting stiff, which can help waterproofing,though I'd imagine an o-ring may be rather better

Assuming the headset shell isn't cracked and the rubber reflector ring is in good condition, the most common place I've seen for leakage is the cable entry, especially if the cable is rather old.

 

[MatthiasM]

The quick&dirty-method for 100% tight switches are reed contacts inside and a magnet outside, but may make trouble with compass survey. non-magnetic solutiona may be pass-throughs with o-rings for rotational switches (like scurion has) or seal caps for pushbuttons.

 

[Lurker]

My current switch has a fibre washer with a liberal helping of silicon grease so maybe a rubber o-ring would be a good idea.  I had sealed the cable entry point with silicon sealant so hopefully the leak isn't coming from there (but it's not out of the question!).  Some sort of sealed push button was definitely what I was thinking of, although if I manage to completely 'pot' all the circuitry it might not even matter if the headset is a bit leaky.
Oh well, in the meantime I will just have to stick to nice warm, dry caves
Lurker

 

[darkplaces]

Oldham headsets arnt waterproof AT ALL!

Who told you all Oldham headsets were waterproof?

 

[Lurker]

Well, it's more that I thought I'd done what was necessary to make it waterproof - I certainly realised it would leak without the extra grease/glue in various places.

 

[Peter Burgess]

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