my (first) homemade caving headlamp

[vtunderground]

I haven't been very happy with any headlamp I've taken caving, so I decided to roll my own.

It has an aluminum case with a Lexan window. It has a pair of Seoul P4 LEDs (bin U3SVNH) run by a pair of SOB400 buck converters, controlled by a 4-position rotary switch. One of the LEDs is focused through a Carclo 20mm frosted spot optic, and the other LED is bare (for the widest possible flood beam).

Position 1 is OFF
Position 2 is just the flood LED, resistored at about 40 lumens.
Position 3 is just the flood LED, regulated at about 100 lumens.
Position 4 is the flood + spot LEDs, regulated at about 100 lumens each.

The battery pack, cable, headband, and front bracket are from a 4xAA Petzl Zoom Zora. My headlamp pivots up & down on the Zoom front bracket, which is nice. My headlamp looks huge, but it's really about the same size as the original Zoom head.

The cable gland, case, and switch are all sealed, so the light SHOULD be water resistant. I'm not sure I'd take it diving though 🙂

Initial observations (considering that I haven't been able to take it caving yet):

The light is BRIGHT, and very floody 🙂 . The frosted Carclo optic is nice, the spot beam diffuses perfectly into the spill from the other LED.

I like the interface, so far. It's nice & simple. I like the rotary switch, but it takes up a lot of space inside the case. I could have used a smaller case if it wasn't for the switch... so I might go for a different type of switch next time (if I can't find a smaller sealed rotary switch).

Even on the 200 lumen setting, the light doesn't seem to get hot in use. Slightly warm, but that's it.

 

[ifor powell]

Looks smart. I susperct I would of tried to protect the corners of the lexan cover. You will have to report some more after taking it down a proper cave....

 

[NYCaver]

This is really cool to see. It's really similar to what I'm working on now in shape/size and method of control. Mine will be utilizing 4 LED's and TaskLED driver but overall, quite similar. Where did you get the aluminum case and what method did you use to seal it?

 

[vtunderground]

Where did you get the aluminum case and what method did you use to seal it?

It's a Hammond project box, from mouser.com. It came with a foam seal, I just used the Lexan window instead of the aluminum lid that came with the box.

 

[uk_caver]

It's great to see people making their own caving lights.

I think twin beams are definitely the way to go, both for flexibility and redundancy.
There are also few things as annoying as having to use a tight beam in a confined space, where a flood is just so much better.

I use a similar aluminium box ~60mm square for a P7-based photo light, and that doesn't get unmanageably hot even running for bursts of 8-10Watts, so I'd have thought you should be fine thermally with ~2x1Watt

At the risk of boring anyone who's heard me say it before, I'd suggest at least trying sticking a small conical reflector round the flood P4 and seeing what you think of the resulting beam, given that the cost is effectively nothing.

Mentioned in this thread
http://www.candlepowerforums.com/vb/showthread.php?t=155894&page=2
and probably elsewhere.

Imperfections in the reflector can cause some minor lumpiness in the beam, but that's generally only noticeable on a white wall, not underground, and I think the advantages of more throw while still having effectively a flood beam seriously outweigh the loss of extreme-wide light that is often not really usable.

 

[vtunderground]

At the risk of boring anyone who's heard me say it before, I'd suggest at least trying sticking a small conical reflector round the flood P4 and seeing what you think of the resulting beam, given that the cost is effectively nothing.

I definitely considered it. I've been playing around with the Carclo 10170 reflector, but for this light I wanted a much wider spill beam than the 10170 could give me (I wanted to be able to light up the ground at my feet while the light is pointed straight ahead).

 

[uk_caver]

My light is in a housing with a fixed downwards tilt (which works out fine except for pretty much everything except for looking up vertical shafts).
Because of that downwards tilt, it does mean that I can get away with losing the flood beam outside maybe 50 degrees from the LED axis, since it does mean that even then, the flood extends down far enough that I can't really look 'underneath' the beam.

Possibly that could be slightly too tight a beam for a tiltable light when the light was set pointed straight forwards with the head upright, though home-making reflectors from film, they can be cut to any depth, so trading off wider beam angle against extra forward intensity is always a possibility.

Also, if cutting a reflector from metallised film, as long as you don't cut out so much that the reflector gets mechanically unstable and distorts, I guess there's nothing to stop you having a reflector with a trimmed lower edge, to give a flood that goes down more than it goes up or sideways.

Whatever, I think it would be best to initially get used to a naked P4 to give you a good base for comparison, then maybe try some kind of conical reflector and see if you notice any meaningful loss of light at the edges, and, if so, whether you feel that the central brightening you get is worth the peripheral loss, so it's really a suggestion for future experimentation.

 

[uk_caver]

I'm interested in how you chose the power levels for your light - was it a case of looking at/experience of other caving lights or headlights, thinking about runtimes or heat issues, and/or other things?

 

[NYCaver]

UK_Caver, I like your idea of a conical reflector with the down-side trimmed for more light at your feet. I'm debating reflector vs. bare LED for my current build and it seems this would be a good compromise. I think I'll try grinding down one side of a 10170 and compare with the stock version.

To both of you, in your experience do you think there's much benefit in having a central brighter area in the flood mode of a headlamp? Where does flood + spot come into play the most vs pure flood?

vtunderground, have you experimented much to see how much glare there is from the bare LED?

 

[Yucca Patrol]

Great job on your headlamp. There is such a need for quality caving headlamps that is going mostly unanswered.

 

[uk_caver]

UK_Caver, I like your idea of a conical reflector with the down-side trimmed for more light at your feet. I'm debating reflector vs. bare LED for my current build and it seems this would be a good compromise. I think I'll try grinding down one side of a 10170 and compare with the stock version.

Depending on the reflector silvering, it might be worth applying some sealant on the cut edge (smear of epoxy, nail varnish, etc. Some reflectors do seem to corrode from cut edges, especially when there's damp around.

To both of you, in your experience do you think there's much benefit in having a central brighter area in the flood mode of a headlamp?

I think there's certainly something to be said for a centre-biased flood, since that does fit fairly well with may of the target scenes underground - I spend more time looking along passages, down climbs, and across chambers than face-on at walls, so the centre of my beam is often lighting up things which are much further away from me than the things the beam sides and bottoms are lighting up.

Where does flood + spot come into play the most vs pure flood?

I think that depends a lot on how bright the flood beam is, and how tight/relatively bright the spot beam is.
A pure flood even at decent power levels doesn't have a great throw, and can often not be too good at picking out paths at any distance.

I think mixing spot and flood with the right balance of intensities can give a good light for much moving around, at a reasonable power output.
Because of having a tight spot, if I just want a little distance-enhancement of a flood beam, I only mix in a much lower-power spot to get a decent blend of intensities. That's often the light I cave with most - it means I can still see distant things to some extent, but with a beam that is still predominantly a flood.

 

[vtunderground]

I'm interested in how you chose the power levels for your light - was it a case of looking at/experience of other caving lights or headlights, thinking about runtimes or heat issues, and/or other things?

I really picked the light levels for exploring abandoned iron mines (rather than caves). The mines around here have much darker walls than caves, and 100 lumens is about what it takes to begin to see well. My 50-lumen EOS is almost useless in the mines, but my 130-lumen Apex does just fine (although the spot beam is too tight for easy walking in rough terrain).

I picked the "low" level through trial and error with different resistors, until I found a dimness that seemed like it would be perfect for small passages / snack breaks / etc...

 

[vtunderground]

To both of you, in your experience do you think there's much benefit in having a central brighter area in the flood mode of a headlamp? Where does flood + spot come into play the most vs pure flood?

vtunderground, have you experimented much to see how much glare there is from the bare LED?

I've always wished for a caving headlamp that was pure flood. Personally, I find the spot in the middle of a headlamp beam to be annoyingly distracting. The problem, of course, is that when you're in big rooms or long passages you might want a light that can reach out as far as you can see, not just 50' in front of you. I tried the light with a Carclo frosted medium optic, but felt like it added more "flood" than "throw" to the beam.

The bare LED in my headlamp wastes a little bit of light inside the case (even though it's positioned as close to the window as I could get it, mounted on an aluminum post), and there is a little bit of glare from the edges of the Lexan window. I expected this, but luckily the front of my helmet blocks the glare from view. Past that, the flood beam is wonderful.

 

[TorchBoy]

Great work, VT.

do you think there's much benefit in having a central brighter area in the flood mode of a headlamp? Where does flood + spot come into play the most vs pure flood?

I think there is. Our central vision needs the most light and when we're wandering around underground we're looking ahead; having that little bit extra range is nice. On the other hand, when crawling through really small passages it's probably better to have pure flood. So it depends. Finding a balance would depend a bit on personal preference and what you do underground.

I agree that having two separate LEDs (for spot and centre-weighted flood) is the way to go.

 

[NYCaver]

The bare LED in my headlamp wastes a little bit of light inside the case (even though it's positioned as close to the window as I could get it, mounted on an aluminum post), and there is a little bit of glare from the edges of the Lexan window. I expected this, but luckily the front of my helmet blocks the glare from view. Past that, the flood beam is wonderful.

Actually, I was referring to glare in respect to someone looking at you, but experiencing glare yourself would be bad too.

I've always wished for a caving headlamp that was pure flood. Personally, I find the spot in the middle of a headlamp beam to be annoyingly distracting. The problem, of course, is that when you're in big rooms or long passages you might want a light that can reach out as far as you can see, not just 50' in front of you. I tried the light with a Carclo frosted medium optic, but felt like it added more "flood" than "throw" to the beam.

Hmm, I'm constantly revising my headlamp design based on testimony like this. Right now, plan is to have an ~80 degree flood from a reflector + ~40 degree center biased beam. This would be the only flood option for the light because my wiring and power source require at least the combined vf of 2 led's. Other than that there would be a spot made up of a tight 6 degree beam + ~12 degree beam. All 4 could be on at once for a large & long passage.

 

[uk_caver]

Most people I cave with in the last few years have had a flood beam that used first naked LEDs, and then ones with very small reflectors.
Even with the naked LEDs, glare only really seems to be a potential issue up close, and then it's largely avoidable unless looking directly at the person's light, and in situations where that happens for more than a brief time, people tend to turn their lights down.

Despite a ~5-fold increase in brightness over that time, I haven't found glare to be something that got worse, if anything, I'd say it feels to have become less noticeable.
Maybe it's something you generally get used to avoiding, and maybe having the reflector making a larger source makes it easier to automatically avoid looking at.
Possibly it's also partly that I've spent a fair amount of time making lights and otherwise playing with LEDs, so I may have got fairly well practised at avoiding disturbing my central vision.

 

[vtunderground]

The glare when looking at the light isn't any worse than from a reflectored light of similar output.

I recommend frosted optics for multi-optic setups, just because the frosting smooths the beam out & helps the multiple beams blend together more smoothly.

 

[dom]

Nice job VT
Are you going to bolt it to your helmet?
Hope it works well for you.

Cheers
Dom

 

[vtunderground]

Are you going to bolt it to your helmet?

That's the plan. I went with the Zoom Zora battery case (same as the Petzl Duo case) because it's actually designed to be screwed to a helmet.

 

[vtunderground]

I did a runtime test today, and with 4 newish Duraloops (charged yesterday) on the highest setting I got three hours of regulated output.

Does this seem a little on the low side? I'm thinking so. Could I be losing efficiency because I'm using two drivers? Or was I just too optimistic about how long it could run at 200 lumens?

I'm hoping to be able to do a runtime test on the middle setting either this weekend or sometime next week.