Petzl DUO caving light modification

Anyone who has followed my previous projects can guess that this year too I will build a caving headlamp :)
I.e.: a super durable, helmet mounted headlamp with a dual optics.

For this year challenge, I want to rebuilt a classic caving headlamp: the Petzl Duo

Since the 90's this light considered as the best caving light by the many cavers because of its great durability and waterproofs.
During the years many upgrades to the original light tried to keep it relevant with recent LEDs improvements but since the plastic body does not allow heat dissipation it could not provide same brightness as the modern lights.
In the 2nd post of the tread I will describe the history of this legendary caving light.

My dream is to make a light that will look as close as possible to the original light but will provide the same brightness as the modern caving lights, and of course to preserve the durability and waterproofing.

I am planing to completely rebuild the light:
1. Replace the old bulbs with new LED emitters.
2. Add a modern driver with my new FW.
3. Add an Aluminium heatsink to the plastic body.
4. Change the switch to a momentary switch.
5. Modified the 4*AA battery box to 2*18650.

Basically I am planing to change EVERYTHING, but since I am still using the original body I guess it need to be under the modification category....

So I did some research on this iconic caving lamp.

1st generation
The first generation was introduced on 1999 (I thought it was a lot earlier around mid 80's)
It had 2 light source: a 6v bulb and a 6v halogen bulb.
The light come with one replacement bulb of each type and had a special place to store them.
I could not find data on how many lumens each bulb produced but it was very low.
The halogen bulb could move inside the reflector to change the beam type.
The operation of the light was very simple move the switch up turn on the halogen, move the switch down turn on the regular bulb, switch in the middle - turn of.
While in of mode the switch had a mechanical lock off.


All generation had few variations: (I don't have all the variations so these pictures are from the internet)
1. Duo - the original headlamp with rubber bands

2. DuoBelt - with longer cable and bigger battery box for 4 C cells to carry on the belt (reduce wight on the head and can keep batteries warm under the closes)

3. Fixo - to mount on a helmet.

4. ATEX - (black color) for hazardous areas (explosives etc.)

5. Explorer - Fixo + Aceto (Carbid lamp) mounts on an EcrinRoc helmet

2nd generation
An upgrade with 5 LEDs was introduced on 2006.
It was a simple PCD with 5 LEDs connected direly instead the old 6v bulb without any driver.
The operation was kept simple (on/off)
The PCB was also sold desperately as an upgrade to the 1st generation
The 5 LEDe output was 40 Lumen for 28 meter and last 65 hours.
The halogen beam was for 100 meters and last 4 hours (no lumen data)
For this version also the locking mechanism for the switch and battery box was made from Aluminum instead of plastic (probably after costumers complained)
I only have the ATEX version for this generation but of course there was also a regular version (and also belt, fixo, explorer...)

3rd generation
An upgrade with 14 LEDs was introduced on 2008.
Petzl kept the old halogen bulb with zoom option but offered an upgrade to the led PCB.
The PCB was a lot more complicated with a regulated current and 3 mode of operation:
Maximum: 34 meters, 110 hours, 67 Lumen
Optimum: 36 meters, 148 hours, (no lumen data)
Economic: 15 meters, 183 hours, (no lumen data)
The halogen (same as before) 100 meters, 4 hours (no lumen data)
I only have the Spelios version for this generation but of course there was also a regular version (and also belt, fixo, ATEX...)
Spelios is the successor of the explorer. 14 led Dou mounted on Elios helmet without Aceto

That is the actual light I am planing to modified since it is already mounted to my favorite helmet :)

4th generation
The last official upgrade by Petzl for the Duo was 1W LED to replace the original Halogen bolb.
since it fits to the same place it also had the zoom option

Unoffiacal generations
Since Petzl stop upgrading the Duo light (they do make some models named DuoZ, DuoS etc. but not related to the original Duo except from the name)
Some very talented cavers start making their own modules to upgrade the Duo.
The most famous is a British lights manufacturer John Biffin who sells them under the name Customduo.
I have 2 of his modules, 1 to replace the Halogen and one with 2 emitters

As you can see the limitation of this modules is heat dissipation so the maximum brightness is around 500 Lumen :(

This post turn out to be A LOT longer than I thought but I think it explains the history of this light and the reason it is impotent to me to keep the tradition and to upgrade this model to the most advanced LED technology.

Hope i didn't bore you too much

1 Thank

Here for the show :wink:
Good luck for the contest and the mod :wink:

Nice historical review. Best of luck / good fortune.

I suppose water resistance is important. That gets to be a challenge for sealing and cooling at the same time while retaining the original “look”.

Today I started Working on the light :)
Sine I want to restore this light for a long time I did some research a while ago and figure out that to enable decent brightness I will have to allow the heat dissipate from the sealed body using an external heat sink so the first step was to remove all the old components from the body and make some place for the new components and heat sink

1. Take everything apart

2. I mean everything

3. Remove unnecessary plastic supports (don't worry I will add Aluminum supports instead)

4. make place for a rear heat sink

5. And now it is ready for the new components

It is the big challenge in this protect I hope I will mange to do it Although I don't like using glue, I think that it is the best option for this mission.

With my wood lights, I sometimes joke that I don’t worry about making them waterproof because the glue I use is not waterproof. :wink:

Looks like a good start.

Thanks for the reserch. I came to speleology only 10 years ago and have not seen duo era. Very interesting.

Good to see you are making a good light for caving, YuvalS. :+1:

A waterproof wooden lights sound interesting, consider use another glue :)

I still see some cavers using them, mostly with the CustomDuo inserts but they are rare now

That is the only type of lights I build

Had some progress with the body today.I cut 4mm aluminum I had at home to the shape of the internal space of the light in order to have some mass to absorb the heat and conduct it to the rear end where I will place the heat sink.

Cut cardboard templates

Saw it using a Jigsaw

First I glued it in place with heat resistant RTV

Then I glued it with headsink plaster

And clamp everything together till it dry

I use the hide glue because it cleans up very well. The waterproof wood glues can appear to have the squeezed out glue cleaned of completely but sometimes when one clear coats (or stains) you see a difference in coloration where there was a dried and near invisible film of waterproof glue. It doesn’t always become apparent until too late, after clear coat has been applied.

A water proof wood light might float. Could be a cool idea. Maybe I’ll have to think about that one. Include a motor and propeller/fan that could cool it in air?

I spend a lot of time waiting for wood glues to dry.

A bit more progress today:
I had to file the heat sink so it fits to the roundish shape of the light and the helmet and also to add small piece of aluminum to fill a small gap left a the side of the light

Using the cardboard technique to find the correct shape for the heat sink

Fitting the aluminum piece for the small gap

Gluing everything with thermal plaster

And waiting....


After the Heat sink plaster cured, I did s bit more sanding to fit it perfectly to the helmet mount (had to leave a small gap to allow airflow to help with cooling.
I also drilled the place for a 12 mm waterproof momentary switch

Then, I drilled a hole for the switch wires (winch I forgot drilling before gluing :facepalm)

And (as promised) sealed all gaps between the aluminum and the original body with glue to maintain waterproof

That heatsink looks nice, definitely better than only plastic.

Good job with cutting and squeezing in the aluminium heatsink parts. :+1:

Good to see progress.

I’ve been stalled.

I took a break from working on the body and moved to the battery box.
Although the body is more interesting, the real challenge for me in this build is the battery box since it was designed for 4*AA batteries and the it is really hard to squeeze bigger 18650 cells into it.
another problem is the contacts, since I want to use 3.7V, one contact have to be placed on the lead and I have to find a way to wire this contact to the bottom part. I really have no Idea how to do it without risking with contacts or wiring problems.

Anyway, the first step was to remove all the old AA parts. Because the plastic structure is deep and none of my tolls was able to remove all the old parts and make place for 18650 I had melt the plastic at the bottom of the box using my old soldering iron (did it in a well ventilated place to avoid birthing melt plastic :) )

Original AA contacts

After melting the bottom parts

Not enough place for 4 cells

This project is up my alley! I’ve modded/retrofit l9ghts from incandescent to LED and it’s not easy so great job so far. For the batteries have you considered using 14500’s? They are not as high capacity as 18650, but you can use them in parallel for more capacity. Or just use 3 18650 unless you need series or series/parallel.