Petzl Zoom LED Conversion: The Final Chapter

I have written a few times about my long-running project to convert my old Petzl Zoom incandescent headlamp over to a high output LED light source. This past weekend I used some spare boards to convert my brothers headlamp and did a better job documenting the process, so I thought I would write a final blog post on the subject that consolidates all of the information.

Anyone who spent time climbing or backpacking in the 1990s will be familiar with the once-ubiquitous Petzl Zoom headlamp (pictured below), which used an incandescent bulb and a 4.5V MN1203 alkaline battery.

These have disappeared with the advent of much smaller LED-based headlamps such as the Petzl Tikka, but I had a couple of them kicking around and thought it might be fun to overhaul them to have high-output LEDs and rechargeable batteries. For a light source I chose the Cree XLamp MC-E, which is an array of 4 high-output white LEDs in a single package. It is a "lighting class" LED, meaning that it is normally used for interior lighting. Some people might read that and think "overkill", but to me that reads "perfect". The Cree XLamp is pictured below, where you can see the 4 separate dies.

The maximum current for the LED array is 700mA, which corresponds to a total power of 9.5W and a total light output of 700 lumens. In laymens term, this will suck down a lot of power and will be stinkin' bright. Molto bene! So, having sorted out the light source, the next step was to find an appropriate power source. I wanted something rechargeable so the original MN1203 battery was out. I still wanted to house it in the same battery compartment which narrowed things down a little, but luckily I was able to find a 5000 mAh lithium polymer battery with an identical outline to the MN1203 (though it was considerably thinner, and about 2 ounces lighter). Here is the original battery in the case:

And here is the old MN1203 side-by-side with the new LiPo battery:

The next step was to design the circuit. The schematic is pictured below, the key components are two National Semiconductor LM3410 LED drivers to push a constant current through the LEDs (each driver handles two LEDs, they overheat if one is used to drive all four), a Microchip MCP73833 to handle the battery charging, and an AVR ATTiny13 to run the show.

I iterated a few times on the design to arrive at the one pictured above (thermal modeling isn't one of my strong suits, so findings like the single LED driver overheating didn't occur until I built the circuit). The main PCB layout is shown below:

A secondary PCB was also designed to mount the quad LED array; as will be seen in the assembly sequence the main PCB is housed in the battery enclosure while the LED PCB is housed in the front bulb housing. The first reason for this is heat dissipation: both the LED and the LED drivers generate a considerable amount of heat, so having them separate leads to fewer thermal problems. The second is because I wanted to have a flashing red LED on the back of the headlamp since I will be using it for running outside in the dark, and I want people coming from behind to see me in addition to seeing where I am heading. Having the main PCB in the battery enclosure meant that I could mount the flashing red LED on it and have it protrude through the case. The PCBs were fabricated by the good folks at DorkbotPDX.

Now that the design has been explained, let's start building it up! The first step was to replace the bulb in the front unit with the LED array. Here is a shot of the bulb in the housing:

The reflective lens unit unscrews, leaving the bulb and its mounting exposed:

A little bit of surgery easily excised those parts, leaving me with an empty housing:

Now I needed to put something back in there. That something was the LED PCB that I had built, with the board outline sized to fit snugly in the circular housing. Here is a shot of that PCB, you can see the LED mounted in the middle. The exposed square of copper is an array of vias, to allow for better thermal dissipation from the LED array which has a thermal connection underneath the body.

The board has a matching exposed square of copper on the back, onto which I placed a heatsink to further improve the thermal dissipation (9.5W is a lot of heat for a small space!). Here is the heatsink on the backside, with the wires connected that will run back to the battery enclosure at the back of the headlamp:

The next step was to thread the wires through the front housing and slot it into place:

Next up was to swap out the battery, and perform surgery on its enclosure to allow the switches, red LED, and charging connector to be installed. The rear enclosure with the new battery fitted in is shown below:

Here is a shot of the back of the battery enclosure. At the top is a mini-USB connector to supply 5V for charging the battery (the data lines are unused), and below that is the red LED (it looks white, but when illuminated it puts out red light). On the right is a push button switch to turn the unit on and off, and on the left is a momentary tactile switch that is used to adjust the brightness of the front LED (through the ATTiny13 PWM'ing the enable pins on the LED drivers) and to turn the flashing rear LED off. This is done by holding it down for a few seconds, which causes it to cycle through the different modes.

Okay, now for the main PCB, this is pictured below with some temporary connections for testing:

The header on the bottom is for programming the MCU (using the freely available AVRdude and an Arduino running ArduinoISP as the programmer), and the big blocks on the upper part of the board are the inductors for the boost converter circuits of the LED drivers (they need to step the 3.7V battery voltage up to about 6.8V to drive two white LEDs in series). Next up was to place the main PCB in the enclosure and wire it up to the LEDs, the switches, and the battery:

With that completed, the final step was to close everything up and hold my breath while I hit the power switch:

We have lift-off! To give you an idea of how much brighter it is, I placed the revamped headlamp next to another old one with the original incandescent bulb equivalent of a brand new MN1203 battery (a power supply set to 4.5V hooked up to the battery terminals), turned out the lights, and took some photos:

Can you guess which is which? Definitely a little brighter! I also made a few videos showing some of the functionality of the converted headlamp (for example, when it is charging the rear red LED pulses slowly and then switches to steady illumination once the charging is complete), they are linked to below. First, the pulsing behavior when plugged into the 5 V adapter and charging:



Second, here is one demonstrating the different modes and how they are accessed using the single button:



And finally, a brightness comparison to a Petzl Tikka 2 with fresh batteries:



Okay, I think that is everything. I promise there will be no further posts on the Petzl Zoom conversion (unless maybe one blows up resulting in a good story), all future head lamp posts will concern the fully custom headlamp that I am working on with my brother Trev (hopefully I can finally write the firmware for that now I am all done with this stuff).

Headlamp Mount

This past Christmas I was back home in Toronto visiting family, and was able to spend some time hanging out with my brother Trev and his family up in Barrie. Among other things, we spent some time working on the headlamp that we are designing together including sewing a head mount for it that incorporated the plastic mount that Trev designed and had fabricated. Here we are working away, with Trev doing the actual work and me pretending:

And here is Trev modeling the final product, before mounting the headlamp:

And here it is with the LED unit mounted, note how low profile it is. This headlamp is being optimized for outdoor adventures. The electronics being used to drive it are just some temporary off the shelf parts.

Blammo! Here it is in action, with the array of 3 high intensity LEDs each being driven with 700 mA and cranking out a lot of lumens:

In related news, I just got the custom PCBs back with the drive circuitry, here is one all built up and placed on the battery we will use (5000 mA LiPo single cell). Trev is working on designing a case that will house the battery and the drive electronics, which are comprised of charging circuitry (the LiPo cell can be charged through the mini USB connector on the left), two drive circuits and barrel connectors so that two of the LED units seen above can be driven at once (we like going overboard; one will have a wide angle lens and the other a narrow angle lens), mode switches for changing the brightness of the LED units, and a microcontroller to make everything work. It should be pretty awesome, get yours on pre-order now!

Rebel LED Headlamp

Avid followers of this blog (hi Mom!) may remember my earlier post about the project that I did to replace the guts of an old Petzl Zoom incandescent headlamp with a rechargeable battery and a high output quad LED array. It worked pretty well, the headlamp is now a real barn burner which I use regularly for running at night and outdoor adventures. While naturally the new electronics are pretty buttoned up (aside from slowly melting the bulb housing where the LED now sits; thermal modeling is not one of my strengths), the old Petzl case which I retrofitted has some shortcomings. Namely, it is big and clunky, having been designed for a much larger battery and incandescent bulb. The new electronic assembly makes it lighter, but I really need a redesigned case as well.

As it would turn out, my brother Trev is a mechanical engineer who likes building stuff, and he also has an interest in nighttime outdoor activities. He had been working on a headlamp project also where he was designing and building the housings but then using stock electronics, the inverse of my approach. So, we naturally decided to combine forces and build the ultimate headlamp. I have created a board which is an updated version of the one I did for the Petzl headlamp, it is in fabrication and should be back in a week or two. In the meantime, to allow Trev to start designing the battery housing I found some really cool software for exporting 3D models of PCB layouts from Eagle. Here are the results:

It exports into Google Sketchup, but from there you can export it as a .STL file which can be opened by Solidworks and other CAD packages. Pretty awesome! Trev has also been busy on his end, machining the LED housing and whipping out some CAD for helmet, head, and handlebar mounting options. He had them rapid prototyped by Shapeways, check out the results on his blog. We're pretty excited to see it coming together, I'll post some updates as we continue to build them up.

Costa Rica - Day 8

After rolling out of bed and enjoying a nice breakfast consisting off the remnants of the food we had purchased during the trip, it was time to head to the Tamarindo Airport to catch our flight back to San Jose so that we could spend a day exploring the city before flying back to Seattle on the next day. After a nice chat with the owners of Los Villas (Isabelle and Alejandro) we hopped in the BeGo and headed out in search of gas for a refill before returning it. We had assumed that Tamarindo would have a gas station, being a sizeable town, it does not. We had then assumed that Playa Flamingo had a gas station after having been informed that it did by a few travel websites, it once did but is now closed. One our last attempt before giving up and returning the BeGo with an empty tank we finally located one in El Llano, and then headed back to Tamarindo to return the BeGo. It was a sad morning to part with our trusted friend, Roanne even penned a heartfelt little tune called "The BeGo and Me" (ask her to sing it for you next time you see her). Here I am enjoying one last quiet moment with the BeGo before being shuttled off to the airport:

We arrived at the Tamarindo airport to find that it set a new record for most rustic airport we had flown out of (except maybe for a ski plane on a glacier in Alaska, but that doesn't really count as an airport). However, the single propellor plane that we would be flying on did arrive on time and looked quite new, so we happily climbed on board for the one hour flight back to San Jose. Here is the view out of the plane's window after we had boarded, at the only other plane on the airstrip that sunny morning:

We both had window seats (in fact, everyone did, because in a plane that small every seat is both a window seat and an aisle seat) and so were afforded some nice views of the countryside as we took off. Here is a view of the airstrip that we had flown from:

And another looking back out toward the coast:

We had a smooth landing in San Jose, and after disembarking (much more fun on a small plane like that where you get to climb down 3 steps onto the runway) we hailed a taxi and headed into San Jose for our final Costa Rican accommodations at the Hotel Grano de Oro. We have made a tradition of staying in an upscale hotel on our last night in a big city on our vacations, and the Hotel Grano de Oro was no exception, being an immaculately maintained building with really nice rooms, friendly staff, and a great restaurant. After a short snooze in our room we then headed out to explore San Jose, first making our way through a few markets and down some of the busy, pedestrian-only streets:

We then conducted a general walking tour of the city, making our way past the National Museum which had some nice outdoor sculptures with one of the granite spheres that archeologists have found in Costa Rica:

We also saw some nice outdoor murals:

And numerous other sights. As dusk started to fall we made our way back to our hotel, which had some nice outdoor Christmas decorations:

Costa Ricans seem to be crazy about Christmas, every hotel that we stayed in had Christmas trees already up and decorated, decorations on room doors, and all throughout the hotel. We had a nice dinner that night at the hotel restaurant which served French food (though not as good as the night prior in Tamarindo) and then headed off to bed.

The next morning we woke up and after a delicious breakfast we packed our bags one final time and began our journey back to Seattle. We really enjoyed our time in Costa Rica, and if I had to distill all of the travel advice we would pass on into one sentence, it would be: Check out the rain forests and go surfing. Adios!

Costa Rica - Day 7

As you may have noticed in the pictures up until now, I uncharacteristically have a mustache. The reason for that is because I was participating in Movember, a month-long event in which brave men grow mustaches for the purpose of raising awareness for men's health issues such as prostate cancer. While I had semi-enjoyed my monthlong attempt at growing a mustache, as it was now December, the time had come to shave it off (much to Roanne's delight).

And, dear reader, while I have your attention, let me quickly explain my rationale in growing a standard-issue, no-nonsense police officer's mustache as opposed to something more elaborate. My explanation is motivated by criticism I have received along the way, particularly from my lovely wife who complained that I wasn't growing a "funnier" mustache. The reason for that is, in my opinion, by growing an obviously "funny" mustache with handlebars, soulpatches, or other accoutrements along for the ride, you are immediately communicating to the world that your mustache is intended only as a joke. By making your mustache so clearly ironic, you are dissociating yourself from it, as if you had an accompanying sign that said "don't worry, I never normally have a mustache". To me, it takes more bravery and courage to grow a "serious" mustache, so that when people see you they think maybe you always have a mustache and it is just your standard look. Anyway, enough pontificating about the philosophy of moustaches, here it is enjoying it's last few rays of tropical sunshine before the appointment with my razor and shaving cream (actually, with Roanne's pink disposable razor and some soap since I had brought neither a mustache nor shaving cream on the trip):

Here I am spreading the soap and getting ready to whip out the lady bic:

And finally, the pink scythe goes into action and makes quick work of the fruits of my Movember labours:

With my newfound cleanshaven look we were off to the beach, which was just across the road from our residence. Along the way we passed a pretty sizeable lizard:

And then made our way along a nice boardwalk through a lagoon:

To finally reach the beautiful white sand beach of Playa Avellanas:

Upon reaching the beach we had a stroll up and down it and then set up shop in some shade under a tree where Roanne set about her chosen activities of alternate reading and snoozing:

And I rented a surfboard and headed out to get pounded by the waves:

The surfing was a lot more fun here than the previous day in Playa Carmen, as it involved trying to paddle into real waves instead of just riding white water (which is pretty easy and not legitimate surfing). It was a lot more difficult and a lot more work, but there were lots of waves and not many people out so there was no pressure and on the rare instances when I did catch a wave it was really fun. Here I am paddling for a wave:

And here I am riding in to shore on the white wash, unfortunately the odds of me catching a real wave at any time were sufficiently low that it was never caught on camera:

We had the entire day at the beach so I was able to surf for an hour or so then come in and recover while lounging on the beach, and then repeat, broken up in the middle of the day with a delicious lunch at a beachside restaurant called Lola's (so amazing, I forgot to take any pictures but everyone should go here if they get a chance). The afternoon brought more of the same, here is my freshly shaven face posing with my approving wife during some relaxing:

As the sun began to drop the tide was nearing its high point which made for better waves in this location, as evidenced by the increasing numbers of local rippers out in the waves:

So, it was clearly necessary to don the rash guard one more time:

And head out to catch a few last waves on our final full day on the beach:

Good times! After returning the board we made our way carefully back across the boardwalk in the near-darkness, and headed back to our Villa. For dinner we headed into the nearby beach town of Tamarindo and ate at an amazing French restuarant called the Langosta Beach Club, also highly recommended. We then headed back to our Villa with the final notable event of the day being the discovery of a frog staking out the tap in our open air bathroom: