Make a DIY underwater canister dive light for scuba diving
Copyright: All pictures, electronic design and concepts on this site are copy written. Copyright Matthew Skinner 1st May 2005. Please contact me before reproducing any contents from this web site.
Here is my first DIY dive light after its first SCUBA dive. More pictures at each step of the building process are on page two.
After seeing a few HID and MR16 halogen canister underwater dive lights I wanted to build my own. The main reason for looking at DIY dive lights was that commercial lights cost around us$500+ here in Australia for basic models which were far from perfect for my needs. After searching the internet I came across a few different designs and none were foolproof or well thought out in the existing DIY dive-light pages. Either the designs required expensive tools like a lathe, took a long time to custom make parts, or the light was not strong enough to withstand enough water pressure.
I wanted an under-water dive light for scuba diving which was.
I dived with others who owned 35 watt halogen canister dive-lights which used SLA batteries, however they produced less and yellowish light when compared to HID dive lights for numerous reasons which was not the fault of the globe. After multiple dives it was clear that 40 to 50 minutes was all they would run for which was not enough time to walk to the shore, wade out and snorkel to deep water, go for a 1 hour dive and then swim back to shore and find the car. Most shore dives at night that I do regularly needed 1.5 hours of torch life from the moment I leave the car to when I have packed the gear back into the car, so the cheap lights did not fit my needs and the ones that did cover my needs were well over 4-5 times more than what I could build a much better custom underwater canister dive light for.
The quest had begun..
Having a background in professional stage lighting for years I know a lot about lamps, from how to look after them for optimal life, to choosing the right one for the job. For primary diving lights there are three commonly used types, Halogen, HID and now LED. LED technology is now bright enough to easily overpower both a 10 watt HID and 50 watt Halogen. LED has many advantages then the other two mentioned, so I have now added instructions on how to install LEDs into this maglite build if you do not wish to use Halogen which is a cheaper solution. Halogen when over driven (more on this below) is an excellent choice when you need to use a light for both narrow beams on one dive, and then a wide flood as a video light on another. Being able to change is probably Halogens only advantage over LED.
I get a lot of people emailing me asking what the LED globes that are sold in stores are like, the answer is not very good. LED's need to be kept cool otherwise they will overheat and stop working. The globes sold in stores are designed to replace halogen globes around your house using air cooling in places with very little air movement. Because they are designed to work in fittings which were designed for hot halogens, they need to limit the performance of the LED's to prevent them from over heating and failing to work. This means the globes are producing less light so the globe does not overheat and then stop working after a few minutes of use. Luckily for divers we have water all around us to keep the LED's cool, and this allows us to make an LED which far out performs anything you can buy ready made in a shop. Getting rid of the heat does require a special heatsink, and I am now producing and selling these so you can make a high performance LED dive light with no special tools.
Disadvantages of HID when compared to LED
I'll speak very generally about the most commonly used lamp and ballasts in HID dive lights at the moment, advances are being made as HID are used in car headlights which is forcing them to be improved and developed. LED's are being improved at a much faster rate.
These are the reasons why most manufacturers have stopped producing 10 watt HID dive lights in favour of LED technology. Shortly they will also take over the 18 and 24 watt HID part of the market.
Over Driving a Halogen, lamp life and cost.
As mentioned above a Halogen based light still has a few advantages over LED, by being easy to change the globe between dives. When on a budget the ability to change from a normal dive light to a video light can save you a lot of money and the need to have two different lights. Halogen based lights are also easier and cheaper to build then LED, although this is quickly out weighed by the extra burntime a LED will give from the same sized battery pack. Halogen can be made to create white and lots of light that will over power a 10 watt HID, you can do this at the cost of reduced life of the $2 halogen globes by over driving them. This can be done without reducing reliability by using a Dive Light Genie.
A HID will last <1000 hours in ideal conditions when creating white light, and a halogen will last around 200 hours (depending on how high a voltage you use) when creating the same white light under ideal conditions. HID lamps cost us$100 and up, compared to us$2 for a cheap halogen lamp. It makes halogen lamps overdriven very good value for money, especially when you consider how many hours you are likely to go diving with a torch in a year. Another good reason is if the light head is flooded which may happen, a cheap mr16 is not a big deal to replace and all stores keep them in stock even in remote places. ie on a diving holiday. All globes including HID will produce nice light when new, and as they get older will dullen and change color, an old HID lamp will no longer be as bright and white as it once was when new, the same is true of halogen. The cost of putting in a new globe makes halogen very attractive.
Beam angles is another consideration I took into account when choosing the lamp to base my DIY dive light on as a narrow beam (spot) looks/is brighter and penetrates dirty water without backscatter much better than a Flood (wide angled globe). This is the reason why commercial HID lights look to be so much brighter than halogen lights as the HID globes normally have a much narrower and tighter beam of light. People rarely compare apples with apples and think HID is the best you can get which is not really the case depending on what your needs are. As some dives I would want a flood 38 degree to light up a huge area evenly, and other dives I would want a spot 10 degree light to reach further, I found cheap halogens allowed me to change the light to suit the dive and conditions. A 10 degree spot in dirty water not only allows you to see further it also makes signaling to a buddy much easier. Try doing an OK signal with an underwater flood dive light, it just does not work and you end up blinding your dive buddy with your underwater torch. Sorry to anyone who dives with me when I take the light and camera :)
To give you an idea of the life of a halogen globe at different voltages.10 cells = 12.0 v = 6,000 hours
12 cells = 14.4 v =1,500 hours
14 cells = 16.8 v = 350 hours
17 cells = 20.4 v = 120 hours
18 cells = 21.6 v = 50 hours
The same is true of dimming the globe below the rated voltage.
This table shows the amount dimmed does not translate into a linear energy saving, this is why the overdriving works so well at the expense of lamp life. The current stays roughly the same as you increase the voltage, so the burn time is not reduced and extra light at a whiter color is created. It will turn a 50 watt halogen globe into a 70+ watt globe due to the extra voltage.
Choosing the underwater dive torch head was an easy task, I wanted a very bright canister dive light and this meant HEAT and lots of it, so an aluminum light head and glass would be needed to conduct the heat away from the globe. To deal with the heat a modified aluminum Maglite torch was the best solution to making the torch fast and cheaply. The picture below shows the C sized Maglite (any C or D sized Maglite will work) end with a MR16 halogen globe inside. Below are diagrams for two different ways to seal the light, the first being easier to source the parts (1 piece of glass and 2 orings) and build with the second method being stronger. I personally went with the second method which requires two pieces of glass to be glued together as I felt this would withstand more water pressure and be more reliable due to only 1 oring. Getting some glass that's the right size can be difficult for the smaller diameter to form the step, but if your keen and ring around some places have some scrap that they allow you to have.
Good news is that no mods are needed to change from one design to the other, so you could always build the easy mod first and upgrade to the second way in the future. The standard zbattery lens by itself should be fine to < 30m depth but please do your own testing and let me know how you go.
To protect the globe and lens from heat when its used out of water, I used the Dive Light Genie which will allow you to dim the light to create less heat when above water or else you burn yourself on the Maglite after a few minutes of use at full power. The larger top piece of glass can be purchased from www.zbattery.com or anywhere that sells police or army supplies. The smaller lens for the second design is custom made by a local glazier for not much money as I ground it smooth on the edges myself. The advantage of this stepped lens design is that the water pressure sucks the lens onto the Maglite the deeper you dive and improves the seal. The same design is used to seal the otter box and just about every dive light on the market, its a very proven design. The glass is also suspended by orings and not hard against metal which is yet another reason to go with the stepped lens.
This picture shows the EZ Maglite mod drawn by "fhman" which is easier and cheaper to build however I feel it's not as good as the harder to build stepped lens which is shown below and also shown in more detail on page 2.
Here's the stepped lens design which does not show the original o-ring above the glass to fully shock mount and isolate the glass from metal to glass contact if its dropped or the metal is not perfectly flat. See page 2 for more pictures on this design.
Since I am aiming at a 50 watt globe this means for a 1 hour dive, a 4.5ah battery pack will be needed roughly as a bare minimum as batteries don't give you the full ratting over 1 hour, but over a 10 hour drain. The faster you drain a battery the less efficient it is at giving you back all of the stored charge. To work out the ah rating for a 1 hour burn time you use the formula, Watts / Voltage = Amps. When overdriving you don't use much more current so base all your calculations as if you are using 12 volts to make things simple. The globe is designed to be 50 watts at 12 volts so we use these for any calculations. For an example, 50 watts divided by 12 volts is 4.2 amps. If you were to use a 4.5 ah pack without my dive light genie electronics you would find you would only get around 46 minutes of burn time this is due to the efficiency mentioned above, however due to the voltage regulation and other unique features the DLG, my electronics gave me back the time I needed for a 1 hour dive without needing to use a smaller globe or larger battery and hence canister. I find the battery lasts >30% longer just by having a Dive Light Genie installed. This is explained on page 3 of this guide as to why this happens.
As Ni-Mh and Ni-Cad have very flat discharge curves, they are difficult to measure how much charge is left in them, they also very quickly drop to 0v not giving a warning that they are almost discharged. This makes it difficult to ensure the battery is not over drained which will damage a battery, and that you have enough time to finish your dive before the light goes out. I designed the dive light genie to overcome this, to give some warning and to protect the battery.
So a good choice for an underwater dive light battery pack is either SLA because they are so cheap and are already available in 12 volt packs, Ni-Mh for their small size and weight and greater life, and also LiFePO4 batteries. The more advanced a battery is, the more care they need to have a long life and hence why I designed the electronics to take care of these considerations for the scuba diver.
In the end I wanted a small dive light canister to keep me streamlined underwater, so NIMH was chosen over SLA due to their size and weight. I didn't consider Li-ion, LiPo and LiFePO4 packs because of the complications a charger for these cells present which can be overcome with PCB's inside the battery pack. If you do not have a PCB inside a lithium pack then you really need a charger to charge each cell by itself so that each cell will be discharged at the same time in the pack. What can happen is that one cell becomes empty, but the combined voltage of the other cells is still above the voltage of an empty pack. With Ni-Mh this happens but is solved by slow charging or a fast charger like my design which will fast charge and then use a slow charge at the end to balance the pack. This is why slow chargers for nimh are so popular as they eliminate the pack from going out of balance and this is why I think NiMh is still better suited for most people doing DIY.
With LiFePO4 cells having the advantages of Lion/lipo without the disadvantages, they are promising and worth considering as some cells allow you to screw them together with no soldering making them great for DIY. If your interested then have a look at these cells LiFePO4 with M6 screw thread. Two of those cells would work really well with some LEDs and would make for a very small light.
A huge saving can be made if the larger SLA type batteries are used so if cost is important read the section of battery types above and make a choice on what you find more important. Here's a picture of a cheaper SLA dive light using the otter box 3500 as a canister to hold a SLA. The switch is a magnet which moves over a reed switch inside the Maglite, this means no holes are made for a switch. SLA are much larger and are only 12 volts so the light is not as white, only two of the reasons I spent the extra to make a Ni-Mh version.
Here's a light built by Claustrox using the otterbox 3500 and a SLA. After a few months of diving he made a Ni-Mh version as its worth paying to get smaller and lighter NIMH cells.
This picture shows how my dive light fits 14 C sized batteries inside my canister before the umbilical lead is fitted for the torch head. The cd is showing the size of the largest side of the dive light canister as this is very small and the whole canister fits inside my bcd pocket ! Please be aware that it does not show the way my pack is wired. After building my own and a lot of people emailing and asking for this pack to be pre made, batteryspace have now started to offer this pack pre made. Click here for details.
For the canister I considered making my own out of PVC pipe, however the time spent building and sourcing the pipe with a thick enough wall was difficult in Australia at local hardware stores. Sewerage pipe was a good candidate, however I really wanted a clear canister for the backup LED lighting in the canister that I had in mind with the electronics. After a lot of searching I came across the www.otterbox.com range of pre made water proof cases. They are rated at 30 meters or 100 feet and could easily be pushed much further as plenty of people including myself have already done many times to 50m. Advantages of the otter box range is they come in clear or colors, were ready made, pressure tested, had a belt clip and lanyard pre installed, and not to mention the latches for holding the lid down was already supplied and fitted. The price of stainless clips and the cost of glue and plastic would probably end up more and I would have to do a lot of extra work, possibly needing a lathe which I don't have access to. For the asking price of these I couldn't justify wasting time making my own. I worked out the otter box 8000 could be used for a 12 volt battery pack, or if I wanted to overdrive the globes, more room would be needed and the 9000 model was then the perfect size. The result was a cost effective ready made canister that didn't lower the quality of the home-made dive light. As I wanted a high performance and very bright light, the dive light canister needed to hold 14 C sized batteries to over drive the globe.
At first I was worried about a plastic canister however on one of the first dives I dropped the canister with battery inside 4 feet onto a large rock. I was worried about cracks as it was a nasty fall onto a sharp rock, however on inspection the plastic was not even marked. I am surprised just how tough the plastic is which I think it is made from poly carbonate which is a strong material.
Please note all information on the dive light genie HALOGEN electronics can be found here. The LED Genie is a driver for LED's with some unique and handy features.
I've now uploaded a video demo of my electronics in operation, to keep it a small download I didn't show off all the features only how simple it is to change the level of light. Download or watch underwater canister dive light demo video.
The electronics I designed for my light are useful in any light, even if the light is running at 12 volts and is not being over driven with a higher voltage. All of the features will benefit any dive light and can be retro fitted to any DIY dive light or commercial dive torch which has been store bought. The electronics are now available in kit form and pre-made. The design is copy written and patent's are applied for.