Make a DIY underwater canister dive light for scuba diving

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Copyright

All pictures, electronic design and concepts on this site are copy written. The Australian and international copyright belongs to myself and has been fully documented. Copyright Matthew Skinner 1st May 2005. Please contact me before reproducing any content from this web site.

Design Requirements

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.

• Brighter than a 10 watt HID canister dive-light.
• Outputs white not yellow light with even light coverage for good photography and true colors underwater.
• Small and streamlined as I hate gear hanging off me underwater.
• Cost effective.
• Quick to make with common parts.
• Reliable to 40m / 130ft deep.
• Flexible to suit all diving conditions.
• Good burn time, enough power for 1 to 2 hours of burn time.

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..

Globe / Lamp

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 two commonly used types, HID and Halogen both which have advantages and disadvantages. LED technology is also emerging rapidly, however currently the 3 and 5 watt LED's in the market are not bright enough for a primary light even when used with a lens to focus the beam. If you use multiple LED's you then can't find a decent lens to focus them all down to a powerful beam that will penetrate a decent distance through water. Led's are great for backup lights but can't meet the requirements of a canister dive light, although this will change over the next few years.

HID lamps use a high voltage arc in a gas to create the light and are very efficient with a 10 watt HID lamp only drawing 10 watts of power but creating 30 watts of light output equivalent to a halogen lamp. Some people compare a 10 degree hid to a 36 or 50 degree halogen and claim the HID is much brighter, but really you need to be aware of how specs can be twisted by people selling globes or lights. The HID also burns at a very high temperature and creates a white light, not yellow like a MR16 halogen at 12 volts. To make colors appear natural underwater white light is needed. White light is also much nicer on the eyes and a lot better for video and still cameras.

All the manufacturers and sales people are pushing HID, and yes HID suits some divers needs as they do give a very long burn time, but here's what a lot of people going into purchasing HID do not know and what turned my attention back to Halogen technology.

I'll speak very generally about the most commonly used lamp and ballasts in dive lights at the moment, advances are being made and better specs are being released.

• HID's start 1000 times best case, so you cant turn the light on and off a lot of times before the globes life is over regardless of the hours the globe has done. The ignition of the HID globe is very harsh and the life of a HID is a combination of running hours, the number of starts as well as a lot of other factors.
• To get close to the 1000 starts, the ballast needs to take around a minute to turn the globe fully on, up to correct color and to stop flickering. If the ballast does it faster then the start-up ignition of the globe is more damaging and you'll find your globe blows after less starts then 1000. This means you can't get lots of light quickly.
• When you turn the globe on you should not turn it off again for at least 2 minutes to look after the expensive globe. So for looking in ledges during the daytime where the light is turned on and off for a quick look the HID globe will blow very quickly.
• The globe will not re-strike when hot. This means if you turn the HID off you can't turn it back on until the lamp cools, which can take a few minutes if the ballast looks after the globe correctly. Most ballasts will allow a re-strike after 20 seconds or less, once again at the loss of lamp life. Some ballasts also support hot re strike but these are not common and always cost a lot more and once again are at the expense of less life from the expensive globe.
• When the HID globe exceeds its life span there is a small but very real chance of the globe exploding, which could break the lens and flood the light. Video projectors use timers to keep track of how old the globe is to warn owners when to replace the globe to avoid damage to the video projector. I have not seen any dive lights with this feature yet.
• Very difficult to source spares when over seas in remote places.
• Very costly to replace or keep a spare globe.
• They run on a few thousand volts making them more dangerous to use around water.
• They are less reliable and more expensive than halogen but as technology improves this is sure to change.

Whilst HID is still a good option for a dive light, I also know about over driving a Mr16 halogen globe above the manufacturers ratings. The idea behind over driving is not new and is used in many applications. For example, photographers use special halogen lamps which have a life of 20 hours and create pure white light. Here's a PDF document which has real data on just what you can expect from over driving a mr16 globe. The specs to look at are CCT (constant color temp) and CP (candle power) which is interesting to see how much extra light and whiter output you will get for a small increase in voltage. 5700K is achievable at 19 volts with 3,500 candle power and around 200 hours of lamp life under these conditions. 200 hours is a lot of night diving and for a cheap globe this is the way I prefer to run my dive light as the idea behind DIY is to build something which is great without spending a lot of money. Overdriving does increase the risk of a cold globe blowing when turned on due to the extra heat, this is only one of many reasons why I designed the dive light genie dive light dimmer electronics to allow the safe usage of Halogens at a higher voltage. I've now been diving the light for more than 300 hours and still not blown a globe.

Comparing lamp life and cost.

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.

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.

Torch head

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.

Switch

Choosing the battery.

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. 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 any more current so base all your calculations on 12 volts as the globe is designed to be 50 watts at 12 volts, and will be in fact a higher wattage globe at a higher voltage. For example, 50 watts divided by 12 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, however due to the voltage regulation and other unique features the DLG gave me back the time I needed for a 1 hour dive without needing to use a smaller globe or larger canister. I find the battery lasts >30% longer just by having a Dive Light Genie installed.

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, however 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, or Ni-Mh for their small size and weight and greater life. They need a lot more care 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 and the big task of creating some electronics to do lamp and battery management was also undertaken, more on this later. I didn't consider LION because of the massive complications a charger for these cells presents, they are very easily damaged, and the huge price tag. In the future I will build a pack to fit this canister with insane burn times out of lithium ion cells but only after many test dives and the price of lion falls as I can make do with a 1 to 2 hour burn time.

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.

Dive Light Canister Choice

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. 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 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 is made from poly carbonate which is a strong material.

Dive light parts and sources

Tools Needed

• Drill Press.
• Drill Press Clamp or vice.
• Metal Hand File or angle grinder which is faster.
• Drills.
• Hole Saw with sprung teeth in multiple sizes.
• Hacksaw.
• Soldering Iron or you could use crimp or screw terminal blocks to join wire.

Custom Electronics

Please note all information on the dive light genie electronics can be found here.

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.