After inspiration by ucfdiver's DIY canister light thread on a DIY light, I decided to build an LED "HID" canister light. After looking at a few sites and combining some ideas I'm going for a system based on three 3W lights with a lithium ion battery. My estimated budget is $170. I will be updating this post as I work on the light. For the time being, this post should be considered a draft since I have not yet finished and tested the light. That said I am going to try to give a lot of details for anyone else who may want to follow a similar path.
Design
The basic circuit involves the battery powering a LED driver which powers the set of LEDs. The basic LED driver takes an input voltage and provides a constant current for the LEDs.Since I don't spend too much time in caves, I decided that I could try a dual-power light for really dark stuff and only slightly dark stuff. I found an LED driver that allows for adjustable output, thus I can make seperate full and low power settings. To switch between them a toggle switch and resistor network will be necessary. I'll give more details later in the building section.
LEDs
As mentioned above, I am planning on using LEDs as the source of light. These should provide a brigher light than HID with less heat and longer burn time. After looking through various sites on DIY lights I settled on using three 3W LEDs as these should provide plenty of light for only about $8 each. The specific model I choose was a Luxeon K2: White LED since it is mounted and optics are readily available.
I am adding pre-made optics to these LEDs. The base lens has a 3 degree spot, which is smaller than most dive light so I am getting a few attachment lenses to offer other spot sizes. After I build the light, I'll post photos of the patterns and my opinions on what to use. My guess is that for most divers the 6 degree diffuser would be good, probably something wider if you want to use these for a video light. I'm interested in seeing what the elliptical 4x27 degree lens will look like as well as a combination of different lenses.
LED Driver
As mentioned, I will be using an LED driver that has an adjustable power level. These devices put out a constan current so that the LEDs will have a constant brightness with better efficiency than limiting current with a resistor. I got a 3021 BuckPuck that runs at 1A of current and is adjustable. One could easily use the non-adjustable version to save a few dollars.
Battery
Batteries are a major design factor in this build. The size of the batteries will specify the size of canister and the time that the light should last on a charge. Since the high power LEDs each have a 3.5-4 volt drop for each LED, I will need a total drive voltage of at least 3Leds x 4Volts each = 12V. Since the driver is likely to not be perfect and I have a little extra electonics I am going with the next larger typical Li-ion voltage of 14.8V. One could use a larger voltage, but it may not help your burn time while adding weight to your canister.
My LEDs have a high continuous current of 1 A or 1000mA. To get an estimate for possible burn tiem we divide the battery capacity by the current we plan on using. Since I only dive recreational now, I'll say 2 hours of light should be plenty for any given day. Since 2hours x 1A = 2 Ahr or 2000mAh a 2400mAh batery should provide around 2 hours of light at full power.
Since Li-Ion cells are so small, I am going to thinking of building my canister for a slightly larger 4800mAh battery and have the option to upgrade later. This should be easy as the largest dimintion across this battery is only about a half inch larger because this battery has a square cross-section and the other is rectangular. This upgrade would give an estimated 4.5 hours of light.
Canister
For the Canister, one could go the easy and expensive route with a pre-made canister sold by the batttery website. This option is simple, but the smallest size cost more than the budget for my entire light. They also list what size batteries fit in each canister option.
I am choosing to make a canister similar to the one ilistrated on this site: Battery Space :: View topic - DIY Canister-Style Dive Light This should cost closer to $30 to make. Since the battery has a width of about 1.9 inches and the larger potential upgrade has a maximum width about 2.25 inches, I'll try for a smaller set of PVC pipe fittings than he uses. His battery is about 2.8 inches across.
Light head
I have not worked on this too much as the dimentions and drawings of the LED mounts and lenses are not as detailed as I would like. I will put more up on design after I get the LEDs and lenses in.
For now I'll mention that there are two typical styles of light head, a linear arrangement on a rectangular block or a triangular arrangement on a circular block. Some builders choose to use a flashlight head, but I am not sure that the three LEDs will fit well in this so at this point I'm planning a custom built head. I plan on making the front plate removable, so I think I will have an easier time making sealing surfaces for an o-ring with a circular format. I like the rectangular style better, but I don't have a CNC machine available and I don't think my milling machine skills are good enough to make a rectangular o-ring slot.
Options
There are many options available. I will elaborate later, but you can use different batteries, LEDs and canisters. I am making a dual-power light, but a single power light would be a little easier and have fewer switches.
As mentioned above, an alternate number or type of LED can be used. Keep in mind that the power supply must be able to provide 3.5-4 volts for each of the LEDs driven. Thus if you made a 4 LED light using the above LEDs you would need a batter with atleast 16V. Also mentioned was the options of different lenses for the LEDs. I ordered many differnt lenses, and I'll post picts of what they do in the testing section after I get some building done. Then you can decide for yourself what is best for your applicaion.
Batteries are available in many sizes and a few options are mentinoed above. There are even more powerful packs such as a 10.4Ah battery, that shuold be able to provide as much as 10 hours of light on the system described above. This item may require a longer canister. My infomal survay of batteries indicartes that this is the largest practical battery for this applicaion.
For the budget minded you can also use other types of batteries. For example one could use 14.4V NiMH which could provide twice the total power for a similar price, but a larger size.
Refernace sites
DIY HID light by user Jimothy
Battery Space :: View topic - DIY Canister-Style Dive Light
ucfdiver's scubaboard discussion
http://www.scubaboard.com/forums/do-yourself-diy/225238-project-log-diy-canister-light.html
3X5watt thead at Cave Diver's Forum
3X5watt - Cave Diver's Forum
Revision History
March 20, 2008 - Initial draft
Design
The basic circuit involves the battery powering a LED driver which powers the set of LEDs. The basic LED driver takes an input voltage and provides a constant current for the LEDs.Since I don't spend too much time in caves, I decided that I could try a dual-power light for really dark stuff and only slightly dark stuff. I found an LED driver that allows for adjustable output, thus I can make seperate full and low power settings. To switch between them a toggle switch and resistor network will be necessary. I'll give more details later in the building section.
LEDs
As mentioned above, I am planning on using LEDs as the source of light. These should provide a brigher light than HID with less heat and longer burn time. After looking through various sites on DIY lights I settled on using three 3W LEDs as these should provide plenty of light for only about $8 each. The specific model I choose was a Luxeon K2: White LED since it is mounted and optics are readily available.
I am adding pre-made optics to these LEDs. The base lens has a 3 degree spot, which is smaller than most dive light so I am getting a few attachment lenses to offer other spot sizes. After I build the light, I'll post photos of the patterns and my opinions on what to use. My guess is that for most divers the 6 degree diffuser would be good, probably something wider if you want to use these for a video light. I'm interested in seeing what the elliptical 4x27 degree lens will look like as well as a combination of different lenses.
LED Driver
As mentioned, I will be using an LED driver that has an adjustable power level. These devices put out a constan current so that the LEDs will have a constant brightness with better efficiency than limiting current with a resistor. I got a 3021 BuckPuck that runs at 1A of current and is adjustable. One could easily use the non-adjustable version to save a few dollars.
Battery
Batteries are a major design factor in this build. The size of the batteries will specify the size of canister and the time that the light should last on a charge. Since the high power LEDs each have a 3.5-4 volt drop for each LED, I will need a total drive voltage of at least 3Leds x 4Volts each = 12V. Since the driver is likely to not be perfect and I have a little extra electonics I am going with the next larger typical Li-ion voltage of 14.8V. One could use a larger voltage, but it may not help your burn time while adding weight to your canister.
My LEDs have a high continuous current of 1 A or 1000mA. To get an estimate for possible burn tiem we divide the battery capacity by the current we plan on using. Since I only dive recreational now, I'll say 2 hours of light should be plenty for any given day. Since 2hours x 1A = 2 Ahr or 2000mAh a 2400mAh batery should provide around 2 hours of light at full power.
Since Li-Ion cells are so small, I am going to thinking of building my canister for a slightly larger 4800mAh battery and have the option to upgrade later. This should be easy as the largest dimintion across this battery is only about a half inch larger because this battery has a square cross-section and the other is rectangular. This upgrade would give an estimated 4.5 hours of light.
Canister
For the Canister, one could go the easy and expensive route with a pre-made canister sold by the batttery website. This option is simple, but the smallest size cost more than the budget for my entire light. They also list what size batteries fit in each canister option.
I am choosing to make a canister similar to the one ilistrated on this site: Battery Space :: View topic - DIY Canister-Style Dive Light This should cost closer to $30 to make. Since the battery has a width of about 1.9 inches and the larger potential upgrade has a maximum width about 2.25 inches, I'll try for a smaller set of PVC pipe fittings than he uses. His battery is about 2.8 inches across.
Light head
I have not worked on this too much as the dimentions and drawings of the LED mounts and lenses are not as detailed as I would like. I will put more up on design after I get the LEDs and lenses in.
For now I'll mention that there are two typical styles of light head, a linear arrangement on a rectangular block or a triangular arrangement on a circular block. Some builders choose to use a flashlight head, but I am not sure that the three LEDs will fit well in this so at this point I'm planning a custom built head. I plan on making the front plate removable, so I think I will have an easier time making sealing surfaces for an o-ring with a circular format. I like the rectangular style better, but I don't have a CNC machine available and I don't think my milling machine skills are good enough to make a rectangular o-ring slot.
Options
There are many options available. I will elaborate later, but you can use different batteries, LEDs and canisters. I am making a dual-power light, but a single power light would be a little easier and have fewer switches.
As mentioned above, an alternate number or type of LED can be used. Keep in mind that the power supply must be able to provide 3.5-4 volts for each of the LEDs driven. Thus if you made a 4 LED light using the above LEDs you would need a batter with atleast 16V. Also mentioned was the options of different lenses for the LEDs. I ordered many differnt lenses, and I'll post picts of what they do in the testing section after I get some building done. Then you can decide for yourself what is best for your applicaion.
Batteries are available in many sizes and a few options are mentinoed above. There are even more powerful packs such as a 10.4Ah battery, that shuold be able to provide as much as 10 hours of light on the system described above. This item may require a longer canister. My infomal survay of batteries indicartes that this is the largest practical battery for this applicaion.
For the budget minded you can also use other types of batteries. For example one could use 14.4V NiMH which could provide twice the total power for a similar price, but a larger size.
Refernace sites
DIY HID light by user Jimothy
Battery Space :: View topic - DIY Canister-Style Dive Light
ucfdiver's scubaboard discussion
http://www.scubaboard.com/forums/do-yourself-diy/225238-project-log-diy-canister-light.html
3X5watt thead at Cave Diver's Forum
3X5watt - Cave Diver's Forum
Revision History
March 20, 2008 - Initial draft
