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Yet another DIY canister light

Discussion in 'Do It Yourself - DIY' started by M_Bipartitus, Mar 20, 2008.

  1. M_Bipartitus

    M_Bipartitus Divemaster

    # of Dives: 100 - 199
    Location: Seattle, Washington, United States
    840
    8
    18
    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
     
  2. M_Bipartitus

    M_Bipartitus Divemaster

    # of Dives: 100 - 199
    Location: Seattle, Washington, United States
    840
    8
    18
    Build

    Building to come

    Parts list

    ******** This is not yet a complete list ********
    Parts list wth vendors (prices as of March 2008)
    * indicates optional, see text.

    Order from Newark (US - Electronic Components Distributor | Newark.com)
    Description____________Part Number___Quantity__Price each___Mfr. #
    Toggle Switch__________21F716________2*______10.82______ 7101TZQE
    Sealing Boot___________83F8121_______2*_______5.70______ C1131/27


    Order from LED Supply:

    Description____________________Part Number _____Quantity___Price each
    Spot Base Module - 3&deg _______L2-OPK2-1-003______3 ______2.25
    *Oval Sub-Lens - 4x27&deg_______L2-OPK2-1-427S ____3 ______0.65
    Spot Diffuser Sub-Lens -6&deg____L2-OPK2-1-DIF6 _____3 ______0.65
    *Wide Sub-Lens - 12&deg _______ L2-OPK2-1-012S _____1 ______0.65
    Luxeon K2: White K2 Star HC_____05027-PW14 ________3 ______7.49
    BuckPuck: 3021-D-E-1000 _______03021-D-E-1000 _____1 ______14.99



    Order from Battery Space.com

    Description_____________________Part Number______Quantity___Price
    Li-Ion 18650 14.8V 2400mAhr______LCH3P1S4I2WR_____1 ______59.99
    Smart Charger (1.5A) for 14.8V______________________1 ______26.95
    *Salvo Canisters fro DIY HID ______DV-SALVOHID(D)___1 _____219.95


    BTW, does anyone know how to make tables in posts? (please PM if you do as a reply below would be a bit OT)
     
  3. M_Bipartitus

    M_Bipartitus Divemaster

    # of Dives: 100 - 199
    Location: Seattle, Washington, United States
    840
    8
    18
    Testing
    Reserved for future use
     
  4. nwbrewer

    nwbrewer Barracuda

    # of Dives: 200 - 499
    Location: Woodinville, Wa
    291
    5
    18
    Looks like you've done your research. For the lighthead you can actually fit 4 LED's into a D-cell maglight head. As far as the switch goes, since you are going to use a controller anyhow, you may consider a reed switch. It'll be cheaper, and removes a potential leak point.

    You also may just consider using one of Seoul Semiconductors P7 LED's, 900 lumens, 10watts at 3.7 volts. May be worth looking into.

    Good luck with your build.

    Jake
     
  5. M_Bipartitus

    M_Bipartitus Divemaster

    # of Dives: 100 - 199
    Location: Seattle, Washington, United States
    840
    8
    18
    Are you aware of any LED drivers that can do the rated 2.8 A of this LED? I would prefer not to have to build a current controller.
     
  6. nwbrewer

    nwbrewer Barracuda

    # of Dives: 200 - 499
    Location: Woodinville, Wa
    291
    5
    18
    I think most folks are thinking that they will just direct drive them until someone comes up with one. Alternately you can put 3 700ma drivers in parallel, that should get you 2.1A, and they're cheap enough from Kaidomain or deal extreme. I'm thinking I may upgrade mine and just direct drive it off of some 18650 batteries. EE isn't my field, I'm learning as I go....

    Take a look over at candlepower forums, those guys are nutty about bright lights!

    Jake
     
  7. cfelliot

    cfelliot Manta Ray

    # of Dives: 200 - 499
    Location: Portland, Maine
    577
    10
    18
    I have the K2s and the L2 reflectors and lens. Thanks for the tip on the BuckPuck driver. I am going to use 9 of the K2s and it looks like a 1A BuckPuck will drive 3 leds with around a 15V supply.

    I'm taking a slightly different approach with a handheld head and a clip on battery pack and cable. I want to mount the stars to a heatsink that extends from the back of the head into the water for cooling.

    Great research, thanks!
     
  8. nwbrewer

    nwbrewer Barracuda

    # of Dives: 200 - 499
    Location: Woodinville, Wa
    291
    5
    18
    If you use an Maglite head, and put in an Al or Cu heatsink that touches the Mag body, and use some thermal grease at the interface point, it should conduct out into the water pretty well.
     
  9. M_Bipartitus

    M_Bipartitus Divemaster

    # of Dives: 100 - 199
    Location: Seattle, Washington, United States
    840
    8
    18
    It shouldn't be too hard. Just a small resistor (~.1 or 1 ohm) to sense current, a fixed reference to compare to, an opamp to compare the two, and a drive transistor. I might try it at some point. I already ordered the LEDs above, so I'll be testing those out before ordering more LEDs.
     

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