SunwayLED
Results 1 to 16 of 16

Thread: Midnight Light: Inspired by Project Lamplighter

  1. #1
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,826

    Default Midnight Light: Inspired by Project Lamplighter

    Calipsoii's Project Lamplighter thread here

    Cali created a very tiny, low-drain LED light to keep on his keychain as a 'find-me' with a different wow factor than a tritium vial. Rather than take his thread off topic, I'll post the build of a larger, more-powerful, but similarly-purposed device.

    My plan:

    To develop a small, keychain-carry device with output visible in normal room lighting conditions as a super-find-me, also usable as a low-level light.

    Higher current drain (whole milli-amps instead of nano-amps) requires either big primaries or rechargeable secondaries. My fabrication tools are limited, leading me to permanently-installed batteries with trickle charging. One hackish way to achieve this is with USB-powered trickle charging and a voltage-limiting Zener diode across the NiMHs. There are other ways, including having the battery case openable to charge as normal. But I've wanted to build a light like this, so I'm combining two projects.

    Below is a 'rough draft.' I tend to do this for projects, using duct tape liberally.

    Quote Originally Posted by potpot View Post
    The only "issue" that I see with using one or more AAA's is that it'll be a bit large for a keyfob.
    Almost. I actually plan to rebuild it into a side-by-side configuration to see how it feels that way. 2xAAA with a 5mm LED sticking out the front is awfully long, but side-by-side is close to the size of a lot of GITD key-finder things I see as branded freebies. Right now it's ugly-duck awkward, but i have plans. Plans that include 2 300mAh 1/3AA cells and built-in charging. It'll be massive relatively speaking, but only about like having a chapstick on my key ring. I want one that is not only visible, but acceptable as a midnight light. For my purposes, I think I'll get about 100 hours of life on a charge at this high setting.


    The critter in my desk drawer. The inverted-cone thing makes an interesting beam pattern - a darker circle ahead like a minimag, but a good spread of light otherwise. I might dab a bit of hot glue and see if I can get a more spherical compromise than the torus of light output I get now.


    The whole thing, on some duracells that came with some flashlight or another. I read 2.54v across the LED with my cheap multimeter, and around 2.5mA. I don't trust it at such low range.


    In office-lighting conditions, it has a bit of 'extra' glow to it. In the dark, it stands out like a beacon. For my build, I plan:

    USB micro socket with 160Ω resistor to charge batteries at a trickle
    2 1/3AA NiMH cells with a zener diode (hackish overcharge protection) [14.5mm Dia x 16.7mm Height]
    Maybe a high/low switch
    Total size should be around 15mm diameter, 40mm long. So, about like a fat AAA, maybe.

    This all assumes I find a case for it. It'll be tricky to design one from essentially found parts. Although I do have a drill now.
    My biggest light-hog is my camera.

  2. #2
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,826

    Default Re: Midnight Light: Inspired by Project Lamplighter

    I don't trust my multimeter, but I'd estimate current to be in the 1 mA range rather than 2.5 mA. For 2x AAA, this gives a theoretical ~400 hours output - but it's essentially direct-drive, and will dim down over time as mentioned in the Lamplighter thread. I believe that's why Calipsolii used control electronics on his. With the planned recharging, this shouldn't be as much of a problem for my project - but we'll see!
    My biggest light-hog is my camera.

  3. #3
    Flashaholic sunny_nites's Avatar
    Join Date
    Mar 2010
    Location
    USA
    Posts
    187

    Default Re: Midnight Light: Inspired by Project Lamplighter

    I like it!
    So many LEDs, so little time...

  4. #4
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,826

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Here's a size comparison for the side-by-side format. I suggest going with this sort of build, if you can wrangle a case for it.



    I'm considering other built-in charging methods so that I can feed this fob as a whole. SO far it looks like a trickle-CC LM317T is one option, with no voltage cap.

    5v - 1.7Vdrop = 3.3vMax, in theory. I'll have to investigate this.
    My biggest light-hog is my camera.

  5. #5

    Default Re: Midnight Light: Inspired by Project Lamplighter

    hey it's messy and you need to be careful with making a temporary form, but once you've got it all worked out with the mini usb charging port, resistor and battery (how about super capacitor?!) you can use a two part epoxy and pour a body for it... fully potted.
    The brighter the light, the darker the shadow.

  6. #6
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,826

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Quote Originally Posted by eh4 View Post
    hey it's messy and you need to be careful with making a temporary form, but once you've got it all worked out with the mini usb charging port, resistor and battery (how about super capacitor?!) you can use a two part epoxy and pour a body for it... fully potted.
    Clear 2-ton epoxy was about my plan, but I dream over turning out finely machined casings for projects like this. Ah well. A tip I've heard is to stuff some blue stickytack into the (switch, charge plug, etc) to keep the epoxy out of where it's unwanted.

    Super capacitors get a lot of press, but they wouldn't work well for this project. I'm a huge fan of simplicity, and a supercapacitor's capacity is mostly voltage-based. The energy density is low even compared with NiCd, and I'm not eager to add a voltage-regulating component to get the fullest capacity out of a capacitor. I mean, if I go with simple trickle charging, here's the present component list:

    2 cells
    1 LED
    2 resistors (one for LED, one for current-limiting)
    Micro USB plug

    My understanding of supercaps indicate that the main shortcoming here is capacity. NiMH last long enough for these purposes, anyway. Some supercaps die outright after 1000 cycles.
    My biggest light-hog is my camera.

  7. #7

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Looking good AnAppleSnail!

    You snagged the LED from a string of Christmas lights didn't you? I have the same ones all over my Christmas tree - they give really excellent visibility compared to the standard 5mm domed one.

  8. #8
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,826

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Quote Originally Posted by calipsoii View Post
    Looking good AnAppleSnail!

    You snagged the LED from a string of Christmas lights didn't you? I have the same ones all over my Christmas tree - they give really excellent visibility compared to the standard 5mm domed one.
    Yes indeed, and I've got tons more of them. And I think I've decided to skip the Zener for charging - my research suggests I can make this even more over-simplified, and simply limit the full-cell current to less than about 1/10th C, and put in about 1.6x the cell's capacity (1/10th C for 16 hours)

    Dead cell voltage: 1.0v
    Charged voltage: 1.4v

    With a 100-ohm charging resistor, I get 30mA charge when dead, and 22mA charge when charged
    With a 70-ohm charging resistor, I get 43mA charge when daed, and 31mA charge when charged

    That's close enough to spec for me, assuming the cells stay reasonably paired. I don't know if the long-term effects of low-level drain will be a big problem, but now I know just how to wire this.

    I'm still pondering a chassis. I've had bad luck with epoxy holding well for split rings. Suggestions? I can always just go for it and add zip ties later, but that doesn't look very good.
    My biggest light-hog is my camera.

  9. #9

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Quote Originally Posted by AnAppleSnail View Post
    I'm still pondering a chassis. I've had bad luck with epoxy holding well for split rings. Suggestions? I can always just go for it and add zip ties later, but that doesn't look very good.
    Not really, sorry.

    I'm using a piece of transparent rigid PVC filled with hot glue and drilled. The PVC gives more than enough strength to the split ring.


    The friction fit between the tail and body is starting to wear out though, so I'm looking into getting a more elegant metal housing machined locally.

  10. #10
    Flashaholic sunny_nites's Avatar
    Join Date
    Mar 2010
    Location
    USA
    Posts
    187

    Default Re: Midnight Light: Inspired by Project Lamplighter

    How about if you take a small gauge solid copper wire, shape it in a U and secure it to the back of your light with tape. You could use that to hold the split ring. You would probably want the U to more of a horseshoe shape so the tape would have a better chance of holding it.
    So many LEDs, so little time...

  11. #11
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,826

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Quote Originally Posted by sunny_nites View Post
    How about if you take a small gauge solid copper wire, shape it in a U and secure it to the back of your light with tape. You could use that to hold the split ring. You would probably want the U to more of a horseshoe shape so the tape would have a better chance of holding it.
    I've looked at some options and settled on a steel 'sled' made from found parts in my apartment. My main challenge has been getting epoxy to hold flexible materials like wire. The forces on the non-bonded wire concentrate at the surface of the epoxy holding the wire, and either crack the epoxy or fatigue the metal. The 'sled' is stiff enough that it's not a problem, although I deliberately weakened the bond between it and the USB drive - in case of failure, I'd like it to unglue rather than breaking things.


    Here is the present version.

    2xAAA NiMH. ~90 mA charge current. 2-stage, direct-drive and ~2.5kOhm resistor. Also contains 1GB USB flash storage.

    Boost mode is a bit dimmer than a 5mm LED direct-driven by a fairly fresh CR2032. It's quite bright for night-time navigation of my apartment and stairs.


    Contrast find-me mode: Barely visible in office lighting. Plenty visible in dim or dark areas.
    Last edited by AnAppleSnail; 12-08-2011 at 10:19 AM.
    My biggest light-hog is my camera.

  12. #12
    Flashaholic sunny_nites's Avatar
    Join Date
    Mar 2010
    Location
    USA
    Posts
    187

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Has a cool "Transformers" kind of look.

    Is the other light on your keychain the type with a small circuit for on/off rather than a hold for on.
    So many LEDs, so little time...

  13. #13
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,826

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Quote Originally Posted by sunny_nites View Post
    Has a cool "Transformers" kind of look.

    Is the other light on your keychain the type with a small circuit for on/off rather than a hold for on.
    Yes, it's a fauxton clone I got as a freebie for some web security consultation in another forum. Its cell is so nearly dead the control circuit trips after about 5 minutes.

    I want to source some smaller rechargeable cells. My calculated runtimes for one like this (with findme/boost) is ridiculously long (900 mAh at about 3 mA boost or <0.1mA estimated findme). I haven't been able to find coin NiMH cells, but 50-100mAh in such a format would be nice. Any suggestions?

    In summary, this project consumed epoxy, a 1GB USB drive, an LED, two resistors, and half of a $8 4-pack of NiMH AAAs. I think the overall build budget is less than $10 of storebought things. Anyone who is curious can knock out the build in an afternoon, depending on your epoxy.

    The only real trick is to sand the cells so the solder sticks:

    Use the +/-, not Data +/- on the USB stick. With most AAAs you'll want 33-50 ohms for charging, and 0-8kOhms for the LED.
    Epoxy two layers together at a time to avoid too much mess
    Switches are optional because I can't leave well enough alone. The non-switch Mk1 is far smaller than this Mk3.

    So if you have an old USB drive and an LED kicking around, build one! They come in as many colors as you have LED, and your red LEDs might light on just one cell.
    My biggest light-hog is my camera.

  14. #14
    Flashaholic* archimedes's Avatar
    Join Date
    Mar 2011
    Location
    CONUS, arteriosus
    Posts
    2,862

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Quote Originally Posted by AnAppleSnail View Post
    ....I want to source some smaller rechargeable cells. My calculated runtimes for one like this (with findme/boost) is ridiculously long (900 mAh at about 3 mA boost or <0.1mA estimated findme). I haven't been able to find coin NiMH cells, but 50-100mAh in such a format would be nice. Any suggestions?....
    I have a few lights and other gadgets that run on N cells, and I have found a source for a NiMN version of these (with about 500 mAh)....
    IF 2 = 1 THEN 1 = 0

  15. #15

    Default Re: Midnight Light: Inspired by Project Lamplighter

    Quote Originally Posted by AnAppleSnail View Post
    I want to source some smaller rechargeable cells. My calculated runtimes for one like this (with findme/boost) is ridiculously long (900 mAh at about 3 mA boost or <0.1mA estimated findme). I haven't been able to find coin NiMH cells, but 50-100mAh in such a format would be nice. Any suggestions?
    The old PC's used to have a little 3.6 volt NiCd battery for the BIOS RAM. Used to be made up of three button cells bonded in series, in a heat-shrunk sleeve. Very small, and should last quite a while for a single LED. I don't know if they are still available, since the new PC motherboards take only Li cells. Another idea would be to look in shops that deal with cordless phone accessories - some have compact batteries, and they are all 3.6 volt stuff.

    You could also think of using a single AA or AAA cell with a switching booster circuit, either discreet or an IC like LTC3490 from Linear Technology.

    I really like your improvising idea!

    john

  16. #16
    Flashaholic sunny_nites's Avatar
    Join Date
    Mar 2010
    Location
    USA
    Posts
    187

    Default Re: Midnight Light: Inspired by Project Lamplighter

    a 10180 LiOn is pretty small and usually good for at least 50mah. Haven't found one with a protection circuit yet though.

    I've never bought anything from these guys but they do have an interesting selection of nimh coin cells: http://www.powerstream.com/Ni-Coin-ceLL.htm
    So many LEDs, so little time...

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •