My unnecissarily complicated lighting system.

Discussion in 'Motorized Bicycle General Discussion' started by TheE, May 21, 2010.

  1. TheE

    TheE New Member

    Joined:
    Jun 26, 2009
    Messages:
    187
    Likes Received:
    0
    Title pretty much says it all. Sure, I could have just bought a decently powered headlight that runs on 3x AA batteries and call it a day, but that would've been too easy :p Anywho, here's what I cooked up:

    Battery: I had a 12V SLA battery lying around that I got at a surplus store a while back, I figured that it would work well since it was meant for deep cycle use and has a 7 AH capacity.

    http://img196.imageshack.us/img196/5005/img0104kn.th.jpg

    The battery is mounted in a bracket I made out of some metal from an old computer PSU and some steel strapping they sell that the hardware store, boy that stuff is really useful. The rear reflector is held on with some freakishly strong double-sided tape. Mabye one day I'll put an LED light there too.

    Generator: Well, something has to keep that battery charged. The dynamo generators they sell on ebay were around $30. I figured it couldn't be too hard to make your own, so I took a decently-sized DC motor and pushed a small LEGO wheel onto the shaft. Using a bench grinder to spin the shaft, it kicked out about 40V unloaded.

    Trying to connect a load to it and take proper measurements proved to be a bit of a challenge, so I just made a little regulator for it with an LM317 to keep it under 15V. I figured it wouldn't kick out enough power to overheat the IC, and if it did, the IC has a built-in thermal shutdown. I bolted a heatsink onto it anyways and put the assembly in some ABS pipe for protection:

    [​IMG]


    The output of the LM317 is connected to the battery through a 10 ohm resistor, I'll spare you the fancy math, but it keeps the current to the battery under 0.5A.

    Let there be light! Now all I needed was a headlight to run off the battery. I found a 21 LED flashlight at the surplus store for $6. Problem was, it was designed to run off 3x AAA batteries, which is about 5V max, and my battery is 12V =/

    Here's a picture of the light:

    [​IMG]


    It came in a camo green. Since my bike is mostly black, I painted it black. It's the cheesy camo so it wouldn't even look good on one of those army bikes I see around the forum.

    The solution to the battery problem was of course another regulator. But burning off 7V @ 750mA in a linear regulator (7805) would get warm to say the least, and it ain't too efficient either.

    That's where the switching regulator comes in:
    [​IMG]


    This little fella can drop 12V to 5V and source up to 1A without breaking a sweat. In addition, I was able to use a variable resistor so I could adjust the brightness of the headlight. Of course, the price for all this is that a switching supply is a fair bit more complex than a linear one. Oh well, making your own PCBs has a certain zen to it.

    And in the end, success! ...at least so far.

    [​IMG]



    I still have to do some testing to see how rugged this setup is. All I know is it's certainly unique!
     
    #1 TheE, May 21, 2010
    Last edited: May 21, 2010
  2. biken stins

    biken stins New Member

    Joined:
    Jul 11, 2008
    Messages:
    156
    Likes Received:
    0
    Good job.
    What is the expected life span ?
    Are you able to run a tail light off the same set up ?
     
  3. obd1kenobi

    obd1kenobi New Member

    Joined:
    Dec 28, 2009
    Messages:
    79
    Likes Received:
    0
    Nice! I like the variable resistor option...
     
  4. TheE

    TheE New Member

    Joined:
    Jun 26, 2009
    Messages:
    187
    Likes Received:
    0
    I haven't the faintest idea as to the lifespan, I'm hoping to do some testing soon to see how well it holds up. Either way, everything is modular and thus easy to replace :D

    I could run a taillight off the same setup, but I'd probably build it completely from scratch so I wouldn't need a third regulator, heh.
     
    #4 TheE, May 22, 2010
    Last edited: May 22, 2010
  5. diceman2004

    diceman2004 New Member

    Joined:
    Aug 26, 2009
    Messages:
    568
    Likes Received:
    0
    sweet , nice job with the regulator idea .
    i,m rumming 2 ( 3volt leds , setup at 6 volts ) - off a 9volt battery
    so far so good .

    i have found you can overvolt led,s a bit , but if you go too much , it can dammage the led,s and then they don,t run off the lower voltage they were rated for any more .
     
  6. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

    Joined:
    Mar 20, 2008
    Messages:
    6,169
    Likes Received:
    18
    I use those same LED flash lights for bike head lights!
    It seems way too easy to just replace the AAA batteries every month or so & have less to go wrong, & less clutter on the bike... :rolleyes:
     
  7. Patr1ck

    Patr1ck New Member

    Joined:
    Apr 15, 2010
    Messages:
    213
    Likes Received:
    0
  8. TheE

    TheE New Member

    Joined:
    Jun 26, 2009
    Messages:
    187
    Likes Received:
    0
    Yeah, I looked at those mini-gens too. I like how they draw power off the magneto so you don't have to be moving...It just sucks that they cost more than half the price of the engine itself.

    I wonder if you can build one yourself...can't be that hard...
     
  9. Retmachinist

    Retmachinist New Member

    Joined:
    Oct 21, 2008
    Messages:
    637
    Likes Received:
    0
    I use the 12v SLA battery, with a 12 l.e.d. headlight bulb, 3 l.e.d. tail light bulb, and 12v motorcycle horn. I just charge the battery on the bench every couple months.

    John
     
  10. Junster

    Junster New Member

    Joined:
    Jun 2, 2009
    Messages:
    445
    Likes Received:
    0
    Hobby Shops sell sub-c ni-cad batteries for r/c cars. They are just the right size to make a end to end straight battery pack that will slip inside your seat tube. Slip the cells in a fat piece of shrink tubing after you wire it and tie something to it to pull it out if you need to. The draw from bike lights makes the pack very long lasting. If you have a frame with a fatter seat tube you can also rob cells from a old rechargeable drill pack and make one that fits inside the seat post itself.
     
    #10 Junster, May 23, 2010
    Last edited: May 23, 2010
  11. Goat Herder

    Goat Herder Gutter Rider

    Joined:
    Apr 28, 2008
    Messages:
    6,250
    Likes Received:
    2

    Seat post battery storage! Thats a sweet Idea. Had not thought of that yet. Thats what I love about this forum! Will have to pack them in well for rattle sounds do able though.
     
    #11 Goat Herder, May 23, 2010
    Last edited: May 23, 2010
  12. TheE

    TheE New Member

    Joined:
    Jun 26, 2009
    Messages:
    187
    Likes Received:
    0
    Hah, hiding batteries in the seat tube, now there's an idea. You could probably just slide a bunch of NiMH C cells down the tube and they'd connect themselves in series for ya.

    Either way, I'm just glad I no longer have that SLA battery sitting on my desk, taunting me to do something with it. I'll probably wait till it goes bust before I start looking for a stealthier solution.
     
    #12 TheE, May 23, 2010
    Last edited: May 23, 2010

Share This Page