Machines > DIY Light Project
Since I commute
to work everyday, I wanted my bike to be lit up like a christmas tree
so when I get run over dead, people will know, without question, it
was the other guy's fault.
The lights on my bike were pretty pathetic - they worked great back
when you were hiding from Nazis flying overhead looking for things
to drop bombs on, but 3 watts @ 6 volts doesn't do much during the
commute hour. Hell, even with three 100 watt bulbs at 120 volts I
can't find my goddam shoes in the middle of the room.
recently, there just was not a good solution for bike lighting that
didn't involve big batteries or long extension cords. LEDs, those
little lights that annoy the hell out of you when you are trying to
sleep, are very, very, low amps, and just in the past year or so,
have become amazingly bright. They are really well suited to the low
current available on a bike. If you have ever used an LED flashlight,
then you would have some idea - and those flashlights are using old
technology. The new LEDs are ten times as bright, and as you will
see, they are cheap enough and low-powered enough to use ten or twenty
- not just the four or six that your stingy flashlight uses.
This is a quickie
diagram (not to scale...) of my set up:
Search on eBay
for 'super bright white LED ' and then find some that are 10,000 mcd
or more. I paid 30 cents each, and bought 50 at a time. They are cheaper
if you buy them straight form China, but I always look around for
someone in the US who sells in bulk.
I used a 100k resistor on my first project, as diagramed above, but
since then I got lazy and haven't bothered. So far, after months of
commuting, my bike hasn't burst into flames and no bulbs have gone
dead. But YMMV, so you can figure out exactly what applies to your
set up here:
I bought them at Radio Shack. Everywhere here, I quote Radio Shack
stock numbers, but they are total crap merchants and I in no way endorse
shopping there. They are creepy assholes who take advantage of technologically
ignorant people. You would be better off to buy online from one of
the millions of electronic stores. That said, we are only talking
about $5 worth of stuff, so make sure you annoy the guys there for
at least an hour getting this stuff together for you. DO NOT buy your
LEDs there. They have dim, overpriced LEDs there. THEY WILL NOT WORK.
I used a 100VDC
1500mA bridge rectifier, Radio SHack # 276-1152, which is about the
size of a 1/8 slice of a pencil eraser with four wires sticking out
of it. I don't know what the hell that rating means, but I tried a
smaller rectifier and it didn't work so I tried this one second and
it did work.
I got a little hobby circuit board, about 1 inch square.(#276-150)
THe LEDs had two leads, the longer of which HAS to go to positive
electricity, or the LED burns out instantly. ALl the positives and
all the negatives can be soldered together. The Bridge Rectifier has
a + on one of the leads, and that wire gets connected to the resistors
that connect to the LEDs. The wire OPPOSITE, not next to the + wire,
gets connected to the neg lead off the LEDs. The other two wires from
the bridge rectifier get hooked up to the generator in any order.
I am using some
~20,000 MCD LEDs that require about 3.6 Volts. But don't stress the
specs on your LEDs - the more volts you put thru the brighter the
light, and the suppliers/manufacturers/eBay Sellers just slap whatever
rating they want on the damn thing, so no sense stressing the numbers.
Please note that
the LEDs have a long and a short lead. THe long is POSITIVE. I snip
the negative leads short to exaggerate the difference. Nothing is
a bigger bummer to have 19 LEDs and one dark one in the middle.
note, that I am using a big old soldering gun that isn't really meant
for circuit board work, so my solders are pretty messy. But we aren't
painting famous pictures here, we are connecting two wires. And even
if we were painting famous pictures, we're gonna wrap them with electrical
tape at some point so no one can see your shoddy work anyway.
the circuit board. I start with a row of four. Plot them out so you
have room on the board. I am using 16 here, but LEDs are cheap and
you can use lots more. For my daughter's bike, I used 25 and it runs
off a cheap sidewall bottle generator. Plenty of juice!
Before you say
anything, I know I have the circuit board backwards - the shiney copper
rings are supposed to be on the back for you to solder to, but my
big SUV of a solder gun can't do solders in such close quarters, so
I flip the board over backwards to prevent shorts.
Bend the Positive
wires out of the way, and bend the Negs all the way over. This should
hold the lights in firmly while you work.
One by one, bend
each Neg wire around the guy next to it, and cut off the excess wire.
I run all the Positive wires to one side, and the Negs to the other.
Here is the first
row all cut off and sodered all neat-like. Note I marked the Positive
and Neg side, since otherwise I would forget after the first solder.
all your rows done, and then you wire all the positives together on
one side, and all the negs together on the right. At this point, you
can run the light of either 2 or 3 AAA batteries, or the output of
a Dynahub or bottle generator. When you run the 6V thru the Bridge
Rectifier, it gets knocked down to 4.8V or something like that. Close
enough for Government work!
Thru the whole
system, on every component, I strip about a half inch off all the
positive leads, and just a little tiny bit of the Negs, as you can
see in this picture.
from the front, look how nice it looks! We can fix that later.
is what we have, which is all the bulbs wired in parallel. Each row
is wired in parallel, and the the four rows are wired together also
can also do this, if you can only find LEDs rated at 2V or 3V. Each
row is wired in parallel, but then one row is wired in series with
the next. Note how the Neg from row one is connected to the Positive
in row two. Then I wire the two series in parallel. THis way works
with 4 AA or AAA batteries, or off a Dynahub (but it won't be wuite
as bright as the 3.6V lights in parallel.
There! That should
about confuse anyone! Now go to the bike store and buy yourself a
$300 Quartz halogen bike light, you cheapskate.
a little clip there, and little clip there, and the board is roundy-er!
the back up in electrical tape.
feed the wires thru where the incandecent bulb screws in.
This is a non-destructive
way to adapt an old light. You could also take a dremel tool and cut
the backoff the reflector for the light to fit from the back. That
looks a lot better from the front. I'm too lazy today to do that.
little duct tape to hold it in place...
it so it looks halfway decent.
Now the reflector
fits back in the shell, and I snake the wires out the back and connect
them either to a battery pack or a generator/bridge rectifier/resister
set up. I connect everything together with little wire nuts so I
can change my mind later with out cutting wires.
Here is a diagram
of the Dynohub component:
on the bridge rectifier is clearly marked. The neg is directly opposite,
and the other two are interchangable. Use one big resister, instead
of a zillion for each LED. Probably maybe a 10K, 5 watt resister
ought to do it, but you might want to use the calculator to be sure.
Or do what I do, and screw the resister.
I take the bridge
rectifier and sheild the leads with some little bits of heat tubing,
and connect it directly to the Dynahub, and then wirenut the wiring
to the other two leads. No one notices the Rectifier down there,
and it's easy to get to for making changes. You can also stash it
in the light housing, along with some rechargable batterries if
you want to get fancy.
If you really
want to get fancy, you can wire up some rechargable batteries on
a double-pole center-off switch with a big old diode and hook that
up too. With the diode on one side of the switch, you have three
choices: ON will run the lights all the time, and if you go fast
enough, the batteries will charge from excess electricity. OFF will
run the lights just off the generator and save the batteries for
night time. ON thru the diode will run the lights JUST off the generator,
but excess electricity will still recharge the batteries.
A WORD OF WARNING: I don't go fast. If you go fast, all of the time,
you might want to be a little more careful on matching the voltages
on everything. I have found that after a couple weeks, my batteries
can't keep up and I have to pull them out and recharge them overnight
if I want the lights to be full brightness at a stoplight. If I
went fast all the time, in theory, the batteries would eventually
explode instead of slowly discharging as they do. (Because when
you go fast, more electricity than the LEDs need is produced, and
the excess goes to recharge the batteries...) What I do currently,
is shut the batteries off on short runs (such as my commute) and
turn them on with the diode on long 10+ mile rides. This way, I
hope, the batteries will always be fully charged when I need them
at night. So far, it has worked. Make sure you hook up the diode
the correct direction.