Now you guys out there must bear with me on account that I ain't got no decent photo camera and I use my good ol' cell phone's camera, which I think helps me a lot even though the pictures ain't what I'd like to be presenting on this here place.
Alrighty, let's begin with a little background. I ride my bike to work everyday because it's about 15 minutes as the crow flies to get to my workplace, but I ride early in the morning or somedays late at night, because I get my shifts changed usually on weekends. Now I ride across some mighty dark places and it's actually a street with 2 lanes for each way, where big ol' buses and cars tend to travel fast because it's a road that is usually deserted on those hours of the day and no police patrols the area during that time too, and ain't nobody reportin' anything 'cause it's an industrial area (nobody lives around and security guards don't care).
Concerned about my safety, I decided to start off a project to put some light on my bicycle, but I wanted something bright and economic on power consumption, so I opted out for them LED thingamajigs. For powering those little things I had a Ni-Cd battery pack from an RC car from my brother, which didn't work properly and he didn't care about it and never wante to take to the store for replacement (he was 3 about a couple of years ago when the car was bought).
About the LEDs, I was told by the guy at the shop that the ones he sold me could boost up to 7000 mcd each. You can use the ones that best match your likes and needs, but I'm making this instructable for the following specs:
Source voltage: 9Vcc
Voltage across LED: 3.2 Vcc
LED current: 100 mA
If you decide to go for some higher-rate LEDs, you have to change resistor values to match them to the LEDs of your choice. To get to know which resistors should you use, get the technical info about them and go to www.ledcalc.com, you enter the info about your LEDs there and the calculator tells you what resistors are good for your array, as well as options to connect them.
Also, all the instructions are based on the installation on a Specialized mountain bike.
'Nuff background. Here's the parts list:
- 3x Mega-bright 5mm LEDs
- 3x 68 ohm @ 1 Watt resistors
- 9.6v rechargeable RC car battery pack
- 16 or 14 AWG wire or any wire that's not so thin but not too thick, twice as long as your bike. Preferrably get red and black wires, so you can color-code the leads going from the battery to the lamp.
- A case in which we're goin' to stuff all these things in. In my case, I used an ol' an' crappy SNES game cartridge.
- Soldering iron and its respective stuff
- If you're going for the SNES cartridge, you'll need a GAMEBIT screwdriver or make your own tool to open the cartridge.
- Drill with a drill bit that matches the diameter of your LEDs. Mine were 5mm so, I used a 13/64 drill bit (can't tell if it's 3/64 or 13/64 because the drill bit is kinda rusty at the insertion area and couldn't read the value that well)
- Hot glue gun
- Zip ties
- Insulating (electrical) tape and/or heatshrink tube
If youre still goin' for the SNES cartridge, also get:
- A small metal bracket or strip, preferably from thick, strong but bendable metal. (Suggestion: you can use those included with car stereos or power door lock actuators)
- A couple of small bolts and nuts (your choice here)
- A hose clamp big enough to go around the steering handle.
I ain't responsible for your outcome of this instructable or if you got burned with the soldering iron or whatever happens to you or your stuff. This here's just an idea to make it the same or do your very own.
Step 1: Drillin' the Holes
When using the SNES cartridge, try fo find a place in which you can picture an imaginary wide rectangle on, preferably where edges can help you as a guide, this is to be able to make measurements to get the LED separated evenly and aranged on a straight line. OK, so I measured the middle part of the SNES cart with the ruler from the inside of the cartridge. In order to get the LEDs to be separated evenly, just divide the total length by 1 more time than the amount of LEDs you're using. In this case, I divided it into 4, because I need 3 separations to get 4 chunks of space, being the LED the separation point. Don't get it? Ok..
Draw a rectangle. Draw 3 vertical lines across the width of the rectangle, regardless of the distance between each other. How many rectangles do you have now? So if you want the 3 vertical lines to be separated the exact same distance, you measure the total width of the rectangle and divide it into 4 and you get the measure for the 3 lines to be separated the same distance. Still don't get it? Go ask an elementary school math teacher.
For those who got it, you'd be probably asking: why all this explanation?, you just would have said: divide the total measure in half, then get the two halves split equally in two. Remember not all the numbers can be divided into 2 with a round number that is a pair as a result. What if you wanted to put 5 LEDs?
When making the markings, draw a vertical line following pretty much as the ones on the ruler. To get the LEDs arranged on a straight line, just measure the half point of the imaginary rectangle's height at the very point where you made the separation marking, so you end up drawing "+" symbols, with the center of those symbols marking the exact location of the LED.
Make your measurements as prescribed and drill the holes carefully. Then, glue the LEDs in place with the good ol' hot glue.
Step 2: Wiring the LEDs
2 LEDs in series using a single 27 ohm @ 1/2 watt resistor
1 LED in parallel using a single 68 ohm @ 1 watt resistor.
I soldered the LEDs like that, but found out that the 2 LEDs with the 27 ohm resistor were slightly-but-easily-noticeable dimmer than the single LED with the 68 ohm resistor. Since I bought more components than needed, I decided to go for the 3 LEDs to go in parallel with a 68 ohm resistor on each one, for maximum brightness. LEDs can be wired in several ways in order to save space and money, but you have to fiddle around to get what you want. Google on how you can get this done or follow the very same steps as I am. You'll have good results with the components I used.
Go and solder them LEDs with the appropriate resistor for your case. If you're a rookie at soldering, try not to spend too much time touching the LED leads with the soldering iron. Believe it or not, you'll fry the LEDs and the resistors.
Solder wires long enough to reach the place you'll be installing/placing the battery on.
Once you're done, try to glue the wires and anything that seems loose to the body of the cartridge.
NOTE: Make sure you match the LED's polarity, otherwise they won't turn on. Resistors are preferably soldered at the positive lead, but if you solder them at the negative lead, it won't affect the result. Just watch that positive wire goes to positive on the LED and negative to negative.
Step 3: Test
Step 4: Installation
First off, you want to drill a hole on the top center and another one on the bottom center on the back of the rear cover of the cartridge. If the metal strip I told you about is not pre-drilled, measure and drill holes correspondingly on it, so you can bolt the back of the cartridge to it. DO NOT ATTEMPT TO ASSEMBLE THE CARTRIDGE UNTIL YOU'RE DONE CLAMPING ITS BACK ON THE BIKE.
You want to bolt the metal strip so it looks like an upside-down SNES cartridge lollipop. We want to bend the top at the height of the center of the cartridge's top shoulder, so it makes some kind of "7".
Use the hose clamp to bolt the "7" shaped metal strip (with the back cover of the catridge already bolted to it) it to the tube that connects the steering shaft to the handle of the bike. Bend the "7" so the cartridge tilts to your desired height, but just make a preview adjustment, as you need the lamp to adjust it correctly.
Step 5: Assembly
Figure out where are you installing the battery and plan a route for the wire. Cover all the wire with insulating tape or heatshrink tubing or anything else you'd like to cover them with and try to make a clean job by trying to hide any wires other than the brake and gear shift cables once done with the tape. Remember to have enough cable hanging from the light as it tends to be pulled when turning left or right (repending on which side the cables are protruding from the cartridge or the casing you're using. In my case, the cables were sitcking out from the left side)
I used zip ties to keep the wire hidden below the top tube of the bike's frame.
Step 6: Project Finished
I've attached some pictures testing the light on dark conditions. Sorry for the last two creepy, Silent-Hill-esque pictures, but again, my phone's photo camera is not that good at taking pictures on dark conditions.
Any questions, comments, error reports are welcome.