Headlight Plans

Disclaimer: These pages are for educational purposes only. Although these are plans for "do-it-yourself" headlights, I take no responsibility for any damage that arises from viewing, following, or modifying the contents of these pages.

Update 12/2003: Only thumbnails are available for the pictures. All the large pictures were lost in a harddrive crash. Sorry!

One - Battery and Charger

I bought my 12V 7Ah lead-acid gel-type battery and charger from Mouser Electronics. I was able to order on-line and have it shipped to me via UPS. The package arrived in just a few days. I recommend using Mouser, they filled my small order quickly and professionally.

The charger is a 12V 0.8A that charges the battery using a fast charge, but won't destroy the battery because it switches to a float cycle. Below is a picture of the battery with some of the wiring on top.

I added a fuse for protection against overcurrents. Since the battery is 12V,and the light 20W, I needed to send 20W/12V = 1.67A down the line, so I picked a 3A fuse. I figured that would probably protect the battery from any major short circuit. I picked up the fuse at Radio Shack (an electronics parts store).

Two - Headlight

I went to the local hardware store (Eagle Hardware and Garden) and browsed through their low-voltage lawn lighting section. I was able to find a 12V, 20W Halogen floodlight by Malibu (with a metal housing and a ground stake). I was looking for a spot light, but I couldn't seem to locate one. The headlight cost about $10 and comes with a screw-on ground stake, so it can stand up on its own.

I cut the connectors off the wire and removed the ground stake. Where the ground stake used to screw on, there were some threads. I matched these up with some 1/2" diameter PVC pipe, so Ifigured I could make a mounting out of PVC. Below is a picture of the headlight mounted on the handlebars of my bike.

Update 9/2000: I have purchased a new bulb to replace a burnt out one. The new bulb is similar to the old one--a 12V, 20W halogen, but it's much brighter than my previous one because it comes with a better reflector. It's still not as tight of focus as I'd like, but it's certainly bright!

Three - Headlight Mounting

After finding out that the light would screw onto a threaded male 1/2" PVC pipe fitting, I went to the PVC section. I found a 1" non-threaded by1/2" threaded T (the 1" is the main through section, the 1/2" is the part where the pipe intersects). I got a 1/2" threaded male to 1/2" threaded male adapter, which fit nicely into the T intersection and the light. Thus I formed the main mounting for the headlight. Below is a picture of the mounting without the headlight attached.

Update 9/2000: I now mount the headlight using an L-bracket attached to my front rack. The hold is a lot better and it looks good too.

Old New

In order to get the T onto my handlebars, I had to cut out the bottom quarter. I used a dremmel tool (a high-speed rotating cutter), although a hacksaw would probably have cut cleaner. I cut a small piece of rag cloth (from a sock) to go underneath the T--to spare my handlebars from abrasion. I then slid the Tover the handlebars (it took me a few times to cut enough away to actually slide it on). Finally, I fastened one side of the T to thehandlebars using a pipe clamp. This keeps the headlight from rocking back and forth.

Four - Wiring/Switches

I used many automotive quick disconnects to get my system together. I probably could have gotten away with less, especially if I had any skill with the crimper at all. I should have purchased a good crimper before trying this. The picture below shows some of the wiring, switches and a "Y" that I made.

Update 10/2000: Now that I have my motor, I use my motor battery to power the headlights. This eliminates a little extra weight and makes it easier to use, since I don't have to charge two batteries. The plug to the battery is just a microphone plug. Since the motor battery was 24V and I'm using 12V on the battery, I needed a converter. I picked up Willie Hunt's LVR3E, which is a voltage regulator. The electronics fit inside a 35mm film canister and are shown in the picture below. The film canister is mounted on in my main triangle, on the down tube right next to the fork.

Wiring Plug to 24V Switch

I used male plugs for the positive and female plugs for the negative. This was so that I would never reverse a connection, but in retrospect I might have done it differently. I say this because having the two connectors of opposite genders makes it very easy to accidentally plug one into the other, causing a very ugly short circuit. I think if I were to do it over again, I would use either different types of connectors for positive and negative, or I would at least paint the connections to indicate the differences.

I picked components that could withstand at least 3A. I figured I needed 18 gauge wire or thicker (smaller gauge = thicker wire). I also needed to get at least 3A switches. I wanted a rating of about twice what I expected to see during normal operation. I used 16 gauge lamp cord, which Eagle (the hardware store) gladly cut for me. I believe I used 20 feet, but a lot of that was mistakes. At least it was cheap!

Five - Battery Mounting

I mount my battery to my rear rack by placing it inside a walkman-case. I went to Fred Meyer (an all-purpose store which includes electronics) specifically looking for something to hold the battery,and I found this walkman case with a waist strap. To fit the battery, I cut away an interior compartment. It's a tight fit, but it works very well. To mount it, I cut away most of the waist strap until there was just enough to go around my rear rack. I snap the strap together underneath the rack, and it stays put.

Update 9/2000: Since breaking one of the straps on the walkman case, I have been forced to put the battery in one of my panniers. However, with my new front rack, the battery location is a lot closer to the headlight so I don't need so much wiring.

Rear rack mounting

The above is a picture of the back of my bike. The battery is in its normal position, although I left the strap unbuckled to show where it fits.

Price List
Item Description Price (US$)
Headlight Malibu 20W floodlight, metal housing with ground stake $12 HW
PVC T 1" non-threaded (sides) by 1/2" threaded (top of T) $1 HW
PVC adapter Male-male 1/2" gray $0.50 HW
Pipe clamp 1 3/4" (1.75") pipe clamp (If I remember right) $0.50 HW
Battery PowerSonic sealed lead-acid battery gel-type PS-1270 12V 7Ah $18 EL
Charger PowerSonic battery charger 12V 0.8A $40 EL
Switches Two rotary dial 3A switches $3 HW
Wire 20ft 16 gauge black lamp cord $4 HW
Inline fuse case 3A inline case $2 RS
Walkman case Found at Fred Meyers, cut out insides $5 FM
Quick disconnects 5 packages of 6 pair (I know I wasted a lot!) $10 AU
L-bracket Twisted using a pair of pliers $2 HW
Legend: AU - Auto parts store, EL - Mouser electronics, FM - Fred Meyer, HW - Hardware store, RS - Radio Shack
Tools & extras that I already had: rags (for under the PVC T), crimping tool (to get quick disconnects connected to the wire), zip ties (to tie down wire along bike frame), screwdriver (for tightening pipe clamp), scissors (to cut out insides of walkman case)