(two different methods to mount to the helmet)
Alien Eye III Bicycle Helmet Safety Light |
| The Alien Eye III safety light is my latest bicycle
night riding creation. I commute to work on my bike and I know that the
automobile drivers aren't always on the look out for cyclists when it is dark. I
have noticed that cyclists even with a good handlebar light, can be over looked by
drivers especially coming up on intersections with parked cars in the
area. The advantage of a helmet light is that it is high off the ground and
most of the time is higher than the tops of most cars. When your handle bar mounted
light is being blocked by the parked cars, the helmet mounted light can be seen over the
parked cars and other traffic. This is critical when approaching
intersections. This light does not use any type of lenses and the beam angle is
quite wide. This helps keep the light simple, small, low weight, and yet still very
effective. One disadvantage I see with typical helmet mounted lamps is that no one has discussed the potential safety hazard of having a ridged, bulky unit mounted to the front of your helmet. A bulky lamp is just the opposite of what you want mounted to an impact absorbing bicycle helmet. What happens in case of head on crash to the protection that is supposed to be provided for by the helmet when it is compromised with a bulky and strong head lamp? With my Alien Eye blinker I was always concerned about the glass that the lamp was made of, and what would happen to it in a crash situation. The original Alien Eye also has a very strong aluminum casting, and was already too bright for street use.
Alien Eye I Alien Eye II Blinker Alien Eye III With these thoughts of safety in mind, and just wanting to play around with the newer inexpensive flat G4 LED assemblies, I cobbled together the Alien Eye III safety head light. To keep the size and mass down, I decided not to integrate a blinker circuit in the light. The blinker extends battery life and improves visibility to drivers, but complicates the packaging of the lamp. A blinker circuit could be made and plugged in line at the battery pack end. The light with cable and two part epoxy mount weights just 15 grams. This light is not intended to provide lighting for the cyclist to see but rather provide a low intensity wide angle light so that the cyclist can be seen by pedestrians and automobiles. This keeps the light very simple, light weight, low cost and very easy to build. The light is very small (23 mm in diameter and 7 mm thick) and not mounted with a ridged system. There is no glass or bulky metal parts. In an emergency the light can easily "break away". This why I call it the "safety light".
I bought the LED from Reichelt in Germany for 4.95 Euro You can find similar ones on Ebay. To weather proof the LED I mounted it in a 23 mm coin holder. (Air tite, Leuchtturm) You can buy these at your local coin shop for 50 cents or so. The thickness of this LED was reduced to fit in the coin holder by removing the white plastic case and the bridge rectifier soldered on the backside. The rectifier connections were then bridged with solid pre-tinned wire. Since the LED will be driven by batteries (DC), the rectifier is not needed as long as you keep the polarity straight. If you mess up the polarity then you will burn out the LED! Materials for the project: LED, coin holder, epoxy, two part epoxy putty, shrink tubing, wire, and double sided Velcro connector, plastic wrap. Cost. about 7 Euro.
Apply a piece of tape to the LED side of your light to protect it from smudges from the two piece epoxy putty.
With course sand paper, lightly sand the back of the light to help the putty stick better. Form a wedge in the epoxy putty it on the Velcro. Stick the light on the other side. Correct the form of the putty and fix the horizontal angle and side to side. After curing, remove the tape from the lamp face. When wrapping the Velcro in the helmet, then the "hook" side should be on the outside.
You can mount the batteries in a back pack, in your jersey. I have a small 12V Li Ion battery that can mount towards the back of the helmet, more out of harms way from a head on crash. Since all of the LED are distributed it does not get too warm in anyone place to melt the plastic of the coin holder.
Alternative Mounting to the Helmet:
Punch 3 mm hole in the middle of a piece 60x10 mm
Velcro. The 19 mm Velcro is wrapped around the helmet with the "hook" side touching the helmet.
Stick the 10 mm Velcro with female button snap to the
19 mm Velcro. The light is turned on simply by plugging it in the
battery pack. |
The LED is a G4 LED, 12V, 1 ± 0.2 Watt, cool white, 15 SMD LED,
35 lumens, Ø 23mm, 8 mm thick (will be reduced to about 4 mm be removing the rectifier),
with 120º beam angle.
Assembly
process: 
Removable
Mount for the Helmet: (see also new alterntive below) 
The next
step is to use two part epoxy putty to make a custom shaped wedge to get the angle of the
lamp horizontal with the wearing position of your helmet. 
Mix the
two part epoxy putty and apply it to the "hook" side of the 23 mm piece of
Velcro. The epoxy will stick better to the "hook" side than to the
loop side.
If you the
two part epoxy does not stick well to the Velcro you can also attach it with a few very
small tapered screws. 
