Low profile 3.6 V Bike Helmet LED light

Bicycle Helmet Safety Light "Atom"
This light is my latest night riding creation. It uses a standard 3.7V LEDs with integrated heat sink. Each LED (front and rear) puts out about 25 Lumens, which is bright enough to be seen by drivers, or pedestrians when riding your bike at night. This light is not conceived to be a light powerful enough to replace a regular bike head light. It does however have enough light to illuminate the speedometer, and the immediate area. With good 2500 mAh batteries the lamps should burn at least 8-10 hours before recharging is needed. My new design is smaller than all my previous designs. It is powered by 3 x AA standard rechargeable batteries. The previous designs were 12 V and the small battery was always a problem. This design is improved since it has an integrated red tail light on the battery clip. To turn on the lights, just press the clip on the battery pack. The 3 AA batteries, in a standard plastic holder, are strapped to the helmet with double sided Velcro. Since the LED is a 3.7V LED, and the battery pack is 3.6V, there is no electronic circuitry or current limiting resistors to mess with. The three rechargeable batteries will not exceed the LED's capacity. As the batteries lose strength the light intensity will also decrease. You can gage the remaining battery life on the light's intensity. The light should not be used with 1.5V non-rechargeable batteries, without a current limiting resistor as the total voltage of 3 batteries will be 4.5 V and is enough to burn out the LED. Background: 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, and especially early in the morning. This time of year it is dark both going to work and coming home. My ride is completely in the dark this time of year. I have noticed that when I ride, even with a good handlebar light, I 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 roofs of the 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 the other traffic. This is critical. My experience is so positive with this concept that I will not go out in the dark without a helmet light anymore. The near misses I had before with cars don't happen anymore. I have the sense that the drivers are giving me more room since they have recognized my presence sooner. This light does not use any type of lens and the beam angle is quite wide. This helps keep the light simple to build yet still effective since it can be seen from a wide angle by drivers. 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 ridged head lamp? "Atom" Safety Light II Safety Light I Alien Eye I Alien Eye II Blinker The light and battery attaches quickly and effortlessly to the helmet. The light is very small (10 mm in diameter and 7 mm thick) and is simply strapped to the helmet with double sided Velcro band. There is no glass or bulky metal parts. In an emergency the light can easily "break away". The lamp is held to the helmet using a magnet. The magnet sticks to a small flat head screw, screwed in the polystyrene foam of the helmet. The light with cable and niodinium magnet mount weights just 13 grams. The battery pack weights 109 grams. The LED The LED is a Avago "Moonstone" ASMT-MW62 1/2 W 3.7V, which is compact, flat and perfect for mounting on the magnet. Moonstone LED Conrad 180869-62 1.80 € I have found no need to weather proof the LED. It is sealed and I have ridden in the rain numerous times with it. Water does not affect it. Materials for the project: 2x ASMT-MW62 1/2 W 3.7V LEDs, a few grams of two part epoxy putty, shrink tubing 2x 2.4Ø x 10 mm, 2x pcs 0.4 mm tinned solid wire, double sided Velcro (19 mmx280), 300 mm two conductor cable, Battery holder 3x AA, 9V battery clip with removable cover. 77 mm long section of a mtn bike inner tube, small wood screw, small magnet (10 mm or so), 3x AAA batteries. Red plastic from a old reflector. I will show you below how to fabricate your own red lens for the tail light using red plastic from an old reflector. Assembly process:
Strip the leads of the cable and tin them. Slip the shrink tubing over each lead	Solder the "+" lead to the terminal with the "o" next to it. Solder the other terminal.
Shrink the tubing over the connection	Affix the LED to the magnet with the two part epoxy putty
Fabricating the lens A red LED is available but in a 1 W version. At the time it was not available at Conrad. I have since ordered two to play with. The red LED costs twice as much as the 1/2 W led and would need a current limiting resistor. It should be possible to integrate that LED with a 10 ohm resistor. The LED has a very intense light. A thick lens is needed to keep the red color from being washed out. With the two washers shown below, the lens comes out twice as thick (about 3 mm) as with one washer. To make the lens you will need 2 washers with about a 6.5 mm inside diameter and one with a 5 mm inside diameter, two pieces of flat metal (I use aluminum) and a wrench socket with an opening > 6.5 mm.
As mold for the red lens, glue two washers concentrically together. 5 mm ID and 6.5 mm ID	Se the washers on a flat piece of metal on a heating element. Here I used a stove. Place a small piece of red plastic on form. The finished lens only weights 0,1 gram.
With medium heat melt the plastic into the form. You can use a knife to push the material in the form.	With the knife, cut away excess material
Remove form and plate from the stove. Quickly take a second piece of flat metal and press the plastic flat. Cool form under water.	Flip the form over so the small diameter is down. Place the form over a wrench socket and punch the red lens out of the form.
Red lens separated from the form with rough edges.	To remove the rough edges, use a duplicate washer with 6.5 mm ID and set the lens in it.
Flip the lens/washer over and punch the lens out again shearing off the excess and rough edges.	Finished lens.
	Again on the heated stove, place the lens in the single washer on medium heat.
When the plastic is heated up, quickly remove the plate and plastic from the stove and lightly press the LED onto the lens to match the inside diameter of the LED. Cool it all under water.	Finished lens shown mated with LED diameter. If the lens is loose you can glue it with two part epoxy to the LED.
Connector Assembly The 9V clip connector has a removable cover. I use this connector for all my lamps with battery holders since it can be soldered and is sturdier than the plastic foil type 9V connectors. Here is the link on how to prepare the connector to the state shown below. 9V connector assembly
Solder the other end of the cable to the battery clip. Solder the solid tinned wire as shown.	Assemble the battery clip cap. Solder the wire to the appropriate polarity terminal on the LED.
Encapsulate the LED and connections in the two part epoxy putty. When the putty is semi-hard you can smooth it out with light finger strokes.	Load batteries in the holder. Slip into the mtn bike inner tube. Press connector on battery.
View from behind. Lamp left (MP3 player right)	Screw the flat head screw into the helmet. Clip magnet to small screw.
View from the front.
The light is turned on simply by clipping it on the battery pack with the 9V clip. The 3.6 V battery pack is in a bicycle inner tube and, velcroed to the helmet on the back side.