Helmet light with front, rear, and side LEDs for cycling visibility and safety.
- Forward facing 15° amber LED
- Rear facing 30° red LED
- Side facing 45° amber LEDs
- Controlled with a single button
- Remembers its last used setting
- Strobe patterns: Daytime strobe, fade, blink-blink-blink-blink-low, battery saver
- LED dims when the battery is low
Step 1: Materials
- 2 - 18650 LiFePO4 cells (May substitute with 5 or 6 AA NiMH cells)
- 1 - 2 cell 18650 battery holder
- Enclosure (A waterproof 18650 battery holder was used)
- Copper cladded board for etching
- Ferric chloride
- Plastic strips (You may cut them from plastic bottles)
- Hot glue
- 22 AWG wires
- Cable ties
- Aluminum bars
- 4" screw
- #6-32 screws
- 5 - amber 3W LEDs
- 1 - red 3W LED
- 1 - 15 degree LED lens with holder
- 1 - 30 degree LED lens with holder
- 4 - 45 degree LED lenses with holders
- Electronic components (Refer to the BOM)
Note: For safety, LiFePO4 or NiMH cells should be used. If 3.7V Li-ion cells are used, they should have a protection chip.
Step 2: Rear LED Heatsink
- Cut the aluminum.
- Drill holes on the flat for attaching two aluminum angles on each side and the rear LED. The four 45 degree facing LEDs would attach to the angles.
- Make threaded holes on the edges of the four angles which would hold the side LEDs.
Step 3: Front LED Heatsink
Drill and tap four holes on the angles which would hold the front LED. The screws would protect the lens holder.
Step 4: LEDs Attached to the Heatsinks
Use JB Weld to attach the LEDs to the heatsinks.
Step 5: LEDs Wired
The LEDs will be wired in series. For extra flexibility, you can use silicone insulated wires.
Step 6: LEDs With Lenses
- Carve the lens holders to make room for the wires.
- Attach the lens holder on top of the LEDs with hot glue.
- Attach the lenses to their holders.
Step 7: Self-Levelling Mount for the LEDs
To properly aim the rear light, a self-levelling mount should be used. I used two layers of plastic from a bottle for rigidity.
- Drill the plastic strip for the cable ties.
- Drill one hole on each side for the screw used for holding the light. The holes should be levelled.
- Once levelled, trim off any excess plastic.
Step 8: Circuit
The circuit is similar to that of my daytime visible bike light except that it uses a step-up converter instead of a step-down converter. The LED's forward voltage must be higher than the battery's voltage. If you're using red or yellow LEDs, the battery's voltage should be less than 1.5V per LED to prevent them from glowing during standby. That means if there are six LEDs, your battery pack should not exceed 9V.
Step 9: Protect the Switch From the Weather
Tape may be used to protect the switch from the rain. The non-sticky side should be facing the switch.
Step 10: Code
The code will be uploaded to the ATtiny85 IC. Arduino 1.6.6 was used. The strobe patterns in the code were updated.
From the Arduino program, use the settings
- Board: "ATtiny"
- Processor: "ATtiny85"
- Clock: "8 MHz (internal)"
- Programmer: "Arduino as ISP"
Step 11: Light Installed on the Helmet
Use velcro to attach the battery holder, front LED, and the circuit's enclosure to your helmet.
Step 12: Possible Upgrades
- Use Cree LEDs for higher efficiency.
- Move the front side lights to the front of the helmets to balance the weight and improve visibility if there are other accessories.
- Use thinner and smaller aluminum bars to reduce the weight.
- Use smaller footprint LEDs to allow smaller heatsinks to be used.
Step 13: Using the Circuit for Bike Lights
If you want to build a bike light, you can use the same circuit board. If you increase the battery pack's voltage, you may need to change the values of R1 and R2, and change the value of batteryCutoffADC in the code.
I used the same circuit board for my 10 LED tail light shown in the video.