Intro: 20W LED Bike Headlight With Side Visibility
This bike light uses two white Cree XPL LEDs and has amber LEDs facing 0 and 45° for daytime and side visibility. It has different patterns for different conditions, 3 minutes boost mode, sleep mode, and a battery monitor. It also has solid modes. A custom 3A LED driver and two 15mA LED drivers were included in this Instructable. It has a maximum luminous flux of 2300 lumens. It can be powered by 3 LiFePO4 or 3 Li-ion batteries.
Step 1: Microcontroller Module
In this module, an ATTiny84 microcontroller was used as the LED driver's PWM source and to store the bike light's program. It has two LED drivers for the 5mm LEDs with 15mA selected.
Step 2: Custom Made 3A Switching LED Driver Module
The Isense resistors used were two 0.47R in parallel, giving a value of approximately 0.23R. You can use a different value but make sure you update its values in the program. Make sure that they have a sufficient power rating for 3A.
Step 3: Wiring the 3A Switching LED Driver
The switching LED driver module was externally wired to its PWM source. Since it operates at a high frequency, noise is an issue which means the driver's feedback wire needs to be twisted with its ground wire. This prevents picking up common mode noises which affects the readings, reducing the drive current's accuracy.
A possible way avoiding the need to twist the wires is to install the Isense resistor on the microcontroller module instead.
Step 4: Program
Upload the program to the ATtiny84 microcontroller. Use the settings external 20 MHz and 4.3V BOD. EEPROM needs the BOD to be reliable. The program has blink patterns to indicated the selected battery chemistry.
Step 5: Attach LEDs to Heatsink
The LEDs should be spaced far enough to prevent the lenses from touching each other. How glue was used to glue the optics. A bike reflector mount was attached to it.
Step 6: Assemble Amber Light Unit
Wire the LEDs so that they are in 2P3S configuration. Four LEDs were aimed at 0° and two at 45°. If you have a straight or riser handlebar, you may be able to aim them 90° unobstructed. You can experiment with different positions such as the head tube, bar ends or drops. You can try aiming two halfway between 0 and 45° for improved coverage. Hot glue the unit for strain relief and to keep the LEDs from moving.
Step 7: Install the Bike Light
An acrylic cover was installed on the 3A bike light for protection.
A 2 cell 26650 battery case was used as an enclosure for the circuit boards.
A 3 cell 18650 battery holder with balance pins was used. A 3 cell balance connector, fuse holder, and power connectors were soldered to the pins. This allows balance charging without having to remove the cells from the holder every time you charge it.
The circuitry and battery holder were attached to the pannier rack with velcro straps. This method saves room for pedalling compared to installing them onto the frame. The wires for the lights were attached onto the top tube.
The two buttons were on the battery holder.
Step 8: Alternative Installation Option: Top Tube
Attach an angle bar to a mount. An extra hole was drilled onto the u-lock mounting bracket and two holes were drilled to the bar. Duct tape was used to attach the circuitry's box to the modified mount.Two plastic bags were used for water resistance.
The benefit of this option is that the wires can be shorter and there's more space on your pannier rack which can be used to store your tire repair kit. If my horn setup wasn't there, it would have likely worked.
Step 9: Aim the Bike Light
Aim the high powered light onto the road. If your beam has cut-off, you can aim it further without increasing the glare to other road users
The amber light should be aimed straight.
Step 10: Using the Bike Light
- To turn on the lamp, hold power button for medium duration.
- To turn off the lamp, hold power button for medium duration.To select battery chemistry, hold power button for long duration.
- To increment the mode, hold power button for short duration.
- To select the mode type, hold power button for long duration.
- To turn on boost mode or extend it, hold the boost mode button for short duration.
- To turn off boost mode, hold the boost mode button for medium duration or longer.