Road Bike Daytime and Side Visible 350mA Light (Single Cell)

This bike light has front and 45° facing amber LEDs driven up to 350mA. Side visibility can improve safety near intersections. Amber was selected for daytime visibility. The light was installed on the handlebar's left drop. Its patterns can be distinguished from turn signals because only solid, fade, and short flashes were used. It can be powered by a single LiFePO4 or Li-ion cell, or 3AA NiMH cells which can make it a gift idea! Its battery life ranges from 2 to 48 hours on a 1800mAh LiFePO4 cell depending on the pattern.

Step 1: Circuit

Step 2: Install the PCB

A 2 cell 18650 case was used as the enclosure.

A one cell 18650 holder was attached to the case and stabilized with hot glue.

The momentary button was installed next to one cell holder. Hot glue was used to hold the button in place.

Step 3: Add Screws to Enclosure

The screws make installation on the bike easier and more secure. Cap nuts or glue can be used to avoid damaging the weatherproofing bag. Inside the enclosure, the screws were hot glued to insulate them.

Step 4: Program

The Instructions on how to operate the bike light were in the code.

The settings were:

• 8 MHz (internal)
• ATtiny85

Step 5: Bend Metal Bar

Make sure the metal bar is long enough to hold three LEDs. It will be bent. A clamp with two pieces of wood were used to hold the metal bar while it was being bent.

Step 6: Drill the Bar

The holes will be used to allow attaching cable ties to them. Make sure that the LEDs can still be attached to the bar.

Step 7: Attach the LEDs

3W amber LEDs were used. They were ordered on eBay.

JB Weld was used.

15 degree lens was used for the forward facing LED.

30 degree lenses were used for the 45° facing LEDs.

Step 8: Wire the Light

Hot glue was on the edges so that they're no longer sharp.

Step 9: Install the Bike Light

A tail light mount was used to attach the lamp unit to the bike. Four holes were drilled into the mount and four cable ties were used to attach it. Hot glue was used to stabilize it.

The light was installed on the handlebar's left drop. The circuitry was installed on the top tube next to my horn setup. You can use tape to protect the wires.

Other possible locations for the lamp include:

• Top tube
• Head tube
• Handlebar
• Stem
• Bar end

Find a place for the circuitry. For example,

• On the bike light
• Frame
• Handlebar
• Saddle bag
• Frame bag
• Pannier rack
• Water bottle cage mount

Step 10: Safely Connecting and Disconnecting the Bike Light

Since the bike light has a boost converter, there's a risk of high voltage which can cause stresses on the LEDs. Following the procedures avoid the risk.

Connecting the bike light:

1. Connect the bike light cable

2. Connect the battery cable

Disconnecting the bike light

1. Disconnect the battery cable

2. Disconnect the bike light cable

If the output was disconnected while it was on, it will reset. Wait at least 10 seconds before reconnecting the LED. The discharge resistor R8 will discharge it. It takes 10 seconds for the voltage to fall by almost two thirds which will make it safe for the LEDs. The calculation was based on a supply capacitor of 100uF, a discharge resistor of 100k, and a trip voltage of 16.7V.

Step 11: Possible Improvements

Wire a rear light in series with the front light. This allows the same circuitry to power both lights. You can use it as a backup for your existing rear light. It'll still be single cell but the battery life would decrease by about one third. You'll need to make an adapter that allows you to wire it in series. Different connectors can be used so that mistakes in connecting them are impossible.

Use higher quality LEDs such as Cree or Luxeon for higher lumens per watt. My LEDs were no name brand.

Use smaller footprint LEDs so that a smaller light assembly can be made. A smaller unit saves room for other accessories. Luxeon sells LEDs with 10mm base plates which are less than half as wide as the ones that were used here. You can try angle bar with a shorter flat bar.

Install another lamp on the other drop so that it functions as a turn signal. Two LED drivers would be needed.

Attach the LEDs to non-metallic materials instead of metal. Since the average power is lower with flashes, you can get away with attaching them to plastic or wood, giving you more options such as 3D printed mounts. You can use hot glue. Make sure you modify the code to dim the solid high setting to avoid overheating.