A water resistant “see me” bike light that also works great on kayaks.
Deets
This is a water-resistant (I would guess IP 65) bike and kayak light that attaches via a Go-Pro style mount. With 28 WS2812 LEDs this light is not going to light up your surroundings at twilight, but it does help folks see you… and can let everyone know where the party’s at.
Power
My requirements here were that it should be relatively compact, USB rechargeable, and provide ample power for the LEDs to shine at full brightness. I used a single 18650 cell wired to a 3v->5v boost converter which supplied both the Arduino Pro Micro and the LEDs through a switch.
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| Bike Light power system ready to be wired up |
This layout made the power system relatively compact. The 18650 cell I used has 3500mAh of capacity and is rated to discharge at 20A (claimed on datasheet… maybe for short periods?), which is plenty to drive the 28 LEDs in the light at white full brightness (~1.7A @ 5V) without issue: \(60mA * 28LEDs \sim 1.7A\)
The boost converter is the limiting factor. I haven’t been able to find an excellent high-amperage 3->5V boost converter - the one I now use for these sorts of things has a 2A @ 5V rating. I’d love to find a compact version with a higher rating.
Control & Effects
This light is primarily geared towards being seen, not necessesarily lighting up your surroundings. In practice it does provide a bit of increased visibility - especially when the sun truly goes down - but that’s not its main purpose. I designed the effects with that in mind. I utilized the fantastic FastLED library to create a couple custom modes, and also used some of their default/demo modes. The effects I ended up liking most were:
- Solid white (most useful for seeing what’s in front of you)
- White strobe (good for on-street riding as a “see me” light)
- Slow color fade (nice compromise between visibility and style)
- Party mode (let’s folks nearby know who to follow to find the party. Based on the FastLED confetti function.)
The pushbutton just cycles through these programs. The switch cuts off power to the Arduino and LEDs, but lets still lets the boost converter charge the battery if it’s plugged into USB.
Prototype & Improvements
I made a quick functional proto to test out some ideas. The knob rotated a potentiometer to control the brightness of the LEDs, but in practice I never wanted these a lower than full brightness. Other than the owl face, I didn’t really like the shape - too boxy from having the battery sideways.
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| Bike Light prototype |
For the prototype I included a potentiometer controlling brightness. I figured I could use this knob to dim the light and skirt around the cyclist’s debate of whether one dims/covers their light when passing a fellow cyclist going the opposite direction in the dark (my position: don’t cover… but also no strobe on the trail!). In practice it was a nuisance to turn the knob and it really only made sense to run the light at full brightness since it’s not pumping out hundreds of lumens.
The flat-top lens I made for the proto was not ideal either. I opted for a snap-fit lens, which was not good for water ingress protection. And since this was a visibility light, I wanted more side illumination and decided to revise the lens to have more side visibility.
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| Bike Light prototype |
I have a habit of personifying prototypes and I do miss the character of this one. It had a nice face with what seemed like a squinty eye. Made me think of a discerning owl.
Final version
For the final version I opted for a somewhat retro-inspired design. The housing was a bit more sleek & water-tight, and the lens more aero.
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| Bike Light final version |
The internals remained mostly the same, though I did remove the potentiometer, flip the battery orientation, and add a USB charge port at the back.
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| Bike Light final version internals |
The light is working well, and has even survived some decently wet kayaking adventures!
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| Bike Light mounted on Kayak |
Improvements
The main improvement I would make here is re-thinking the water-proof seal on the charging port. Currently it’s just a removable flap piece with no gasket. It works okay, but I expect this to be the way that water would get in if submerged or installed incorrectly.
