Bike Wheel Light Flashes Just Right

When it comes to safely riding a bike around cars, the more lights, the better. Ideally, these lights would come on by themselves, so you don’t have to remember to turn them on and off every time. That’s exactly the idea behind [Jeremy Cook]’s latest build — it’s an automatic bike light that detects vibration and lights up some LEDs in response.

The build is pretty simple — a coin cell-powered ATtiny85 reads input from a spring vibration sensor and flashes the LEDs. This is meant to complement [Jeremy]’s primary bike light, which is manually operated and always on. We especially like that form follows function here — the board shape is designed to be zip-tied to the spokes so it’s as close to the action as possible. He cleverly used cardboard and a laser cutter to mock up a prototype for a board that fits between the spokes. Pretty cool for your second professionally-fabbed PCB ever, if you ask us. Ride past the break to check out the build video.

If you don’t think fireflies on your spokes are enough to keep you safe, go full rainbow party bike.

22 thoughts on “Bike Wheel Light Flashes Just Right

  1. The lights on my bike are fully automatic, a dynamo running off the rear wheel powers the lights which have a built in capacitor or some such storage device that charges as Iā€™m riding and keeps the lights illuminated for about 10mins after I stop so they stay on while Iā€™m stopped at an intersection or in traffic .

  2. When the wheel spins the spring accelerometer short circuits and the LEDs turn on. When the wheel stops the spring accelerometer open circuits and the LEDs turn off. So why the heck does this thing need the added cost and complexity of a micro-controller? Just to blink the LEDs?

      1. Yeah from about 6:33 when you’re saying what else you might try “No Attiny85 period” I caught that on first watch, so realised you knew the mass in the switch would just keep it powered when spinning, or I’d have been making the same comment.

      2. Well actually blinking the LEDs might not be a bad idea, they might attract more attention. But perhaps more important since the LEDs are are off for a percentage of time, the battery will last longer, you might even be able to put the micro-controller to sleep between the flashes. Another thing the micro-controller can do is write a message out on a row of seven (or more) LEDs using the Persistence of Vision (POV) effect. But for that to work you will need to use a more sophisticated sensor and write a lot more code. Using one LED you can make a stationary POV smiley face on your bicycle wheel. Putting LEDs along the full length of the spoke allows for generating some really complex displays. It’s all been done before, just Google POV Bicycle Wheel or Spoke POV. I’d be be surprised if you can’t just buy a working spoke POV display device today on Ebay or AliExpress.

        1. Flashing lights are very bad for safety!
          This has been researched extensively. Two factors cause this:
          – Flashing lights cause target fixation in drivers, and make them more likely to run into you.
          – Flashing lights make it harder or less accurate for a driver to instantly see the direction and distance of a cyclist.
          Aside from that, flashing lights are associated with emergency vehicles that have right of way over all other traffic. If you see one in your mirror, you are supposed to make some room.

          These are all reasons why in the Netherlands, you are not allowed to carry flashing lights as a cyclist.

          1. > Flashing lights cause target fixation in drivers, and make them more likely to run into you.

            And apparently more so if the driver has been drinking. I’ve seen it referred to as ‘target acquisition’ (by someone on HAD?), but ‘target fixation’ seems a better description.

            And for DUI drivers, even solid lights are a problem. As drivers we’re conditioned to follow the lights ahead of us. DUI drivers focus on following the vehicles – lights – ahead of them.

            Three times I’ve been stopped at night by police officers, telling me to: turn all my lights off (solid, none flashing), get off the road and ride my bicycle on the sidewalk, so the DUI drivers don’t hit me from behind. The explanation was without lights on, the DUI drivers will be past me before they even see me.

          2. Also not allowed in the UK but there are still lots of them about and they are really hard to see properly. I doubt that anyone that uses flashing LED lights on a push bike has ever had to cope with one while driving a car.

          3. Interesting, I did not know about this. A few days ago I was driving at night in my neighborhood and passed without incident a person riding a bicycle equipped with a rear-facing blinking LED safety lamp. It’s a good thing we were not in the Netherlands where supposedly I would have been transfixed by the blinking light causing me to hit the bicycle!

        2. One interesting use of POV, if you double the led current, but leave it on for 100uS and off for 1000uS, since rods and cones in the eye fire, send off their info, and have to recuperate for a few mS, your eye sees them as twice as bright for 1/5th the power.

          I read this a while ago, and I have no direct experience, and the timings are out of leaky wet ram, but I believe this is true, and a way to use the ATTINY to get better battery life.

  3. Where do you ride? San Diego? No weather protection at all. Cap standing tall will break loose with shock and vibration, use an axial lead cap or lay one down and zip tie down to the board. Pinpoints of light from the side, not rear at all. The smaller the light source the farther away it looks and is harder to see as well. A good taillight should be 3 or 4 inches (1dM) round and that whole surface is lit up.

  4. If I wanted increased safety in the trafiic I would direct the lights forward and backward – not to the sides. And I would go for red/orange back and white front to tell approaching vechiles in which direction I am going. Sort of what Reelight does.

  5. I agree that the micro controller is brutal for the battery life and the potential is not leveraged in this POC. But there is potential in using a microcontroller here. Persistence of Vision can create patterns with the LEDs as they spin, which is a great use of the micro controller.

    I just really appreciated the video for showing how simple it is to design and fabricate a custom PCB. What a wonderful age this is!

  6. In the 1980s I had some small orange lights on my bike’s spokes that used a ball bearing that flew outward as the wheel rotated to actuate a small switch. Small incandescent bulb powered by an AA cell. I seem to think they came from Halfords or some other local bike shop.

  7. “When it comes to safely riding a bike around cars, the more lights, the better. ”

    When it comes to safely riding a bike around cars, assume each and every driver is actively out to squash you. The less they see and the more you pay attention, the safer you’ll be. If you rely on being seen, you’re dead.

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