Brake Light Backpack Overpowered With LED Pixels


Here’s another Flora Arduino based project from [Becky Stern]. It’s a backpack with brake lights and turn signals for use when motorcycling, but it should work just as well for bicyclists. From this view the project looks pretty normal, but things get downright crazy when she decided to use the WS2801 pixels for the LEDs. Sure they take all the work out of driving an array of LEDs, and they offer full color and dimming levels. But when you see the bulk of cabling and PCBs this adds to the project (shown in the video after the break) we think you’ll agree that this was an interesting choice.

That issue aside the project is a lot of fun. The system doesn’t patch into the motorcycle’s electronics. Instead, it uses an accelerometer to detect when the brakes are applied and light the LEDs according. The turn signals are switched with an RF remote control that can be mounted on the handlebars.

Anyone looking to hack outerwear with electronics can learn form the fabrication techniques used here. [Becky] details how to make holes in the bag and sew parts to them, as well as using Sugru to waterproof vulnerable components.

44 thoughts on “Brake Light Backpack Overpowered With LED Pixels

  1. It boggles my mind how anyone could put this much time and effort into making brake lights and not consider the fact they need to work at traffic signals and stop signs. I mean, really? REALLY?

    “Does it have turn signals?”
    “Does it have different colors?”
    >Sure, sure
    “Can I make my own custom animations?”

    “Does it light up when I’m using the brakes?”
    >…Uh, sometimes?

    1. Why does it need to light up at stop signs? If it’s dark, you’d better be using your regular lights anyway. This is an addition, not a primary brake light.

      It lights up when you’re braking, not when you hit the brakes. Different function. Bicycles don’t have anything of the sort, so the addition might be interesting.

      I like it, although there’s a slight bit of overkill.

      1. When I approach a stop sign, I look what the person in front of me is doing. If they are not braking and the intersection is clear, I assume they are moving forwards into the intersection and I adjust my deceleration so that I will come to rest exactly where they just were, on the line. Driving is all about anticipating what is ahead of you. If someone on a motorcycle was sitting in the middle of the road, stopped, but not indicating a stop, it is VERY possible that someone would see them, assume they were moving at roughly the same speed, and plow into them at full speed. This almost happens to me pretty much any time some idiot is driving incredibly slowly in the fast lane, another situation where some kind of warning light would be useful.

    2. Why would the brake light need to work at traffic lights and stop signs? That’s what the traffic lights and stop signs are for! It’s not like a motorist can’t see past you.

      Accelerometer-based motorcycle brake lighting is already available commercially; this takes it up a notch and adds bicycle compatibility. Motorcycles can downshift and engine-brake as hard as a car moderately braking, but the brake light won’t illuminate. Adding an accelerometer gives car drivers extra warning.

  2. Using an accelerometer for this scenario seems like a dumb move for something which is supposed to give you extra safety – should have used a couple of RF modules, transmitter wired to the bike’s brake+turn signals and the receiver in the backpack.

    Or instead of transmitter & receiver modules, transceiver modules so you can have an indication on the bike’s handlebars that the backpack isn’t responding (ie battery drained or forgot to switch on)

  3. Can I ask what the hell are the little “dots”
    on the rear of the bike,
    in the location where an actual
    ***Break Light***
    would normally be located ??
    Why not just put something useful
    on the bike itself?

  4. Being that this is hack a day with an audience of brilliant engineers, do any of you above trolls have any examples or specifics of the perceived faults in her design? In other words, How would you wirelessly tie into a motorcycles signal light circuits to accomplish the same thing AND still make it compatible with a bicycle? With some decent signal analysis to detect flukes, I could see this working quite well given the correct logic and that the controller is polling the accelerometer at a good enough resolution to give a large enough sample in one second to detect and throw out any out-of-bounds samples

    1. Obviously you would use a raspi to tell an arduino to control some servos that press the buttons on the remote. Then you just stick a camera on the back of your bike to watch the lights and use OpenCV to tell when you’re using the brakes/turn signals.

  5. This is a neat idea but it would be nice if it was tied into the bikes electrical system somehow. Whats the cheapest way to have something communicate wireless without line of sight? I have a duemilanove and a bunch of led’s to play around with.

    1. To clarify, there must be ~9″ separation between the brake and turn signal indicators.
      In case of ‘combined’ brake / turn indicators, the separation must still be maintained between left and right indicators.

    2. Reading the code, the brake light overrides the signals. As long as the accelerometer’s reading above the threshold value, it stays inside the brake illumination loop and ignores the switches. Tweakable, obviously.

      As for separation, the brakes are red and the signals are (appropriately) amber. An overly-concerned rider could tweak the code to assign pixels to mutually-exclusive “left”, “right”, and “brake” groups.

      Red turn signals make for a guessing game (brakes, signals, or hazards?) unless you can see the entire vehicle and all of its lamps are in good working order, which is often unknowable. Hard to believe they’re legal in the US.

  6. Given the girl’s name (Becky Stern) combined with of the brief outdoor video, I would hasten to guess this is NYC. If you’ve ever driven in NYC, you’ll know that most of the time you’re stuck at a traffic light with no acceleration at all. So basically this project is useless.

  7. What I don’t understand – if this is supposed to be a “wearable” board – why are they soldering to it? I know they’re marketing their product – but it seems silly to use this over a regular board just because you’re using it on something that’s fabric. Shouldn’t they be using conductive thread?

  8. How many people trashing this here ride motorcycles? I prototyped something similar and quickly realized the accelerometer approach was necessary, after initially just tapping into the brake light circuit… in fact if I could only do one, I’d use the accelerometer – motorcyclists frequently use engine braking, which does not cause the brake lights to light up, and which often catches tailgating cars by surprise. I’m far more concerned with communicating the fact that I’m engine braking than anything.

    Also, if I was tapping into the brake lights line, I wouldn’t use wireless – just plug in… there are many wearable motorcycle accessories that draw power off the bike (heated jackets, for instance), so it’s not so unusual to have a wire connecting you to the bike – you can use a springy cable so you have some play without a lot of slack, but you don’t need much.

    Of course, no reason not to integrate both… I’m still deciding where to mount this thing (don’t want to poke holes in a jacket, don’t think helmet mounting is ideal) – considering a simple harness that I could either wear directly, or wrap around my backpack when I have it on.

  9. I found these guys online the other day called VATA7… Similar concept, but theres a lot more functionality to it. Im also not so sure about the aesthetic of this whole design. I kind of their products better, considering it actually mimics the look of a brake/blinker light system on a motor vehicle. This looks more like a conceptual art piece. I bought one of their backpacks, and i have to say, i love riding it up the coast on my way back from work. Check them out, its worth a look anyway. Happy riding everybody.

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