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MAKE subscriber Dan Wagoner sent us this digital gear indicator project he spotted on the Arduino forums -

I did this as a practice project for building a gear indicator for my motorcycle. The idea is that by monitoring the revolution speed of the rear wheel and of the driving pedal I can calculate which of the 6 gears the bike is in. It’s not terribly useful on a bicycle but I think it will be handy on the motorcycle.

On the motorcycle I’ll be intercepting pulses to the tachometer to get the engine RPM. For the bicycle I’ve got a magnet mounted on the pedal arm and a reed switch on the frame that trips every time the magnet comes by. On both the bicycle and the motorcycle the rear wheel speed is detected the same way with a reed switch and magnet. The reed switches are both cannibalized from failed cycle computers.

“Terribly useful” or not, I’ll take any excuse to ride around with a bike-mounted breadboard! Check out the Arduino code + info on Bill’s site. Combining this with a few other onboard sensors could make for an info-tastic handlebar display – and course you could always add some LED matrix turn signals to fully deck out your ride. Just be sure to use some weather resistant enclosures.

Collin Cunningham

Born, drew a lot, made video, made music on 4-track, then computer, more songwriting, met future wife, went to art school for video major, made websites, toured in a band, worked as web media tech, discovered electronics, taught myself electronics, blogged about DIY electronics, made web videos about electronics and made music for them … and I still do!



  1. Harvey Finn says:

    I have invented an alternate type of gear indicator for road bikes.
    It will also work on other types, but not all configurations.
    The indicator is called GEAR MIRROR*. It is especially helpful on
    Touring rides. It does not require any batteries and weighs 31 grams. It is injection moulded.
    It attaches to the handle bar with zip ties in a couple of minutes and at a glance shows you what gear your
    in. I have been riding with it for 4 years. It is made of urethane with a 30% glass
    fill so it is just short of bomb proof.

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