Cheap Open-source Pace Clock Keeps Your Practice On Schedule


Pace clocks are used in a variety of sports, from swimming to track. The systems are typically expensive however, often beyond the reach of smaller organizations and underfunded programs. For their electrical and computer engineering final project, Cornell students [Paul Swirhun and Shao-Yu Liang] set out to build a much cheaper alternative to commercial pace clocks, with a far simpler wireless user interface.

Their clock uses an ATmega32a to handle all of the processing which is paired with a RN-42 Bluetooth module for communicating with Android smartphones. Their seven-segment displays are built using custom PCBs that they designed and fabricated for the project which are controlled by TLC5940NT LED drivers. The Android software allows users to connect to the pace clock remotely, creating any sort of multi-layered swimming or running routines.

When the project was completed, the pair tallied their total hardware cost to be under $250 apiece at low production volumes. Even when taking assembly time into account, their solution is several magnitudes cheaper than similar commercial systems.

Stick around if you are interested in seeing a demo video of their final product in action.


10 thoughts on “Cheap Open-source Pace Clock Keeps Your Practice On Schedule

  1. I’m liking it although I don’t know if I’d want to fork out that much for one. Saying that, I dunno how much commercial versions go for.

    Btw anyone know what the deal is with ‘open-source’ being stuffed into titles lately? Most projects featured here on HaD are “open-source” so no I’m curious why it’s suddenly being put in titles.

  2. Man I can’t wait for ECE, this is awesome! I would think the time for the signal to be sent from the phone to the receiver would be too much lag for such delicate timing, but it looked super responsive in that video. These guys are bros.

  3. Hi Everyone,

    [I am one of the designers]. A few comments: 1) our project title did not include “open source”, the editors added that to this post. What is different from the Colo. Time Systems (CTS) ones, though, is that anything with bluetooth can control it, and that multiple platforms can compile to the byte-code which is uploaded to the microcontroller. That means you could make a program in any language (some coaches use excel) that uploads through your laptop’s bluetooth or bluetooth dongle. By contrast, CTS ones use a proprietary connector, special cable, and signaling protocol that you have to reverse engineer to use. See ( where they did exactly that to get a CTS system to connect with a laptop.

    As with cost, yes they labor is intense and for a product you would need a large-volume order from China to make it competitive. However, I have not found anything as bright as 18x 1200mCD LEDs per segment (even brighter if you run them closer to absolute maximum ratings). If you’re interested, I have built two professionally-packaged ones with monolithic display boards, and the wiring is much less severe.


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