Reflective Sensor Becomes Kart Racing Lap Counter

Once you have a track and a kart to race on it, what’s missing? A lap counter that can give your lap times in hardcopy, obviously! That’s what led [the_anykey] to create the Arduino-based Lap Timer to help him and his kids trim those precious seconds off their runs, complete with thermal printer for the results.

The hardware uses an infrared break-beam sensor module (a Velleman PEM10D) to detect when a kart passes by. This module is similar to a scaled-up IR reflective object sensor; it combines an IR emitter and receiver on one end, and is pointed at a reflector placed across the track, up to 10 meters away. When a kart breaks the beam, the module reports the event to the rest of the hardware. Only needing electronics on one side allows the unit to be self-contained.

An obvious shortcoming of this system is the inability to differentiate between multiple karts, but for timing a single driver’s performance it does the trick. What’s great about this project is it showcases how accessible hardware is today; a device like this is possible to put together with what are essentially off-the-shelf components available to any hobbyist, using an Arduino as the glue to hold it together. We’d only comment that a red-tinted piece of plastic as an overlay for the red display (and a grey-tinted one for the green) would make the LED displays much easier to read. Still, this is a very clean and well-documented build. See it in action in the video embedded below.

If race timing that can handle multiple vehicles is more your speed, we’ve previously seen DIY lap counters intended for drone racing.

8 thoughts on “Reflective Sensor Becomes Kart Racing Lap Counter

  1. If each kart had some bright RGB LEDs on the side facing the lap counter, with each kart having a unique RGB color, perhaps Sparkfun’s ISL29125 RGB sensors could be used to keep track of which kart is breaking the beam.

    Race conditions would have to be dealt with, but that could probably be dealt with using multiple RGB sensors and a scheme of mounting the kart LEDs at different locations.

    1. How about white LEDs on the transmitter and different colors of retroreflectors/combinations of colors? This would make for easy mounting on the karts and prevent problems with powering something on the karts.

  2. have a ‘flag pole’ setup on the kart so that each kart has a unique height pole. The sensor stack would read the pole heights so kart one only triggers the bottom sensor in the stack, kart 2 read sensor 1 and 2….. and so on

  3. You can also place the timer on the cart and have it triggered by a colored strip ,detected by a color sensor, on the start line. Drivers will know their lap time and if you want a leader board you can broadcast it using esp wifi.

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