The objective benefits may be almost nonexistent today, but there is still something satisfying about rowing through the gears in a car with a manual transmission. If that car was made in the past couple of decades, there is a good chance that it has an indicator on the dash to tell you what gear you’re in. But older cars usually don’t have an indicator, which is why you might want to follow Vaclav Krejci’s guide to add one.

The great thing about this project is that it is easy to perform — even for beginners. Gearheads that don’t typically touch electronics can complete this build with some patience. Once done, it will display the current gear and a visual diagram on a small OLED screen, which the user can then mount anywhere in their car. 

This works using an arrangement of four Hall effect sensors that detect the strength of the magnetic field coming from a permanent magnet attached to the gear shift lever. The principle is similar to triangulation, because the values detected by the four sensors can be used to calculate the position of the magnet. That isn’t very precise, but it doesn’t need to be for an application like this.

The four Hall effect sensors mount onto a custom PCB. That connects to an Arduino UNO Rev3, which the user can tuck away inside of a center console. The Arduino performs the calculations, then updates the OLED screen with the results. Krejci even demonstrates how the user can simulate the entire circuit using WOKWI, which is very useful for ironing out kinks before building a hardware prototype.