Nixie Tube Speedo

Nixie Speedo

The Nixie speedo is designed to fit into a stock P200 housing and use the stock speedo cable. The nixies are IN-12's and the driver board contains an atmega8u2, a Taylor Edge high voltage driver, and a bunch of BSS131 FETs. A hall effect pickup for calculating speed.

Principle of operation: The speedo cable is driven from a gear in the front wheel hub. The rotating speedo cable spins a magnet inside the speedo housing. To calculate speed, a latching hall effect sensor is used to detect the rotating magnet. The rate at which the magnet is rotating is proportional to the rate of the front wheels rotation. Based on the diameter of the front wheel, the speed can be calculated. The nixies are all low side driven via the BSS131 FETs.

Updates to follow: Formula for calculating speed, source code, and some additional images of the speedo housing.