I developed a prototype Electronic Throttle Controller as my final year project at CPIT in 2001. The system consists of a 68HC11 based main board, a stepper motor and driver board, a pedal position sensor and an engine speed sensor.
An Electronic Throttle Controller replaces the mechanical linkage between a cars accelerator pedal and throttle. Breaking this linkage frees the designer to allow inputs from systems other than the drivers foot to control engine speed. Such a system can be used in launch/traction control systems, gearbox controllers and anti-stall systems.
The main board is a double sided PTH design, I was lucky to have a friend with connections in the PCB manufacture business, making this design possible with the non existent project budget. It is a fairly conventional 68HC11 expanded memory design.
Stepper Motor Driver
The stepper motor driver is based on the ULN5804 motor driver IC from Allegro. I used a motor from an old 5 1/4″ floppy drive for the prototype demo. I housed it in an aluminium box with perspex lid for demonstration purposes.
Engine Speed Sensor
The engine speed sensor is based on a dual element Hall effect sensor from Allegro. Below is a concept drawing for the sensor, and the potted prototype.