Aftermarket Cruise Control for Mechanical Throttle Bodies

This is an aftermarket cruise control for mechanical throttle bodies using Arduino and later model rear axle abs/speed sensor. This was created as a standalone device to add cruise control to vehicles that have rear abs/speed sensors not being used. This specific speed sensor used is from a 2002-2009 Chevy Trailblazer. The abs/speed sensor on this vehicle outputs a voltage based on the speed of the axle's rotation. This voltage can be mapped onto the Arduino for speed ranges that are determined from real world driving and actual tire size. With this method, the speed cruise control can be quickly adjusted for all application and for seasonal tire changes. This current idea is partially underdeveloped due to parts delivery issues, but this can be further developed for application later.

Purchase Items

1. Arduino UNO
2. Bread Board
3. Nema 17 stepper motor
4. TB6600 Stepper Driver
5. Power Supply/Large 12v Battery
6. Throttle cable (cord used for demonstration)
7. Microswitch

3D Print:

1. Housing
2. Throttle 'Lever'
3. Microswitch Brace

Above can be seen the wiring diagram for the stepper motor and driver. (TB6600 Stepper Motor Driver with Arduino Tutorial) The schematic here matches mine, however I added 2 buttons to set cruise and to "kill" the cruise function. Along with this, there is the microswitch that is being used and all of the pins for these additional features can be seen in the code.

Above can be seen the assembled cruise control prototype. Because of delivery, the final throttle cable and throttle lever could not be implemented, however conceptually all the components are there. In future iterations, the following modifications need to be made: Throttle cable attachment, Throttle lever to attach to, Bolt holes for stepper motor and micro switch bracket. In this prototype, the pieces were temporary thermally bonded using marine grade polymer.

Above is the code for the cruise control. At first it defines all the pins and variables being used for the system. If this is to be integrated with a real vehicle, the "kill" switch would needs to be hooked up to both the cruise "off" switch and brake/clutch switches to prevent the system to be running when it's not needed. When either condition is true, the motor rotates towards the microswitch until it activates and indicates the stepper motor has returned to the start position. If the cruise button is pressed, it grabs the voltage of the wheel speed and attempts to hold with the adjustable throttle position defined. More positions can easily be added by repeating the program for position A for required positions based on throttle response, a vehicle's power band, and gearing ratio. Speed input could be easily changed to GPS based if it is desired.

Here can be seen a modified version of the code to demonstrate the cruise control feature without speed hooked up.