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Mini Cooper Xbee

Posted: July 4, 2016

Introduction

I wanted to play around with some XBee modules so I figured another little radio control car circuit might be fun. Like some other R/C car circuits I did before, I picked out a cheap R/C car, this time a Mini Cooper S, ripped out their radio control circuit, and replaced it with my own. To control the car I have software written on a PC using SDL that takes input from the gamepad and sends commands over another XBee to the car. The software also reads from an IP camera and draws the video in the display window.

Related Projects @mikekohn.net

RC Cars: IR Toy Car, IR Toy Car dsPIC, Bluetooth RC Car, RC Drag Race, WiFi RC Car, Xbee RC Car, RC Food
Motors: Linksys Copter, Brushless Controller, IR Toy Car, Balsa Airplane

Explanation

For this project I'm using an MSP430 for the computer. This timeinstead of making my own H-Bridge or using a raw motor control chip like I did before, I got a Pololu DRV8833 motor control board. The reason I went this route is because the L293 chips I normally would use require 5v logic and I didn't feel like adding extra circuitry for it and the H-Bridge is a lot of soldering.

The command set the MSP430 understands is:
0x00: NOP (heartbeat to let the car know it still has a connection to the netbook)
0x01: Car horn on
0x02: Car horn off
0x03: Brakelights on
0x04: Brakelights off
0x05: Headlights on
0x06: Headlights off
0x80: Steering motor 0x80 + (0 to 63) where 0 is full left and 63 is full right
0xc0: Drive motor 0xc0 + (0 to 63) where 0 is full speed backwards and 63 is full speed forwards

Videos

Testing the system with the car lifted off the ground. https://youtu.be/7xrZcLHLOow

Pictures

Mini Cooper S with XBee circuit

Here is the car still in the box and the circuit not quite finished. At the top is the XBee, in the middle the MSP430, and at the bottom a Pololu DRV8833 motor control board.

Mini Cooper S with original R/C circuit

Here's the car opened up with the original circuitry still installed.

R/C car with XBee circuit

Here's the car opened up with the new circuitry.

R/C car with XBee circuit and WiFi security camera

Here's the car with the WiFi security camera on top. To support the camera on the top of the car I got some plastic cocktail stirrers and snapped them to fit the size I need. I put some putty under the camera to support it on the bottom and used masking tape to hold it all together. Pretty ugly, but it works.

R/C car with XBee circuit and WiFi security camera

Here's the car from a different angle with the WiFi security camera on top.

Source code
xbee_car.asm

Copyright 1997-2018 - Michael Kohn