RC Battle Car

Inspiration

After seeing this post on HackaDay I had to make one for myself. The end goal is to make a sort of Mario Kart using real RC Cars. The vehicle started out as a New Bright 1:16 RC Truck from Target.

Chassis

The chassis of the RC car is a cheap plastic piece of crap. The main drive motor is a little toy motor that has been geared way down. The stock model ran on four AA batteries. To give it a little more umf I am running it on 12 volts from a 3S lipo battery. Eventually I will probably fry the motor but I am not worried about it.

Steering

The stock steering setup only allowed for full left, full right and straightish directions. After trying a few things I ripped the stock steering out a put in a Hitec HS-81 servo. To install the servo I used some clear corner protector material from the hardware store. The type that you put on the corner of a wall to prevent it from getting to dented. The plastic angle was super glued to the chassis and a control horn was epoxied to the control arm of the stock steering.

Power

I added a larger switch on the bottom of the chassis. The size of the switch is overkill but its what was in the junk drawer. The stock swith was attached to the stock control board and it would not have been easily reused.

Stock Electronics

The stock control board is pretty cheap. It contains the H-bridges for controlling the drive motor and the steering motor. My original plan was to hack the board to gain access to the motor drive signals but that ended up being more trouble than it was worth. The controller had digital buttons for the direction controls. They were stop, full forward/reverse or full left/right. Since I wanted to have something more analog for the controls the controller and control board both went into the scrap pile.

New Control Board

The new control board uses a PIC16F886 running at 20Mhz for the control brain. The old 27Mhz radio was replaced with a 900Mhz unit from Linx Technologies. The main drive motor is powered by an Allegro A3951S. The part has been discontinued so hopefully I don't blow any up. I started using two stacked L293Ds for the motor driver but the stall current on the motor proved to be more then the chips could handle as during testing I released the magic smoke and the car came to a slow stop. Fortunately the A3951S has current limiting so stalling the vehicle should not cause any magic smoke. The steering servo is driven by the micro using interrupts and timers. There is an extra servo port on the control board in case I decide to at a turret or something else. The massive 1800uF capacitor is not really necessary but I had some lying around so I figured why not.

New Control Board Installed

The new control board mounts to the chassis using some 6-32 screws. The board fits in pretty close to the same area that the stock board did.

Camera Mounting

The camera was mounted to the body of the vehicle using some more of the corner protector and Velcro. The antenna now sticks out through a hole in the roof for better reception.

Camera Front View

The camera is mounting in the center of the windshield to give the driver a good view of the road.

New Base Controller

The base station controller is currently only exists on a breadboard. The human interface is provided by a Playstation 1 controller in analog mode. The brains of the base station is a PIC16F876A running at 12Mhz. The PIC sends packetized commands to the Car which then executes those commands. The LCD on the bread board will be replaced by the one in the black box. Currently the only thing displayed on the LCD is the output of the Playstation controller. Eventually it will have more status information.

Base Station

The base station is used to control the vehicle. The receiver for the camera is mounted in the box with the LCD on top. The LCD is from a Game Cube. Not the same quality as the PS1 screen but it was cheap at the time. The black box was reused from a previous college related project.

Batteries Loaded

The battery for the car is loacated in the bed of the truck. It is a 11.1V 3S 1300maH LiPo battery. The controller processor uses one of its analog inputs to monitor the battery voltage to prevent the pack from being over discharged. If the pack gets to low the car will stop driving the main drive motor and the steering servo. The wireless camera has its own 9V battery. The camera has to have its own supply as it is really bad about picking up noise from the motors.

Video coming soon!!!