Radio controlled mini cars don’t last forever. Sometimes they get stepped on and sometimes the battery won’t charge anymore. In any case, when the radio transmitter and receiver still work, it may be an opportunity to hack a 4 output digital controller.
The receiver unit is from a Bensu Mini Racer. They all seem to have slightly different electronics under the hood but most serve the same functions; forward, reverse, right and left. IR control systems for these cars may pose unknown problems that you will need to address.
An h-bridge type circuit is used to control the voltage to the motor. The motor is replaced by 2 LEDs in reverse polarities. When Forward button is pressed one LED lights. When the reverse button is pressed the voltage polarity switches and the other LED lights.
The steering is accomplished with 2 electro magnets. Energize one magnet and it pulls the steering mechanism for a left turn, the other to the right. Replace the coils with LEDs. Polarity matters. (This receiver switched the ground connection. Not sure if they are the same for all)
The battery in the Bensu car was 1.2 volts. This was barely enough to light the LEDs and needed a higher voltage. A 1.5 Volt battery was used to power the receiver without producing any smoke. Higher voltage may be require the addition of resistors in line with the LEDs to limit current flow.
With the LEDs and battery hooked up, the receiver can be tested. Power up the transmitter. One LED should light up for each of the buttons on the transmitter. Press 2 buttons and unexpected combinations will appear. Such is life.
The LEDs were for test purposes. Replace all the LEDs with the LED side of an optocoupler (see previous blogs). Hook the photo transistors to the joystick port pin 1 to 4, and ground. You should be able to play a game that requires you to move in 4 directions and not use a trigger button. PacMan comes to mind.
This may have limited use on a game machine. Being able to wirelessly trigger events from a remote position may be what you need for that computer project. Radio waves will go through solid objects so your remoteness may only be limited by the transmitter power.
Plus, you also have that feeling of pride that only comes from keeping one more piece of electronics out of the landfill.
NOTE: This receiver has been used with a Mindstorms/HiTech prototype board and an Arduino Uno. Slight modifications to the circuits were required for each.
NOTE: Optocouplers are my friend.