How to Program a Remote to a Toy Car: Overcoming Signal Loss Issues

Controlling a toy car with a custom remote can be a fun and educational project, especially when you delve into the world of microcontrollers like Arduino. Many hobbyists and parents find themselves wanting to replace a lost or broken remote, or even upgrade the control system of a toy car for a more personalized experience. Often, this involves using Infrared (IR) remotes as a cost-effective and readily available solution.

However, DIY enthusiasts often encounter a common problem: signal loss. Imagine you’ve successfully programmed your Arduino to control the car’s movements – forward, backward, left, and right – using an IR remote. Everything works perfectly as long as you’re actively pressing buttons. But what happens when you release the button, or the signal is interrupted? The car might continue its last command indefinitely, potentially leading to crashes or getting stuck.

This article addresses this very issue, inspired by a real-world problem faced by a hobbyist attempting to control a toy car with an Arduino and an IR remote. We’ll explore the challenge of stopping the car’s motor when the remote signal is lost and discuss potential solutions to ensure your toy car behaves as expected.

The core of the problem lies in how the Arduino code interprets the absence of a signal. In many setups, the code is designed to react to received signals. When a button on the remote is pressed, an IR signal is sent, decoded by the Arduino, and translated into an action – like moving the car forward. However, when the button is released, or the remote is out of range, the Arduino simply stops receiving new commands. It doesn’t inherently know that the signal is lost and should stop the car.

Let’s examine a typical code structure to understand this better. The provided code snippet uses the IRremote.h library for Arduino to read signals from an IR remote. It sets up motor controls and uses a switch statement to perform actions based on different remote button presses:

#include <irremote.h>

int RECV_PIN = 3; //IR signal pin
IRrecv irrecv(RECV_PIN);
decode_results results;

void setup() {
  Serial.begin(9600);
  Serial.println("Enabling IRin");
  irrecv.enableIRIn(); // Start the receiver
  Serial.println("Enabled IRin");
  pinMode(6, OUTPUT);   //motor controller sleep
  pinMode(8,OUTPUT);   //drive 1
  pinMode(9,OUTPUT);   //drive 2
  pinMode(10,OUTPUT);  //turn 1
  pinMode(11,OUTPUT);  //turn 2
}

void loop() {
  digitalWrite(6,HIGH); //motor driver on - LOW signal can be used to turn off motors when signal lost

  if (irrecv.decode(&results)) {
    Serial.println(results.value, HEX);

    switch(results.value)
    {
      case 0x952D6661:
        Serial.println("Forward Straight");
        digitalWrite(8,LOW);
        digitalWrite(9,HIGH);
        digitalWrite(10,LOW);
        digitalWrite(11,LOW);
        break;
      case 0x23262881:
        Serial.println(" Forward Left");
        digitalWrite(8,LOW);
        digitalWrite(9,HIGH);
        digitalWrite(10,LOW);
        digitalWrite(11,HIGH);
        break;
      case 0x919A644A:
        Serial.println(" Forward Right");
        digitalWrite(8,LOW);
        digitalWrite(9,HIGH);
        digitalWrite(10,HIGH);
        digitalWrite(11,LOW);
        break;
      case 0xE213B5FC:
        Serial.println("Back");
        digitalWrite(8,HIGH);
        digitalWrite(9,LOW);
        digitalWrite(10,LOW);
        digitalWrite(11,LOW);
        break;
      case 0x9AC34E4B:
        Serial.println(" Back Right");
        digitalWrite(8,HIGH);
        digitalWrite(9,LOW);
        digitalWrite(10,LOW);
        digitalWrite(11,HIGH);
        break;
      case 0xDAE44B8A:
        Serial.println(" Back Left");
        digitalWrite(8,HIGH);
        digitalWrite(9,LOW);
        digitalWrite(10,HIGH);
        digitalWrite(11,LOW);
        break;
      case 0x64CBF9DA:
        Serial.println(" Turn Left");
        digitalWrite(8,LOW);
        digitalWrite(9,LOW);
        digitalWrite(10,LOW);
        digitalWrite(11,HIGH);
        break;
      case 0x607B80BB:
        Serial.println(" Turn Right");
        digitalWrite(8,LOW);
        digitalWrite(9,LOW);
        digitalWrite(10,HIGH);
        digitalWrite(11,LOW);
        break;
      case 0xEE587246:
        Serial.println(" Neutral");
        digitalWrite(8,LOW);
        digitalWrite(9,LOW);
        digitalWrite(10,LOW);
        digitalWrite(11,LOW);
        break;
    }
  }
 irrecv.resume(); // Receive the next value
}

This code effectively reads IR signals and controls the motors based on received commands. However, it lacks a mechanism to handle signal loss. The default case in the switch statement won’t work here because the issue isn’t an unknown signal, but the absence of any signal.

To solve this, we need to implement a way for the Arduino to recognize when it hasn’t received a signal for a certain period. Here are a couple of effective approaches:

1. Timer-Based Approach:

This method involves setting a timer every time a valid signal is received. If the timer expires before a new signal arrives, it indicates signal loss, and the motors can be stopped.

• Implementation Idea:
  • Introduce a lastSignalTime variable to store the time of the last received signal.
  • In the if (irrecv.decode(&results)) block, update lastSignalTime to the current time using millis().
  • In the loop() function, outside the if block, check if the current time minus lastSignalTime exceeds a certain threshold (e.g., 100 milliseconds).
  • If the threshold is exceeded, it means no signal has been received for too long, so stop the motors by setting all motor control pins to LOW (or the appropriate ‘stop’ state for your motor driver).

2. “Stop” Signal from Remote:

If your remote sends a specific “stop” code when all buttons are released, you can explicitly handle this in your code.

• Implementation Idea:
  • Identify the “stop” code sent by your remote when no button is pressed (you can use the serial monitor to read the codes).
  • Add a case in your switch statement for this “stop” code.
  • Within this “stop” case, include the code to stop the motors.

While the “stop” signal approach can work, it relies on the remote consistently sending such a signal. The timer-based approach is generally more robust as it handles cases where the remote signal is lost due to distance, obstruction, or remote malfunction, not just when a specific “stop” button is pressed (or lack thereof).

By implementing a signal loss detection mechanism, you can ensure your toy car behaves predictably and safely, stopping when the remote control is no longer actively sending commands. This refinement significantly improves the user experience and makes your DIY remote control project much more practical and enjoyable.