Introduction: RC Powered Electric Toy Car

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By: Peter Tran 10ELT1

This tutorial details the theory, design, manufacturing and testing process for a Remote Control (RC) powered electric toy car using the HT12E/D IC chips. The tutorials detail the three stages of car design:

  1. Tethered cable
  2. Infrared control
  3. Radio Frequency control

A troubleshooting section is also available to solve common issues which may arise.

Supplies

Base Car Kit

  • 1x Line Following Robot Kit (LK12070)

Tethered Cable Phase

  • 1x Prototyping Breadboard
  • Breadboard Jumper Cables
  • HT12E IC Chip (with socket)
  • HT12E IC Chip (with socket)
  • 1x 1MΩ Resistor
  • 4x Momentary Button Switch
  • 1x 47kΩ Resistor
  • 4x LED
  • Power Supply

Infrared Transmission Phase

  • 1x Infrared Transmitter (ICSK054A)
  • 1x Infrared Receiver (ICSK054A)

Radio Transmission Phase

  • 1x 433MHz RC Transmitter
  • 1x 433MHZ RC Receiver

Integration into Base Car Kit

  • 2x Prototype PCB Board
  • 1x L298N Motor Driver

Step 1: Understanding the HT12E/D IC Chip

The HT12E and HT12E IC Chips are used together for Remote Control system applications, to transmit and receive data via radio. They are capable of Encoding 12 bits of information which consists of 8 address bits and 4 data bits. Each address and data input is externally programmable or fed in using switches.

For proper operation, a pair of HT12E/D chips with the same address/data format must be used. The decoder receives the serial address and data, transmitted by a carrier using an RF transmission medium and gives output to the output pins after processing the data.

HT12E Pin Configuration Description

Pins 1-8: Address pins to configure the 8 address bits, allowing 256 different combinations.

Pin 9: Ground pin

Pins 10-13: Data pins to configure the 4 data bits

Pin 14: Transmit enable pin, acts as a switch to allow transmission of data

Pin 15-16: Oscilloscope OUT/IN respectively, requires 1M ohm resistor

Pin 17: Data output pin where the 12-bit information comes out

Pin 18: Power input pin

HT12D Pin Configuration Description

Pins 1-8: Address pins, need to match the configuration of the HT12E

Pin 9: Ground pin

Pins 10-13: Data pins

Pin 14: Data input pin

Pins 15-16: Oscilloscope IN/OUT respectively, requires 47k ohm resistor

Pin 17: Valid Transmission pin, acts as indicator for when data is being received

Pin 18: Power input pin

Why is the HT12E encoder used?

The HT12E is widely used in remote control systems, due to its reliability, availability and ease of use. Many smartphones now communicate via the internet, but most smartphones still feature an HT12E to avoid internet congestion. While the HT12E uses the address to transmit with the transmitted data, with 256 possible combinations of 8-bits, it's security is still very limited. As a signal is broadcasted, it is impossible to trace the transmitter, making the signal address potentially guessable by anybody. This address limitation makes the use of the HT12E suitable only at a shorter distance. At a shorter distance, the send and receiver can view each other, like the TV remote, Home Security, etc. In commercial products, some remote controls can replace others as a 'universal remote'. Because they are designed for a shorter distance, many devices have the same address input for simplicity.

Step 2: Constructing the Base Car Kit

The Base Car Kit for this project is from a Line Following Robot Kit. Construction and manufacturing steps can be found in the following link: https://m.media-amazon.com/images/I/D1q5OEF-z7S.pdf.

The Base Car Kit will eventually be converted to become a RC controlled car, using the HT12E/D IC Chips.

Step 3: Tethered Cable Phase

  1. Use a prototyping breadboard and prototyping jumper cables.
  2. Follow the above schematic diagram to mount and connect the components to the breadboard. Note, the only connection between the two ICs are pin 17 on the HT12E to pin 14 on the HT12D.
  3. Test the design by ensuring the LEDs connected to the HT12D light up when their respective switch on the HT12E is pressed. See the Troubleshooting section for assistance with common issues.

Advantages of a tethered cable setup

  1. Reliable and stable due to no risk of external objects as interference
  2. Relatively cheap
  3. Simple and straightforward to set up and troubleshoot
  4. Not susceptible to inference by other external sources

Disadvantages of a tethered cable set up

  1. Impractical for long-distance data transmission
  2. Cost becomes significantly higher with a long-range transmission
  3. Difficult to relocate or reposition to different locations
  4. Operator is required to remain in close proximity to both transmitter and receiver
  5. Reduced flexibility and mobility of use

Step 4: Infrared Transmission Phase

  1. Disconnect the direct tethered cable from pin 17 of the HT12E, connect the output pin of an infrared transmitter and connect the transmitter to power.
  2. Disconnect the direct tethered cable from pin 14 of the HT12 D, connect the input pin of an infrared receiver and connect the receiver to power.
  3. Test the design by ensuring the LEDs connected to the HT12D light up when their respective switch on the HT12E is pressed. See the Troubleshooting section for assistance with common issues.

Advantages of an infrared transmission set up

  1. Secure for short distances due to the requirement of line-of-sight transmission
  2. Infrared sensor does not corrode or oxidise over time
  3. Can be remotely operated
  4. Increased flexibility of use
  5. Increased mobility of use

Disadvantages of an infrared transmission set up

  1. Cannot penetrate hard/solid objects such as walls, or even fog
  2. Infrared at high power can be damaging to eyes
  3. Less effective than direct tethered wire set up
  4. Requires specific use of frequency to avoid interference from an external source
  5. Requires external power source to operate transmitter

Step 5: Radio Transmission Phase

  1. Disconnect the infrared transmitter from power and pin 17 of the HT12E, connect the output pin of the 433MHz radio transmitter. Also, connect the transmitter to ground and power.
  2. Disconnect the infrared receiver from power and pin 14 of the HT12D, connect the data pins of the 433MHz radio receiver. Also, connect the receiver to ground and power.
  3. Test the design by ensuring the LEDs connected to the HT12D light up when their respective switch on the HT12E is pressed. See the Troubleshooting section for assistance with common issues.

Advantages of a radio transmission set up

  1. Does not require line-of-sight between transmitter and receiver
  2. Not susceptible to interference from bright light sources
  3. Easy and simple to use
  4. Can be remotely operated
  5. Increases flexibility

Disadvantages of a radio transmission set up

  1. Might be susceptible to crossover from nearby users of other radio transmission systems
  2. Finite number of frequencies
  3. Possible interference from other radio broadcasters, eg: radio stations, emergency services, truck drivers

Step 6: Prototype Radio Transmitter

  1. Transfer the components for the radio transmitter from the prototyping breadboard to a prototyping PCB.
  2. Solder the components, with reference to the diagram from step three.
  3. Use solid tin wires to connect the circuit together, using sleeved wires where overlaps occur to prevent short-circuiting.

Step 7: Prototype Radio Receiver

  1. Transfer the components for the radio receiver from the prototyping breadboard to a prototyping PCB.
  2. Solder the components, with reference to the diagram from step three.
  3. Use solid tin wires to connect the circuit together, using sleeved wires where overlaps occur to prevent short-circuiting.

Step 8: Prototype Motor Driver

  1. Solder male sockets to ports: IN1-4 and Motors A-B, to allow for easy adjustments during testing, as per the diagram above.
  2. Solder a female socket to the negative and positive terminals, as per the diagram above.

What is a Motor Driver?
A Motor Controller acts as an intermediary between the car's IC chips, batteries and motors. It is necessary to have one because the HT12E chip can usually only about 0.1 Amps of current to the motor, whereas the motor requires several amps to operate successfully.

Step 9: Integration With Base Car Kit

The following steps are to convert the Base Car Kit into a functional RC Car.

  1. Disconnect the car's battery pack from the circuit.
  2. Solder prototype jumper cables to each motor connection, and connect them to the motor driver as per the diagram in step eight.
  3. Solder the power cable for the radio receiver and motor driver to the now disconnected battery pack.
  4. Connect the output pins from the HT12D (pins 10-13) to the relevant headers on the moter driver as per the diagram in step eight.
  5. Power the radio transmitter using a portable usb battery pack.

Step 10: Testing and Troubleshooting

Testing

  1. Following each construction phase, input into the HT12E should elicit a response (ie either LEDs turn on or motors spin) from the HT12D.
  2. To control the car using the radio transmitter controller:
    • Drive forward: hold both left and right motor forward
    • Drive backward: hold both left and right motor backward
    • Turn left: hold right motor forward and left motor backward
    • Turn right: hold left motor forward and right motor backward
  3. Specific performance characteristics which can be tested are:
    • Speed
    • Range (of radio transmitter/receiver)
    • Response time
    • Reliability
    • Agility
    • Endurance (battery life)
    • Ability to operate in various terrain and surface type/conditions
    • Operating temperature limits
    • Load-carrying limit
  4. Should no or an incorrect response occur, follow the troubleshooting guide below:

Troubleshooting

  1. Motors spin the opposite direction to what was intended
    • Adjust the order of which the prototype jumper cables are connected on the motor driver (all pins can be switched around)
    • The circuit is short-circuiting: check the solder joints and jumper cable connections
  2. Motors/circuits do not power on
    • The circuit may not have enough voltage/current to turn on
    • Check for a missing connection (including power)
  3. Transmit enabled light is not working
    • LEDs are polarised, ensure it is in the right orientation
    • The LED may have blown due to too high current/voltage
    • The circuits are genuinely not receiving signals, check connections again
  4. Radio transmitter/receiver is not strong enough
    • Check to see if other people are also currently using the radio transmitters/receivers
    • Add an additional antenna (can be a wire) to boost connection
    • Point the transmitter/receiver in the general direction of each other, they may of low quality