Remote Control Car

Today (or tonight, however you work best) we will be making a remote control car. We will be going over the process of building the car, from using a pre made set to make the car itself, to prototyping a remote on the breadboard, then finally soldering our remote together and using it to control the car. We will be using radio transmission for our car, and the HT12E/D chipset to encode and decode the data we are sending to drive our car.

Firstly, let's go over the chipset that we will be using in this tutorial to facilitate the radio transmission method of controlling our car.

HT12E/D
The HT12E/D set of chips acts as an encoder and decoder. The HT12E is, as the name implies the encoder, and the HT12D is the decoder. The encoder sends an encoded signal via radio waves to the decoder. There is an oscillator in both the encoder and the decoder - this ensures that they are operating at the same frequency, and that the decoder is able to actually receive the signal from the encoder. The HT12E outputs a four word encoded transmission that is then able to be received by the decoder. The transmission essentially gives either an on or off state for each of the four channels on the chip. A possible transmission could be: on, off, off, on. In our scenario each of these channels transmits different signals to the car to tell it to move either left, right, forwards, or backwards.

This diagram below shows the pins that we can find on the HT12E encoder chip. The VDD and VSS pins each connect to the power supply. The pins that are labelled AD8, AD9, AD10, and AD11 are data pins. On our circuit we use them for the buttons, as they accept input from the buttons that determines which of our LEDs should be turned on or off. This again translates into the movement of our car, as the buttons on our circuit board are what we use to control the movement and direction of the RC car. The OSC1 and OSC2 pins are for our resistor that is connected to the chip, which provides a source of external resistance for the oscillator that is contained within the chip. This is important because the oscillator is vital to the overall function of the chip.

Step 1: Making the Car (This tutorial was created by Declan)

The set I will be using to make the car today is a simple tank drive car kit, with a light sensor to follow a path. Your car does not need the light sensor, but a tank drive car is needed for the method we are using today. This first part of the guide is made to suit those working with the same kit I am.

Supplies:

1 Circuit board

1 battery pack

2 gearbox motors

2 Wheels

2 Rubber wheel rings

1 3cm Bolt

2 Red LEDs

2 White LEDs

1 Button

1 Nut

1 Cap

2 1cm screw

4 Wires

2 photo resistors

1 Lm393 ic chip

2 100 uf capacitors

2 103 potentiometers

2 s8550 transistors

2 1k ohm resistors

2 10 ohm resistors

2 3.3k ohms

4 51 ohm resistors

1 Soldering Iron

1 Spool of solder

1. It is generally best to solder in the shortest components of a circuit first, in order to get a nice and clean soldering, so we will be soldering resistors in first.

2. Solder in transistors

3. Solder in capacitors

4. Solder in potentiometers/variable resistors

5. Solder in the IC chip

6. Solder in the button

7. Solder in LEDs and sensors. Make sure that the white LEDs are about a centimetre off the board and the sensors about a further 0.5 centimetres further out.

8. Place the rubber rim around the wheels, then screw the wheels to their respective motor with the short screw 9. Solder the wires to the pads and then to the motors

10. Test the wires are the correct way around by powering the car and holding the sensor to a black surface. If the wheels are spinning clockwise when held in the right direction, then the wiring is correct. If not, fix it.

11. Place the motor to the boards, being sure to check which way it goes and to use the adhesive backing

12. Screw in the bolt, and secure it with the nut. Then put the cap on the bottom on the screw.

Materials:

1 breadboard

1 5 V power supply

1 433MHz Rx receiver radio chip

1 433MHz Rx sender radio chip

1 1M ohm resistor

1 47k ohm resistor

2 270 ohm resistors

1 spool of copper wire.

1 wire stripper

1 pair of wire cutters

1 HT12E chip

1 HT12D chip

2 IC sockets

4 LEDs

4 buttons

1. Secure a supply of wires for your breadboard that are of the right thickness and type to be able to hold firmly into the board. Ensure that you have enough wire to connect each element of your circuit together, and that you strip the ends of each wire to ensure that the exposed wire can then be inserted into the necessary holes.

2. Place your HT12E/D chips onto opposing sides of your breadboard - the specific placement does not matter, so long as you ensure that the pins for each chip are on opposite sides of the central channel in the breadboard. Also ensure that you have enough space around the chips to place your leds and radio components.

3. Take your wires and begin the process of connecting them to the pins of the decoder and encoder chips. On the encoder you will need to be connecting the 2, 4, 9, and 14 pins directly to ground (i.e. the negative row on the breadboard in this scenario). You’ll need to connect the 2, 4, and 9 pins on the decoder to ground. On the encoder, connect pin 18 to your power. On the decoder chip you will also need to connect 18 to the power.

4. Connect your 10, 11, 12, and 13 pins on your encoder chip to ground. While the diagram that we have been provided shows that we should be connecting these chips to a series of buttons, this step will come later in the process once we have connected our LEDs and radio transmitters. The buttons will be what controls the direction of our remote control car, and the LEDs will be there to help us tell if the circuit is not functioning correctly.

5. Take the 1m ohm resistor and use it to connect pin 16 to pin 15 on the encoder. This can be done in a variety of ways, and while it doesn’t matter what hole you place the legs in so long as they’re in the same column as the pin, you might find it easiest to place one leg of the resistor in the highest hole in the column, and the other leg on the lowest hole. Take your 47k ohm resistor and connect the 16th hole on the decoder chip with the 15th hole, using the same method as above if you find that it works well for you.

6. Now you must find an open space on the board in which you will be able to place your four LEDs - this is where the previous advice given comes in handy, as placing the chips in the proper manner will have ensured that you now also have the space to fit in the LEDs. Place the positive leg of each of your LEDs in a different row of the same column. Then place the negative legs of each led in a different column, spacing them out one hole further each time. Thus the first, or top, LED will have its negative leg one hole away from its positive, the second LED will have it two holes away and so on. Now we must connect the negative legs of each of your LEDs to the decoder chip. Remembering that columns on the breadboard are connected together, we will place a wire in the hole above each of the LED’s negative legs. We will then con

7. Take your 270 ohm resistor and place one leg in the very top hole of the column containing the positive legs of the LEDs. Then, connect the other side of the resistor to the positive row on the breadboard.

8. Now we must take a wire and connect pin 17 of the HT12E chip to pin 14 of the HT12D chip. This will allow us to test the connection and function of the LEDs. We will need to connect the breadboard to power to conduct this test. By removing the end of one of the wires that connects the LED’s from the encoder, we should see the corresponding LED turn on. You might need to switch the direction of your LEDs if you see the opposite effect, or you might need to reassess the positioning of your wires if you do not see any of the LEDs turn on no matter what you do. Now that we have made use of this wire to test out our LED circuit, and made sure that the LEDs do in fact function as we intend them to, we can remove this wire and prepare our circuit to function purely off the use of radio transmitters to send our information back and forth between the encoder and decoder chips.

9. Take your radio circuit and divide it into its two halves - the small circuit is the sender, and the big circuit is the receiver. Take the sender circuit and place the three pins into three holes in your breadboard. Connect the left most pin on the receiver to pin 17 on the encoder. Connect the middle pin to power and the right pin to ground (i.e. negative).

10. Take the receiver circuit and place the four pins into four holes somewhere on your breadboard. Now use a wire to connect the far left pin to power, as well as the far right pin. Connect the left middle pin to pin 14 of the encoder.

11. Now place your four buttons somewhere that is easily accessible on the breadboard. Align them as shown in the diagram below. Now we can take each of the wires that are connected to pins 10 to 13 on the encoder chip and connect one of each of them to each individual button. Then we can take another wire and connect the other side of each button individually to ground.

Materials: (you can re-use the parts from the breadboard)

1 HT12E chip

1 HT12D chip

1 1M ohm resistor

1 47k ohm resistor

1 270 ohm resistor

1 433MHz Rx receiver chip

1 433MHz Rx sender chip

1x spool of copper wire

1 pair of wire cutters

1 pair of wire strippers

1 motor driver

1 three pin male to female socket

1x four pin male to female socket

2 circuit boards

1 soldering iron

1 spool of solder

4 buttons

1. Solder in your IC chips onto the PCBs. Follow the positioning shown in the images above. Solder on your female to male sockets for the radio chips, as this will allow you to easily plug and unplug them from the PCBs when necessary.

2. Solder in the resistors - it might be a bit tricky to balance them properly, so if you find it easier to solder the resistors in first do so, but make sure that you have planned out where to place your chips.

3. Solder the buttons onto the PCB with the HT12E chip, following the positioning shown above.

4. Solder in your wires that connect to the VCC pin.

5. Solder in your ground wires.

6. Solder in your wires to connect to the buttons - these should connect to pins 10-13.

7. Solder in the rest of the miscellaneous wires, as shown in the above images.

8. Connect your receiver, remote control and motor control circuit to power to be able to test your car

9. Test the car to ensure that it is working properly.

10. Rejoice in having a working car that definitely didn't take *much* more effort than it should have!