What it shows
A remote control flashes an invisible infrared LED in a coded pattern, and a receiver module decodes it into a number. The Arduino can read that number and act on it, so any old remote becomes a controller for your projects.
The science
The remote sends bursts of infrared light, switched on and off in a pattern at a carrier of about 38 kHz. The receiver module filters this carrier and outputs a clean digital pulse train. The IRremote library measures the pulse lengths and turns them into a code, for example a hexadecimal number. Each button has its own code, and the sketch uses a switch statement to match the code to an action.
Materials
Cost: under Rs 1,500. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- An Arduino Uno or compatible board
- A VS1838B or TSOP1738 infrared receiver module
- An old TV or set-top box remote with fresh cells
- Three LEDs with three 220 Ω resistors
- An SG90 micro servo
- A breadboard and jumper wires
Safety
For this project: USB power only. Do not use remote controls that have cracked battery cases or leaking cells.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Connect the receiver: its three pins to 5 V, GND and signal on pin 11, checking the pin order from its markings.
Install the IRremote library and run the example that prints received codes.
Point the remote at the receiver, press buttons 1, 2, 3, OK, left and right, and write down each code.
Connect the three LEDs with 220 Ω resistors to pins 3, 4 and 5 and GND.
Connect the servo signal to pin 9 and its power to 5 V and GND.
In the sketch, use a switch statement: buttons 1 to 3 toggle the LEDs, left and right move the servo by 15 degrees.
Filter out repeat codes (0xFFFFFFFF) so holding a button toggles once.
Test the range and angle from which the remote still works, and record the longest working distance.
What you should see
Pressing keys on the old remote toggles the three LEDs and turns the servo left and right.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1What kind of light does a remote use?
Infrared, which is invisible to the eye.
2Why is a 38 kHz carrier used?
It makes the signal stand out from sunlight and lamps, which do not flicker at that rate.
3How can you see the remote’s light?
Look at its LED through a phone camera: it appears pale purple when a button is pressed.
4What does the library decode?
The pattern of pulse lengths into a button code.
Take it further
Control a 2WD robot from the remote, using four keys as forward, back, left and right.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.