Now you can have all the remotes of your house in a device that fits in your hand with Arduino, never fight for who has the TV remote again!
To make it you will need:
- Arduino (I used a cheap copy of the arduino UNO).
- LCD keypad shield, (I bought mine from dealextreme)
- 1x Infrared LED (standard ~940nm)
- 1x Infrared sensor.
- A computer. (That can run the arduino compiler program)
Step 1: Intro:
Infrared light has been used quite a lot for many different applications in many fields, one of them is communication, specifically between remotes and domestic devices, what allows us to control them without leaving the comfort of our sofa.
The process of communication between an emitter (the remote) and a receiver (the device) starts when the user presses any button of the remote, this device has an oscillator and a preconfigured chip that allow the signal to adopt a square waveform with a frequency of 39kHz, depending on the button pressed, the chip will use a determined signal code.
This signal travels through the circuit until it reaches the infrared LED, which transforms it into a series of pulses of invisible light (~940nm). If any sensor it's in it's range those pulses will be transformed into a quadratic wave that will indicate what to do according to the programming of the device.
To create a remote we want to capture those pulses, which will have a certain amplitude in time, we also want to know the time between those pulses so we can reproduce those pulses with voltage and time as the only variables.
Step 2: The hardware.
In this instructable we won't need to work hard creating complicated circuits, instead, our work will be centered on the code we are going to implement.
The hardware we are going to use is the Arduino and the LCD keypad shield, which will help to visualize the menu that will order the codes by their function and the remote they come from .
Notice that this shields usually come without the pin headers, without them we won't be able to use the pins that remain free.
If your shield don't has them just go to your local electronics store and buy a female pin header, cut it and sand the edges with sandpaper, then just solder them into place.
We will use 2 different setups depending on whether we want to gather of send the codes:
Step 3: Gathering the codes.
Before we can create a functional remote we will need to gather the codes of the remotes we want to use, we will use an infrared sensor to do so.
To set up the circuit, we can follow the sketch in the pictures, connecting the signal pin of the sensor to the pin 2 and the other pins to 5V and ground.
The code we will be using is from an Adafruit tutorial, I made some changes in order to make our job easier.
Now comes the boring part, once the code has been uploaded and the sensor connected we go to "Tools" and we click on "Serial Monitor". You will see a message that says "Ready to decode IR!", now, by pressing any key of the remote while facing the sensor, we will be able to obtain the code.
If you use the version I provided the readings will appear in a code form ready to be pasted and interpreted by the Arduino main program, we just need to take care of storing this code to avoid losing it, to do so we can open a .txt to paste and label this signals now converted into code.
IMPORTANT: the program reads the time the signal is high as well as it is low, before you send the signal the program is already counting the time it is low, that time will appear as the first reading and it is useless so it must be deleted. Also, many of the code is unnecessary since it's repeated to make sure the device get's it, if you can find a pattern I suggest you to cut the code and save space, if you just copy and paste it all it's OK but you might be pasting too much redundant information.
TIP: If the Arduino compiler show this message "Serial port 'COM3' not found. Did you select the right one from the Tools > Serial Port menu?" your Arduino isn't connected or the port isn't recognized.
Once we have all the codes we want we can move on to the next step.
Step 4: Preparing our code: menus and submenus
Before being able to send the codes we need to visualize what are we sending, we will need to create a menu with all the functions (or submenus) we want to use.
Creating a menu it's easy, but it can be quite confusing, I've added lots of comments about the functions of each part in the main code.
I would have liked to use a library but instead I built it all in a single monolithic program so you don't have to download anything else, that way it's easier to learn how it works, creating a menu is quite useful and a must-learn task for every programmer.
Once you open the code file, the first thing you want to look for the code that appears at the first image surrounded by a green square, this constants limit the domain of the menus and submenus, to specify the number of menus you want to create you have to take into account there will be a menu 0, meaning that if we input a 2, the program expects to have three menus.
See the third picture to make yourself an idea of how the limits work, basically, if you try to read an array that doesn't exists because it's out of the domain, the program will notice it and will return you to the original position.
Once this has been done, you have to specify the name of the menus at the menu char array (see picture 2), the code is designed to have three menus, but you can add as many as you want by repeating the structure of the 4th image and making the corresponding adjustments in the array and in the domains.
The submenus will be all contained in a single array, so you must write the functions of each menu in the submenu array, then you have to specify the limits of these submenus at code surrounded by the green square, of course if you add or remove menus you have to add or remove this constants.
The program is designed to track your position in the menu/submenu array, for example, if you change of menu, it's variable will also change, that way, when you press the select button you are sending the menu and submenu indexes, in which you are, to the code sending function so it can chose between a series of cases to find the code that matches that function inside the menu.
To put the codes you just have to copy and paste the code obtained when reading the remote signals to the corresponding menu and submenu cases. (see picture 5), you have to pay attention so the function index matches the case number or your remote will be a chaos.
Once you have finished with all this save it and you'll have your very own remote code.
Step 5: Testing it.
Once you've finished with the code it should be able to work, make sure you place the infrared LED from digital pin 3 to ground, pin 3 is a PWM pin, other pins won't work.
Left and right buttons control the menus, up and down control the submenus, select sends the code attached to the corresponding submenu inside the menu.
If you want to have much more power and range you can use several LED's and use a transistor as shown in the picture. I say this because the power supplied by a digital pin is limited to 40mA, enough to lit one or two LED's but not enough to lit an array of 5 LED's for example.
The resistor value for the base (middle pin of the transistor) should be around 1-2k.
Due the high frequency switching a resistor may not be needed since the LED's will handle the power. (I've tried this myself with a standard IR LED and a 5V supply from the digital pin 3 with no problems)
TIP: If you want check if it works you can see the IR light by using a digital camera.
If you have any questions or comments I'll be glad to hear them.
Thanks for watching and don't forget to vote :)