I had heard about GPIO pins on the raspberry pi and decided to do something with it. And with the holidays coming, wouldn’t it be great to be able to turn on and off your light display from the web! This is a pretty simple project that creates a web app for controlling lights. It uses the Raspberry Pi for the internet connection and a wireless remote control to turn on and off the lights. The tricky thing is to connect the Raspberry Pi GPIOs to emulate pressing the buttons on the remote control.
Step 1: Parts
• Raspberry Pi
• Remote controlled outlets
• Ribbon cable
• PCB board
• Soldering gun
• Wire cutters
• Wire striper
Step 2: Web Server setup
I choose the Web2Py framework for it’s ease of installation and use. Installation is very simple. Follow the instructions (repeated here) at http://web2py.com/books/default/chapter/29/13#One-step-production-deployment
Connect your R-PI to the internet. Logon to your R-PI and enter the following at the command line:
chmod +x setup-web2py-ubuntu.sh
Follow the instructions on the screen. This step will take several minutes and you may see some errors in the process, but it seems to work anyway. The mail configuration is not really important, you can just set it as “no configuration”. When asked about your location and such, the values aren’t critical, do your best. The most important thing is to remember the admin password that you select during the installation
Once the installation is complete you should be able to connect to web2py server from your computer. In your computer’s browser enter the address to your Raspberry Pi. It is very important that you used https when connecting to the web2py server. Your URL will look something like:
https://192.168.2.179/ or https://rasberrypi
You may see a security warning in your browser. That’s OK, you can safely ignore this warning. If everything worked correctly, you should now see the welcome page for Web2Py.
Step 3: Make the board
Probably, the hardest part of this project is to figure out how your remote control works.
As Dave Jones says, “don’t turn it on, take it apart!”. Open up the case on your remote control. I hope your’s is as easy as mine, it just had 3 screws. Look carefully at the board on your controller and find where the buttons are, most likely they are traces on the PCB activated by rubber button. Follow the traces connected to the button, there should be 2 connections to each button. One side of the button will be connected to a chip on the board (it will either be a black rectangle with legs, or a black plastic blob), the other end will be connected through a resistor to either the battery + or the battery -.
In my case, the buttons were connected to the + of the battery. This means that the button “pulls up” the micrcontroller line to the supply voltage when it is pressed. To emulate the press of a button, we will connect the GPIO of the Raspberry pi through a resistor to the of the button that is connected to the chip on the board (rectangle or blob).
The first schematic shows how the buttons were connected on my remote. The second schematic show how to inject the signal from the Raspberry Pi.
I created a board to make this as small as possible and be able to add the extra hardware into the case for the remote. The layout for the board is included. I used surface mount resistors because I had some, also the values aren’t that important, 330 Ohm – 1K Ohms would be good choices. If you have different values and through hole resistors, that’s fine, it will work fine. Also, creating a custom board for this is not required, you can certainly solder resistors directly to the remote’s board. (good luck :))
Step 4: Connect to the controller
So for connecting to the controller all you had to do is find the pads in the back of the controller that connect to the microcontroller. I had some wire hanging around so I soldered the pads to the board and the ribbon cable with the right pins corresponding to the GPIO pins on the Rasp Pi. I had to use my multimeter find the right pins.
Use your dremel or file to make a slot in the back of the remote case so that the ribbon cable comes neatly out the back.
For more detail: Raspberry Pi GPIO home automation
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