2. 433MHz
2.1. Introduction
In the Netherlands, and perhaps beyond our borders too, there is a simple system for remote switching of lights, called Klik aan Klik uit (KAKU). Although not the cheapest option available, it is quite affordable, especially if you use the APA3-1500R Starterset.
Although a complete Internet solution is available using "The Cloud", I decided that one of my Pi's would be just as good.
There are a number of steps to be taken to get a working solution. I have tied to keep it as simple as possible. This means that I have not always chosen the cheapest solution.
2.2. Step 1: Transmitter hardware
The KAKU works at 433MHz. That means we need a 433MHz transmitter. These things are cheap and it does not really matter which one you choose. I took this one. I use female-female jumper wires to connect the transmitter to the Pi.
![IMG_4137.JPG](block/IMG_4137.png)
Pin
|
Color
|
Function
|
Comment
|
1
|
black
|
Ground
|
|
2
|
blue
|
Data
|
|
3
|
red
|
Vcc
|
5V; maximum is 12V
|
4
|
yellow
|
Antenna
|
marked ANT; should be 16.7 cm
|
These are connected to the Pi as follows:
![IMG_4134.png](block/IMG_4134.png)
In practice, this means that GPIO14 is used:
![pipin.png](block/pipin.png)
2.3. Step 2: Transmitter software
To test the set-up, we need some software to send control signals. In general, all source software is under ~/src in my set-up. You might want to follow that. So, mkdir ~/src if that directory does not exist. Also, you need GIT, so sudo apt-get install git if you haven't done that earlier.
The software set-up comes in two parts:
-
the libraries to send the signals
-
a front-end to do the switching
First, install the libraries. In buster, this should be part of the distribution, but it doesn't hurt to make sure it is installed.
sudo apt-get install wiringpi
Next, a simple CLI front-end:
cd ~/src git clone https://github.com/chaanstra/raspKaku cd raspKaku g++ -o kaku kaku.cpp -I/usr/local/include -L/usr/local/lib -lwiringPi
Get a simple wall-plug from KAKU, plug it in ans do sudo ./newkaku 1 A on within two seconds. And Lo and Behold: It switches! You can switch it off again with sudo ./newkaku 1 A off
Install newkaku in /usr/local/bin and make it set-uid:
sudo cp newkaku /usr/local/bin sudo chmod u+s /usr/local/bin/newkaku
2.4. A website to switch
CLI is for real geeks; if you want to show your familiy and friends that it works, you will need a simple website.
2.4.1. Install a webserver
First that means that you should install a web server. My choice is Apache. I also dislike installing by hand. I therefore use an Ansible playbook.
tasks/main:
--- - name: install apache become: yes apt: name: - apache2 - name: enabled mod_rewrite apache2_module: name=rewrite state=present become: yes notify: - restart apache2 - name: enable cgi become: yes apache2_module: state: present name: cgid notify: - restart apache2 - name: copy default site become: yes copy: src: 000-default.conf dest: /etc/apache2/sites-available notify: - restart apache2
handlers/main.yml
--- - name: restart apache2 become: yes service: name=apache2 state=restarted
files/000-default.conf
LoadModule cgid_module modules/mod_cgid.soServerAdmin webmaster@localhost DocumentRoot /var/www/html ScriptAlias "/cgi-bin/" "/var/www/cgi-bin/" ErrorLog ${APACHE_LOG_DIR}/error.log CustomLog ${APACHE_LOG_DIR}/access.log combined
If you are not using Ansible, use the 000-default.conf and put it in sites_enabled
2.4.2. The website
I made a directory /var/www/data/kaku where all the data for my CGI script is stored. In that directory, there are two files:
-
data
-
codes
In the codes file, the codes for switching are placed:
0;all;11110001,11110002,11110003,11110004 101;switch 1;11110001 102;switch 2;11110002 103;switch 3;11110003 104;switch 4;11110004
The data file is used for a simple timer interface to the cronjob.
The scripts are in CGI script and cronjob (a workable version) or at https://github.com/ljmdullaart/kakuweb (the most recent version).
2.5. note
Raspberry Pi is a trademark of the Raspberry Pi Foundation.