Here's an intro to how you can get started with a Internet of Things hobby project. It may also help you to get your kids interested in coding
It started out as a halloween prank, with a skull that turns laughing when people come near a sonar: ...and was expanded to a little MQTT/Internet of things demo with "Face Tracking" in Minecraft:
In this article I will introduce you to MQTT - a popular protocol for "Internet of Things" projects, and show how you can combine it with Raspberry Pi and Arduino as a start of a IoT project in your own home. If you are interested in teaching your kids to code, you will also find an intro to how you can mix IoT with Minecraft, hence tapping into endless possibilities for games and fun. I have a special interest in this, being one of the coordinators of the Norwegian movement "Lær Kidsa Koding!" - a cousin to code.org in the U.S. and Computing at School/Code Club in England.
I stumbled across MQTT while I was looking for ways to combine Minecraft and Arduino allowing us to introduce the concepts of Internet of Things (IoT) to kids. I posted some questions about MQTT in the ScriptCraft forum, whereupon Walter implemented support for it over a weekend! I really like his work with Scriptcraft, and hope that this article can contriute to its popularity.
The Arduino alllows you to interface with the physical world using a phletoria of sensors. You can also control motors, servos, and relays, allowing you to control electrical appliances in your household.
The Arduino is extremely forgiving, and there are thousands of articles on how to connect things. For communications and logic, people tend to turn to the credit-card sized $35 Linux-based Raspberry Pi. I have also found this to be the best combination, since the Arduino is rather limited in the processor- and memory-compartment.
sudo apt-get install mosquitto mosquitto-clients
In my line of work, I have been involved with messaging and integration several times, and the tools we use tend to be rather bulky, infested with large XML-configurations, and are hard - if not impossible - to grasp for kids. MQTT (Message Queue Telemetry Transport) was originally developed by IBM as an extension to the MQ Series platform, allowing it to collect measurements from devices over narrow-bandwidth connections. It is designed to be robust, has a low overhead, and has a few tricks up its sleave to handle dropped connections. It implements a simple publish-subscribe integration pattern. Since MQTT is a rising star among IoT enthusiasts, you will find lots and lots of articles about it elsewhere, and I have added some links at the end of this article. Here are some of the features that I think makes it especially suitable for IoT and hobby projects:
Chances are that you are alredy using MQTT daily: Facebook messenger uses it to push notifications to all mobile clients.
Here's an excerpt showing the messages going back and forth in my example:
The left arrows indicate the messages that the broker receives, and the right arrows are issued from the broker. When it detects that the skull has company, it starts controlling the servos. The "facetracker" in Minecraft publishes the sine values of the vector from the skull to the player, allowing the broker to calculate the right servo positions. When a lever changes position, the LED is turned on or off accordingly.
MQTT is so simple that my children instantly could follow the message flow and suggest changes.
This illustration from IBM shows how it is customary to let a broker control the environment. It is in my opinion quite ideal for an IoT context, since several brokers can subscribe to the same sensors. The status/incoming tail of the path tells whether the message contains a command or info
As you can see in the video, the skull movements are quite fluid, since the facetracker updates several times per second. I have ordered a RasPi camera, and intend to use the OpenCV library to make a real facetracker. I hope it won't be too scary for the kids on Halloween...
Here you see the combo that controls the skull. It looks quite complicated with the logical level converter. Once I got the Arduberry, it became much, much simpler.
The Separate Power supply for the Servo Shield:
A tip: You need to test all servos to see what their limits are. Avoid using the max/min values. And the code needs to be adjusted so that it fits your servos.
When you read the code, please keep in mind that I had to learn three new languages with their paradigms, while having a lot of fun. The code isn't as pretty as it should be if you want to use it professionally, but I have tried to make it readable. If you fix something, you may send a pull request :-)
softserial_srvshield_command.ino controls the skull. It communicates with dispatcher.py on the Raspberry PI. The pair implement a simple ping-pong protocol, since the servos must be allowed to complete their movements before the Arduino can accept a new command.It uses the softserial library to communicate with the RasPi through the GPIO pins.
serial_report_distance_v2 reads the sonar. It is based on example code for the sonar, not much of my doing. The Arduino (/arduino/2 on MQTT) is connected using USBSerial, since one-way communication is fast enough. The python script reporter.py is running on one RasPi and publishes the sonar readings to MQTT
reporter.py simply reads the sonar distance from Arduino 2 and publishes them to MQTT
dispatcher.py subscribes on MQTT commands for Arduino 1, and queues them up internally, allowing each command to be executed and acknowledged.
broker.py is the brains of my IoT setup. it subscribes to MQTT reports from both Minecraft and Arduino 2, and sends off commands to Arduino 1 or uses the internal speaker via Pygame. I needed to keep the main thread "alive" to monitor the queue, so I use Pythons (rather poor) multihreading capabilities to delay execution of some commands.
I re-implemented the logic using Node-Red. Much more fun and much much more suitable. Check out this article: Node-RED: How it simplifed my IoT project – and how YOU can rapidly prototype for the Internet of Things. The link to my Node-RED flow on Github: flows_raspberrypi.json
leverpull.js is loaded using the js refresh() command in the shell that starts the minecraft server. You need to execute it AFTER you have logged in to the Minecraft client so it can "find" you. It subscribes to the player move, lever pulled, and block break events, and publishes a number a number of messages to MQTT, implementing the "sensors" that I described above.
Everything can be found on Github. Feel free to copy and use as you like. It is licensed as CC-BY-SA.
For more complete solutions, Forrester Research pays special attention to the following pioneer vendors:
It is early days, and It may take a long time until the world agrees upon the standards that can take IoT to general acceptance. In the meantime, it is fun to play with Arduino and Raspberry Pi!