ZigBee prototype project

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Using wireless technology in combination with UniPi board v1.1

INTRODUCTION – MOUNTAIN COTTAGE AUTOMATED

As UniPi develops further and further, new possibilities arise before us. We work on new projects as well as our customers. Until now, UniPi has always been wired. But with all the hard work put into the development wireless communication for our control unit is becoming true in the near future. Actually, we already test the prototype project.

Member of our team has decided to improve comfort of his mountain cottage in the Austrian Alps using both wired and wireless communication. The project focuses on heating management, temperature and humidity measuring and unwanted presence monitoring.

Project goals

The project aimed to fulfil a following set of goals. 

  • Already build – as the cottage was built years ago, the goal is to minimize needed construction work on the building
  • Old boiler - water for the central heating is heated by a 30 years old oil boiler. The goal here is to use it for the system.
  • Remote control - as the owner does not live in Austria, a remote control may be convenient for continuous monitoring. 
  • Equitherm regulation - the new heating system has to be smart and able to adapt to constant environment changes.
  • Intrusion detection - in case the cottage will become a target of burglars, the system should be able to warn the owner and notify the local police. 

About ZigBee – Which frequency are you on?

To keep construction work needed at minimum, wired technology is not an option. Because of this, ZigBee wireless sensors were used. But there is a question - what is ZigBee?

ZigBee is an open wireless standard for the Internet of Things, allowing for mutual communication between a number of smart devices sharing the same standard. The main advantage of ZigBee is its open nature, compared to other solutions using proprietary technology such as Z-Wave. For more info about ZigBee and the ZigBee Alliance, follow the link here. 

One of the two NYCE’s wireless Motion Sensors used in the project.

One of the two NYCE’s wireless Motion Sensors used in the project.

Connection schema – How did we build it?

To get the overall idea about the system connection lets to have a look at the complete connection schema below and following system description.

The connections schema of all the devices and measurement sensors

The connections schema of all the devices and measurement sensors

As usual, the UniPi 1.1 is used as the master control unit, but on this specific project, Raspberry Pi 2 model B was used as the CPU. Connected to it, a ZigBee chip was used to provide remote motion sensors access. Aside from motion detection, these sensors are also able to collect temperature and humidity readings as well. 

ZigBee ETRX357 module for the control of wireless sensors

ZigBee ETRX357 module for the control of wireless sensors

This project is the first combination of wireless IoT technology and the UniPi board. This application is only a prototype, but the communication between sensors and the UniPi was found to be without significant issues and compatibility problems. That means the UniPi is very close to the full support of wireless smart home devices.

A 1-Wire 8-port hub, collecting data from several 1-Wire thermometers, is connected to the unit's 1-Wire port. 

Distribution board with UniPi. The ZigBee chip is marked with the red rectangle.

Distribution board with UniPi. The ZigBee chip is marked with the red rectangle.

The picture above shows the detail of the distribution board of the house. Three relays ensure the system's functionality, fourth is used as a power supply switch for the UniPi itself. The installation also allows manual control if needed. 

Relays are marked with numbers, corresponding with numbers used in the system schema shown before.

  • Relay 1 serves as a switch for a stronger relay on the left which controls the water heater.
  • Relay 2 is a switch for the circulation pump
  • Relay 3 switches the old oil boiler for central heating
  • Relay 4 then controls the control unit's power switch

The software behind all of this?

The whole system runs Mervis, our official PLC software in accordance with the IEC 61131-3 standard. Mervis communicates via a proxy server, users then can display SCADA (Supervisory control and data acquisition) system interface. Temperatures, humidity and movements are periodically logged into a cloud database and can be later sorted and viewed according to chosen criteria.

For the programming work, ST language was used. This language is one of the supported methods for PLC programming according to IEC 61131-3 standard. 

Mervis SCADA web interface with custom stat readings seen from the smartphone.

Mervis SCADA web interface with custom stat readings seen from the smartphone.

Mervis is an extendable system with numerous plugin support, and even despite the project does not include it, Mervis can be easily connected to a weather forecast. This can be used for creating a fully automated watering system, able to react to weather changes. There are many possibilities and we are sure we will soon come up with another project. 

The boiler room with the distribution board.

Boiler room with the distribution board.

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