IoT HVAC Control System PoC

Solution Requirements

1. System components that can properly exchange data despite physical obstacles (concrete and brick structures, elevation differences, windows)

2. Easy for customers to install at home or in the office

3. A minimum range of 70 m between transmitters and receivers

4. A connectivity protocol that extends the sensors' maximum battery life

To verify our solution, we began the project with a Proof of Concept. The system would incorporate a custom device for receiving data from sensors installed on the HVAC equipment (thermostat, air conditioning, ventilation).

Solution

Hardware Platform

Softeq implemented a hardware platform for communication between connected devices. 

The system is based on Sub-1 GHz transceivers with embedded MCUs, which can transmit data over long distances using the IEEE 802.15.4 connectivity standard. In addition to the standard antenna connection, we used Antenna Diversity, a technique that improves the quality and reliability of wireless networks in urban environments.

With our design, the battery life of connected devices can last up to 180 days when transmitting a signal every 10 seconds. Our devices are powered by conventional 1000 mA batteries, which are easy to source and can be replaced by users, without the aid of a technician.

Hardware Market Research and Device Cost Estimation

We conducted market research, negotiated with the hardware manufacturers, and found the most cost-effective implementation option.

We examined the transceiver modules currently available on the market including NXP, Texas Instruments, and Microchip. To make sure that they meet the customer’s requirements, we developed custom firmware and test cases for each module. Despite some differences in the sensitivity and gain parameters of the RF amplifiers, the tests showed insignificant discrepancies in their range and power consumption. Therefore, we were able to select a hardware module based on cost and technical support services.

As a result of negotiations with vendors and their distributors, we were able to accurately calculate the cost of the device. According to our estimations, using the Texas Instruments module will result in lower overall solution costs. It is also more convenient to program and provides a more standardized method of communication.

Communication Protocol

The team came up with a custom communication protocol for more flexibility and cost-effectiveness.

We developed a custom low-level data transfer protocol based on IEEE 802.15.4, which is capable of reliably transmitting the necessary data over long distances. It also provides installation flexibility, allowing us to adapt the data flow and transfer speed to the actual environment where the system is installed.

In addition, the custom protocol helps the client to save on costs associated with the use of standard protocols when releasing the device to the market, including alliance membership expenses and trademark licensing fees.

Connectivity Implementation

Option 1: P2P Connection

By connecting the transmitting devices to the receiver we reached a minimum data transmission distance of 300 meters. This method enables a more stable connection and results in a lower end cost.

Option 2: Mesh Network

We connected transmitters into a self-organizing custom Mesh-network based on the 6LoWPAN low energy network protocol. Using this method, we registered a minimum transmission distance of 1.5 km.