RAK7204 Environmental Sensor Testing by Florian Haslhofer

The RAK7204 is a LoRaWAN™  node that serves as an environmental monitoring station. The high-precision sensors, can measure changes in temperature, humidity, gas pressure and provide an indoor air quality index.

See how a RAKstar Florian Haslhofer did an honest review and testing of RAK7204 and its capabilities.

"I tested the RAK7204 environmental sensor. It is based on a BME680 sensor and can measure temperature, humidity, air pressure and gas resistance. It is ideal to monitor the air quality in a room.

The design is nice and clean, and the case feels very stable. Also, the size is well-chosen for a qualitative look.

A RAK811 LoRa module is used as a controller for the application and communication to a LoRa concentrator. On the PCB is also a micro USB port for updating bootloader and firmware. One big advantage of the RAK811 module is the usage for most common LoRa-frequencies in a single chip. It is possible to change the same sensor between 433MHz, 868MHz and 915MHz (and even more, just have a look at the datasheet).

Image source: Froilan Haslhofer, Actual photo and result

About temperature, humidity and air pressure is nothing to comment. Standard values with given accuracy from the manufacturer. But there is more to say about the air quality index promised on RAK's website.

First of all, we should be clear, the BME680 doesn’t measure CO2. It is a sensor for VOCs (volatile organic compounds). But the number of VOCs in the air is also a comparative value for the air-quality. It will be represented by a so-called 'gas resistance ‘.

When I got the sensor, I was only able to receive temperature, humidity and air pressure from the sensor. No air quality. After a few messages with an engineer from RAK, he told me, that there are still troubles with the air quality index. You should know that Bosch (the sensor manufacturer) doesn’t provide the formula for air quality index calculation directly. Instead, they have some pre-compiled libraries for specific controllers.

Since the update from 2019-10-17, RAK7204 provides the raw value from the sensor, the gas resistance. It’s better than nothing, but it’s not the promised “air quality index” which, can be a simple value for the indication of good or bad air quality.

All in all, the sensor is a good product for a fair price.  The problem with the air quality index will be hopefully fixed with the next update."