Versatile LoRa device – sensor interface

A versatile LoRa end device has been designed for connecting different sensors to LoRa network. It’s primary use can be LoRa weather station but is not limited only to enviromental applications.

LoRa sensor interface – typical application

Typical “weather” application is shown in image above: 1-LoRa sensor interface, 2-Particle sensor, 3-Sun shield with temperature and humidity sensors, 4-UV-index and illumination sensor, 5-solar panel for autonomous operation

Sensor interface

Sensor interface consists of power management, communication and microcontroller. Interface is assembled inside plastic housing. PCB is suitable for standard electrical installation junction boxes, exuiped with cable glands for outdoor use. Sensor interface has several inputs for sensors and power sources. Complete system with all enviromental sensors is shown in following diagram:

LoRa sensor interface, populated

Power management

Two power selectors provide automatic switchover between mains, solar or battery operation. Battery is managed with on-board Li-xx battery charger and Li-xx battery protection circuit. Additionally, a low power fuel gauge is added for monitzoring battery state. Voltage form selected power source is then regultated with Buck/Boost converter to 3,3V. Additional 5V supply is provided with boost converter. Complete power management is shown in following block diagram:

Power management

PCB

Schematic diagram is shown below (download PDF here).

Schematic diagram

 

Layout is on PCB with outline dimensions 65x65mm. Layout files are available. If interested, please request altium project file via email.

Assembled module is shown in image below:

 

Assembled PCB

Assembly diagram

There are several connectors and test points on-board with following functions:

Connectors and test points

Housing

Module can be assembled inside standard junction box. Recommended Gewiss GW44205 Assembly steps are shown below:

1. Drill 4 holes for bracket:

Holes for bracket

2.Drill holes for cable glands (PG7)

Housing with holes for cable glands

Cable glands locations are shown in the following drawing:

Cable glands location

3. Use 3D printer and make bracket for the box:

Bracket for mounting on the pole

4. Attach bracket to the box

Assembled bracket

Bracket mounted on the plastic box

Software

Starting point for software development is my repository on GitHub with all required libraries: https://github.com/s54mtb/LoRaDunchy

Check also the project for standalone PM Sensor.

More detailed software section will follow after testing.

 

Testing

Sensors will be tested in laboratory soon. Please visit this regularly for the updates.

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