LoRaWAN systems are being rolled out to provide low power, wireless Internet connectivity for smart sensors and other devices. Whilst cellular telemetry offers longer distances (30 plus km instead of 10) the 1 and 2W power of the modems means high power consumption , which must be supported by large power supplies. LRraWAN transmitters are typically 100 mW so draw a fraction of the power of cellular systems, allowing for the development of compact battery and solar powered sensors.


lora node_100


The WAN part of the technology comes from the term Wide Area Network, the term given to computer networks that are accessible to the public. LoRaWAN provides “IP”  based connections - the same type used across the rest of the Internet. So a device with a LoRaWAN transceiver, can send data to a server anywhere on the Internet. In cellular systems, you subscribe to a network provider who issues you with a SIM card which is inserted into the device. As long as your device is within range of one or more towers operated by that carrier the device will be able to send data.  By comparison LoRaWAN devices are registered with a LoRaWAN server and will push data through any LoRaWAN Gateway which receives their signal. If two Gateways are in range, an arbitration process e decides which one will transfer the information to the LoRaWAN server - which may be installed anywhere in the world.




As the vast majority of the sensors in use in the environmental monitoring market utilise the SDI-12 protocol, it seems sensible to make a LoRaWAN device to suit. Hence the Tekbox TBS12 and TBS-L1 SDI-12 to LoRaWAN Bridge.


TBS 12






The first variant of the TBS12 was integrated into the body of the Otto Soil Moisture Probe and used to prove the concept. With power from a single use Lithium battery, the unit proved a valuable test bed and fed information back in to  the development of the fully fledged version.




The TBS12 is available with either a single use battery or solar charged battery. The former  can be used in applications with low sensor counts and long log / transmit intervals. The latter  is perfect for multi-sensor probes, multi-sensor configurations and for applications requiring short log / transfer rates (e.g. 15 min).




To keep installation simple, sensor connections are made using Cage clamps (rather than screw terminals). Configuration and testing are carried out over a USB po rt..




SDI-12 to LoRaWAN Bridge




The TBS12E is a simple SDI-12 to LoRaWAN Bridge suitable for a range of simple monitoring applications. The TBS12E is supplied in a powder coated aluminium case and is powered by a set of 3 off C sized alkaline batteries. In most applications these will easily provide a year’s data between battery changes. The case is fitted with an antenna connector on top and a sensor socket on bottom. You can connect a wide range of SDI-12 compliant sensors to the TBS12.




LoRaWAN Data Logger / Telemetry Unit




Whilst the TBS12 is designed as a head for the Otto soil moisture probe, the TBS-L1 is a general purpose SDI-12 to LoRaWAN Bridge. It allows any compatible SDI-12 sensor to feed data in to a LoRaWAN Network.




The L1 is built around a vented enclosure. Connections to external sensors are made via cage clamps on the PCB, with cables routed through cable glands on the bottom of the case. Power comes from an external solar cell  and the main PCB includes a built in battery charger with Lithium battery. The LS1 includes a DC-DC converter which generates the 12V supply needed for the SDI-12 sensors.




The L1 is programmed using Tekbox’s LoRaWAN GUI (Graphical User Interface) a Windows program, supplied free of charge to purchasers of the  TSB12 or L1. Using the GUI, users can set all of the LoRaWAN communications parameters (network and application session keys, device ID, operating frequencies etc) and set up the commands needed to read the attached SDI-12 sensors. In addition, the GUI supports a direct command mode, allowing users to send commands to either the LoRaWAN Modem or SDI-12 sensors.


Tekbox LoRaWAN Broker






Whilst most suppliers want to lock you in to a single end to end solution (from node to display) we believe in the importance of choice: leaving you to select the SDI-12 sensor of choice, to feed it to the LoRaWAN Network of your choice and to display it in the presentation software of your choice.




To support this, TekBox have developed a MiddleWare server application (Broker)  which takes the characters  produced by the Lora WAN Server and adds all of the Meta-Data needed to turn it in to useful data: information such as the tag’s  Measurement Units, validation limits, display limits ; device level information such as the site’s GPS coordinates and time zone. The MiddleWare then provides flexible tools with which you can access both the raw and meta data: MQTT,  CSV, text, XML and JSON formats, FTP export etc. If you have a custom API we will add support for that as well.