A LoRa Relay Based System for Detonating Explosives in Underground Mines
Philip Branch, Tony Cricenti
Abstract
In this paper we present our work on the use of LoRa as a network technology for detonation of low explosives in underground mining. Using explosives underground is a potentially hazardous activity that mining companies are keen to make safer by removing personnel from near the site of the detonation. Currently detonation is commonly carried out using lengths of copper cable or infrared transmission, both of which limit the distance between the initiator and the explosives. The wireless technology LoRa, is an attractive alternative. LoRa has a much longer transmission range than infrared transmission and other wireless technologies such as WiFi and ZigBee. We have developed and trialed in a working underground mine a prototype system for carrying out such detonations. The system makes use of LoRa as a multi-hop message passing system from an Initiator to a Detonator via a number of Relays. We describe the messages that are passed through the network. We also describe how we deal with contention, broadcast storms and duplicate messages. Our approach is robust, easy to deploy and gives deterministic delay. We also present measurements of signal strength taken underground. Our results indicate that underground LoRa wireless transmission suffers severe fading without line of sight but where this is a line of sight underground, we show that LoRa propagates considerable distances.