Design Of Monitoring System For Mine Anchor Cables Stress Based On ZigBee

Roadway support is a measure to prevent mines’roof and sides from collapsing in the coal mine safety aspect. Prestressed anchor cable support is widely used in roadway support recent years. In order to acquire change trend of anchor cable stress quickly and handily at each measuring point, it is need to monitor exactly and real-time stress values of roadway’s stratum surface.Anchor cable stress monitoring system based on ZigBee is made up of anchor cable sensors, communication substations, communication main station and upper computer. Inner eight strain gauges of sensors are connected in the way of active full bridge, each bridge arm has two series strain gauges, and their pasted positions are symmetrical with direction of axle wire. Directions of pasted strain gauges in two next bridge arms are vertical. This structure can eliminate effect efficiently which produced by eccentric load and temperature effect. Communication substation can amplify, analog-digital convert, display and transmit wirelessly the acquired stress data. Data is transmitted by the way of " hand in hand", that is,one communication substation at each measuring point receives the previous substation’s stress data, packages data together and transmits to next substation, when it comes to damaged substation,monitoring system can skip this substation and continue to communicate with next substation. There are switching circuits in the substation boards, devices can switch to power off or power down mode by software setup when they are in idle state, and can wake up automaticly when they need to work, to a large extent,this way reduces system power consumption. Communication main station is a bridge in the monitoring system, on one hand main station receives all communications’data, and stores data,displays data, transmits data to upper computer by Ethernet, on the other hand, main station receives commands to manage all communication substations. All modules of communication substations and main station are designed by these measures like adding protection circuit, increasing wiring width, expanding heat radiation area and so on to prevent boards from producing phenomenon of heat and spark lighting. This design is in accordance with demand of intrinsic safety circuit.Monitoring system can transmit automaticly,exactly,real-time pulling force of anchor cables in roadway support anytime, compared to traditional mechanical measurements, it has a great promotion in productiveness aspect. There are many measures to guarantee running stability of system, low power consumption and expandability can improve system performance to some extent, it has great significance on building information and digitalized mines.