Advanced Embedded Systems: Wireless Sensor Network for pH Sensing - Prof. James Conrad, Study notes of Electrical and Electronics Engineering

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ECGR-

Advanced Embedded Systems

Wireless Sensor Network for pH

Sensing

Sushant Sengupta

• Application.• Working.• Architecture.• Introduction.Sensor Network for pH Sensing

Introduction

• Three types of nodes:- General nodes: They are simply dispersed in water.

communication.computer and uses a RF transceiver for wirelessHost node: It is placed on land & physically connected to a

transducer to communicate with the submerged nodes.transceiver to communicate with the host node, and acousticinformation across the water/air boundary, using a RFUplink node: The uplink node (floating green sphere) transfers

Introduction

lines).communicate acoustically (redscattered throughout the lake andThe nodes (blue spheres) are

is directly attached to a computer.the host node (black sphere) thatthrough which it communicates totransducer, and a RF transceivercontains both an acousticThe uplink node (green sphere)

Explanation of Block Diagram

operation.module that oversees the sensor nodeThe critical components are the main controller

signal to/from the transducer.amplifies and modulates the output and inputThe acoustic transducer interface circuitry that

power supply.raw sensor signals to digital information, and theThe sensor interface circuitry that converts the

Explanation of Block Diagram

magnetoelastic sensor arrays to monitor ambient pH.of sensors in this work they are equipped withAlthough the nodes can be equipped with different types

communicates with the computer via RS232 protocol.The host node contains only a RF transceiver, and

acoustic transducers.transducers, while the rest of the nodes contain onlyThe uplink node contains both RF and acoustic

The Sensor Node

made of PVC pipe.on a frame that slides into the protective frameThe circuit modules and batteries are mounted

anchor.connected to a concrete block acting as anBefore deploying the sensor node is sealed and

PVC cap, with its front end exposed to water.The acoustic transducer is mounted inside a

The Sensor Node

through which water flows.3 cm in diameter PVC cap,open pipe, fitted through aarray is mounted within anThe magnetoelastic sensor

information.transduce sensorsolenoid, which is used tocreating in effect aaround this open pipe,gauge wire is wrappedA 100-turn loop of 40

• Aqueous Sensor Network Design

which is 4.out a broadcast signal containing its identity,To establish a network, the host node first sends

scheme.The signal is modulated using on-off modulation

conversion before transmission.The data is encoded with one-byte-to-twelve-bits

• Aqueous Sensor Network Design

format is:The broadcast signal

• Aqueous Sensor Network Design

The identity of the node is stored in the

From

field.

The

Command

field is set to 01 indicating this is

a broadcast signal.

The

Level

field indicates the number of nodes

the host node starts at 1.this broadcast signal has passed through, with

The

Checksum

field is used for error detection.

Aqueous Sensor Network Design

node has received the host’s broadcast signal:^ An acknowledgement signal back to the host to indicate that the

• Aqueous Sensor Network Design will also receive it.hierarchical level as Node 6,3, which is at the sameout a broadcast signal, NodeNote that when Node 6 sends

node of higher level.accept only signals from anode is programmed toTo avoid confusion each

Node 3 and the host node.Node 6 will be ignored byHence, the broadcast from

• Aqueous Sensor Network Design The relayed sensor data has the form of:acquire sensor data and transmit it at a predetermined time interval.After all nodes know the identity of their parent nodes, they will