Designing of a microcontroller based multi-sensor system

Abstract

A wireless network containing small interdependent sensor nodes is called WSN (wireless sensor network). Environmental quantities like Light, Temperature, Pressure, Motion, Humidity, Sound etc. are to be measured and monitored with the help of this system. The data that is measured by these sensor nodes is sent to a base station using RF (radio frequency) communication. The communication between the nodes and the base station can be a single hop communication or it can be a multi hop communication depending on the remoteness of the sensor node. The base station also controls the whole network. On each sensor node there are various hardware components. Some of those are Microcontroller, Sensor or Transducer, Radio Frequency Transceiver, Battery or some other power source. Several other components are used for signal processing purpose to bring the sensor output signal in proper form and for proper power supply required for main components. The components required for this purpose are voltage regulators, Amplifiers, resistors, capacitors and crystal oscillator of different frequencies. The main aim of this thesis is to achieve the communication between different sensor nodes and a single receiver simultaneously. The receiver that is base station should be able to display the information received from the sensor nodes. Three similar nRF24L01 nodes were designed and tested to check their functionality. An Attiny85 microcontroller was used to design the sensor nodes and at the base station ATmega328 microcontroller was used. These microcontrollers are programmed in C with Arduino 1.0.5-r2. The signal received from the sensors is converted from analog to digital by the Attiny85 microcontroller and delivered it to nRF24L01+ where it is sent by the radio. The communication between base station and PC is established by a USB connection.