Question:
Write a report about the Sensors and Wireless.
Sensory information can be sent through wireless nodes to be received by the remote locations. The report shows how the LDR can send the sensory information, through the terminals 1 and 2 of the probe, which work as input sensors and the other probe, 3, works as an output sensor. This LDR diagram is similar to the diagrams of the IR and TEMP. Wireless sensors consist of small devices and so have their computational power limited and these sensors have applications in wider area. When the transmitter and receiver diagrams of 433MHz is considered, transmission of the sensory information is transmitted nu using the transmitter, MT-12E and antenna receivers, through the wireless sensors. Data collection is made possible in better way, in the scientific studies. but, face pins failures are experienced, during the wireless part design. Since, one of these pins is not able to transit the signal to the remaining parts, this must be resolved with a quick remedy. The ways of tacking the design of the circuit, demonstration of the circuit and implementation of the circuit are discussed in this report.
Wireless Sensors and Network
Wireless sensors are usually connected among each other and become a network, called wireless sensor network to monitor various conditions in the environment, like sound, temperature, light, pressure, etc. The data collected in the environment is passed to the main, usually at the remote location, through the network. The modern networks of the wireless are more of bi-directional and are well enabled with the sensor activity control.
The wireless sensors are usually connected through the network and each of the entity or a point. Each of this node is connected to either one sensor or sometimes even to multiple sensors. The sensor network node usually have majorly vital parts, such as radio transceiver that consists of an antenna internally or sometimes external antenna connected to it, an electronic circuit to interface with the sensors, a microcontroller and majorly a source of energy, which is either a battery or energy in the form of energy harvesting embedded.
The wireless sensors are usually networked with the topologies that may be a simple star network to the advanced networks, such as multi-hop wireless mesh networks. The networks usually implement the propagation techniques, like routing or flooding.
The wireless sensor networks have increasingly more number of applications in several industries.
The wireless sensors networked to collect and transmit the data to the remote locations have the following characteristics.
Wireless sensors can have wider range of applications, from a simple temperature sensing to an advanced applications, like sensing the earthquake symptoms. No matter it is a simple or advanced application, it is important that the following three basic requirements are met.
All the physical components and parts of the wireless network become the hardware of the system. There are sensor nodes available in smaller sizes, for compact circuit and system and extensive research is going on for design and development of still tiny sensor nodes and makes them available for lower cost. gateway is also an important part of the system, which acts as a bridge in between the wireless sensor network and the rest of the networks.
Wireless sensor network function is enabled and optimized through the software installed for them. The software is based on various protocols and algorithms that are used to address various issues, such as self-configuration, increased lifespan, fault tolerance and robustness.
The operating systems for the Wireless sensor networks are typically lesser complex, compared to the operating systems used for computer systems.
Sensor Design
Design and Description
Sensor used here is a light sensor and is the simplest and interesting circuit to design and operate. This sensor is configured as a light detector, shadow detector or shadow detector, as it needs to detect the light intensity. The present circuit deployed the shadow detector, which turns the LED on, when the bright light is focussed on the LDR. This circuit can be changed to a light detector, just by swapping the 2nd and 3rd op-amp pins. In this case, the LED is turned is turned on, when there is darkness present on the LDR. It should be ensured that the pins, 1, 5 and 7 are not connected. Output is extracted from the pin 6. This pin is connected to one LED, through a resistor of 330 Ohm in this circuit. The same system can be used for the IR and TEMP sensors. Security system may also be added to this circuit.
Calculations
For LDR,
When the LDR is OFF,
When the LDR is ON,
For TEMP
When the TEMP is ON,
When the TEMP is OFF,
For the IR,
When the IR is ON,
When the IR is OFF,
ElectroMagnetic Interference Sources
The major EMI source can be the converters of power electronic, motor, computer power supplies, permanent magnets and many other similar equipment present in the laboratory. This interference can be minimized by switching off all the, converters of the power electronics, present in the laboratory. Alternatively, EMI filters that are both active and passive are also used for reducing the EMI effect.
Encoder and Decoder Roles
Data is received parallel from D0 to D3. The role of the encoder is to covert this 4 bit parallel data into the serial data to forward and transmit through the TXM 433 MHz transmitter, through DOUT. Conversely, this serial data will be converted back to the parallel data of four bit, by using HT12D.
Implications of 433MHz Band
There are legal implications associated with the 433 MHz band, as it is not regulated as it is available as license free. So, anyone can use this band for the purpose of experiments (Louis, Matthew & Raju, 2005). The maximum distance covered by this devices varies from 1 to 1.5m and it can be extended by using the repeaters, like slave nodes. This extension is possible by using either long antenna or using the frequency, other than 433 MHz, which is stronger than it.
Sensor Circuits
Figure: Circuit for Proximity Sensor
P1 is used to achieve to make certain adjustments on the proximity sensor’s sensitivity of the circuit, to get certain distance. The door has to be opened automatically, when the P1 is adjusted, so the sensor has to be kept over the door, at even front part. The detector is made from an oscillator along with the T1, and the function and need for the oscillator is for the stability of the frequency, since it needs Clapp one. The oscillator circuit consists a capacitor and is derived from the sensor’s surface and this oscillator is configured with 1 MHz frequency. The switching is adjusted with P2, but it is important that the metallic objects are not taken closer to the proximity of the circuit, as the relays won’t be close. Aggressive liquids can be detected with the help of this circuit, as the surface of the sensor won’t contact the liquid at aggressive state.
Figure: Circuit for Light Sensor
The light switch sensor circuit is used to connect the lamp, while the light is faded. After the switch is ON for the lamp, the status is maintained and continues this status for specific period of time. This time can be set in between 1 to 5 hours, using P1. The oscillator is kept at 4060, using the S202DS2 semiconductor relay.
Figure: Circuit for Temperature Sensor
There is a heater element is deployed by connected in series with 16A, controlled by a pulse transformer. Sometimes, the zero crossing detector would be lower comparator, producing a square wave of 60Hz. The relay circuit is operated similar to the upper two comparators.
The communication in the circuit is established through the radio receivers and transmitters. The links can be created in various configurations, so that the performance can be maximized. These links become the parent links that can make the information transmitted to the rest of the links present in the network.
The desing of the circuit is based on the radio frequencies, rather than the transmission through infrared, as the radio frequencies are proved to be reliable and stronger compared to the transmission through infrared and radio frequencies can travel longer distances than the infrared transmission. In addition to that, infrared transmission can be propagated only if there are no obstacles, but radio frequencies have no limitations with obstacles. Infrared signals have inference problems, from the sources of other infrared, however, this is not the problem with the signals of the radio frequencies.
Figure: Circuit of RF Transmitter
Initially, the data is received through Do to D3 pins, by the encoder, IC HT12E. The encoder then converts this four bit from parallel to serial and the data is trapped through DOUT. The serial output data from Dout is sent to TXM 433 MHz, via the Pin2. A0 to A7 address inputs provide the security for the data. It is also done by the logic ONE or ZERO (GND) also. The status of the A0 to A7 should be matched both at the ends of the transmitter and receiver. So, the transmission of the data can only be done by TXM 433 MHz, only when TE or Transmit Enable is low. The internal oscillations required for HT12E are provided by the external resistance, with the help of the 750K Ohm resistor.
The circuit is employed with the a receiver, which receives the signals, transmitted by TXM 433 MHz. The data receives is passed to HT12D, via the DIN pin, where the data received in a serial format is converted to parallel data of four bits, at D0 to D3. Similar to the transmitter circuit, the address pins A0 to A7 status must match in the system towards the intended operation of the system. The LDR is connected to HT12D’s pin 17 and glows, if the transmission of data is successful from the transmitter to receiver.
The sensors can form the parts of the machine, by linking them together, by huge computational power, relatively, when compared to the sensors employed individually. The sensors’ abilities of broadcast are usually affected by the higher content of moisture. The functionality of the circuit can possibly achieved, by allowing the sensors to be recognized, since the strengths of certain connections are based on the modifications performed over the conditions, which cause the hindrances.
Capacitive sensors are accurate, in terms of respiratory rate monitoring in real time and so are employed in the circuit. Many of these circuits are designed and developed using operational amplifiers, as these amplifiers have the quality factor (Q) improved.
Conclusion
Wireless sensors are collection of smaller devices, having their computational power to be limited and they have the applications in wider area. The design of circuit is based on the radio frequency transmission, rather than infrared, as the radio frequencies are more reliable and stronger. The major EMI source can be by equipment, such as motor, computer power supplies, power electronic converters or permanent magnets in the laboratory.
References
Akyildiz I. F. and Kasimoglu I.H. (2004). “Wireless Sensor and Actor Networks: Research Challenges”. Ad Hoc Networks 2
Dargie, W. and Poellabauer, C. (2010).Fundamentals of wireless sensor networks: theory and practice. John Wiley and Sons
Matthew, L., Raju, K. & Louis, W (2005). ISM-Band and Short Range Device Regulatory Compliance Overview, SWRA048, 1: 1-15
Peiris, V. (2013). “Highly integrated wireless sensing for body area network applications”. SPIE Newsroom
Sohraby, K., Minoli, D., Znati, T. (2007). Wireless sensor networks: technology, protocols, and applications. John Wiley and Sons
Tiwari, Ankit et al., Energy-efficient wireless sensor network design and implementation for condition-based maintenance, ACM Transactions on Sensor Networks (TOSN).
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