ABSTRACT
This page explains the project on “Power Monitor ” which was implemented in 2008 and finalized in 2009 at C.K. Pithawalla College Of Engineering And Technology, Surat
With the recent push for green energy and environmental friendliness, more and more people are concerned about their personal daily power usage. We designed a microcontroller-based device which measures various aspects of AC power and acts as a computer-controlled remote switch. The user will be able to insert the device between the wall socket and an electrical appliance to measure the amount of AC power being used by that appliance. Also it will enable the user to hunt down any faulty or inefficient equipment that is using more energy than it should. The Software developed in ‘C’ is used to monitor the energy usage with data display in a computer as well as an LCD.
Our device calculates and reports the following parameters in real time:
- Load Voltage (volt)
- Load Current (amp)
- Frequency (Hz)
- Power Factor
- Active Power (watts)
- Reactive Power (VAR)
- Apparent Power (VA)
In addition to measurements, our device also has a relay that allows the microcontroller to trip off the supply to the appliance under test during over-voltage conditions.
Acknowledgement
We take this opportunity to express our sincere thanks and deep sense of gratitude to Prof. Milind B. Trivedi from C.K. PITHAWALLA COLLEGE, Surat, Gujarat, India, for his immense support, spending his precious time and providing deep, core knowledge to us regarding our project work and layout. Without his support , it would be impossible for us to complete our project.
Patel Swapneel A.
Patel Amitkumar D.
Bharatia Nirajkumar J.
Patel Sanjay P.
Jariwala Sandeep P.
Patel Swapneel A.
Patel Amitkumar D.
Bharatia Nirajkumar J.
Patel Sanjay P.
Jariwala Sandeep P.
Logical structure
The block diagram is shown in Figure 1. The device sits between the mains line and the appliance under test. Current measurements occur on the neutral line. The relay is switched on the AC live line. A potential transformer is used to step down the voltage to the correct levels. The analog values are converted to digital values which are then fed to the microcontroller. The microcontroller is programmed to calculate the values of frequency, active power, reactive power and apparent power from the values of current and voltage. A zero-crossing detector is used to detect the zero crossing of current and voltage waveforms which is used by the microcontroller to calculate the power factor. Digital display of the evaluated quantities is made available on a computer using ‘C’ programming as well as on an LCD connected to the microcontroller.
Block Diagram
Connected LCD
Applications
- Domestic
At home it can be plugged into the refrigerator, TV, computer, microwave, electric heater, stereo etc. And at work it can be used to check out the energy consumption of various bits of equipment such as computers, photocopiers, fax machines, and fans.
- Industrial
This device can be used for load monitoring of an entire industry. Such devices can also be connected in an industry at various points near the loads to keep a record of the energy consumption of the particular loads and remove or repair the faulty loads.
Also, as the power factor of a particular load is measured using this device, efforts can be made to improve the power factor to required limit i.e lagging power factor can be brought near unity. Thus system efficiency is increased and also the penalty on poor power factor is reduced or eliminated. Major advantage is that near unity power factor not only avoids penalty, but also brings in incentive from Electricity Board for higher power factor. All the above savings in revenue expenditures improves the bottom line of the industry directly adding to the profit.
- As Wattmeter
Just by pulling out four studs M, L, C & V as shown in above figure, this device can also be used as wattmeter for measuring power upto certain range applicable for laboratory purposes.
Future Enhancements
- Graphical Display of the measured quantities
The ‘C’ program designed for this device allows the user to observe only the numeric values of the various measured quantities. But by changing the software part i.e designing the ‘C’ program in ‘Graphics’ mode, the user will also be able to observe the measured quantities in form of real time graphs along with their numeric values.
The user then will be able to analyse the fundamental component as well as the harmonics through Fourier analysis of the graphs and efforts can be made to reduce the harmonic content of the measured signals.
- Automatic ON-OFF of the Relay
The Relay in this device trips off automatically and disconnects the appliance under test from the main supply if the line voltage goes above or below specified limits and then the device has to be turned on manually. Certain modifications in the software part of the project can enable the user to also turn on the device automatically when the value of line voltage comes back within normal specified limits. Thus the turning off as well as turning on of the device can be made fully automatic.
CONCLUSION
On completion of this project, we conclude that a micro-controller can be efficiently used as a digital measurement device. The basic concepts of micro-controller interfacing to computer as well as application of ‘C’ programming are clearly understood on implementation of this project. Such a device is very useful and of utmost economical importance in our day-to-day life. Analog measurement devices available in market are bulky, costly and of less accuracy. Our device is simple, compact, cheaper and of sufficient accuracy. This micro-controller based device is also more efficient as compared to other such digital measurement devices available in market and it also has a overload trip feature which enhances its qualities.
