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N.SRINATH • Mar 9, 2015

Stand-By Mode Power Optimizer

Project Abstract / Summary : We hope to present a fully automatic standby power management system for home appliances concentrating in stand-by mode power saving. Our goal is to predict usage accurately and to activate or deactivate the power outlets appropriately without user intervention. Our project aims at developing a customized device that can detect and automatically cut off devices that are under the standby mode for a long term.
In recent years due to the increase in the energy crises the use of power is forced efficient energy conservation. Although electrical appliances draw a relative 80% of power in standby mode, standby power significantly contribute to total energy consumption as most appliances remain in standby mode for long periods. A simple solution to eliminate standby mode consumption of appliances would be turning off the switch or unplugging it from the power outlet when the device is idle.

— Power usage is sensed using current sensors. A current to voltage convertor is employed to convert current to voltage. A bridge rectifier then, rectifies the voltage from AC to DC, and it powers a microcontroller.
— The analog voltage is taken and given to an ADC, which generates equivalent digital signals. This is sent as input to the microcontroller.
— The microcontroller generates control signals and takes suitable action. The time delay for stand-on mode without turning off can be programmed and can be varied according to the user.
— The novel idea is to power the controller without any external supply, so true power preservation is done and usage is monitored.

The circuit consists of a MSP430 microcontroller or any other equivalent controller in central terms. It is surrounded by relay drivers, current sensors and ADC’s etc. As explained in the proposal, the current is sensed, converted to voltage, compared in the microprocessor and suitable actions are taken.
The contraption is viable as it is logical and uses true components and terms in its implementation.
The novel idea is to power the controller without any external supply, so true power preservation is done and usage is monitored.
The project aims at realizing the circuit on minimal terms. Large scale implementation at product level demands huge costs and research. But the project tries to implement the contraption as a prototype.

Project Execution Plan :
A current sensor continuously sense the signals. Current sensors are used to produce an alternating voltage to the current being measured . The current output has to be converted to a voltage . The interface circuit consist of a bridge rectifier which converts the AC into DC since, microcontroller MSP430 requires a DC input only . A rectification circuit is followed to reduces the ripples.

The microcontroller can be programmed for various time delays , “turnoff device time” i.e how long to wait before a turning off a circuit .Here, relays are used as electrically operated switches. Current flowing through the coil of the relay creates a magnetic field which attracts a levers and changes the switches contact. The coil current can be on or off so relays have two switches position. The input terminal is a logical output either 0 or 1 if it is given from a microcontroller. When the voltage is 0 the, base emitter voltage of the transistor is less than that of cut off voltage. So the transistor is off and hence no current flows through the transistor collector. This switches off the transistor’s collector terminal. This switches of the relay. If it is 1, the base emitter voltage is greater than cut off and the transistor is switched on and current flows through the relay circuit.
In wireless terms of implementation, a remote (radio frequency transmitter) of particular frequency is used which sends the encoded signal to the receiver. It decodes the signal and sends the decoded signal to the cut off relay. And the relay will close which retains the supply to the device.

Why did you choose to work on this project topic : Energy efficiency has been a major cause of concern for today's world. In such an inefficient world, stand by mode consists of about 15% of the total power consumed. TV sets, AC's , computers and refrigerators etc. when working in standby mode are consuming 10-20% of the power of that of normal working mode. This power can be saved by using a simple embedded project which uses a micro-controller and a current sensor. This power saved on a annual basis may account to nearly 20% extra saved power which will make a huge impact worldwide and also help in the cause of fossil fuels. This is the main idea behind this project. "Power saved, is power generated".

Project Category : Electrical / Electronics / Communication
Participating Team From: Third Year

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