OVER VOLTAGE DETECTION

PROJECT DESCRIPTION

In this project we will wirelessly transmit information if current or voltage exceed. We will use RF technology .we will use RF module of 433Mhz. its available in the market. The project Current detector cum controller is very much useful for controlling the load in any industry. In this project we are measuring the current consumed by all the loads connected in a house. If the load current exceed the set value of current the load will be disconnected immediately. The heart of the project is microcontroller AT89S51 and current sensing transformer. The current sensing transformer is used to sense the current consumed by load. The current sensed by the current sensor is converted into voltage and feed to the ADC0804 for analog to digital conversion. The digital equivalent of the current is read by microcontroller AT89S51 from the ADC0804. The digital value of current is processed my microcontroller and displayed on LCD. We have provided a 16x2 LCD display for displaying the value of load current and set current. For changing the value of set current there are two keys called UP/DOWN keys. The UP/DOWN Keys can be used to increase or decrease the value of set current. One key is provided to reset the load supply after an over current trip. Five different loads are connected for testing purpose. The load supply can be can be switched ON/OFF through  a relay controlled by microcontroller. We have used 5V regulated supply for microcontroller AT89S51, ADC0804, LCD and 12V unregulated supply for relay circuit.

The figure – 1 above shows the basic architecture of 8051 family of microcontroller.

Features

• Compatible with MCS-51™ Products

• 4K Bytes of In-System Reprogrammable Flash Memory

– Endurance: 1,000 Write/Erase Cycles

• Fully Static Operation: 0 Hz to 24 MHz

• Three-Level Program Memory Lock

• 128 x 8-Bit Internal RAM

• 32 Programmable I/O Lines

• Two 16-Bit Timer/Counters

• Six Interrupt Sources

• Programmable Serial Channel

• Low Power Idle and Power Down Modes

Description

The AT89C51 is a low-power, high-performance CMOS 8-bit microcomputer with 4K bytes of Flash Programmable and Erasable Read Only Memory (PEROM). The device is manufactured using Atmel’s high density nonvolatile memory technology and is compatible with the industry standard MCS-51™ instruction set and pinout. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C51 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. The AT89C51 provides the following standard features: 4K bytes of Flash, 128 bytes of RAM, 32 I/O lines, two 16-bit timer/counters, five vector two-level interrupt architecture, a full duplex serial port, and on-chip oscillator and clock circuitry.

In addition, the AT89C51 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The Power down Mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.

Pin Description

VCC

Supply voltage.

GND

Ground.

Port 0

Port 0 is an 8-bit open drain bidirectional I/O port. As an output port each pin can sink eight TTL inputs. When 1s are written to port 0 pins, the pins can be used as high impedance inputs. Port 0 may also be configured to be the multiplexed low order address/data bus during accesses to external program and data memory. In this mode P0 has internal pull-ups. Port 0 also receives the code bytes during Flash programming, and outputs the code bytes during program verification.

External pull-ups are required during program verification.

 (i) Block Diagram of the System:

BLOCK DIAGRAM

WORKING OF CIRCUIT:-

POWER SUPPLY:-

 In the power supply section we use one step down transformer with two diode as a full wave rectifier. Output of the rectifier is further converted into smooth dc with the help of the filter capacitor. Output of the capacitor is further connected to the ic regulator to provide a stable voltage to the microcontroller. Microcontroller requires a regulated 5 volt dc power supply for smooth operation. Here we use ic 7805 as a positive regulator to provide a 5 volt dc power supply.

Rectifier and regulator

          In this lab you will construct and analyze a full wave rectifier and a shunt voltage regulator. All component types in the example circuit are available in OrCAD – Capture  libraries for simulation.

I. Introduction

1.1 The Full Wave Rectifier

The first building block in the dc power supply is the full wave rectifier. The purpose of the full wave rectifier (FWR) is to create a rectified ac output from a sinusoidal ac input signal. It does this by using the nonlinear conductivity characteristics of diodes to direct the path of the current.

Figure 1. Common four-diode bridge configuration for the FWR

Diode Currents

Consider the current path in the diode bridge rectifier. In the positive half cycle of Vin, diodes D4 and D3 will conduct. During the negative half cycle, diodes D2 and D1 will conduct. As a result, the load will pass current in the same direction in each half cycle of the input.

Design Concerns

• Reverse current does not exceed the breakdown value
• Power dissipation limit P = Vd Id is not exceeded

Diode Voltages

·        Forward Bias

o        If we consider a simple, piece-wise linear model for the diode IV curve, the diode forward current is zero until Vbias >= Vthreshold, where Vthreshold is 0.6 V to 0.8 V. The current increases abruptly as Vbias increases further. Due to this turn-on or threshold voltage associated with the diode in forward bias, we should expect a 0.6 to 0.8 V voltage drop across each forward biased diode in the rectifier bridge. In the case of the full wave rectifier diode bridge, there are two forward biased diodes in series with the load in each half cycle of the input signal.

o        The maximum output voltage (across load) will be Vin - 2 Vthreshold, or ~ Vin - 1.4 V.

o        Since some current does flow for voltage bias below Vthreshold and the current rise around is Vthreshold is more gradual than the piece-wise model, the actual diode performance will differ from the simple model.

·        Reverse Bias

o        In reverse bias (and neglecting reverse voltage breakdown), the current through the diode is approximately the reverse saturation current, Io. The voltage across the load during reverse bias will be Vout = Io Rload.

o        In specifying a diode for use in a circuit, you must take care that the limits for forward and reverse voltage and current are not exceeded.

1.2 Filtered Full Wave Rectifier

The filtered full wave rectifier is created from the FWR by adding a capacitor across the output.

Figure 2. Filtered full wave rectifier

Component List