Controller Circuit

Humidity Sensing and Digital Clock Employing Memory Mapping

As the name of the project shows, here we are going to discuss three things togerther,

1. Measuring Humidity, using Humidity sensors, Interfacing of Humidity sensor with microcontroller 8051
2. Developement of digital clock using microcontroller 8051
3. Understanding the memory Mapping of microcontroller 8051

So here is

Introduction of the Project:-

The main focus of this project is to implement the methods to obtain the data from the low voltage operated sensors and their digital interface to microcontroller or microprocessor, a part from this the technique of memory mapping is also implemented along with the serial interface for both transmission and reception with hyper terminal.


The input to this project is a time varying voltage from sensor calibrated by the ADC as +10 to –10 volts. The output is the actuation of the alarm after every 1 hour also it can be made to alarm when the humidity exceeds some threshold value.

The serial communication techniques are also a part of this project, when the system is booted the initial messages from the controller is transmitted to the PC, and can be viewed on the hyper terminal and then user update the system by sending time from the hyper terminal, hence we have implemented both transmission and reception.

Humidity Sensing and Digital Clock Employing Memory Mapping

Table of Contents

1 Objective of the project based on microcontroller 8051
2 Implementation Details of Humidity sensing project
2.1 Humidity Sensors
2.2 Humidity Transducers or Humidity Transmitters
2.3 Humidity Display and transducer consideration
2.4 Selection of Humidity Sensor
3 LCD Overview (Liquid crystal display)
3.1 Function Description of LCD
3.1.1 Registers of LCD
3.1.2 Busy Flag (BF) of LCD
3.1.3 Address Counter (AC) of LCD
3.1.4 Initializing by Internal Reset Circuit of LCD
3.1.5 Pin Assighnment of LCD
3.1.6 Data Write into LCD
3.1.7 Assembly Language program for LCD code
4  MAX 232 serial communication of microcontroller and PC
4.1 DB9 connector used for serial data communication and RS232 cable
4.2 Testing Circuit of humidity sensing project
5 ADC0804 introduction and features
5.1 Interfacing the ADC0804 to the AT89C51
6 DAC0800 introduction

7. 82C55 PROGRAMMABLE PERIPHERAL INTERFACE
8. Circuit Diagram
9. Code (program written in C51 for microcontroller 8051)

After going through this project or tutorial of 8051 you would be able to do following tasks.

1. You would have idea of hardware and software of the microcontroller 8051.
2. you will come to know the usuage of microcontroller ATMEL AT89c51 or AT89s51.
3. You will get information about the working of different general purpose components and their usuage along together to make some useful project or application based on microcontroller 8051.
4. The function and features of ADC0804, DAC0800 are discussed, you would come to know how these components can be interfaced with microcontroller.
5. LCD is discussed in detail so, after going through this project you would feel easy to work with LCD.
6. You would be able to interface the LCD with Microcontroller 8051.
7. Humidity sensors are also discussed here in some detail, so you would be able to handle these sensors with now fear.
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