Design And Construction Of An Electronics Letter Box With Counters And Wireless Feedback

ABSTRACT

This work is on design and construction of an electronic letter box with counters and wireless feedback. This   project is developed for the users to find out whether any letter is inside the letter box and also to display the number of letters inside the letter box thereby sending the senders name via mobile phone.

An IR Transmitter and Receiver are connected at the opening of the letter box.  In normal operation, the rays transmitted from the transmitter falls on the receiver.  When anyone puts letter inside the letter box, the letter hides the rays and thereby the receives no signal at the particular instance.  Thus it  senses that there is a letter inside.

The microcontroller connected with the sensor counts that there is one letter inside.  When the next letter is put inside the letter box, the sensor senses the letter and the microcontroller counts two.  The same way it counts all the letters inside.

A display and buzzer is connected inside the house.  The owner of the house can identify the number of letters inside the letter box and the name of the sender via phone.

When the letter box is opened, the microcontroller resets and the count goes to zero.

CHAPTER ONE

1.1                                                        INTRODUCTION

A letter box, letterbox, letter plate, letter hole, deed, mail slot, or mailbox is a receptacle for receiving incoming mail at a private residence or business. For the opposite purpose of collating outgoing mail, a post box is generally used instead.

Letterboxes or mailboxes consist of four primary designs:

• A slot in a wall or door through which mail is delivered (through-door delivery)
• A box attached directly to the house (door-to-door delivery)
• A box mounted at or near the street (curbside delivery)
• A centralised mail delivery station consisting of individual mailboxes for an entire building
• A centralised mail delivery station consisting of individual mailboxes for multiple recipients at multiple addresses in a particular neighborhood or community
• An electronics circuit

In this system, When letter drop by someone into the letter box then the LED attached at the output stops blinking which indicates that there is a letter in your letter box. To identify the presence of a letter in the box we have connected a LDR as well as source of light. LDR is a special kind of resistor whose action based on the intensity of light declining on it. In the time of total darkness LDR resistance is approx 1 mega ohm while at the time of bright light its resistance is 2-5 ohm. In this circuit the light source is adjusted with the LDR in such a way that the light will directly drop on the LDR so that when any letter comes inside the letter box it will chunk the light beam and LDR will be beneath darkness.

1.2                                           SIGNIFICANCE OF THE STUDY

This project is very useful in institutions; house etc to identify the letters inside the letter box and also sends the senders name via cellphone.

1.3                                             OBJECTIVE OF THE PROJECT

The objective of the project is to design a device that When letter drop by someone into the letter box then the LED attached at the output stops blinking which indicates that there is a letter in your letter box and at the same time send this senders name.

1.4                                 ADVANTAGES ELECTRONIC LETTER BOX

Advantage of the letter box is we can find out the presence and absence of letter inside the box without opening the box. Here light depending resistor (LDR) is used as a sensor to detect the presence of letter. Thus this circuit solves the problem of going again and again to the gate of the house to check-up whether a letter is there in the box or not. Working To detect the present of letter, we have used LDR,  a source of light and GSM module to wirelessly communicate with the GSM.

The L.D.R, most important part of this circuit, is a special type of resistance whose value depends on the brightness of the light which is falling on it.
It has a resistance of about 1 mega ohms when in total darkness, but a resistance of only about 2-5 k ohms when brightly illuminated.

The resistance of L.D.R. is minimum when the light falling on is maximum and vice versa when the light falling is minimum. The source of light and LDR is so adjusted in the letter box, that the light will directly fall on the LDR. When a letter is kept inside, it will block the beam of light and LDR will be under darkness.