In this project we will use Camera to check the security . we will use Relay control circuit to switch different camera on scree. We will use high rsolutions camers.
Micro controller interface
Switch on the telephone
ATMEL AT89C2051 Pinout and Description
The 2051 is a low voltage (2.7V – 6V), high performance CMOS 8-bit microcontroller with 2 Kbytes of Flash programmable and erasable read only memory (PEROM). This device is compatible with the industry standard 8051 instruction set and pinout. The 2051 is a powerful microcomputer which provides a highly flexible and cost effective solution to many embedded control applications. The 2051 provides the following features:
~ 2 Kbytes of Flash
In addition, the 2051 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.
2051 – 24MHz DIP Available
The 2051 can be programmed using a device programmer such as the PG302 (Click Here).
We also have Projects that use the 2051 Microcontroller.
This page last updated on April 7, 2003.
In DTMF there are 16 distinct tones. Each tone is the sum of two frequencies: one from a low and one from a high frequency group. There are four different frequencies in each group.
Your phone only uses 12 of the possible 16 tones. If you look at your phone, there are only 4 rows (R1, R2, R3 and R4) and 3 columns (C1, C2 and C3). The rows and columns select frequencies from the low and high frequency group respectively.
Thus to decipher what tone frequency is associated with a particular key, look at your phone again. Each key is specified by its row and column locations. For example the “2″ key is row 0 (R1) and column 1 (C2). Thus using the above table, “2″ has a frequency of 770 + 1336 = 2106 Hz The “9″ is row 2 (R3) and column 2 (C3) and has a frequency of 852 + 1477 = 2329 Hz.
The following graph is a captured screen from an oscilloscope. It is a plot of the tone frequency for the “1″ key:
You can see that the DTMF generated signal is very distinct and clear. The horizontal axis is in samples. The frequency of the tone is about 1900 Hz – close to the 1906 Hz predicted by Table 3 (697+1209).
In this circuit we use ic 91215 as adtmf generator. Pin no 15,16,17,18 is a row and pin no 12,13,14 is a row. All the switches are connected to these pins. Redial button and flash button is connected to the microcontroller output pin s no 13 and 12 . Output from the 91215 is available on the pin no 7 of the ic . Output from the 91215 is further amplify by the ic 741. Here pin no 7 of the ic 741 is connected to the positive supply and pin no 4 is connected to the negative supply. Pin no 6 is the output pin and amplify signal is available on this pin and again further amplify by the two transistor circuit. Output from the transistor circuit is connected to the one coil of the output transformer.
Now when we press a redial number then 91215 generate a pre-dial tones and this signal is further connected to the coil and further pass on the telephone line.
push to on sw
.001 µf,0.1 µf,0.01µf
crystal 11.0592 MHz
speaker 8 ohm
relay 12v 100 ohm
transformaer 6v 500mA
copper clad board
|CIRCUIT AND THEORY ARRANGEMENT|
|CHECKING AVAILABILITY OF COMPONENTS|
|COMPONENT INSERTION AND SOLDERING|
|REWORK OR TROOUBLE SHOOTING|
- Easy to implement
- Low cost
- Components easily available in market.