4 in 1 Burglar Alarm

I n this circuit, the alarm will be switched on under the following four different conditions: 1. When light falls on LDR1 (at the entry to the premises). 2. When light falling on LDR2 is obstructed. 3. When door switches are opened or a wire is broken. 4. When a handle is touched. The light dependent resistor LDR1 should be placed in darkness near the door lock or handle etc. If an intruder flashes his torch, its light will fall on LDR1, reducing the voltage drop across it and so also the voltage applied to trigger 1 (pin 6) of IC1. Thus transistor T2 will get forward biased and relay RL1 energise and operate the alarm. Sensitivity of LDR1 can be adjusted by varying preset VR1. LDR2 may be placed on one side of a corridor such that the beam of light from a light source always falls on it. When an intruder passes through the corridor, his shadow falls on LDR2. As a result voltage drop across LDR2 increases and pin 8 of IC1 goes low while output pin 9 of IC1 goes high. Transistor T2 gets switched on and the relay operates to set the alarm. The sensitivity of LDR2 can be adjusted by varying potentiometer VR2. A long but very thin wire may be connected between the points A and B or C and D across a window or a door. This long wire may even be used to lock or tie something. If anyone cuts or breaks this wire, the alarm will be switched on as pin 8 or 6 will go low. In place of the wire between points A and B or C and D door switches can be connected.

 Circuit Diaram

AUTOMATIC LOW-POWER EMERGENCY LIGHT

Here is a white-LED-based emergency light that offers the following advantages: 1. It is highly bright due to the use of white LEDs. 2. The light turns on automatically when mains supply fails, and turns off when mains power resumes. 3. It has its own battery charger. When the battery is fully charged, charging stops automatically. The circuit comprises two sections: charger power supply and LED driver. The charger power supply section is charging current through diode D5 and limiting resistor R16. By adjusting preset VR1, the output voltage can be adjusted to deliver the required charging current.

AUTOMATIC ROOM LIGHT CONTROL WITH BI DIRECTIONAL VISITOR COUNTER

MICRO-CONTROLLER BASED PROJECT The objective of this project is to make a controller based model to count number of persons visiting particular room and accordingly light up the room. Here we can use sensor and can know present number of persons. In today’s world, there is a continuous need for automatic appliances with the increase in standard of living, there is a sense of urgency for developing circuits that would ease the complexity of life. Also if at all one wants to know the number of people present in room so as not to have congestion. This circuit proves to be helpful. RECEIVER CIRCUIT

TRANSMISSION CIRCUIT

this circuit diagram shows how a 555 timer IC is configured to function as a basic monostable multivibrator. A monostable multivibrator is a timing circuit that changes state once triggered, but returns to its original state after a certain time delay. It got its name from the fact that only one of its output states is stable. It is also known as a ‘one-shot’. In this circuit, a negative pulse applied at pin 2 triggers an internal flip-flop that turns off pin 7′s discharge transistor, allowing C1 to charge up through R1. At the same time, the flip-flop brings the output (pin 3) level to ‘high’. When capacitor C1 as charged up to about 2/3 Vcc, the flip-flop is triggered once again, this time making the pin 3 output ‘low’ and turning on pin 7′s discharge transistor, which discharges C1 to ground. This circuit, in effect, produces a pulse at pin 3 whose width t is just the product of R1 and C1, i.e., t=R1C1. IR Transmission circuit is used to generate the modulated 36 kHz IR signal. The IC555 in the transmitter side is to generate 36 kHz square wave. Adjust the preset in the transmitter to get a 38 kHz signal at the o/p. around 1.4K we get a 38 kHz signal. Then you point it over the sensor and its o/p will go low when it senses the IR signal of 38 kHz.

Automatic door opener with PIC12C508

Circuit Description This circuit can be used to operate an electric strike or an electromagnetic lock on a door. It is not the door being opened/closed, but a small electromagnetic strike which unlocks the door. The opener has the following features currently programmed in software: · automatic operation when a guest pushes the doorbell, the strike is operated immediately - can be set by a switch (SW) · manual remote operation - by pushing a button (BUTTON), the strike is operated immediately · timer delayed operation by pushing the same button longer than 500 ms - the strike is operated after a pre-set time · programmable timer delays for relay operating time and delay before timer opening · two-color LED display shows current state Usage After power-on the circuit will be operating and the display LED will be constant RED when the auto switch is in OFF state and will be slowly changing between red and green when the switch is in AUTO state. Shortly pushing the BUTTON will operate the door relay for about 3 seconds (this delay can be reprogrammed). Holding down the PUSH button for a bit longer will operate the door relay after about 20 seconds. This timer delay is also reprogrammable. The display LED lights in constant YELLOW while the delay timer is running. Delay Programming WARNING: entering inappropriate codes for the timers will result in strange operation (too long/short delays) and you may have to break the power for the device to reset and start again. To enter the delay programming mode, hold down the BUTTON and change the state of the SWITCH. The LED display will turn OFF until the release of the BUTTON. In this mode the software reads the values for the two timers in the form of 4 hex numbers. The first two numbers make up an 8-bit value for the timer of the door opening time and the second two numbers make up an 8-bit value for the delay timer. The values are given in a rough 10 ms unit. · entered digits: D1 D2 D3 D4 · door opening time: D1*16+D2 · opening delay time: D3*16+D4 · to program 3 seconds opening time and 20 seconds delay time you would enter digits 30c8 (3,0,12,8) · to return to the hard-coded original delay times, break the power to the device for a few seconds. Entering digits: press the BUTTON the number of times the digit you want to enter. Eg. if you want to enter digit 8, press the button eight times. To finish entering a digit, wait for about 1 second and the LED color will blink, indicating that the code is stored and you can proceed entering the next digit (if there are more). Not pushing the button for 1 second in this mode will store the digit 0 and proceed with a LED blink. After all 4 digits are stored the program will restart with the new values.

Software the software for the microcontroller is available in source format. It is developed under the Microchip MPLAB development environment, and you will need it or some other PIC compiler to build the object code for the device. If you program the object code, check the fuse settings and make sure that all the I/O pins are programmed to be I/O lines and not OSC or MCLR. In the beginning of the source you find a #define line which sets the PIC chip under which the code will compile. It is a good idea to develop on a 16F84 device and when everything is working, compile the code for the one-time programmable 12C508. Schematic Diagram capacitors on the VCC and VDD lines are not shown, but recommended. Place 100 nF close to the PIC pins VCC & VSS, place 100 nF and 100 uF close to the 78L05 pins VCC & GND. The two LED diodes on the scematic are packaged together in a two-color green-red LED with 3 leads. The button is a break-on-push type for fast&sensitive operation.