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1. Night Security Light Circuit Diagram

 

This simple circuit switches on a light around 2 hours after midnight, the time at which most of the robberies taking place.This simple circuit is build around a CMOS IC 4060 to obtain the required timing. During day time the LDR has low resistance and keeps the pin 12 of the IC1 high, preventing the IC1 from oscillating.

When it is dark the LDR resistance becomes high and the pin 12 of IC1 becomes low and the IC starts oscillating, which indicated by the flashing of LED D3.The values of the timing components R1, R2, C4 are so selected that the out put pin3 of IC1 goes high after 8 hours. That means the high output drives the triac to switch on the lamp around 2’O clock. At morning, the LDR resistance drops and the pin 12 of IC1 goes high and stops the oscillation, making the lamp OFF. The switch S1 can be used to manually ON the lamp. The capacitor C2 prevents false triggering.

  

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2. Microcontroller Based Digital Thermometer

The Digital Thermometer is a device designed for measuring time and temperature used in chemistry laboratory. The circuit of Digital thermometer employs a 89C4051, 20-pin CMOS Microcontroller with built-in 4kB code memory. Temperature was measured by LM35D, National Semiconductor Temperature sensor producing 10mV/°C. The CA3162, 3-digit DVM converts dc output provided by LM35D and sends BCD output to port1 (P1.0-P1.3).  The program read BCD output from the A/D converter, performs digital filtering,10-point moving average, and sends the output reading to a 16x1 line LCD display. A 10ms cputick was used as a timebase producing 1 s for time counting. The LCD displays time in 1 s and temperature in 0.1°C resolutions.

3. Automatic School and College Bell

 

This project works for a school has total of eight periods with a lunch break after the fourth period. Each period is 45 minutes long, while the duration of the lunch break is 30 minutes. To ring this automatic school bell to start the first period, the peon needs to momentarily press switch S1. Thereafter, the bell sounds every 45 minutes to indicate the end of consecutive periods, except immediately after the fourth period, when it sounds after 30 minutes to indicate that the lunch break is over. When the last period is over, LED2 glows to indicate that the bell circuit should now be switched off manually.

 4.Automatic Flush System

In manual flush systems, the user presses a button, which opens a flush valve allowing mains-pressure water to flow into the bowl, or sometimes the user presses directly a flush lever (a handle connected to a flushometer). The valve contains a

pneumatic mechanism that closes it after a preset time. Today, manual flush system has been replaced with a sensor-operated system that automatically flushes the fixture when the user departs. The microcontroller based automatic flush system presented here uses an infrared sensor to detect a user approaching

the fixture, then it waits until the user departs.

5.Variable Power Supply

The most frequently used device in electronic workshops and laboratories is a universal power supply that provides a variable, fluctuation-free output. Here we present a variable power supply with digital control that is simple and easy to construct. The circuit is built around an adjustable 3-terminal positive-voltage regulator IC LM317, CMOS decade counter IC CD4017, timer IC NE555 and 3-terminal fixed negative-voltage regulator LM7912. The AC mains supply is stepped down by transformer X1 to deliver a secondary output of 12V-0-12V AC, 1A. The output of the transformer is rectified by a full-wave rectifier comprising diodes D1 through D4. Capacitors C1 through C4 are connected in parallel to rectifier diodes to bypass undesired spikes and provide smooth and fluctuation-free power. Capacitors C5 and C13 are used as filters to eliminate ripple. Here both negative and positive half cycles are used to obtain positive as well as negative DC output. LED1, along with current limiting resistor R1, is used for mains ‘on’LED3 through LED11 are used here to indicate the voltage levels. The collectors of transistors T2 through T10 are connected to presets VR1 through VR9, respectively, which are used to set the output voltage. Presets VR1 through VR9 are adjusted to get the desired output voltage.

6.PIC Based Volt Meter

7.Bi Directional Visitor Counter Using Microcontroller

Visitor counting is simply a measurement of the visitor traffic entering and exiting offices, malls, sports venues, etc. Counting the visitors helps to maximize the efficiency and effectiveness of employees, floor area and sales potential of an organization . Visitor counting is not limited to the entry/exit point of a company but has a wide range of applications that provide information to management on the volume and flow of people throughout a location. A primary method for counting the visitors involves hiring human auditors to stand and manually tally the number of visitors who pass by a certain location. But human-based data collection comes at great expense.

 Here is a low-cost microcontroller based visitor counter that can be used to know the number of persons at a place. All the components required are readily available in the market and the circuit is easy to build .Two IR transmitter-receiver pairs are used at the passage: one pair comprising IR transmitter IR TX1 and receiver phototransistor T1 is installed at the entry point of the passage, while the other pair comprising IR transmitter IR TX2 and phototransistor T2 is installed at the exit of the passage. The IR signals from the IR LEDs should continuously fall on the respective phototransistors, so proper orientation of the transmitters and phototransistors is necessary.

Two similar sections detect interruption of the IR beam and generate clock pulse for the microcontroller. The microcontroller controls counting and displays the number of persons present inside the hall is also displayed on the seven segment displays. It receives the signals from the sensors, and this signal is operated under the control of software which is stored in ROM. Microcontroller AT89S52 continuously monitor the Infrared Receivers, When any object pass through the IR Receiver's then the IR Rays falling on the receiver are obstructed , this obstruction is sensed by the Microcontroller.

 Bi Directional Visitor Counter Transmitter Circuit Diagram

 Bi Directional Visitor Counter Receiver Circuit Diagram

 Download Circuit Diagram
Download Transmitter Circuit Diagram 

To know More about Bi Directional Visitor Counter Using Microcontroller follow the below post

http://finalsemeceprojects.blogspot.in/2012/11/bidirectional-visitor-counter-using.html

 8.Automatic Home Security System

9.SUN LIGHT ACTIVATED ROOM LIGHT AUTOMATION

This circuit was  sun light operated.When the light illuminated on the ldr,the circuit was in off condition and when light was not falling  the circuit will drive the relay.This light activated relay circuit presented here uses the 555 timer IC and a light dependent resistor or LDR to form a light sensitive relay in an intruder alarm system or for switching on a lamp at Sun set and off at Sun rise. Potentiometer R1 value must be chosen and then adjusted that under normal conditions when the light is falling on the LDR the voltage across the LDR is less than 1/3 of Vcc. The output of the 555 IC is high now. The actual value of R1 will depend on the resistance of the LDR.

When the light fades or is interrupted by an intruder, the voltage across it rises above 2/3 of Vcc, tripping the IC flip-flop. The output goes low activating the relay. When the light is restored, voltage falls below 1/3 of Vcc, again tripping the flip-flop causing the output to go high and the relay drops.

The difference of 1/3 of Vcc between turning on and turning off voltages prevents relay chatter. This differential can be reduced by connecting a resistor R2 shown dotted in the schematic. Its value is about one and a half times of the LDR resistance in its illuminated condition. Use a 6V or 12V relay with a current of 200mA max.