Midnight Security Light

Most thefts happen after midnight hours when people enter the second phase of sleep called ‘paradoxical’ sleep.
          Here is an energy-saving circuit that causes the thieves to abort the theft attempt by lighting up the possible sites of intrusion (such as kitchen or backyard of your house) at around 1:00 am. 
It automatically resets in the morning.
For this you need:
1) bridge rectifier
2) transformer i.e voltage regulator
3)  IC (ic cd  4060)
4) LDR
5) LED & bulb
6) Capacitor & resistance
7) TRIAC 

The circuit is fully automatic and uses a CMOS IC CD 4060 to get the desired time delay. Light-dependent resistor LDR1 controls reset pin 12 of IC1 for its automatic action. During day time, the low resistance of LDR1 makes pin 12 of IC1 ‘high,’ so it doesn’t scillate. After sunset, the high resistance of LDR1 makes pin 12 of IC1 ‘low’ and it starts oscillating, which is indicated by the flashing of LED2 connected to pin 7 of IC1. The values of oscillator components (resistors R1 and R2 and capacitor C4) . are chosen such that output pin 3 of IC1 goes ‘high’ after seven hours, i.e., around 1 am. This high output drives triac 1 (BT136) through LED1 and R3.
            Bulb L1 connected between the phase line and M2 terminal of triac 1 turns on when the gate of triac 1 gets the trigger voltage from pin 3 of IC1. It remains ‘on’ until pin 12 of IC1 becomes high again in the morning. Capacitors C1 and C3 act as power reserves, so IC1 keeps oscillating even if there is power interruption for a few seconds. Capacitor C2 keeps trigger pin 12 of IC1 high during day time, so slight changes in light intensity don’t affect the circuit. Using preset VR1 you can adjust the sensitivity of LDR1.
            Power supply to the circuit is derived from a step-down transformer X1 (230V AC primary to 0-9V, 300mA secondary), rectified by a full-wave rectifier comprising diodes D1 through D4 and filtered by capacitor C1. Assemble the circuit on a general purpose PCB with adequate spacing between the components. Sleeve the exposed leads of the components.
Using switch S1 you can turn on the lamp manually. Enclose the unit in a plastic case and mount at a location that allows adequate daylight.
           Caution. Since the circuit uses 230V AC, many of its points are at AC mains voltage. It could give you lethal shock if you are not careful. So if you don’t know much about working
with line voltages, do not attempt to construct this circuit. EMP(Engineering mini project.blogspot.com)  will not be responsible for any kind of resulting loss or damage.

Antisleep Alarm for Students

            This circuit saves both time and electricity for students.

       It helps to prevent them from dozing off while studying,  by sounding a beep at a fixed time interval, say, 30 minutes. If the student is awake during the beep, he can reset the circuit to beep in the next 30 minutes. If the timer is not reset during this time, it means the student is in deep sleep or not in the room, and the circuit switches off the light and fan in the room, thus preventing the wastage of electricity.

Things Needed for Making this Antisleep Alarm for Students

• Relay
• Bulb
• Transistor or SCR
• Push to ON /OFF switches
• Resistance & capacitor
• Piezzo buzzer
• Diode
• IC: IC CD4020

           The circuit is built around Schmitt trigger NAND gate IC CD4093 (IC1), timer IC CD4020 (IC2), transistors BC547, relay RL1 and buzzer. The Schmitt-trigger NAND gate (IC1) is configured as an astable multivibrator to generate clock for the timer (IC2). The time period can be calculated as T=1.38×R×C. If R=R1+VR1=15 kilo-ohms and C=C2=10 μF, you’ll get ‘T’ as 0.21 second. Timer IC CD4020 (IC2) is a 14-stage ripple counter.  Around half an hour after the reset of IC1, transistors T1, T2 and T3 drive the buzzer to sound an intermediate beep. If IC2 is not reset through S1 at that time, around one minute later the output of gate N4 goes high and transistor T4 conducts. As the output of gate N4 is connected to the clock input (pin 10) of IC2 through diode D3, further counting stops and relay RL1 energies to deactivate all the appliances. This state changes only when IC1 is reset by pressing switch S1. 
          Assemble the circuit on a general-purpose PCB and enclose it in a suitable cabinet. Mount switch S1 and the buzzer on the front panel and the relay at the back side of the box. Place the 12V battery in the cabinet for powering the circuit. In place of the battery, you can also use a 12V DC adaptor.

Shadow Detector (Short Range Hand Wave Detector)

                  The circuit below works quite well in typical indoor room lighting. I would not recommend its use in direct sunlight. Two small PIN photo diodes positioned about one inch apart form a shadow detector. With no shadow cast on the devices, both devices produce nearly identical current levels. The current is converted to a voltage with two load resistors in parallel with the photo diode. One resistor is adjustable to the two voltages can be carefully balanced under uniform lighting. When a hand or an arm is moved over the sensors, casting a shadow, one device will detect more light than the second, as the shadow moves over the two sensors. 
             
             
               
               
             This triggers an imbalance. A voltage  comparator connected to the two devices detects the imbalance and sends a high logic level signal to an n-channel FET, which can turn on a beeper or activate a relay. If a low power voltage comparator is used, such as the LMC7211, a 9 volt battery will power the circuit for many years. The more popular LM358 would also work but would draw more current.

SIMPLE DIGITAL SECURITY SYSTEM

You can use this simple and reliable security system as a watchdog by installing the sensing loops around your building. You have to stretch the loop wires two feet above the ground to sense the unauthorized entry into your premises. Wire loops 1, 2 and 4 are connected to the A, B and C inputs of 7-segment decoder 4511 (IC1), respectively, while the D input of IC1 is grounded permanently.

The loops are also connected to a dual 3-input NOR gate and inverter CD4000 (IC2) to activate the alarm. Fig. 1 shows the circuit of the digital security system, while Fig. 2 shows the proposed wiring diagram for the loops around the premises. Before using this security system, make sure that loops shown in Fig. 2 are connected as shown in Fig. 1. If you don’t want to use a buzzer, switch it off by opening switch S2. The circuit works off a 9V regulated power supply. However, battery back-up is recommended. A commoncathode, 7-segment display (LTS543) is used for displaying whether the

loops are intact or not. If loop 1 is broken, the display will show ‘1’. If two or all the three loops are broken, the display will show the sum of the respective broken loop numbers. For example, if loops 1 and 4 are broken, the display will show 5(1+4).

When all the three loops are intact, the display will show ‘0.’ All the three inputs of gate N1 remain low to give a high output. This high output is further given to gate N2 and, as a result, its output remains low. This keeps transistor T1 in cut-off position and the piezobuzzer does not sound.

When any loop is broken, the output of NOR gate N1 goes low, while the output of gate N2 goes high. Transistor T1 conducts and the buzzer sounds to alert you. You can mute the buzzer by switching off power to the circuit through switch S1.

Wireless switch

Normally, home appliances are controlled by means of switches,

sensors, etc. However, physical contact with switches may be

dangerous if there is any shorting .So here a tip about how to prepare

a wireless switchs

To prepare Wireless switch  we need

• Transistor / SCR
• LED
• Relay
• Resistor and Capacitor
• IC CA 3140

  

The circuit described here requires no physical contact for operating the appliance. You just need to move your hand between the infrared LED (IR LED1) and the phototransistor (T1). The infrared rays transmitted by IR LED1 is detected by the photo transistor to activate the hidden lock, flush system, hand dryer or else.

            This circuit is very stable and sensitive compared to other AC appliance control circuits. It is simple, compact and cheap. Current consumption is low in milliamperes. The circuit is built around an IC CA3140, IRLED1, photo transistor  and other discrete components. 
           When regulated 5V is connected to the circuit, IR LED1 emits infrared rays, which are
received by phototransistor T1 if it is properly aligned. The collector of T1 is connected to non-inverting pin 3 of IC1. Inverting pin 2 of IC1 is connected to voltage-divider preset VR1. Using preset VR1 you can vary the reference voltage at pin 2, which also affects sensitivity of the phototransistor. Op-amp IC1 amplifies the signal received from the phototransistor. Resistor R3 controls the base current of transistor BC548 (T2). The high output of IC1 at pin 6 drives transistor T2 to energies relay RL1 and switch on the appliance, say, hand dryer, through the relay contacts.

             The working of the circuit is simple. In order to switch on the appliance, you simply interrupt the infrared rays falling on the phototransistor through your hand. During the interruption, the appliance remains on through the relay. When you remove your hand from the infrared beam, the appliance turns off through the relay.

              Assemble the circuit on any general- purpose PCB. Identify the resistors through colour coding or using the multimeter. Check the polarity and pin configuration of the IC and mount it using base. After soldering the circuit, connect +5V supply to the circuit  

Home made Solar cells Power generator

Solar cells generate direct current,so make sure that DPDT switch S1 is towards the solar panel side. The DC voltage from the solar panel is used to charge the battery and control the relay.Capacitor C1 connected in parallel with a 12V relay coil remains charged in daytime until the relay is activated.Capacitor C1 is used to increase the response time of the relay, so switch-ing occurs moments after the voltage across it falls below 12V. Capacitor C1 also filters the rectified output if the battery is charged through AC power.The higher the value of the capacitor,the more the delay in switching.

The switching time is to be properly adjusted because the charging wouldpractically stop in the early evening while we want the light to be ‘on’ during late evening.During daytime, relay RL1 energises, provided DPDT switch S1 is towards the solar panel side. Due to energisation of relay RL1, the positive terminal of the battery is connected to the output of regulator IC 7808 (a 3-terminal, 1A, 8V regulator) via diode D1 and normally-open (N/O) contacts of relay RL1. Here we have used a 6V, 4.5Ah maintenance-free, lead-acid rechargeable battery. It requires a constantvoltage of approx. 7.3 volts for its proper charging.Even though the output of the solar panel keeps varying with the lightintensity, IC 7808 (IC1) is used to give a constant output of 8V. Diode D1 causes a drop of 0.7V, so we get approx. 7.3V to charge the battery.

LED1 indicates that the circuit is working and the battery is in the charging mode.At night, there will be no generation of electricity. The relay will not energise and charging will not take place. The solar energy stored in thebattery can then be used to light up the lamp. A 3W lamp glows continuously for around 6 hours if the battery is fully charged. Instead of a 3W lamp, you can also use a parallel array of serially connected white LEDs and limiting resistors to provide sufficient light for even longer duration. In case the battery is connected in reverse polarity while charging, IC 7808 will get damaged. The circuit indicates this damage by lighting up LED2, which is connected in reverse with resistor R2. However, the circuit provides only the indication of reverse polarity and no measure to protect the IC. A diode can be connected in reverse to the common terminal of the IC but this would reduce the voltage available to the battery for charging by another 0.7 volt.There is also a provision for estimating the approximate voltage in the battery. This has been done by connecting ten 1N4007 diodes (D2 through D11) in forward bias with the battery.

The output is taken by LED3 across diodes D2, D3, D4 and D5, which is equal to 2.8V when the battery is fully charged. LED3 lights up at 2.5 volts or above. Here it glows with the voltage drop across the four diodes, which indicates that the battery is charged. If the battery voltage falls due to prolonged operation, LED3 no longer glows as the drop across D2, D3, D4 and D5 is not enough to light it up. This indicates that the battery has gone weak. Microswitch S1 has been provided to do this test whenever you want. If the weather is cloudy for some consecutive days, the battery will not charge. So a transformer and full-wave rectifier have been added to charge the battery by using DPDT switch S1. This is particularly helpful in those areas where power supply is irregular; the battery can be charged whenever mains power is available

KNOCK ALARM

Apparatus need  to prepare this:

• IC555
• Transistor PNP &NPN
• Piezzo electric sensor
• Loudspeaker
• Diode
• LED
• Resistor & capacitor

This circuit (Fig. 1), used in conjunction with a thin piezoelectric plate,
senses the vibration generated on knocking a surface (such as a door or a table)

to activate the alarm. It uses readily available, low-cost components and can
also be used to safeguard motor vehicles. The piezoelectric plate is used as the sensor.
It is the same as used in ordinary piezobuzzers and is easily available in the
market.
The piezoelectric plate can convert any mechanical vibration into electrical variation.
As it doesn’t sense sound from a distance like a microphone, it avoids false
triggering. The plate can be fixed on a door, cash box, cupboard, etc using adhesive. A 1-
1.5m long, shielded wire is connected between the sensor plate and the input of the
circuit. When someone knocks on the door, the piezoelectric sensor generates
an electrical signal, which is amplified by transistors T1 through T3.
The amplified signal is rectified and filtered to produce a low-level
DC voltage, which is further amplified by the remaining transistors. The
final output from the collector of pnp transistor T6 is applied to reset pin 4
of 555 (IC1) that is wired as an astable multivibrator. Whenever the collector
of transistor T6 goes high, the astable multivibrator activates to sound an alarm
through the speaker. The value of resistor R12 is chosen between 220 and 680 ohms
such that IC1 remains inactive in the absence of any perceptible knock.
When the circuit receives an input signal due to knocking, the alarm gets activated
for about 10 seconds. This is the time that capacitor C5 connected between
the emitter of transistor T4 and ground takes to discharge after a knock. The time
delay can be changed by changing the value of capacitor C5. After about 10 seconds,
the alarm is automatically reset.
The circuit operates off a 9V or a 12V battery eliminator. The proposed installation
of the knock alarm is shown in Fig. 2.
This circuit costs around Rs 75. 

ELECTRONIC BICYCLE LOCK

Guyz In today's generation where all people are driving car ,bikes etc. There will soon a day when we all will on  bicycle .I am not posted some eco- friendly topic just saying after all i also used this vehicles.
Today's post dedicated to those people who still used bicycle and save petrol ,diesel etc.
Generally on cycle there is an mechanical lock  which are not so Good so i am posting an Electronic lock system For bicycle.

To prepare an ELECTRONIC BICYCLE LOCK we need component like:

• Resistor and capacitor
• LED
• Zener diode
• ON OFF switch
• IC UM3561
• And a Loudspeaker

The electronic bicycle lock described here is a worthwhile alternative for bicycle owners who want to make their bicycles ‘intelligent’ at reasonable cost. One of the benefits of building it yourself is that the circuit can be used for virtually any make of bicycles. In the circuit, input jacks J1 and J2 are two standard RCA sockets. A home-made security loop can be used to link these two input points. Around 50cm long, standard 14/36 flexible wire with one RCA plug per end is enough for the security loop. Fig. 1 shows the circuit of the electronic bicycle lock. It is powered by a compact 9V battery (6F22). Key lock switch S1 and smoothing capacitor C2 are used for connecting the power supply. A connected loop cannot activate IC1 and therefore the speaker does not sound. When the loop is broken, Zener diode ZD1 (3.1V) receives operating power supply through resistor R2 to enable tone generator UM3561 (IC1). IC1 remains enabled until power to the
circuit is turned off using switch S1 or the loop is re-plugged through J1 and J2.

Assemble the circuit on a general-purpose PCB and house in a small tinplate enclosure. Fit the system key lock switch (S1) on the front side of the enclosure as shown in Fig. 2. Place RCA sockets (J1 and J2) at appropriate positions. Now, mount the finished unit in place of your existing lock (as shown in Fig. 3) by using suitable clamps and screws.

ANTI-THEFT ALARM FOR BIKES

This circuit consists of transmitter and receiver sections. The transmitter (IRLED1) is fitted on the back end of the front mudguard and the receiver sensor(IRX1) is fitted on the central portion of the crash guard of the bike such that IR rays from the transmitter directly fall on the sensor when the front mudguard comes in line with the body of the bike. The transmitter section is built around timer 555 (IC2), which is wired as an astable multivibrator with a frequency of around 38 kHz. The output of IC2 is further amplified by transistor T1 and given to an infrared light-emitting diode (IR LED1), which continuously transmits the IR frequency. The receiver section uses IR receiver module TSOP 1738 (IRX1), which is normally used in TV receivers. The receiver module senses the IR modulated frequency transmitted by the IR LED. When no IR rays are incident on the sensor, its output is high. But the output of the IR sensor goes low when it senses the modulated IR signal. The output of the receiver module is given to a negative voltage comparator built around IC LM311(IC3). The input voltage at pin 2 of IC3 is fixed by using the voltage-divider network comprising resistors R7 and R8.When IR rays are not incident on the IR receiver module, the voltage at pin 3 of IC3is greater than the voltage at pin 2. As a result, the output of comparator IC3 is low. But when the receiver senses IR rays from IR LED1, the voltage at pin 3 of IC3 is lower than the voltage at pin 2. As a result, the output of the comparator goes high. The output of the comparator is given to a latch made up of JK flip-flop (IC4). The low-to-high going pulse from the comparator makes the output of IC4 high until it is reset. The output of IC4 is latched and used to energies relay RL1 via transistor T2. The relay is connected to the negative terminal of the bike’s horn, while the positive terminal of the horn is connected to the positive terminal of the battery via resistor R1. The energized relay drives the horn, which continues sounding until you press reset switch S2 momentarily. At night, lock your bike using the handle lock and switch on the circuit using switch S1. Since the IR transmitter (IRLED1) and the receiver (IRX1) will not being line of sight, IR rays from IR LED1 will not be incident on the sensor. When anyone tries to move the bike away, the IR transmitter and the IR receiver will come in line of sight and the IR rays from the IR transmitter will be incident on the receiver. This will make the output of the comparator (IC3) high. The pulse from the comparator will make the output of latch IC4 high and transistor T2 will conduct to sound the horn via relay RL1.

Burning Bubbles

• A. Small container with water
• B. Cheap cigarette lighter
• C. Matches
• D. Dish soap

How-to:

1. Add a few squirts of liquid soap to the dish of water. Gently stir the water until the soap dissolves but try not to create bubbles yet.
2.  Submerge the lighter in the water and hold down the button that releases the butane. Butane-filled bubbles will slowly begin to accumulate on the surface of the water. To speed things up, you can use a butane refill canister.
3. Using a match, carefully light the bubbles. You should do this outside in a clear area.

Homopolar Motor

Materials

• A. "AA" Battery
• B. Neodymium Magnet
• C. Copper Wire, 18 Gauge
• D. Needle-Nose Pliers

              

                 

How-to:

1. Place the neodymium magnet on the negative terminal of the battery. The magnet used here was 0.5 inches in diameter and 0.25 inches thick. Anything near that size will work, but normal ceramic magnets are too weak. You can buy neodymium magnets at K&J Magnetics.
2. If your copper wire is insulated you need to remove the insulation. Bend the wire into any shape you want, but be sure it makes good contact with the positive terminal of the battery as well as with the circumference of the magnet. Bending the wire into a pretty yet functional shape takes lots of patience. See the photos for two examples of shapes you can make.
3. Balance the copper wire on top of the battery and make small adjustments in the shape until it spins quickly and easily. The battery will only last a few minutes with the wire on it.