AUTOMATIC PHASE CHANGER PROJECT

AUTOMATIC PHASE CHANGER  PROJECT

101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical

Today I have brought you a circuit that will not allow your work to stop, if your  three face machine  and the voltage of one face is reduced or it breaks down then it helps you and changes the face in an automatic way.

 However, there is a need to use an appropriate rating fuse in the input lines (R, Y and B) of each stage.  The circuit provides the correct voltage through the relay from the second stage to the same power sup ply lines where the correct voltage is enabled.  Using this, you can operate all your devices even when the correct voltage is available in single phase.

The circuit is built around a transformer, comparator, transistor and relay. Three identical sets of this circuit, one each for three phases, are used. Let us now consider the work of the circuit connecting the red cable (this is called the 'R' phase).

Fig1; circuit Diagram

 The mains power supply phase R is stepped down by transformer X1 to deliver 12V, 300 mA, which is rectified by diode D1 and filtered by capacitor C1 to produce the operating voltage for the operational amplifier (IC1), the voltage at inverting pin 2 of operational amplifier IC1 is taken from the voltage divider circuit of resistor R1 and preset resistor VR1.  VR1 is used to set the reference voltage according to the requirement.  The reference voltage at non-inverting pin 3 is fixed to 5.1V through zener diode ZD1.

Till the supply voltage available in phase R is in the range of 200V - 230V, the voltage at inverting pin 2 of IC1 remains high, i.e.  , more than reference voltage of 5.1V, and its output pin 6 also remains high.  As a result, transistor T1 does not conduct, relay RL1 remains de animate  and phase 'R' supplies power to load L1 via normally closed (N / C) contact of relay RL1.

As soon as phase - R voltage goes below 200V, the voltage at inverting pin 2 of IC1 goes below reference voltage of 5.1V, and its output goes low.  As a result, transistor T1 conducts and relay RL1 energises and load L1 is disconnected from phase 'R' and connected to phase 'Y' through relay RL2.

Similarly, the auto phase - change of the remaining two phases, viz, phase 'Y' and phase 'B' can be explained. Switch S1 is mains power on or off switch. 

Use relay contacts of proper rating and fuses should be able to take - on the load when transferred from other phases.  While wiring, assembly and installation of the circuit, make sure that you: 

1. Use good - quality, multi - strand insulated copper wire suitable for your current requirement

2. Use good - quality relays with proper contact and current rating. 

3. Mount the transformer (s) and relays on a suitable cabinet.  Use a Tag Block (TB) for incoming / outgoing connections from mains.

Note:  During testing in the lab, we used a 12V, 200 - ohm, single phase changeover relay with 6A. Similarly, ampere-rated fuses were used. If the input voltage is low in two stages, the load L1 and L2 may also be connected to the third stage. In that case, a fuse with a higher rating would be required on the third stage input which is carrying the total load.

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                  ANTI  THEFT  ALARM 

101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical

You can use this circuit to thwart theft. It sounds an alarm when someone tries to intrude into your home or office by hitting pushing or knocking the door. The sensor element is  a condenser mic, which is fitted inside the house on the entrance door, preferably on the door frame. Hitting, pushing or knocking the door will generate some noise. This is detected by the mic and fed to the preamplifier section of the circuit, which is connected to the buzzer through Flip-Flop. Thus the buzzer when someone hits and knocks at the entrance door.
The circuit can be divided into three sections, namely, preamplifier, flip-flop and power supply. In the preamplifier section, transistors T1 and T2 amplify the signal received from the condenser mic, developed during knocking. The output of the preamplifier is used to clock JK flip-flop CD4027.

In the JK flip-flop section, dual JK flip-flop CD4027 is employed and only one of the two flip-flops is used. The flip-flop is inhibited when both 'J' and 'K' inputs are low. The 'K' input (pin 5) of IC CD4027 is grounded, whereas J' input (pin 6) is connected to Q output (pin 2). The output of the preamplifier is connected to the clock input(pin 3) of IC1.

Fig1;circuit diagram

The amplified signal is fed to JK flip-flop IC1. Once this flip-flop receives the input through condenser mic, the output goes high and remains high until it is reset through switch S1. The output of IC1 drives buzzer PZ1 via NPN transistor T3. So the buzzer sounds when someone knocks at the door. It remains 'on' until you press reset push-to-on switch S1 at pin 4 of IC1.

power supply section

In the power supply section, the secondary of transformer X1 is connected to the rectifier. The rectified output is used to charge the 12V, 4Ah battery via switch S2 and also fed to regulator IC2, which gives 9V regulated power supply to operate the circuit. To charge the battery, push switch S2 to 'on' position and after charging switch it 'off.' The battery will provide backup power in the event of power failure. 

To sum up, the sound produced in front of the condenser mic is amplified and used to trigger IC1. Thus sounds until it is reset. the buzzer At the same time, LED1 glows to give visual indication. 

Assemble the circuit on a small PCB and house in a small cabinet. Now fix the unit near the front door with condenser mic at the door panel. LED1 gives visual indication and buzzer provides audio alarm.

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                MAGIC LAMP PROJECT

101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical

This lamp produces fascinating light. It requires a decade green and blue LEDS . The colour control is based on a simple switching logic using twelve 1N4148 diodes.

The circuit works off a 9V battery. It uses a 4017 decade counter clocked by a simple flasher (blinking) LED1. When decade counter IC CD4017 (IC1) gets clock through blinking LEDI, it advances one by one up to seventh output and resets at the eighth out- put.

Fig1;circuit diagram

 As a result, red, green, blue, yellow, magenta, cyan and white colours are produced in a cyclic manner. Altering the values of current-limiting resistors R5, R6 and R7 changes the colour impact of red, green and blue LEDs. Make sure that the resistance values are well within the current-carrying limits of red, green and blue LEDs.

The colour sequence of the LEDS can be changed by interchanging the output connections of the decade counter. A suitable light guide renders beautiful effects.

 Should you require a speed variation in the clocking, use 555 IC in place of flasher LED1. Replacing the red, green and blue LEDs with higher- wattage versions and using suitable driver transistors will create a powerful magical light effect.

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                SOUND SENCER ALARM 

101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical

This 6V battery - operated circuit triggers an acoustic buzzer when a sound is detected . It can also be used as a cheap acoustic type glass break detector and or ambient sound level monitor.

The circuit has an ordinary condenser microphone MIC1 as a sound sensor.  Sensitivity of this microphone can be changed to some extent by changing the value of the bias resistor R1.  When the circuit is powered by a 6V battery through switch S1, it goes into standby mode and the red LED1 lights up to indicate that the circuit is ready for use. 

When microphone (MIC1) detects a sound, electrical signal from the microphone is amplified and  processed by a small - signal amplifier wired around transistor T1 (BC547). 

Fig1; circuit diagarm

Amplified signal from the collector of T1 is passed to electrolytic capacitor C4 through diode D1 (1N4148).  Transistor T2 (BC547) conducts and triggers the monostable built around the timer IC NE555 (IC1).  As a result, buzzer (PZ1) at the output of IC1 starts sounding for a fixed duration, determined by the values ​​of resistor R7 and capacitor C5, PZ1 can be replaced with an electromagnetic relay to drive heavy external electrical loads such as power sirens,

Assemble the circuit on a general purpose PCB and enclose it (including battery) in a tamper - proof cabinet. glue the condenser microphone at the rear side of the window / door glass to be protected, and connect the microphone to the sensor circuit using a short length of transparent screened cable.

note.  Using a glass break sensor may cause false alarms by confusing the breaking of glass such as cook ware, or the sound of bells, with the sound of breaking windows.  •

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FIRE SECURITY ALARM PROJECT

        OVER TEMPERATURE ALARM

101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical

This circuit can be used as a warning device which triggers alarm whenever the temperature exceeds a preset level.  It can also be used as a door - alert or general warning signal.

The circuit can be divided into three part .

1. Control section

This section enables disables the pulse oscillator de pending at the temperature produced near the thermistor, which is used as a sensor.  Thermistor used here is a heat sensitive device that acts as a variable resistor.  Around normal room temperature, its resistance remains high.  but decreases with increase in temperature.  The wiper of potmeter VR1 is connected to the base of transistor TI.

The collector of transistor T2 goes high when thermistor's temperature becomes higher than preset temperature level.  High voltage of collector of T2 is used to enable the pulse oscillator.

2. Pulse oscillator section

This section is built around gates N1 and N2.  The NAND gate N1 has one of its inputs (pin 1) used for control.  It oscillates when controlling section provides high voltage at pin 1 of gate N1.  On the other hand it does not oscillate when control input pin 1 of gate N1 is held at logic low.  The timing capacitor and resistor values ​​of the pulse oscillator can be calculated as follows: f = 1 / (2.2 R9xC1)
 A very low - frequency (pulsed oscillator) output is available at pin 4 of gate N2 used to enable / disable the audio oscillator  .

3.Audio oscillator section

This section is built around gates N3 and N4 The output of the pulse oscillator is fed to input pin 9 of gate N3.  When output of pulse oscillator goes high audio oscillator starts oscillating.  This frequency is given to the base of transistor T3 to drive buzzer PZI, which starts producing an intermittent beep sound.  The beep rate depends on the values ​​of capacitor C2 and resistor R11

Fig1; circuit diagram

At normal condition, thermistor THI keeps the base of transistor T1 low.  Transistor T1 is cut off and T2 conducts, keeping collector voltage of T1 high while collector voltage of 12 is low.  As a result both the oscillators silent are disabled and buzzer remains Silent 

On the other hand, when the temperature of thermistor goes high, the base of transistor T1 also goes high.  Transistor T1 conducts and T2 cuts off, resulting in collector voltages of T1 as low and T2 high.  Both oscillators oscillate and buzzer produces intermittent sounds.

Assemble the circuit on a general purpose PCB and enclose it in a suitable cabinet Connect the thermistor TH1 using two wires and preset on the front panel.  Mount the buzzer firmly on the enclosure.  Use 6V battery or a 6V adapter to operate the circuit.  Alternatively, you can use a 9V PP3 type battery also ..

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                                               ALERT  TIMER  PROJECT 

101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical

This timer is a useful tool for those who often forget to turn off the devices in time.  Super Pose You want to boil water in your electric kettle or cook something on your gas.  You switch on the kettle or gas and simultaneously press the S2 momentarily to enable the warning circuit.  The ten-minute buzzer reminds you of what you were doing.

The circuit is constructed using an N channel enhancement - mode field effect transistor BS170 (T1).  It does not attract any power at idle and is less than 15 micrograms when working.  In terms of simplicity, the car key 12V fob battery would be an ideal choice.

Fig1;circuit diagram

Momentarily pushing switch S2 charges capacitor C1 rapidly via resistor R1.  When the voltage on capacitor C1 exceeds the threshold voltage at the gate of T1, it starts charging the reservoir capacitor C2.  Transistor T1 remains in stored state as long as the voltage on C1 is greater than FET gate's threshold voltage.  The time period of the alarm depends on the value of capacitor C1 and resistor R2, which governs the capacitor's discharge current.

The component values ​​provided here give an on - time of about ten minutes.  You can increase or decrease the time period of alarm by changing the values ​​of capacitor C1 or resistor R1.

 Assemble the circuit on a general purpose PCB and enclose in a suitable cabinet.  Press switch S2 along with your electrical appliance's switch to enable the alert alarm.  Switch S1 is power - on switch.  • 

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FLASHING LIGHT PROJECT

                  FLASHING   LIGHT

101％ working  project hello  friends  today I am gonna  telling  you  about  some  easy  and valuable  electronics projects for  school and  college  practical

Flashing light  produce blinking of light to get your attention.  For example, the white, gleaming strobe lights of airplanes warn other airplanes to fly.  There is a Flashing light circuit in which the LED flashes four times, turns off for a while and flashes four times again.  The cycle keeps on repeating.

The circuit uses two NE555 timers to generate two different frequency patterns.  Both NE555 ICs are wired in an unmistakable multi vibrator configuration.  The frequency of IC1 is determined by resistor R1, preset VR1 and capacitor C1 respectively, and that of IC2 by resistor R3, preset VR2 and capacitor C4.

Output pin 3 of IC1 controls reset pin 4 of IC2 and, with the help of transistor T1, controls the strobe pin 13 ofIC3 . Whereas , output pin 3 of IC2 pro vides the clock frequency to decade counter IC3 . The high pulse at pin 9 of IC3 resets decade counter CD4017 Output pins 3 through 5 and pin 10 drive LED1 through diodes D1 , D2 , D3 and D4 , respectively .

The flashing rate of LED1 can be varied using preset VR1 and the re peat - rate is varied by pre set VR2 . The frequency of IC2 must be equal to or ten times greater than that of IC1 . The observed lighting sequence of LED1 is ' on off - on - off - on - off - on - off off - off ......- on - off on .....

You may use this strobe light on your radio controlled helicopter or mount in the headlamp of your bike or car.  If you observe the sequence carefully, you will notice that it is similar to the one used by alarm clocks.  Connect a buzzer to the output of the circuit to emulate the alarm.

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