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2:51 AM

STAR DELTA STARTER PRINCIPLE CIRCUIT DIAGRAM AND EXPLANATION

Introduction:- A three phase motor has three windings with terminal numbers A1-A2, B1-B2 and C1,C2. In some motor terminal numbers are U1-U2, V1-V2 and W1-W2. These three winding can be connected in two way known as star connection or delta connection. In motor name plate we can get motor type as three phase ac induction motor, kw as 5kw 10 kw, voltage 230 or 400, star or delta conection full load current power factor efficiency duty cycle etc.

Star connection:- In star connection the second point of each winding ie A2, B2, C2 are conected (shorted) to each other making a point known as star point. And remaining three points A1, B1, C1 are connected to 3 phase supply points R phase Y phase and B phase respectively. The connection is as shown in diagram. In star connection the voltage given to each winding known as phase voltage is equal to line voltage/1.732 (root 3). And phase current is equal to line current.



Delta connection:- In Delta connection the second point A2 of first winding is connected to first point B1 of second winding. Again the second point B2 of second winding is connected to first point C1 of third winding. And second point C2 of third winding is connected to first point A1 of first winding. It forms a tringle shape closed circuit by three  winding as arm of tringle thats why it is known as Delta connection. In delta connection winding phase voltage is equal to line voltage of supply. But the phase current is line current/root 3.

So as per name plate voltage and connection a motor can be connected in star or delta connection.
If a motor name plate shows delta connection then  it can be run first  in star  and then in delta.This motor can be used with star delta starter.
If a motor is 400 volt star connection it can not be used with star delta starter because motor can not connected in delta connection.

Principle of star delta starter:- while starting a motor 3 phase supply is given to motor by contactor. While giving direct full voltage to motor causes very high current which causes line voltage drop. To reduce starting current a method used is known as reduce voltage starting and full voltage runnung scheme is used. This is achieved by two way ie

l. by using star delta starter
2. by using auto transformer srarter

Here we will discuss star delta strater.

In old time manual star delta starter was used. but now automatic star delta starters are used.

Construction;- It consist of three starter and one time relay and two push button overload relay. all parts are connected as shown in circuit diagram.


When start button is pressed contactor c1 and c3 pick up and motor start in star conection with reduced voltage taking low current. after few seconds when motor picks up speed time relay oprates and contactor c3 drops and c2 pickup which changes motor connection to delta. now motor runs at full voltage. The overload relay provides protection against overload condition by trippning the motor. When stop button pressed both the contactors drop and motor stops.time relay coil is connected in parallen with c1 contactor coil. c2 and c3 nc contact is used in interlocking so that c2 can pick up only when c3 gets drop.similarly c3 can only pick up when c2 is drop.
I hope this will help full to you. please comment for any more information.
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1:51 AM


SPEAKER CONSTRUCTION AND WORKING

Introduction:- Speaker work on the principle of electomagnetism. A current carring conductor in a magnetic field experience a mechanical force.The direction of force is given by flaming's left hand rule. The force is proportional to the magnetic field and strengh  of current. The direction of force reverse with reversing the direction of current.
Construction:- It consist of a permanent magnet with magnetic field arrengement. A moving coil made of approximately 40 to 60 turns of very thin insulated copper wire. A spider made of hard cloth type material and a paper cone. A conical structure made of metalic sheet. All items are fixed with each other as shown in diagram.



Working:- When amplified audio signal is applied to the coil of speaker coil starts vibrating according to the signal voltage. The spider and paper cone also starts vibrating. Due to the vibration of paper cone sound generete form speaker. This sound is same which is given to the input of amplifier.

Speaker are varies in size, shape, wattage, and ohms. Speaker comes in round shape, oval shape slim shape. They are comes in 5, 10, 20, 40 watts etc, ohms rating are 4 ohm 8 ohm 16 ohm 32 ohm etc.

Checking:- With multimeter we can check speaker, It will show continuty and resistance value of speaker. Also if we touch 1.5 volt supply to the speaker points it gives some sound which indicates speaker is ok. please comment for any further improvement. Thanks
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1:45 AM

Instruction Fetch in a Microprocessor

Instruction Fetch

The above graphic animation illustrates typical operation of an instruction by the processor.

It places the contents of the instruction pointer onto the address bus and fetches the instruction.

Once decoded, the instruction is executed and the instruction pointer altered to point to the next instruction.
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1:40 AM

Working of a Lighter


It works on the principle of Piezo-electric effect.                                
When we start pushing the push button, it presses the hammer and spring assembly to move in the telescopic shaped plastic casing.                      

This force is enough for the crystal to generate a spark.                                                                             
Now, this spark falls on the gas and lights the air-gas mixture. 
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1:28 AM

Wireless Temperature Sensor (nrf24L01 & DS18B20)

As I mentioned about IoT Gadgets in the last blog post, I've been developing an "home automation basestation" and gadgets which connects to that. The basestation (BS) itself is connected to wlan and my server via ESP8266. The BS has an DS18B20 temperature sensor and IR led, which controls my AC unit. It also has an nrf24l01 RF module for external wireless sensors and controllers. For now, I have only one wireless temperature sensor, which also has that same temperature sensor and RF module. More of that, the sensor module has ATtiny2313A microcontroller, 1.5 F 5.5 V super capacitorand a solar cell.

The sensor module would run almost forever with AA batteries but that would have been way too boring, so I used a super cap & solar cell combination to learn something new about the power management optimization, sleep modes and current measurement techniques. I also wanted to use an 8-bit AVR microcontroller at least for this revision, although for ex. Gecko EFM32 would have provided a lot smaller current consumption. Just for simplicity, I also left out the energy harvesting IC with solar cell MPPT tracking and buck-boost SMPS output.
Rev. 1 board. Click to enlarge
Just by looking at the operating voltage ranges of every component, the max. voltage of nrf24L01 is 3.3 V and min. voltage of DS18B20 is 3.0 V, so 3.0 V LDO regulator with a low quiescent current could power everything in this module. This sets the usable voltage range of the cap between 3 V and 5.5 V. The load acts as a constant current sink over the voltage range, if we average out the active and sleep state current consumptions. To calculate the time when the voltage of the super cap drops from 5.5 V to 3.0 V, we can use the formula: t = C * [(V1-V2)/I]. So for ex. 1.5 F and 20 uA would make 187 500 seconds, which is ~52 hours with the assumption that we don't put any charge in during that time.

The rev. 1 model was quite large because it had a jumper for every voltage rail, so I could measure the current consumption of any individual component. There was also 3 capacitors (1.5 F, 0.47 F and 330_uF) behind the jumpers so I was able to change the connected capacitance. Rev. 2 doesn't have these jumpers and has only one super capacitor, so it's a lot smaller.

Rev. 2 board. Click to enlarge
As I programmed the first working scratch (1 MHz clock) without any sleep modes, the current consumption was approximately 750 uA, which would drain the cap in 83 minutes. As the MCU stays in sleep state most of the time, we want to use the lowest power sleep state, which is "power-down". Power-down disables timers, except the watchdog, which can be used as a wake-up source even in that deepest sleep mode. Watchdog interrupt function is used to cancel the reset flag before the MCU resets. Just by adding the power-down sleep mode, the average current consumption goes down to 130 uA, which is still 5 times too much.
By lowering the MCU clock from 1 MHz to 250_kHz, enabling the "power reduction register" features in ATtiny, reducing the temperature resolution of DS18B20 from 12 bits (0.0625 °C) to 10 bits (0.25 °C), using the deepest sleep mode of the nrf24l01 and by pulling down any unnecessary microcontrollers pins, the current consumption goes down to 27 uA. Further, we don't really need a temperature reading every 8 seconds (longest WDT range), so the final revision of the program reads the temperature in one interrupt cycle, puts the MCU to sleep already during the 250 ms temperature conversion of the DS18B20 and sends the result it in another cycle. That gives one temperature reading per 16 seconds, which is still well enough, but drops the average current consumption to 13_uA.
Click to enlarge
Download files:

Proteus 7.7 schematic & layout files (zip)
Atmel Studio 6.1 project / source code (zip) 

As there is no step-up converter / energy harvesting IC, the open circuit voltage of the solar cell should go quite easily to 5 volts even in mediocre lighting, so the voltage would be higher than capacitor's voltage to allow the charging. The series schottky diode prevents the current from going in wrong direction when there is not enough light for charging. When there is lots of light, the charging voltage needs to be limited to 5.5 V, so the super cap won't blow up. That's done by using a voltage supervisor IC, which controls the mosfet and shorts the solar cell to ground through the 220 Ω resistor, if the voltage goes too high. Zener diode would have been a "single component solution" but they tend to be too leaky in non-conductive region, so it wasn't an option.

Click to enlarge. Sensor module with 2300 uF capacitor(s) as a power supply. Low voltage detection off vs. on
The recommended minimum input voltage range of 3.0 V LDO regulator is ~3.1 volts, but at that low currents, that specific LDO seems to works well above this, although the output voltage obviously starts to follow the input voltage when it goes above 3.0 volts. ATtiny2313A doesn't have an ADC which could be used for voltage monitoring, and the Brown Out Detector would be a bit too extreme, since there's no other option than resetting the whole MCU when it triggers. But there is an analog comparator, which can be used by connecting the internal bandgap reference (1.1 V) and comparing it to the operating voltage, divided with two resistors. I used 100k and 75k resistors, which makes 1.29_V when the operating voltage is 3.0 V. When the operating voltage dips below 2.56 V, the output of the resistor divider goes below 1.1 V and triggers the analog comparator. However, bandgap reference consumes a lot of current (~15 uA) so it's turned on only during the voltage test for a short period of time. If the voltage reaches that point, the DS18B20 doesn't work properly anymore, and measuring the temperature & sending the results are stopped to save some current. At that point we can also send a low voltage warning to the BS. There's also a routine which resetes the system occasionally if the low voltage is detected, so the memory of the MCU, RF module or the digital temperature sensor is refreshed to prevent corruption of the memory and malfunctioning of the system.

Currently I'm logging the temperature readings to my RPi 3 server (just for fun), and the module seems to work very well even in indoor lighting, without a direct sunlight. Next I'm going to put this outdoors when I'll find a good case for it.
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1:24 AM
  Who needs lithium ion battery in your smartphones which needs constant charging after certain time period anymore, and makes us carry the charger whenever we go camping, thanks to the university of Missouri researchers who found out the nuclear battery!  But this might be bad for the people who consider Wi-Fi signals are bad for your health! But it might be a good news for the people who are using the smartphones and other smart devices 24/7.  




     First of all nuclear battery as the name suggests it does not contain any reactor inside it, which might be extremely dangerous and might be a showcase invention if made into a commercial product.  Instead it uses the beta voltaic process to produce electricity.  As the name tells it generates power from the decay of beta particles.  It might sound similar to the photovoltaic cells!  But instead of photons it generates electricity from the beta radiation.


     Beta voltaic techniqueuses a silicon  wafer to  capture  electrons  emitted by  a  radioactive  gas,  such  as  tritium.  It  is  similar  to  the  mechanics  of converting  sunlight  into  electricity  in  a  solar  panel.  The  flat  silicon  wafer  is coated  with  a  diode  material  to  create  a  potential  barrier .  The  radiation absorbed in the surface of any potential barrier like a p-n junction or a metal-semiconductor  contact, would  generate separate  electron-hole pairs which in turn flow in an electric circuit due to the  voltaic effect and if it is connected to external load via the regulator, we can constantly supply the current.


      Basically, Kim and Kwon’s nuclear battery consists of a platinum-coated titanium dioxide electrode, water, and a piece of radioactive strontium-90. Strontium-90 (Sr-90) radioactively decays with a half-life of 28.79 years, producing an electron (beta radiation), an anti-neutrino, and the isotope yttrium-90. Y-90 itself has a half-life of just 64 hours, decaying into more electrons, anti-neutrinos, and zirconium (which is stable). The best thing about using strontium-90 as a fuel is that it produces almost no gamma radiation — so, as far as radioactive materials go, it’s pretty safe and easy to handle. (Still, there’s no avoiding the fact that it’s used extensively in medicine, both for radiotherapy of cancer, and as a radioactive tracer.)


      Asus has already created prototype as in the name of Zenpower Atom which uses radioisotope thermoelectric type process as quoted above. They use Strontium-90 as the radio isotope as it is more easily available than plutonium. Asus quotes that prototype has a lifetime of 5 years to be completely depleted!

     Implanted medical devices are a natural application for beta voltaic power sources, whose life spans of longer time will help the trauma patients.  we can see the return of betavoltaic powered cardiac pacemakers, cochlear implants, intraocular implants, brain computer interfacing devices etc.  However, today`s small scale chemical batteries can provie power only for few months at best, but it can provice power for years!

ADVANTAGES:
  1. reliable
  2. lighter with high energy density
  3. life span of decades
  4. efficient use of end product obtained post nuclear fission and nuclear fusion process as fuel in nuclear batteries!
  5. energy obtained is high
  6. reduces greenhouse effect and related effects
DISADVANTAGES:
  1. high initial cost of production
  2. energy conversion methodologies are not much advanced
  3. to gain social acceptance!
  4. regional and country specific laws regarding the use and disposal of radioactive materials.

     The current research of nuclear batteies shows promise in future applications.  Implementation of this new technology, feasibility of the device will be available for wide range of application,  Nuclear cells are going to be the next best thing ever invented in human history.  

     “But surely having a battery, and thus a mobile device, packed full of radioactive material is a bad idea, and some might even consider having reactor inside a mobile phone will create a global catastrophe or might be a Chinese mission for WW3!” I hear you say. And usually, yes, you’d be right. What makes a betavoltaic battery somewhat safe is that beta radiation can be easily stopped with a thin piece of aluminium!  Gamma radiation, on the other hand, has so much penetrative power that it can only be stopped by a big lump of lead (or other dense metal). This doesn’t mean that beta radiation in itself is safe, it can cause cancer and death, but it’s much easier to control. Just make sure the Betavoltaic nuclear battery casing is more than a couple of millimetres thick and don’t drop it. Ever. But this might be the future of the energy storing devices.  We can see this kind of batteries in local vendor shops soon! 
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1:20 AM
This might be possible in substations while any L-G fault occurs in the transmission side.




               Let us consider a star delta transformer with a primary delta connection and secondary star connection.  The line voltage is V across the two phases.



                If any relay operates due to any fault and the phase B gets opened then, the current incoming to phase B will be zero.


                As we can see from the above diagram the B phase is disconnected.  After this we can see a closed loop formation and circulating current passes through coils in between phases RB and BY.  Thus the voltage is divided between the two phases and V/2 appears on the secondary side.  This voltage division is clearly mentioned in the above diagram.

                  This situation leads to any 3 phase equipment will continue to operate at reduced efficiency.  Motors would be noisy and would overheat leading to decreased efficiency.  Induction motor acts as single phase motor with reduced efficiency.  This problem is common in sub stations and is got rid by minimising the circuit fault clearance time.

                  This can also be cleared using single phasing protection relay.  To see more about transformer rating concept click here.

IF YOU LIKED THE CONTENT PLEASE LEAVE A UPVOTE AND IN CASE OF ANY DOUBT PLEASE COMMENT BELOW WE WILL REPLY TO IT .PLEASE FOLLOW OUR GOOGLE PROFILE AND BLOG FOR FUTURE UPDATES! HAVE A NICE DAY! AND DON'T GET FRUSTRATED WITH THE ADS SINCE IT HELPS TO PAY MY BILLS! LOL THANK YOU FOR VISITING MY BLOG ONCE AGAIN!
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8:09 AM


This circuit is designed based on lM3914 IC (Integrated chip). This IC is LED dot/bar display driver.

Battery Level Indicator Circuit Principle

The heart of this battery level indicator circuit is LM3914 IC. This IC takes input analog voltage and drives 10 LED’s linearly according to the input analog voltage. In this circuit, there is no need of resistors in series with LEDs because the current is regulated by the IC.
Get an idea about the related post – How Automatic Battery Charger Circuit Works using LM317?

Battery Level Indicator Circuit Diagram



Battery Level Indicator Circuit Diagram

Circuit Components

  • LM3914 IC
  • LED’s -10 (Red – 3, Yellow – 4, Green – 3)
  • SPST Switch
  • Resistors – 18KΩ, 4.7KΩ, 56KΩ
  • Potentiometer – 10KΩ
  • 12V Battery (to test)
  • Connecting wires

Battery Charge Indicator Circuit Design

In this circuit LED’s (D1-D10) displays the capacity of the battery in either dot mode or display mode. This mode is selected by the external switch sw1 which is connected to 9th pin of IC. 6th and 7th pins of IC are connected to the ground through a resistor. This resistor controls the brightness of LED’s. Here resistor R3 and POT RV1 forms potential divider circuit. Here pot RV1 is used for calibration. There is no need of any external power supply to this circuit.
The circuit is designed to monitor 10V to 15V DC. The circuit will work even if the battery voltage is 3V. The operating voltage of this IC is 3v to 25v DC. Lm3914 drives led’s, LCDs and vacuum fluorescents. The IC contains adjustable reference and accurate 10-steps divider. This IC can also acts as sequencer.

LM3914 Features

  • Internal voltage reference from 1.2 to 12v DC.
  • Programmable output current 2mA to 30mA.
  • LED driver outputs are current regulated.
  • No multiplexing interaction between outputs.
  • It supports wide range of temperature from 0 to 70 degree Celsius.
  • For bar graph display – connect 9th pin of IC to the supply
  • For dot display – leave the 9th pin of IC
We can also connect different color led’s to indicate the status. Connect D1 to D3 red LED’s which indicates shut down stage of your battery and use D8-D10 green color LED’s which indicates 80 to 100 percentage of the battery and use yellow color for remaining.

With a little modification we can use this circuit to measure other voltage ranges also. For this remove the resistor R2 and connect upper voltage level to the input. Now vary the resistance of Pot RV1 till the D10 LED glows. Now remove upper voltage level at the input and connect lower voltage level. Connect a high value variable resistor in the place of resistor R2 and vary it till the D1 LED glows. Now disconnect the pot, measure the resistance across it and connect resistor of same value in place of R2. Now the circuit is ready to monitor other voltage ranges.
This circuit is most suitable for indicating 12V battery level. In this circuit each led indicates 10 percent battery level. We can extend this circuit to 100 steps by cascading lm3914 IC’s.

How to Operate Battery Level Indicator Circuit?

  • Connect battery to be tested to the input of the circuit.
  • Now adjust the pot RV1 so that LED D1 just starts glowing.
  • Now increase the input Dc voltage slowly and observe the LED’s
  • First led will glow for 1.2V and second LED is for 2.4 V and so on.
Below table shows the status of LED’s with input voltage level.

Battery Level
Percentage
Status of LED’s
1.2V
10
D1 - ON
2.4V
20
D1, D2 - ON
3.6V
30
D1, D2, D3 - ON
4.8V
40
D1, D2, D3, D4 - ON
6.0V
50
D1, D2, D3, D4, D5 - ON
7.2V
60
D1, D2, D3, D4, D5, D6 - ON
8.4V
70
D1, D2, D3, D4, D5, D6, D7 - ON
9.6V
80
D1, D2, D3, D4, D5, D6, D7, D8 - ON
10.8V
90
D1, D2, D3, D4, D5, D6, D7, D8, D9 - ON
12V
100
ALL LED’s - ON



Battery Charge Level Indicator Circuit Applications

  • We can use this circuit to measure car battery level.
  • This circuit is used to calibrate inverter status.

Limitations of the Circuit

  • This battery level indicator works only for small voltages.
  • This circuit is theoretical and may require some changes to work in practical.
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8:01 AM

PIR Sensor based Security Alarm Circuit Principle

The main idea of the circuit is to provide security. This is based on PIR sensor with an IC that produces siren. The PIR sensor detects the IR radiations emitted from the humans and it produces a digital output. This digital output is applied to the Arduino UNO.
Based on the digital signal from the PIR Sensor, Arduino UNO then triggers the UM 3561 siren IC. Thus it produces the sound when any human is detected.
The UM3561 is a ROM IC. It generates multi siren tones like ambulance siren, fire engine siren, police siren, machine gun sound.

PIR Sensor based Security Alarm Circuit Diagram




NOTE: The circuit diagram shows the Oscillator Resistor (between Pin 7 and 8 of UM 3561) as 220Ω but it is 220KΩ.

Circuit Components

  • PIR sensor
  • Arduino UNO
  • UM3561 Siren IC
  • NPN Transistor – 2N2222
  • Resistors 10KΩ and 220KΩ
  • Speaker 8Ω
  • Breadboard
  • Connecting Wires

PIR Sensor based Security Alarm Circuit Design

The designed system consists of Arduino UNO, PIR sensor, UM3561 IC, Speaker, transistor and a couple of resistors. The UM3516 IC is a Siren generator IC. It has 8 pins. First and sixth pins are the Sound effect selection Pins. Based on how they are connected, you can choose between 4 different types of sounds.
In this project, I have left open both the Pin 1 and Pin 6 to produce a Police Siren. Pin 5 is connected to +5V through an NPN Transistor (which is activated by Arduino UNO’s Pin 4).
One end of the 220KΩ resistor is connected to the seventh pin of the UM 3561 IC and the other end is connected to the eighth pin of the IC. Output is taken from the third pin of the IC and it is connected to a speaker through a resistor and transistor.
The base of the transistor is connected to the output of the IC through a resistor of 10KΩ. Emitter pin is connected to the ground while one end of the speaker is connected to the collector, while the other end is connected to +5V.
Coming to the PIR Sensor, its output is connected to Pin 3 of Arduino.

Code


int pir = 3;
int siren =4;
void setup()
{
pinMode(pir,INPUT);
pinMode(siren,OUTPUT);
digitalWrite(siren,LOW);
delay(8000);
}
void loop()
{
if(digitalRead(pir))
{
digitalWrite(siren,HIGH);
delay(10000);
digitalWrite(siren,LOW);
while(digitalRead(pir));
}
}


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