UM 3561 Siren Generator

UM 3561 Siren Generator Sometimes we need a Siren sound generator to add in a Burglar alarm circuit or in Robot based circuit. The simple solution is the Siren generator IC UM3561. By using only a few components around this IC, it is easy to make a Siren Generator. By selecting the Pin connection of Sel 1 (Pin 6) and Sel 2 (Pin 1) we can select different tones.UM 3561 is a programmed ROM IC with an inbuilt oscillator. 

Only one external resistor and a speaker driver transistor are sufficient to make a simple siren generator. The IC requires 3 volts so it works off 2 Pen cells. If the power supply is a higher voltage , use a 3.1 volt Zener to regulate the power to the IC. Internal circuits of UM3561 Inside the IC, there is an Oscillator circuit and the frequency of oscillations is controlled by the external resistor connected to OSC 1(Pin 7) and OSC2 (Pin 8). A 240 K resistor is the recommended value but a 220K will give satisfactory results. Do not change this value, it will change the tone. The oscillations thus generated will be then transferred to a control circuit which functions based on the tone selection through the connections of SEL 1 (Pin 6) and SEL2 (Pin 1) . The control circuit passes the signal to an address counter and then to the ROM. The tone pulses thus generated will be available from the output pin 3. Since the sound is weak, an amplifier is necessary to get loud sound. A single NPN transistor will amplify the sound. If loud sound is needed, use a Darlington transistor. Speaker should be 8 ohms 0.2 watts. A small Mylar Speaker is an ideal choice. Tone Selection 4 Sounds like Police Siren, Fire Brigade sound, Ambulance Siren and Machine Gun sound can be selected by changing the pin connections of Sel.1 (Pin6) and Sel. 2(Pin 1).

4 wheel drive robo car

this is for those people who always want to make their own robot but don't know from where to start. you can make your first robot by simply using DPDT switches along with battery and 9 components. all you need to know is the concept of turning the motor in either direction. by changing the voltages of the motor manually using switches you can move your bot in forward backward or in any direction. I will upload the whole process along with components and circuit diagram very soon.

to buy visit

http://www.ebay.in/itm/261603109137?ssPageName=STRK:MESELX:IT&_trksid=p3984.m1555.l2649

TO download physics of semiconductor devices by SM SZE click on the following link
SM sze PDF

DIFFERENT TYPES Of LED DIODE

This article is best for those people who want to know the different type of LED diodes available in the market. LED known commonly as Light emitting diode is used everywhere. From mobile phones to LED television and LED bulbs, there are numerous applications. LED diodes  are available in various shapes and sizes.

different types of led

the most commonly used and available is 5mm white LED diodes. These LED,s require a voltage of 2-3.5V and a current of 20ma. These led's are best to use in DIY projects and a lot of fun stuff.

TO KNOW HOW TO USE LED,S ACCORDING TO VOLTAGE READ

ABC OF LED

TO BUY LED AT REASONABLE PRICE 

BUY LED DIODES

MUSIC CHIP FOR BIRTHDAY GREETINGS

Want to make your own chip which can produce melodious sound "HAPPY BIRTHDAY" , Honsitak company manufactured a popular ic HK66T-08 which produces sound by adding few additional components. The functioning of HK66T-08 is similar to UM66 series. The circuit diagram of HK66T-08 is similar to UM66.
for more information READ: SOUND FROM IC

HOW TO CONVERT 9V TO 3.3 V

In most of the practical applications we need to power our devices which requires smaller voltages. For example to power UM 66 we require 3V and if we apply 5 V or 9V through battery then UM 66 gets damaged. This is just the example of one type of component which requires small voltage. there are various devices available in the market. so to power these devices we require ZENER DIODE . The circuit diagram of the ZENER DIODE as a voltage regulator is shown below.

TO KNOW HOW TO CALCULATE RESISTANCE USED AND MORE ABOUT ZENER DIODE READ ZENER DIODE AS A VOLTAGE REGULATOR 

PEROVKSITE A NEW MATERIAL IN DESIGNING SOLAR CELLS

Researchers at NANYANG technical university , Singapore have successfully developed a new material that can be used to make cheap solar cells. one can estimate the drop in price of solar cells by the fact that the manufacturing cost of perovksite is five times less than the current solar cell materials. the material is so useful in the fact that it can successfully convert the light into electricity by day and emits light at night. now a days solar cells are widely used in power generation replacing the other ways of power generation. with the development of such a wonderful material the solar power would be available at low price.

why RS232 have a (distinct) logic? Why won't it communicate a 5V(TTL high)?

 "RS232 voltage level is different from TTL level.The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels. Valid signals are plus or minus 3 to 25 volts. minus 3 to plus 3 voltage range is undefined.The range near zero volts is not a valid RS-232 level; logic one is defined as a negative voltage, the signal condition is called marking, and has the functional significance of OFF. Logic zero is positive, the signal condition is spacing, and has the function ON.
The most commonly used RS-232 level converter is MAX232. This IC includes charge pump which can generate RS232 voltage levels (-10V and +10V) from 5V power supply which is required to convert a TTL signal in to RS232 level. The TTL signal is very small in comparison to RS232 level thus we can not directly connect a TTL device with RS232 device as it may damage the TTL device with high level voltage of RS232."

VESTIGIAL SIDE BAND

Vestigial side-band (VSB) is a type of amplitude modulation (AM) technique (sometimes called VSB-AM) that encodes data by varying the amplitude of a single carrier frequency. Portions of one of the redundant side-bands are removed to form a vestigial side-band signal; so it is called Vestigial Wideband Modulation and the portion is called Vestige.

Instead of transmitting only one side-band as SSB, VSB modulation transmits a partially suppressed side-band and a vestige of the other side-band.

The following are the drawbacks of SSB signal generation:

1. Generation of an SSB signal is difficult.

2. Selective filtering is to be done to get the original signal back.

3. Phase shifter should be exactly tuned to 90⁰.

To overcome these drawbacks, VSB modulation is used. It can be viewed as a compromise between SSB and DSB-SC.

PASSIVE INFRARED SENSOR

PiR sensor stands for passive infrared motion sensor. It is based on pyro electric effect that is, it converts heat into electrical energy. It detects the motion of human body and any other living thing which generates the heat. This property of pir is used for detecting the living body and interfacing this module with the micro-controller. The pir sensor has 3.3V output when it senses any body and 0V when there is no motion nearby. It has a good range of 2-7 meters depending on the module and the temperature conditions.

Why a 104(0.1uF) cap to be connected in parallel with DC motors when connected to a uC via any line driver?

When a DC motor runs, the commutator touches the brushes momentarily very frequently which generates a high frequency noise in motor supply. The .1uF capacitor will show a low impedance for this noise and will bypass the this noise. If we do not use this capacitor the noise will travel in DC power supply of uC(micro controller) or any IC and the uC or IC will not function properly and in case of micro controller, restart may occur.

How can AC current pass through the capacitor? There is no connection between charge plates and dielectric. Is it done due to breakdown? How is this possible?"

Alternating charged current arrives at one terminal on the cap. The load to ground is connected at the other terminal of the cap. Actually 'alternating' can be a confusing electrical term to some folks. Think of the charged current as a wave that delivers this positive current from the bottom to the top of the wave and retreats or falls off at the bottom of the other side of the wave. 
This condition is caused from the rotating action of the rotor turning inside the stator fields in a generator. The ground through the load is attracted to the positively charged electrons at the barrier of the cap at the top of the wave from the generator. 
Now, Think charge separation on the ground side. As the electrons become excited on the ground side of the cap at the barrier across from the positive charge (attraction), a vacancy of non-charged electrons has occurred downstream at ground. When the positive charge and current falls at the bottom of the wave from the generator side, the excited electrons at the barrier of the cap on the ground side are now positive (charge separation) and move to power the load and fill the vacancy to ground. This is also the reason for the delay of current and charge moving through a cap to ground. A larger barrier equals a longer delay . Nothing but magnetic field attraction between electrons has happened at the cap barrier. 
This is why a DC current cannot move through a cap. It has no wave. If we pulse the DC, we can get it to move through the cap, but at a lower efficiency than AC.

CHARGING MOBILE BY SENDING SMS

A company named buffalo grid has developed a solar powered cellphone charging station. wireless energy transfer technology is used to charge mobile. all you need to do is just send a message. the system can be very helpful for people living in rural areas. the battery of the cellphone derives its power from a solar panel via a technology called maximum power point tracking. a subscriber with say 90% charged battery level can transfer 40% of his battery level to a friend with less than 10% charged battery, and both of them can enjoy 50% charged batteries in their handsets thereafter In order to transfer or receive battery levels, a subscriber will have to register for this service with TRAI.  TRAI will have “power sources” installed at various mobile towers in the country. The total power stored in these sources will be sufficient to fully charge all the registered mobiles once a day.

CSIR TO LAUNCH INDIA'S FASTEST COMPUTER

India's fastest computer to be housed soon in bangalore. the supercomputer would have a maximum speed of 360 Tera flops( T- flops) speed and constant speed upto 260 T-flops. the machine will be housed at CSIR-4PI.

The system would be capable of performing 250 x 10 12 floating point operations (FLOPS) per second — more than 10,000 times faster than normal dual core processors. super computers in scientific research can be utilized for modelling earthquakes and ocean currents. Today all the 40 CSIR labs in india are remotely connected with supercomputers  which enables all the scientists in CSIR to interconnect with supercomputers

BUZZER

                                         BASICS

Electronic buzzer also called as piezo buzzer is used to produce rich sounds. it is based on the principle of reverse piezo electric effect. whenever electric current is applied to piezo buzzer a sound is produced. the level of sound depends upon the current passing through the buzzer. electric buzzers are available in various sizes. The maximum voltage that a buzzer can withstand without damaging is written on the piezo buzzer. Buzzer do have polarity and it is written on the buzzer. To  produce sound from the Buzzer, it is directly connected to battery or power supply

BLUETOOTH TECHNOLOGY

Bluetooth is a wireless technology for communicating between different devices over short distance. I t provides an ad-hoc approach for enabling various devices to communicate with one another. It was named after the king KING HARALD BLUETOOTH a viking of 10th century who united Denmark and Norway. the main aim of Bluetooth is to share data between different short range devices securely.

TECHNICAL SPECIFICATIONS

It operates in 2.4 GHz ISM band (2400-2483.5). ISM stands for industrial, scientific and medical. the frequencies included in this band are available for free and we does not require any license to use these frequencies. it is based on frequency hopping spread spectrum technique and standard 802.15.1 was devised for Bluetooth. each Bluetooth radio channel has a MHz bandwidth and hops at a rate of  1600 hops per second. transmission is performed in 625 micro slots .the number of bits lost in 1000 Bit transmission is 1 that is one bit is lost when 1000 bits are transmitted. 999 bits are transmitted successfully. Technically this is called bit error rate of 10^-3.

LED'S

                                        BASICS OF LED'S

the new era has begun with the enormous research work. everyday new devices came in the market with amazing features. Now a days LED's are becoming more popular and popular and soon would replace old CFL lights and bulbs.LED's or light emitting diode are the semiconductor devices   which produces light when electric current is allowed to pass through them.The  salient characteristic of LED is its low power consumption with bright light, intensity , efficient , durable and long lasting.

MATERIAL USED IN CONSTRUCTION:-

different colour of  LED's are manufactured , RED and WHITE being mostly used.  the material used in LED's manufacturing being gallium arsenide and gallium arsenide phosphide. different materials are used to produce different colours. these days we have bi-colour or even tri-colour LED's are available which are used in sceneries for creating illusion of dynamic displays. different materials are responsible for producing different colours.

TECHNICAL FEATURES OF LED's

LED's are available in wide voltage range with wattage up-to 10 watts and in variety of sizes. a simple led requires 2-4 V DC supply and 20-80 milli amperes current to function properly. the intensity of led can be controlled by the amount of current passing through the led. the graph between the voltage and current is non linear. The voltage drop across led is 1.5V - 2V . By knowing these features you can design basic led circuits

what happens if voltage above the maximum rating is applied across the LED??

The LED would burn out causing foul smell emitting out of it. so the question arises 

HOW TO GLOW LED ON 9V BATTERY OR ON ANY RANDOM VOLTAGE?

the solution to this problem is the RESISTOR. It opposes the flow of current and drops out extra voltage across it.selecting a right value of resistor is very important. let us now discuss how to select the resistance.

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the value of resistor used to glow led is 370 ohms. how this value comes out... 

"OHMS LAW"

 we know that V=IR

then the value of resistance is given by

                                                           

                                          R={( 9 - 1.5)/20}*1000

       R=375 OHMS

choosing the closest value 370 OHMS

In this way you can design led circuits and extend it using series and parallel combinations. This was all for the basics

in the next post i will discuss some applications involved with led;

FROM WHERE TO BUY LED's
you can buy led's from various online stores like
LED DIODES AT LOW COST