Hobby Electronics

Blinking LED using PIC16F877A Microcontroller

2015-07-27T16:49:00.000+06:00

LED blink using microcontroller is the first step for microcontroller programmer. It is quite easy for the students if he/she know the C programming. In this section you need to know the embeded C language for microcontroller programmin and also need the simulation software to test the .hex code. the simulation software neme is proteous professional that i used. Several tutorials will be found on youtube if you need to teach the operation and settings.

This was my first microcontroller project which have four LED blinkin secquentially.

Tank Circuit and it's uses in Oscillator

2015-02-15T10:38:00.001+06:00

Tank circuit is basically made by an LC circuit. It is also called a resonant circuit, tuned circuit. It is an electric circuit consisting of a capacitor and inductor which is connected together. Tank circuit can store energy by oscillating at the circuit resonant frequency.

The frequency of the resonance tank circuit is given below where XL is the inductance -

Free Download Electronic Workbench 5.12 Full Version

2014-09-24T21:55:00.003+06:00

When you are electronic student, maybe you will not foreign again with Electronic Workbench software or called EWB software. We think that this software very popular in electronic student because many electronic university or collage using Electronic Workbench to create electronic circuit and then simulate it easily.

When you using Electronic Workbench software to help your electronic project, you can draw electronic circuit schematic project using many tools that provided by EWB. You can choose many component that provided to draw your electronic project.

When you want to draw the schematic circuit, you can firstly choose components that needed one by one. And then you can adjust your component according your electronic schematic. You can connected your components one by one according the circuit easily. and then you can continue to simulate your project.

When you want to know how your project will work, you can choose many tools like AFG, Frequency Generator, etc. You can connected many measurement tool to your electronic circuit that drawing and then you can simulate your project to know the working of your circuit schematic.And it is will help you before you implemented your project to real project.

Download Electronic Workbench (EWB) 5.12 Full Version (7 MB)

Memory Organization of PIC16F877A

2014-03-07T00:33:00.001+06:00

The memory organization of a PIC16F877A chip is divided into three sections. They are - Program Memory

Data Memory and
Data EEPROM

Program Memory is a data storage system. It is used to store program which is written by the
user. The program counter executes these stored commands one by one. PIC16F877A device
have 13 bit wide program counter and it is capable of addressing 8K×14 bit program memory
space. This memory is used to store the programs that are written primarily. This memory is
also called Flash Memory.

Data Memory contains a special register like Special Function Register (SFR) and General
Purpose Register (GPR). Data memory is called Random Access Memory (RAM). The stored
variable of program in data memory is deleted after turning off the microcontroller. These two
memories have separate data buses, which make the access to each one of them very easy.

Electrically Erasable Programmable Read-Only Memory is called EEPROM. It is user
modifiable read only memory (ROM) that can be erased and reprogrammed repeatedly through
the application of higher than normal electrical voltage. EEPROM has a limited life that is the
number of hundreds or thousands of times it can be reprogrammed. The life of the EEPROM
can be an important design consideration. A special form of EEPROM is flash memory which
uses normal PC voltages for erasing and reprogramming.

External Oscillator Modes for PIC Microcontrollers

2013-11-01T12:10:00.002+06:00

External oscillator (EC) is made outside of the microcontroller and connected to the pin OSC1 and OSC2 as figure 4.3. The external clock (EC) mode uses external oscillator as a clock source. The maximum frequency of this clock is limited to 20 MHz. Mainly crystal oscillator is used in this purpose.

In this mode the microcontroller starts operation immediately after the power is on. No time delay is required for frequency stabilization.

Figure: External Clock Oscillator Mode with Quartz Crystal

There are three modes as LP, XT and HS. Each modes are used on external oscillator as a clock source. The frequency is determined by quartz crystal or ceramic resonators which is connected to the OSC1 and OSC2 pins and depending on the features of the component in use. Any one mode is used on microcontroller circuits.

LP (Low Power) mode - is used for low-frequency quartz crystal only. This mode is designed to drive only 32.768 kHz crystals usually embedded in quartz watches. It is easy to recognize them by small size and specific cylindrical shape. The current consumption is the least of the three modes.

XT mode is used for intermediate-frequency quartz crystals up to 8 MHz. The current consumption is the medium of the three modes.

HS (High Speed) mode - is used for high-frequency quartz crystals 4MHz or greater. The current consumption is the highest of the three modes.

Line Follower Robot without Microcontroller

2013-08-24T16:25:00.001+06:00

Today I am introducing a new project named - Line Follower Robot. Need not any microcontroller knowledge to make this project.

This is simple circuit where used LM358 Op-amp and the operated voltage is 9volt to 12volt DC. The LM358 contains two op amps which are wired as comparators. Thus the voltage at the inverting terminal (-) is higher than non-inverting terminal (+) the output will be low and when the voltage at the non-inverting terminal (+) is higher than inverting terminal (-) its output will be high.

Outputs of the op-amp comparators are given to transistors which are wired as switch to drive the motors. Diodes D3 and D4 are provided to cancel the negative voltages produced due to the back emf of the motor.

When a sensor is on white color, LED light will be reflected to the corresponding LDR. As a result, resistances of LDR decreases and the voltage at non-inverting terminal (+) of the op-amp will increase. Thus op-amp output goes high and turns on the transistor, which rotates the motor. When a sensor is on black color, LED light will not be reflected to LDR, thus the output of the op-amp will be low and the motor will be off.

Thus when the both sensor are on white color, it will run both motors forward and when any of them on black color it will stop the corresponding motor. Thus the robot turns in corresponding direction since one motor is running.

The sensitivity of the LDR can be adjusted by using the 10K pot. For more accuracy, cover the sensor-LED pairs in a black wrapper through sides in such a way that only the reflected light falls on the LDR. The Line Follower can trace path drawn with black ink on a white chart and the width of the black track should be a litte less than the width between sensors.

Stepper Motor Rotation ( 172.5 degree angle ) without any Microcontroller

2013-06-15T17:11:00.003+06:00

Stepper motor is an electronics device and a brushless DC electric motor that divides a full rotation into a number of equal steps. It is widely used in robotics, industry, computer peripherals, motion control, business machines and many other purpose.

There are many techniques for rotating stepper motor. We need to rotate motor any angle that we want. We know that stepper motor is one kind of digital device or digital motor, for rotating this need sequential clock pulse to the specified coil of the motor. For rotating 360 degree angle need specific number of clock pulse which is depends on the number of coil and its mechanism.

Most of the people use microcontroller for rotating stepper motor any angle and speed. Using microcontroller, stepper motor’s speed control and any angle rotation is very easy, accurate and flexible work. For microcontroller must need to know assembly or embedded C language.

The students who are new or beginners, does not know these language is very difficult to make project related to stepper motor rotation. This topics will help them to solve the problem without having microcontroller knowledge. Because the topics is “stepper motor rotation any angle without microcontroller.”

Though it is quite hard, students will be benefited by this hobby project. This project is fully hardware implemented and design is complicated on the clock IC section. The following project description is given bellow –

Required instruments:

Timer IC- 555 timer – 1pcs
Flip-flop IC – 74109 - 1pcs
Clock IC – 7490 – 2pcs
AND gate IC – 7408 – 1pcs
Jonson Counter – 4017 – 1pcs
Motor driver IC – 293 -1pcs
Relay – 6 volt – 1pcs
Transistor – BC547 -1pcs
Resistors – 150k, 10k and 1k - 2pcs
Capacitors – 4.7 uF, 10nF
Diodes – 4148 – 1pcs
IC driver voltage – 5 Volt
Motor driver voltage – 9 Volt

Stepper Motor:

These stepper motor have 4 pin so have 2 coil. Pin-1 and Pin-3 have one coil. Pin-2 and Pin-4 have another coil. Motor have 48 steps so need 48 pulse for 360 degree rotation. So motor rotate 7.5 degree angle per step or per pulse. The stepper motor internal coil configuration is given bellow:

So the pulse sequence will be Pin-1, Pin-2, Pin-3 and Pin-4. The stepper motor is connected to motor driver IC 293.

Motor Driver IC:

For driving motor, need huge current. Jonson counter IC cannot deliver huge current to operate the stepper motor. For this reason motor driver ic is needed. IC293 is called motor driver ic which need 2 different voltage one is 5 volt and the other is motor driving voltage 9 Volt or 12 Volt. Pin-9 will be connected to 9 Volt or 12 Volt and Pin-16 will be connected to 5Volt. Pin-1 and Pin-9 will be short and connected to 5volt with 10k resistor. Pin-4, 5, 12, 13 is connected to ground. Pin- 3, 6, 11, 14 are output and Pin- 2, 7, 10, 15 are input which are connected with 2^nd Jonson counter IC 4017.

Clock Pulse Generator:

This is the 555 timer based clock pulse generator which is called astable(free running) multivibrator. The output frequency is 1Hz which is fed to the Jonson counter (both IC Pin- 14) and clock IC (first IC Pin-14).

2^nd Jonson counter (HC4017):

Jonson counter is a decade counter which have ten output pin and one input clock pulse pin. When clock pin-14 get pulse then the counter deliver pulse sequentially to the ten output pin. Here we need only 4 pin so the reset Pin-15 will be connected to Pin-10. So the four output pin of the counter are Pin-3, 2, 4, and 7 sequentially. Which will be connected directly with motor driver ic.

N.B: Jonson counter ic driving voltage must be 5volt.

1^st Jonson counter (HC4017):

Similar to 2^nd Jonson counter only the difference is 1^st Jonson counter’s output will be connected inversely to the 2^nd Jonson counter’s output. Clock Pin- 14 of both ic will be connected to the clock pulse generator IC 555 output Pin-3.

N.B: Pin-16 of both IC are voltage pin connected to the 6 Volt relay. 6Volt relay supply the voltage alternatively to the two Jonson counter IC.

Clock IC (SN74LS90N):

SN74LS90N is mainly counter IC used for making digital clock in laboratory work that’s why it is popular as clock ic. Two 7490 are using here to get 23 pulses for rotating 172.5 degree angle. AND Gate IC (7408) is also used here. This circuit diagram is given bellow:

N.B: If you need to know how it works please visit here. IC driving voltage must be +5volt if greater ic not work accurately.

Flip-flop (74109):

This is the flip-flop IC which is configured as a T flip-flop. T flip-flop output depends on the input (which is come from the 7409 ic). Pin-2 and 3 is connected to the output of the SN74LS90N IC. And the output pin-6 is connected to the transistor BC547.

When input is 1 the output is 1 and when input is 1 the output is 0. Again

When input is 1 the output is 1 and when input is 1 the output is 0.

If is most important that every 23^th pulse clock IC(SN74LS90N) give one pulse. So the output of the Flip-flop will be 1 and 0 alternatively on every 23^th pulse. Using this technique transistor will be ON and OFF according to Flip-flop output. And also active and de-active the relay alternatively.

Relay:

The main function of relay is to supply the positive voltage (+5volt) alternatively to the Jonson counters (Pin-16). When 1^st Jonson counter (HC4017) will get the voltage, the motor rotate 172.5 degree clockwise direction and when 2^st Jonson counter (HC4017) will get voltage, the motor rotate 172.5 degree anti-clockwise direction.

Any Angle:

By changing clock IC pulses we can change the angle of the motor rotation.

Capacitor Code Calculator

2013-04-10T01:24:00.002+06:00

Capacitor is a two terminal passive electrical component. It is used to store energy in an electrical field. Capacitor works as a voltage source. The capacitor is used widely and its forms contains at least two electrical conductor separated by a dielectric material, one common construction consists of metal foils separated by a thin layer of insulating film. In electrical circuit capacitors are widely used as a parts.

The static electric field develops across the Di-electric when the voltage or potential difference is applied across the terminals. This occurs when negative charge is on one plate and positive charge on the other plate. Mainly electrical energy is stored in the electrostatic field. An ideal capacitor is characterized by a single constant value capacitance and measured in farads. So we need to know the measurements of capacitor value using the figure. For more information go wikipedia.

Remote Control Regulated Ceiling Fan Circuit Diagram

2013-02-04T19:25:00.001+06:00

The main objectives are - to control the switch using remote as an on/off switch. To determine that the infrared sensor can easily receive the signal from the remote transmitter and to control the Fan speed using regulator.

The 38 kHz infrared rays generated by the remote control are received by IR receiver. Pin 2 of IR is connected to ground, pin 3 is connected to the power supply through R1 and the output is taken from pin 1. The output pulse is set to pin 2 of 555 timers.

Then in pin 2 if the voltage is less than one third of Vcc, a trigger pulse is active.The pulse signal is fed to clock pin 4 of counter IC 74109. Pin 8 of 74109 IC is grounded, pin 16 is connected to Vcc and pin 3 is grounded. The output of 74109 IC is taken from its pin 7. Q1 connected to pin 7 through R3 of IC 74109 drives the relay RL.

The relay is connected through a fan and a regulator. It gets connected to live terminal of AC mains via normally opened (N/O) contact when the relay energizes. If we want to operate a DC 12 volt relay then we have to use a regulated DC 12 volt power supply for DC 12 volt Relay and we have to remember that the circuit voltage not be exceeded more than DC 5 volts.

Fig: Layout of Remote control regulated Ceiling Fan

JK flipflop/IC 74109:

The 74109 are dual positive-edge triggered, JK flip-flops with individual J, K inputs, clock (CP) inputs, set (SD) and reset (RD) inputs; also complementary Q and Q outputs.The set and reset are asynchronous active LOW inputs and operate independently of the clock input. The J and K inputs control the state changes of the flip-flops as described in the mode select function table. The JK design allows operation as a T-type flip-flop by tying the J and K inputs together. In the T Flip-flop sequentially if the i/p is 1, the o/p is 1, then o/p is 0 and again 1.

IR Remote Control Home Appliance Circuit Diagram

2012-11-06T18:06:00.003+06:00

This is the most popular IR Remote control circuit for home appliances like lamp, fan, radio, tv etc to make the appliance turn on/off from a TV, VCD or DVD remote control. It is very simple to build because of few components and simple design.

The circuit can activated from up to 10 metres. The 38kHz infrared (IR) rays generated by the remote control are received by IR receiver module TSOP1738 of the circuit. Pin 1 of TSOP1738 is connected to ground, pin 2 is connected to the power supply through resistor R5 and the output is taken from pin 3. The output signal is amplified by transistor T1 (BC558).

The amplified signal is fed to clock pin 14 of decade counter IC CD4017 (IC1). Pin 8 of IC1 is grounded, pin 16 is connected to Vcc and pin 3 is connected to LED1 (red), which glows to indicate that the appliance is ‘off.’ The output of IC1 is taken from its pin 2. LED2 (green) connected to pin 2 is used to indicate the ‘on’ state of the appliance. Transistor T2 (BC548) connected to pin 2 of IC1 drives relay RL1. Diode IN 4148 acts as a freewheeling diode. The appliance to be controlled is connected between the pole of the relay and neutral terminal of mains. It gets connected to live terminal of AC mains via normally opened (N/O) contact when the relay energises. you can use any NPN transistor inplace of BC548. You can also use SL100 or any NPN transistor lying around you.

The delay depends on the C1 capacitor. Using higher value capacitor will create more delay and using less value capacitor will switch the circuit more than 2 times when you press a remote. Analyse the circuit by placing the 10uf capacitor in place of C1 (100uf).

Automatic Dark Activated LED Light Circuit Diagram using 555 Timer

2012-10-09T20:12:00.001+06:00

555 Timer Touch Activated Alarm Circuit Diagram

2012-07-15T03:54:00.004+06:00

This is the circuit diagram of touch activated alarm system which still activated on load shedding. Alarm system will be activated when someone touch the “touch plate” which is called trigger. In this circuit the most updated part is automatic battery activator which is made by a relay. So don’t upset on load shedding you alarm system is activated. This circuit could be used at your home door, locker, vehicle or metal gate etc.

Automatic Emergency Light Circuit Diagram

2012-05-15T12:08:00.001+06:00

This is the simple circuit of automatic emergency light. It is called dark dependent circuit. A 555 timer IC and LDR is used for this configuration. When light fall on the LDR, its resistance is decrease and in dark position its resistance is going high. Using these characteristics of LDR, automatic emergency light is made.

LDR is called Light Dependent Resistor. Its resistance is inversely proportional to the falling light on its surface. In dark, its resistance is approximately 7k to 10k. When light fall on its surface, its resistance is decrease to less than 1k. In the circuit, a voltage divider arrangement circuit is used here with LDR and 10K variable resistor.

When light fall on the surface of LDR, the resistance decrease to 1k. So the voltage of the timer pin-6 is greater than 2/3 of +V_cc. For this reason the output pin-3 goes low. The base voltage of transistor BC547 is less than 0.75 volt. The transistor is OFF state. So the light is OFF.

In dark position the LDR resistance increase is high so the voltage of the trigger pin-2 decrease to less than 1/3 of +V_cc. The output pin-3 goes high so the base voltage of the transistor BC547 is greater than 0.75 volt. The transistor is ON state. So the light is ON and it emits light.

Digital Object Counter using LDR and digital IC 7490

2012-05-04T09:58:00.000+06:00

This is the simple circuit on Hobby Electronics. In this circuit three modules are used in object counter. 555 timer are used as a monostable mode and astable mode. The other is counter module.

In this circuit 555 timer configured as a monostable mode, is a simple automatic dark sensor circuit that gives output when light falling is blocked on LDR. Pin 3 of monostable circuit has been connected to pin 4 of astable timer. When monostable circuit generates output, astable mode timer starts giving pulses to the counter module. Frequency for counter module is set up using R4, R3 and C2.

7490 acts as a decade counter and 7447 uses the output of 7490 to display numbers on seven segment display. This circuit counts from 0 to 9. You can count 0 to 100 modifying counter module circuit. Just adding few components as well as two counter ic, two display driver and two display. For count 0 to 100, comments on the comments box. You will get complete circuit.

The output will be: If you block light falling on LDR, the number on seven segment display will increase.

4017 LED Knight Rider Running Light Circuit Diagram

2012-04-29T10:36:00.002+06:00

In this 4017 Knight Rider circuit, the 555 timer is wired as an oscillator. It can be adjusted to give the desired speed for the display. The output of the 555 is directly connected to the input of a Johnson Counter (CD 4017).

The input of the counter is called the CLOCK line. The 10 outputs become active, one at a time, on the rising edge of the waveform from the 555. Each output can deliver about 20mA but a LED should not be connected to the output without a current-limiting resistor (220Ω in the circuit above).

The first 6 outputs of the chip are connected directly to the 6 LEDs and these “move” across the display. The next 4 outputs move the effect in the opposite direction and the cycle repeats. The animation above shows how the effect appears on the display. Using six LEDs, the display can be placed in the front of a model car to give a very realistic effect. The outputs can be taken to driver transistors to produce a larger version of the display.

Mobile Incoming Call Indicator Circuit Diagram

2012-04-20T14:48:00.000+06:00

This circuit can be used to escape from the nuisance of mobile phone rings when you are at home. This circuit will give a visual indication if placed near a mobile phone even if the ringer is deactivated.

When a call is coming to the mobile phone, the transmitter inside it becomes activated. The frequency of the transmitter is around 900MHz.The coil L1 picks up these oscillations by induction and feds it to the base of Q1. This makes the transistor Q1 activated.Since the Collector of Q1 is connected to the pin 2 of IC1 (NE555) , the IC1 is triggered to make the LED connected at its output pin (pin 3) to blink. The blinking of the LED is the indication of incoming call.

Notes:

The coil L1 can be made by making 150 turns of 36 SWG enameled copper wire on a 5mm dia plastic former.Or you can purchase a 10 uH coil from shop if available.
The circuit can be powered from a 6V battery.
Assemble the circuit on a good quality PCB.
C1 & C3 are to be polyester capacitors.
The electrolytic capacitor C2 must be rated 10V.

Automatic Street Light Controller Circuit Diagram

2012-03-25T21:44:00.004+06:00

This circuit is an automatic street light controller. Sensors used to detect changes in light is LDR (Light dependent resistor), the working principle of Light dependent resistor is exposed to light when the resistance value of LDR great, but if not exposed to light or dark then the resistance value of LDR.

LDR is a special type of resistance whose value depends on the brightness of the light which is falling on it. It has resistance of about 1 mega ohm when in total darkness, but a resistance of only about 5k ohms when brightness illuminated. It responds to a large part of light spectrum.

When light falls on the LDR then its resistance decreases which results in increase of the voltage at pin 2 of the IC 555. IC 555 has got comparator inbuilt, which compares between the input voltage from pin2 and 1/3rd of the power supply voltage. When input falls below 1/3rd then output is set high otherwise it is set low. Since in brightness, input voltage rises so we obtain no positive voltage at output of pin 3 to drive relay.

Complete Room Securty System Circuit diagram

2012-03-14T17:47:00.015+06:00

This simple circuit is called room security system circuit. The main purpose of this circuit is to secure your room in night. You need not any security guard. When any unwanted person wants to enter your room in night then this circuit raised alarm. On the other benefit, it is always activated on load shedding.

There are five separates parts in this circuit – regulated power supply, relay driver, door switching, alarm system and audio amplifier. First section is regulated power supply. The output of IC 7809 is regulated +9Volt which is converted from 9Volt unregulated power supply. Capacitors are used for removing ripple. A full wave 9 volt transformer is connected in the input of this power section.

The second part is relay driver. Q1 transistor is used for driving relay. When the Q1 transistor is forward bias then the relay is ON and the total circuit gets positive voltage from ac source. In the time of load shedding relay is deactivated and the total circuit gets power from 6Volt Battery.

The third part is door switching. When C1 capacitor’s two terminals are short, transistor Q2 is reversed biased. So Q2 transistor is OFF. When C1 capacitor’s two terminals are open, transistor Q2 is forward biased. So Q2 transistor is ON. For this reason IC UM66 is ON and it generates music which is feed another two transistors Q3 and Q4. A speaker is connected with collector of the transistor Q4 as circuit diagram.

Freeze Protector Circuit

2012-01-24T22:53:00.006+06:00

This is the simple freeze protector circuit diagram. It is also called timing circuit. It is just hobby project for beginners. When you need to operate automatically any device in the fixed time later after coming AC power supply, you can use this circuit.

The voltage amplitude is high when AC power come. Suddenly high voltage destroys the electronics device. For this reason, in the time of load shedding we need to switched off electronics device (Audio/Video player, CD/DVD Player, TV, Freeze or any electronics device). This circuit solve this problem.

Hobby Electronics helps the beginners to know the timing circuit specially using 555 IC timer. NE555 IC is the very simple well known parts. Its configuration is very simple. You can use this timer any simple circuit.

In this circuit use 12volt power supplies. 300k variable resistor is used for timing control. Timing resistor and capacitor are 300k and 1000uF. Only change the value of the variable resistor for your required timing.

The circuit output pin 3 is connected with resistor (10k) and output 12 volt relay. Relay is connected as figured with the device. Making cost is too low. Anyone can make this circuit easily.

Dual Voltage Power Supply 12 Volt

2012-01-19T01:06:00.009+06:00

This is the simple circuit diagram of Dual Voltage Power Supply. It is used for Misc… application. This circuit is called regulated power supply. For this reason the main component of this circuit is Regulator IC. It also needs few components to built. The regulator 7812 is the positive voltage regulator and 7912 is the negative voltage regulator.

You can also use 7809 for 9 volt positive power supply and 7909 for negative voltage power supply.

It regulates voltage from 24Volt to 12 Volt (DC). The transformer input is 110Volt to 220Volt (AC) and the output must be between 12Volt to 24Volt (AC) and current must be 500mA. In this circuit some capacitors are used as a filter for removing repole.

Simple AM Transmitter Circuit

2011-10-31T07:21:00.011+06:00

AM transmitter circuit that can transmit your audios to your backyard.This circuit is designed with limited the power output to match the FCC regulations and still produces enough amplitude modulation of voice in the medium wave band to satisfy your personal needs. You will love this.

The circuit has two parts , an audio amplifier and a radio frequency oscillator. The oscillator is built around Q1 (BC109) and related components. The tank circuit with inductance L1 and capacitance VC1 is tunable in the range of 500kHz to 1600KHz.

These components can be easily obtained from your old medium wave radio. Q1 is provided with regenerative feedback by connecting the base and collector of Q1 to opposite ends of the tank circuit. C2 ,the 1nF capacitance , couples signals from the base to the top of L1, and C4 the 100pF capacitance ensures that the oscillation is transfered from collector, to the emitter, and through the internal base emitter resistance of the transistor Q2 (BC 109) , back to the base again.

The resistor R7 has a vital part in this circuit. It ensures that the oscillation will not be shunted to ground trough the very low value internal emitter resistance, re of Q1(BC 109), and also increases the input impedance such that the modulation signal will not be shunted to ground.

Q2 is wired as a common emitter RF amplifier, C5 decouples the emitter resistance and unleashes full gain of this stage. The microphone can be electret condenser microphone and the amount of AM modulation can be adjusted by the 4.7 K variable resistanceR5.

AM Receiver Circuit Diagram Using ZN414 IC

2011-10-08T16:17:00.009+06:00

A.M. Antenna coil and MW gang connected in parallel. One common point of this parallel circuit connected to the IC ZN414 pin number 2.

Another common point of that parallel circuit connected with two resistors (100kΩ, 1kΩ) in series. A capacitor is connected with the common point of resistors (100kΩ, 1kΩ). A capacitor is connected in series with base of the transistor and the pin number 1 of the ZN414.

One end of the 10kΩ resistor is connected with the collector point of the transistor BC549 and another end is connected with the power supply +Vcc.

And one end of the 100kΩ resistor is connected with the collector and another end connected with base. 105pF capacitor is connected between collector and ground. Pin 3 of IC ZN414 and emitter of the transistor is connected to the ground.

Required Instrument

IC ZN 414.
Capacitor(105pF×1,104pF×2,103pF×1)
MW Gang
Resistor(100kΩ×2,10kΩ×1,1kΩ×1,470Ω×1)
AM antenna
Transistor(BC549)

AM Transmitter Circuit Diagram Using 741 Op-amp

2011-09-24T12:13:00.007+06:00

AM transmitter is a circuit which can transmit message signal to modulated signal. This circuit is designed with limited power and the required power supply of the transmitter circuit is 9 Volt.

The circuit has three parts that is an audio amplifier, radio frequency oscillator and modulator circuit. The frequency oscillator is built with 741 Op-amp and related components. The carrier signal frequency and its amplitude can be varied using variable resistor accordance with V_R1 and V_R2respectively. C₁ and C₂ are the main components to generate the carrier frequency.

Another part of the circuit is an audio amplifier circuit. The audio amplifier is built with 741 Op-amp and related components. A microphone is used to convert the voice signal to the audio signal which is feed to the op-amp’s inverting terminal. This audio signal is amplified by the op-amp. The amplified audio signal is filtered using the capacitor C₇. This output is feed to the modulator circuit.

The main part of the AM transmitter is modulator circuit which is built with the transistor BC109. The carrier signal is feed to the base of transistor and the message / audio signal is also feed to the emitter of the transistor.

Here the required modulated signal is taken from the collector of the transistor which is feed to the output antenna.

Luggage Protector Circuit Using 555 Timer IC

2011-08-30T23:13:00.007+06:00

The circuit is called protector alarm circuit to protect from the theft of your luggage or bags. This circuit is built electronically using 555 timer IC. The alarm will rise highly when the thin wire is cut off by the thief. The circuit configuration using 555 timer IC acts as a astable multivibrator which produce signal tone of frequency of about 1 KHz and produce sound like a shrill noise away the output speaker.

If you need to know 555 Timer configuration click here and download

IC’s 5number pin is directly connected to the power supply. 10k, 68k resistor and 0.01uf capacitor are connected to generate specific range of frequency like as 1KHz. You can change output frequency by changing the value of resistor and capacitor. Pin 1 is directly connected to the ground. Output is taken from pin 3. A 8Ohms speaker is connected to the output for alarm sound. Thin wire is connected as shown in figure.

The wire would be very thin copper like 36 SWG or higher. You can use one gage of normal wire. The driving voltage of the circuit is 5 Volt to 12 Volt.

Transistor AM Modulator Circuit Diagram

2011-08-29T22:16:00.004+06:00

Modulation is the process of changing some characteristics (e.g. amplitude, frequency or phase) of a carrier wave in accordance with the intensity of the signal is known as modulation.

The figure shows the electronics circuit of a simple am modulator. It is essentially a CE amplifier having a voltage gain of A. The carrier signal is the input to the amplifier. The modulating signal is applied in the emitter resistance circuit.

The carrier e_c is applied at the input of the amplifier and the modulating signal e_s is applied in the emitter resistance circuit. The amplifier circuit amplifies the carrier by a factor A, so that the output is A_es. Since the modulating signal is a part of the biasing circuit, it products low frequency variations in the emitter circuit. This in turn causes variations in “A”.

The result is that amplitude of the carrier varies in accordance with the strength of the signal. Consequently, amplitude modulated output is obtained across R_L. It may be noted that carrier should not influence the voltage gain A; only the modulating signal should do this. To achieve this objective, carries should have a small magnitude and signal should have a large magnitude.