Here is a simple IR sensor-based security system which will detect any movement and triger an alarm. This circuit is ideal for use in houses, banks, stores, and other restricted areas where a movement-based alert alarm is required. This circuit is based on an IR sensor in which an IR beam is continuously falling on a photodiode, and an alarm is activated anytime this Infrared beam is broken by any form of movement.

The circuit schematic is shown below.

This security burgler alarm circuit is simple to build and only requires a few components, which are mentioned below.

IR LED

An IR LED (infrared light-emitting diode) is a special-purpose LED that emits infrared rays with wavelengths ranging from 700 nm to 1 mm. So it is invisible to human eyes. IR LEDs are more commonly used in security systems and remote control devices.

Photodiode

A photodiode is a semiconductor device with a P-N junction that converts light into an electrical current. The resistance and output voltage of the photodiode alter in response to the amount of infrared light received.

LM358

The LM358 is an operational amplifier (Op-Amp), and it is used as a voltage comparator in this design. The LM358 contains two independent voltage comparators. We have used only one comparator, with inputs at PINs 2 and 3 and outputs at PIN 1. The voltage comparator has two inputs: one inverting and the other non-inverting (PIN 2 and 3). The output of the comparator (PIN 1) is High when the voltage at the non-inverting input (+) is greater than the voltage at the inverting input (-). If the inverting input (-) has a higher voltage than the non-inverting end (+), the output is LOW.

NE555

The 555 Timer is is configured as a monostable mode in this example. When a falling edge is detected on pin 2(trigger pin), the output voltage rises high for a predetermined duration.

Working of an IR Sensor

An IR LED serves as the emitter, while an IR photodiode serves as the detector. An IR LED emits infrared light, which is detected by the IR photodiode. The resistance and output voltage of the photodiode alter in response to the amount of infrared light received. In this circuit we will detect when there is no light falling on the photodiode and trigger an alarm.

How does the IR based burgler alarm circuit work?

As per the circuit diagram given above, a variable resistor is connected to inverting end of LM358(Pin 2) to adjust the sensitivity of the sensor. A junction of the photodiode and a resistor is connected to the non-inverting end of LM358(Pin 3). LM358 op-amp voltage comparator’s output (PIN1) is connected to the 555 timer’s Trigger pin. The 555 Timer is set to monostable mode in this example.

When the circuit is switched ON and when there is IR radiation towards the photodiode, the voltage across it drops, while the voltage across the series resistor R2 increases. Non-inverting end (pin 3) gets high voltage when compared to inverting end (pin2). Hence the output of the comparator is HIGH, because the comparator output is connected to the 555 timer’s trigger pin, the 555 output is low when Trigger pin 2 is high. As a result, the 555 timer output remains LOW when the IR rays fall on the Photodiode. Read this article to learn how the IR sensor works with the LM358 comparator.

Now when the IR radiation towards the photodiode breaks due to some movement, the voltage across it increases, while the voltage across the series resistor R2 decreases. Non-inverting end (+) gets low voltage when compared to inverting end (-). Hence the output of the comparator is LOW, because the comparator output is connected to the 555 timer’s trigger pin, the 555 output is HIGH when Trigger pin 2 is low. As a result, the 555 timer output becomes HIGH and the he buzzer beeps for a short time. By altering the value of resistor R1 or capacitor C1, the duration of the beep can be lengthened.

Inverting end of LM358 is connected to the 10k pot. Make the necessary adjustments to ensure that voltage comparison works properly.

So, give it a shot and let me know if you have any questions in the comments section below. I’ll be happy to assist you!

The post IR Based Security Alarm Circuit first appeared on Student Projects.

Here is the circuit diagram.

This car parking sensor circuit is simple to build and only requires a few components, which are mentioned below.

IR LED

An IR LED (infrared light-emitting diode) is a special-purpose LED that emits infrared rays with wavelengths ranging from 700 nm to 1 mm. So it is invisible to human eyes. IR LEDs are more commonly used in security systems and remote control devices.

Photodiode

A photodiode is a semiconductor device with a P-N junction that converts light into an electrical current. The resistance and output voltage of the photodiode alter in response to the amount of infrared light received.

LM358

The LM358 is an operational amplifier (Op-Amp), and it is used as a voltage comparator in this design. The LM358 contains two independent voltage comparators. We have used only one comparator, with inputs at PINs 2 and 3 and outputs at PIN 1. The voltage comparator has two inputs: one inverting and the other non-inverting (PIN 2 and 3). The output of the comparator (PIN 1) is High when the voltage at the non-inverting input (+) is greater than the voltage at the inverting input (-). If the inverting input (-) has a higher voltage than the non-inverting end (+), the output is LOW.

Working of an IR Sensor

An IR LED serves as the emitter, while an IR photodiode serves as the detector. An IR LED emits infrared light, which is detected by the IR photodiode. The resistance and output voltage of the photodiode alter in response to the amount of infrared light received. The IR sensor’s basic functioning concept is shown below.

How does the Reverse Car Parking Sensor circuit work?

As per the circuit diagram given above, a variable resistor is connected to inverting end of LM358(Pin 2) to adjust the sensitivity of the sensor. A junction of the photodiode and a resistor is connected to the non-inverting end of LM358(Pin 3).

When the circuit is switched ON and when there is no object near the IR LED and photodiode, then there will be no IR radiation towards the photodiode. Hence the voltage across series resistor R2 decreases. Non-inverting end (pin 3) gets less voltage when compared to inverting end (pin2). Hence the output becomes LOW and the LED turns OFF.

Now when there is an object near the IR LED and photodiode, the photodiode absorbs the IR generated by the IR LED after it is reflected by the object. When reflected IR hits the photodiode, the voltage across it drops, while the voltage across the series resistor R2 increases. Non-inverting end (pin 3) gets high voltage when compared to inverting end (pin2). Hence the output becomes HIGH and the LED turns ON.

Inverting end of LM358 is connected to the 10k pot. Make the necessary adjustments to ensure that voltage comparison works properly.

So, give it a shot and let me know if you have any questions in the comments section below. I’ll be happy to assist you!

The post Reverse Car Parking Sensor Circuit first appeared on Student Projects.

You must use a relay if you want to connect any heavy load. The Relay connection with the Dark Activated automated Light switch is shown in the circuit diagram below.

Circuit diagram

Components required

100k Ohm Potentiometer is a variable resistor that is used to change the trigger point for the LED. That is, how much light is needed for the LED to turn ON and OFF. You can also use a 50k Resister in the place of a variable resistor.

BC547 is an NPN transistor that is used to amplify the current. When there is a small current at its base, it controls the large current at its collector and emitter end.

1N4007 is a PN junction rectifier diode. This allows only the flow of electrical current in one direction only. So, it can be used for the conversion of AC power to DC.

A relay is an electrically operated switch.

How does it work?

During the daytime when there is a light, the LDR has very low resistance and all voltage coming through R1 dropped with the ground. This makes the voltage at the base of the transistor very low and it will not switch ON the transistor. Because the transistor is OFF, the current will not flow through the transistor. As a result, the relay will not be switched ON and the bulb remains OFF.

At night when there is no light, the LDR has high resistance and very less power dropped with the ground. This makes the voltage at the base of the transistor high to turn the transistor ON. Because the transistor is turned ON, current flows through the transistor. It flows from the positive battery terminal, through R2, the relay, and the transistor down to the negative battery terminal. As a result, the relay turns ON and hence the bulb turns ON.

The same circuit can be used for a variety of purposes.

So, give it a shot and let me know if you have any questions in the comments section below. I’ll be happy to assist you!

The post Automatic Street Light Control System using LDR first appeared on Student Projects.

Circuit diagram

Components required

100k Ohm Potentiometer is a variable resistor that is used to change the trigger point for the LED. That is, how much light is needed for the LED to turn ON and OFF. You can also use a 50k Resister in the place of a variable resistor.

BC547 is an NPN transistor that is used to amplify the current. When there is a small current at its base, it controls the large current at its collector and emitter end.

How does it work?

During the daytime when there is a light, the LDR has very low resistance and all voltage coming through R1 dropped with the ground. This makes the voltage at the base of the transistor very low and it will not switch ON the transistor. Because the transistor is OFF, the current will not flow through the transistor. As a result, LED will not turn ON.

At night when there is no light, the LDR has high resistance and very less power dropped with the ground. This makes the voltage at the base of the transistor high to turn the transistor ON. Because the transistor is turned ON, current flows through the transistor. It flows from the positive battery terminal, through R2, the LED, and the transistor down to the negative battery terminal. As a result, the LED turns ON.

The same circuit can be used for a variety of purposes. Check out the Automatic Street Light Control System using LDR application. Instead of LED, bulbs are used using a relay.

So, give it a shot and let me know if you have any questions in the comments section below. I’ll be happy to assist you!

The post Automatic night light using LDR first appeared on Student Projects.

Laser Communication System works on the principle of “Amplitude Modulation” process. In this the amplitude of the carrier is varied according to the instantaneous amplitude of the modulating signal (Input Signal ).

Here,
“Carrier Signal refers to Laser  Beam”
“Amplitude refers to Intensity of Laser Beam”
“Input Signal refers to audio signal”

Hence, The intensity of the laser beam is varied according to the instantaneous value of audio signal and the same is sensed by the optical sensor at the receiver.
This simple Laser Communication System consists of two sections Transmitter and Receiver. At the Transmitter any audio device can be coupled to the laser light by using a transistor operating in common collector mode. Since, In common collector mode transistor acts as Impedence matching device. Due to this intensity of the laser beam changes proportional to audio signal strength.

At the receiver this varying intensity can be sensed by any optical sensors like Light Dependent Resistor (LDR) or photo transistor or Solar cell. The photo transistor is biased and connected to the input of audio amplifier (LM386) which drives the loud speaker.

INTRODUCTION:

Lasers have been considered for space communications since their realization in 1960. Specific advancements were needed in component performance and system engineering particularly for space qualified hardware. Advances in system architecture, data formatting and component technology over the past three decades have made laser communications in space not only viable but also an attractive approach into inter satellite link applications.

Information transfer is driving the requirements to higher data rates, laser cross -link technology explosions, global development activity, increased hardware, and design maturity. Most important in space laser communications has been the development of a reliable, high power, single mode laser diode as a directly modulable laser source. This technology advance offers the space laser communication system designer the flexibility to design very lightweight, high bandwidth, low-cost communication payloads for satellites whose launch costs are a very strong function of launch weigh. This feature substantially reduces blockage of fields of view of most desirable areas on satellites. The smaller antennas with diameter typically less than 30 centimeters create less momentum disturbance to any sensitive satellite sensors. Fewer on board consumables are required over the long lifetime because there are fewer disturbances to the satellite compared with heavier and larger RF systems.

CIRCUIT DIAGRAM

(a)    TRANSMITTER

(b)    RECEIVER

BLOCK DIAGRAM

PCB LAYOUT OF RECEIVER

PCB LAYOUT OF TRANSMITTER

The post Laser Communication System first appeared on Student Projects.

Here for the purpose, we have made four distinct stages for the effective implementation .The stages are described in brief as follows. In the first stage, we are constructing the transmitter circuit that transmits data and sequence bits at infrared frequency. Now the second part is to develop receiver circuit that receives infrared signals coming out from transmitter and convert them into bits. The next stage is to compare the incoming sequence with that of receiver computer. If sequence is matched only then it will be able to catch the data sent by transmitting computer. The fourth and final stage is the make software program that gets the data and displays on computer.

INTRODUCTION

Wireless data transmission between computers is a flexible data communication system implemented as an extension to, or as an alternative for, a wired LAN within a building. It can further be extended to wireless LAN with secure data transmission. For the purpose of secure data transmission a unique code is sent before actual data bits. This unique code is known to receiver. In this project sequence detector at receiver side has been used which is set for a particular code. This sequence detector detects binary bit stream coming out from transmitter and if code of incoming bit stream is matched with the code of sequence detector than rest of bits are received in form of data at the receiving computer’s side. To further enhance the concept of security we are using Infrared waves as a channel between transmitter and receiver because security of infrared systems against eavesdropping is better than that of radio systems. The block diagram of whole system is shown below.

Block Diagram

WIRELESS LAN

Wireless LANs use electromagnetic airwaves (radio or infrared) to communicate information from one point to another without relying on any physical connection. Radio waves are often referred to as radio carriers because they simply perform the function of delivering energy to a remote receiver. The data being transmitted is superimposed on the radio carrier so that it can be accurately extracted at the receiving end. This is generally referred to as modulation of the carrier by the information being transmitted. Once data is superimposed (modulated) onto the radio carrier, the radio signal occupies more than a single frequency, since the frequency or bit rate of the modulating information adds to the carrier.

Multiple radio carriers can exist in the same space at the same time without interfering with each other if the radio waves are transmitted on different radio frequencies. To extract data, a radio receiver tunes in one radio frequency while rejecting all other frequencies.

In a typical wireless LAN configuration, a transmitter/receiver (transceiver) device, called an access point, connects to the wired network from a fixed location using standard cabling. At a minimum, the access point receives, buffers, and transmits data between the wireless LAN and the wired network infrastructure. A single access point can support a small group of users and can function within a range of less than one hundred to several hundred feet. The access point (or the antenna attached to the access point) is usually mounted high but may be mounted essentially anywhere that is practical as long as the desired radio coverage is obtained.

End users access the wireless LAN through wireless-LAN adapters, which are implemented as PC cards in notebook or palmtop computers, as cards in desktop computers, or integrated within hand-held computers. Wireless LAN adapters provide an interface between the client network operating system (NOS) and the airwaves via an antenna. The nature of the wireless connection is transparent to the NOS.

The post Wireless Data Transmission between Computers using Sequence Detector first appeared on Student Projects.

There are three Electronic Modules to be explained. First one is the HORIZONTAL SENSOR MODULE. It employs the timer 555 in the MONOSTABLE MODE. PIN 2(Trigger Pin of 555) is hooked up with a VOLTAGE DIVIDER NETWORK(PLEASE see FIGURE 2). PIN 4(Reset) is hooked up with ANOTHER VOLTAGE DIVIDER NETWORK.

The LDR(SAY LDR A) which is always illuminated by light through FRESNEL LENS ARRAY, has Low Resistance(in presence of light resistance of LDR decreases and vice-versa). We know V(OUT)=V(IN)*[R(bottom)]/[R(bottom)+R(top)], where R stands For Resitance. So in SUNLIGHT, when LDR A’s resistance Decreases, VOLTAGE AT PIN 4 Increases. TIMER is no more RESET. PIN 2 is now lower than 1/3 rd Vcc(as the horizontal LDR 1, say LDR B does not initially receive light through its rectangular slit, so its resistance is high(Rtop=8 K ohms), consequently V(OUT) is low). This triggers the timer which gives a pulse to Decade Counter’s Clock(14) PIN and triggers it. The Decade Counter CD 4017 gives a NORMAL STEP DRIVE pulse to the Horizontal Unipolar Stepper Motor 1(coupled to the tracker unit) to rotate the tracker position so as to receive sunlight(STEP ANGLE of 2 DEGREES). This goes on till the horizontal LDR 1 is fully in SUNLIGHT(resistance low, so PIN 2’S VOLTAGE HIGH). Thus the tracker has followed the SUN Horizontally.

We will come to the Vertical Sensor Module, but first let us see what the DAWN LDR(SAY LDR C) does. At night the horizontal Module timer 555 remains Reset(as LDR A is in darkness so its resistance is high, thus pin 4 voltage is low, and the TRACKER points at WEST(where SUN has set). Next day when SUN rises again in the EAST, the DAWN LDR which is located at the back of the TRACKER, points at EAST. So when it receives sunlight its Resistance goes low, thus Voltage at pin 4 is high and the timer triggers the Decade Counter which in turn switches the Motor on, thus the TRACKER again moves towards the EAST. Then the TRACKER functions as previously.

Now placed with the Horizontal Sensor LDR 1 is another similar LDR 2 which receives the sunlight as and when does LDR 1. SEE FIGURE 3. So now, as LDR B(THE 1st horizontal one) receives sunlight, so does Horizontal LDR 2(SEE FIGURE 1, THESE 2 LDRs are placed together with same alignment properties and separated by an optically insulated coating(from each other).Thus when Motor 1 comes to rest, and as the second horizontal LDR (SAY LDR D),is same way coupled to the second timer’s(of Vertical Module) Reset pin as was the ALWAYS ILLUMINATED LDR A, it brings the second timer out of its Reset mode) by the previously discussed VOLTAGE RELATIONSHIP). EYE SENSOR LDR(SAY LDR E) of the tracker receives sunlight by an Anti-Reflection Coated, small Rectangular Slit, so reacts only when SUN directly points at it. The second 555’s PIN 2 is same way connected to this LDR as was the first 555’s to Horizontal LDR 1. So now that it still not receives sunlight (resistance high, so Vout low) and pin 4 is no more Reset, the second CD 4017 MAKES THE SECOND STEPPER MOTOR 2 Rotate(Coupled so as to only rotate VERTICAL SENSING BLOCK/EYE BLOCK ). This movement continues till the SUN directly points at the EYE of our TRACKER. Then the TRACKER STOPS, pointing very accurately at the SUN.FIG 2 and FIG 3 follows.

In figure 4 I have only shown the Horizontal Motor Control Circuit. The Vertical One uses a similar Decade Counter, NPN Transistors, Diodes(to encounter BACK EMF of Power Transistors due to Fast Switching). I chose for a Step Angle of 2 Degrees for the Unipolar Steppers. They are driven in a Normal 4 Step Sequence, first coil A is energised simultaneously with coil B ,then coil C with coil D. Thus the Motors rotate by 2 degrees each time. The Charging Interval(how long pin 3 of 555’s remains high) is almost in synchronism with the steps/second speed of the motors(here 600 steps/sec.), to avoid FALSE TRIGGERING.

NOTE:

1. For 555 in MONOSTABLE MODE, T=1.1*R*C.
2. For the FRESNEL LENS ARRAY , the standard FL 40(Focal Length=0.4 inches) Or FL 65(Focal Length=0.65 inches) FRESNEL LENSES could be used (with the Grooves facing the LDRs).
3. For the ANTI-REFLECTION COATING, MULTI-LAYER COATING could be used to minimize loss due to REFLECTION. By using alternating layers of a Low-Index material like SILICA and a Higher-Index material, it is possible to obtain Reflectivities as low as 0.1% at Single Wavelength.

CONCLUSION:

We Conclude with the ADVANTAGES of the TRACKER MODULE SYSTEM:

1. Uses SIMPLE, INEXPENSIVE ,EASY TO GET 555 timers and LDRs.
2. The whole System draws only 25 MicroAmperes of Current when the Motors are not rotating.(555 timer’s off-state current req. is very less).BATTERY POWER IS SAVED.
3. The TRACKER not only follows SUN from EAST to WEST and back to EAST in a cyclic manner(Horizontal Motor Module),but also tracks the Angular Movement of the SUN with respect to its ZENITH ANGLE to the Horizon(Vertical Motor Module and EYE).This is a VERSATILE quality for which the TRACKER could easily be used in conjunction with Solar Panels to derive maximum Solar Energy. Fast Motor Response(600 steps/sec.),no FALSE TRIGGERING, a Very ACCURATE System, it requires no Programming Devices(MICROPROCESSORS or MICROCONTROLLERS), so is NOT COMPLICATED.

The post Automatic solar tracking system first appeared on Student Projects.

In a cascade, or multistage, amplifier, the output of the first amplifying device (transistor) is fed as input to the second amplifying device, whose output is fed as input to the third, and so on until an adequate signal amplification has been achieved. In a device such as a radio receiver, several amplifiers boost a weak input signal until it is powerful enough to drive a speaker. Usually, multistage amplifiers are not made of discrete components, but are built as integrated circuits . Another less common group of electronic amplifiers use magnetic devices as their principal components. There are also many kinds of mechanical amplifiers, e.g., the power steering This audio amplifier project is a class AB audio power amplifier using a TDA2003 module power amplifier. It is easy to construct and has only a few external components. The module is designed with short circuit and thermal protection. It can drive loads as low as 1.6 ohm and is capable of delivering over 10 watts from a 16 V DC power supply.

The power supply required for is 8 – 18V DC at 1 Amp or more. Maximum output power will only be obtained with a power supply of greater than 1A at 16V DC, and using 2 ohm speakers (or 2 by 4 ohm speakers in parallel). However approximately 4W RMS can be obtained with a 12V DC, 1A supply into a 4 ohm load. The power supply should be well filtered to reduce mains hum, the on board capacitors alone are not adequate for this purpose but are necessary to ensure stability. Extra filtering is unnecessary if operating from a battery. If two boards are used for stereo, you will need to double the size of the power supply.

Circuit Diagram

Step Taken While Preparing Circuit:

The main purpose of printed circuit is in the routing of electric currents and signals through thin copper layer that is bounded firmly to and insulating base material some times called the substrata. This base is manufactured with an integral bounded layer of thin copper foil which has to be partly etched or other wise removed to arrive at a pre-designed pattern to suite the circuit connections.

From the constructors point of view the main attraction of using PCB is its role as the mechanical support for small components. There is less need for complicated and time consuming metal work or chassis construction except perhaps in providing the [mal enclosure. Most straight forward circuit designs can be easily converted into printed wiring layout the thorough required to carry out the conversion can often highlights any possible error that would otherwise be missed in convention point to point wiring. The finished project is usually neater and truly a work of art. Through proper design of PCB can get noise immunity. The fabrication process of the printed circuit board will determine to a large extent the price and reliability of the equipment. A common target aimed at is the fabrication of small series of highly reliable professional quality PCBs with low investment cost.

There are two types of PCB:-

1. Single sided board
2. Double sided board

Single sided board: The single sided PCBs are mostly used in endearment electronics where manufacturing costs have to be kept at a minimum however in industrial electronics. Also cast factors cannot be neglected and single sided boards should be used whenever a particular circuit can be accommodated on such boards.

Double sided boards: Double sided PCBs can be made with or without plated through holes. The production of boards with plated-through holes is fairly expensive. Therefore, plated through hole boards are only chosen where the circuit complexity and density dose not leave any other choice.

Layout Design:

The layout of a PCB has to incorporate all the information on the board before one can go on to the artwork preparation. This means that a concept, which clearly defines all the details of the circuit, is a prerequisite before the actual layout can start. The detailed circuit diagram is varying important for the layout designer but the must also be familiar with the design concept and with the philosophy behind the equipment. When designing the layout one should observe the minimum size (component body length and weight). Before starting to design the layout have all the required components to hand so that an accurate assessment of space can be made care must be taken so as to allow for adequate air flow after the components have been mounted. It might be necessary to turn some components round to a different angular position so that terminals are closer to the connections of other components. The scale can be checked by positioning the components on the squad paper. If any connection crosses, then one can reroute to avoid such condition. All common or earth lines should ideally be connected to a common line routed around the perimeter of the layout this will act as the ground plane. If possibly try to route the outer supply line ground plane. If possibly try to route the other supply lines around the apposite edge of the layout or through the center. The first step is to rearrange the circuit to eliminate the crossover without altering the circuit detail in any way.

Plan the layout as if looking at the top side of the board first this should be translated in reverse later for the etching pattern. Larger areas are recommended to maintain good copper adhesive. It is important to bear in mind always that copper track width must be at least to the recommended minimum dimensions and allowance must be made for increased width where termination holes are needed from this aspect it can become little tricky to negotiate the route for connections to small transistors. One can effect the copper interconnection pattern in the under side of the board in a way described below Make the interconnections pattern looking like conventional point to point writing by routing uniform width of copper from component to component.

The post 10W Audio Amplifiers first appeared on Student Projects.

Finally I spent only USD $ 6-7  to build the robot.

There is no MicroController so we do not need to programm. I just used comparator IC using LM339, two H-bridge sensor using eight transistors FCS9013, and four transistors, FSC 9012. For the sensor you can use LED and LDR as the light receiver. I changed the LDR sensor to IR sensor.

I built this robot using only the analog comparator and IR sensor, no microcontroller. This is smart idea and very cheap approach.

You can download Click this Download PCB FILE (ExpressPCB file)

Components:

R1, R7, R13, R14, R15, R16 – 330 1/4W +/-1%
R2, R3, R4, R5, R6, R8, R9, R10, R11, R12 – 10K 1/4W +/-1%
R17, R18, R19, R20 – 150 1/4W +/-1%
VR1, VR2 – 20K-50K
Led1, Led3 – LED(red) 3mm Led
Led2, Led4 – LED(green) 3mm Led
Optocoupler – 2 piece

Q1, Q2, Q3, Q4, Q5, Q8, Q9, Q12 – FSC 9013
Q6, Q7, Q10, Q11 – FCS 9012

U1 – LM 339
Battery 9 volt – 1 piece
Motor DVD dc 5Volt – 2 pieces
Tank toys for mechanic and wheel – 2 pieces

There are two line styles, white line on the black floor and black line on the white floor.

If you use black line on the white floor,  you can set the robot if the Right-Sensor is on the dark side or black line and Left-Sensor is on the floor it will go to forward (by swap polarity of the motor). If the Right-Sensor is on the floor and Left-Sensor is on the black line it will go to backward.

That’s it… you can add wireless cam for to see how the robot walk… ^_^ Thank You

This project by Tahan Prahara,

Email: prahara_satria@yahoo.co.id

The post “JavaBot” LINE FOLLOWER ROBOT from Java, Indonesia first appeared on Student Projects.

Here I am using a telephone as a media, which serves main part of this system. By using home phone as a local phone and another phone – either landline or mobile phone as a remote phone we are controlling devices.

Features:-

1. You can control up to 10 devices. It may be any electric or electronic appliances or devices with simple to heavy appliances. Each device is given a unique code.
2. It makes accurate switching, any false switching of device are not done.
3. There is no risk for false switching.
4. Your local phone (i.e., home phone or office phone) can be used for normal use by using a DPDT switch. So you need not use a separate telephone line for this device controlling.
5. To perform any operations through remote phone line, the user needs to dial to the local telephone (to which the interfacing circuit is connected) then the respective code of the device is dialed.
6. This circuit does not require any complex IC, so any one with little knowledge of electronics can construct this circuit, because it does not need any programmable IC’s or programming.
7. This system detects the ringing signal from your exchange with the help of ring detector and automatically switches ON.
8. This device saves your money. This circuit switches OFF after a time of 60 seconds (you can change this switch ON-Time which is discussed in detail in coming section).
9. Before changing the state of the device we can confirm the present status of the device.
10. This circuit gives an acknowledgement tone after switching ON the devices to confirm the status of the device.
11. You can control devices from local telephone. It can also be controlled by PCO.

Taking a tour of the project:

This system uses Dual Tone Multi Frequency (DTMF) technology of our telephone set. Every telephone set will have this facility. We have two type of dialing facilities in our telephone system (i) Pulse dialing mode (ii) Tone dialing mode. Here this system works on tone dialing mode. The DTMF mode is shortly called as tone dialing mode. (Check for availability of tone dialing mode in your telephone set).

This system is divided into two sections

1: Remote Section:

It is nothing but remote telephone set which is present in the remote place. This may be your workspace (office / school) phone or mobile phone or a phone in PCO. Signals are sent through this telephone.

2: Local Control Section:

This is a control system through which you can control your appliances. This contains one telephone line and a control unit. The appliances to be controlled must be connected to telephone line through control unit .Control unit is kept with a sufficient backup.

What is DTMF?

When you press a button in the telephone set keypad, a connection is made that generates a resultant signal of two tones at the same time. These two tones are taken from a row frequency and a column frequency. The resultant frequency signal is called “Dual Tone Multiple Frequency”. These tones are identical and unique.

A DTMF signal is the algebraic sum of two different audio frequencies, and can be expressed as follows:

f(t) = A0sin(2*П*fa*t) + B0sin(2*П*fb*t) + ………..    ——->(1)

Where fa and fb are two different audio frequencies with A and B as their peak amplitudes and f as the resultant DTMF signal. fa belongs to the low frequency group and fb belongs to the high frequency group.

Each of the low and high frequency groups comprise four frequencies from the various keys present on the telephone keypad; two different frequencies, one from the high frequency group and another from the low frequency group are used to produce a DTMF signal to represent the pressed key.

The amplitudes of the two sine waves should be such that

(0.7 < (A/B) < 0.9)V               ——–>(2)

The frequencies are chosen such that they are not the harmonics of each other. The frequencies associated with various keys on the keypad are shown in figure (A).

When you send  these DTMF signals to the telephone exchange through cables, the servers in the telephone exchange identifies these signals and makes the connection to the person you are calling.

When you press the digit 5 in the keypad it generates a resultant tone signal which is made up of frequencies 770Hz and 1336Hz. Pressing digit 8 will produce the tone taken from tones 852Hz and 1336Hz. In both the cases, the column frequency 1336 Hz is the same. These signals are digital signals which are symmetrical with the sinusoidal wave.

Along with these DTMF generator in our telephone set provides a set of special purpose groups of tones, which is normally not used in our keypad. These tones are identified as ‘A’, ‘B’, ‘C’, ‘D’. These frequencies have the same column frequency but uses row frequencies given in the table in figure (A). These tones are used for communication signaling.

Due to its accuracy and uniqueness, these DTMF signals are used in controlling systems using telephones. By using some DTMF generating IC’s (UM91214, UM91214, etc) we can generate DTMF tones without depending on the telephone set.

The post Device control using Telephone first appeared on Student Projects.