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Monday, 4 August 2014

Control Of Environmental Parameters In A Green House

In this project, we will have a look at Control Of Environmental Parameters In A Green House. Agriculture is the source of food supply in the world. So, proper care has to be taken for improving the yield with minimum usage of the available resources such as water, energy etc. The project focuses on the development in the agricultural sector with minimum water usage and the excellent utilization of the solar energy.The main parameters of agriculture are rain,temperature,wind and soil moisture which are found with the of sensors. The output of these sensors are send to the PIC through RF module. The PIC in turn activates the control unit. The control unit consist of exhaust fan, valve and shield. The following are the operations taking place
  • When rain is detected by the rain sensor, shield is activated to cover the field. 
  • The temperature is displayed on the LCD screen with the help of temperature sensor. As the temperature exceeds the threshold value, the exhaust fans are activated. Moisture sensor help to measure the moisture level. If the moisture is low, valve is opened so that water flows through the valve in to the field.
  • Anemometer is used to detect the speed of the wind. The flaps of the window which is placed across the field is rotated depending on the wind speed.
  • Solar cells placed on solar tracker is used to obtain efficient solar energy. These energy is used to power the sensors.
For the large rural distract, the greenhouse production has become a way of being rich. The growth of crop in greenhouse depends on temperature, humidity, wind and other parameters in greenhouse. So it is important to properly measure and adjust the temperature, humidity and other parameters in the greenhouse. The wireless monitoring system is developed, which based on wireless communication technology, does not need cables, adds or reduces configuration at random, possess simple system construction. A greenhouse environment parameters monitoring system based on wireless communication technology has been developed, which realizes the measurement, summary and control of temperature, humidity and the other parameters. To give more Importance to conservation of energy, solar energy is used. To increase the efficiency of the solar panel, sun tracker is also designed.
After many survey and research we finally ended up in doing a project in agricultural sector. To make the irrigation simpler we planned of controlling several environmental parameters. Thus the title to our project was given as 'Control of Environmental parameters in Greenhouse'. The base papers that suits our project were 'Wireless measurement and controlling of Environmental parameters' and 'Remote Sensing and Control of an Irrigation System Using a Distributed Wireless Sensor Network'. In addition to the above, we planned of utilizing a conventional source of energy as a part of conservation of energy. Several sensors were introduced like rain sensor, temperature sensor and soil humidity sensor since rain, temperature and soil water content are the most important parameters in irrigation system. The description of the above mentioned sensors are as follows:
1. Soil moisture sensor: For proper cultivation of crops, proper check on soil moisture has to be monitored continuously .The idea about soil moisture sensor was available
from the webpage 'http://blog.makezine.com/2009/03/04/nocost-soil-moisture-sensor'. According to the web page, it says that if two nail when dipped in plaster of Paris and separated by a fixed distance can act as a soil moisture sensor. The principle of operation was that the resistance of a porous block is proportional to its water content. Thus, wetter the block, lower is the resistance measured across the two embedded electrodes. Thus soil moisture was able to design.
2. Rain sensor: The idea about the rain sensor was available from web page 'http://www.nationalstemcentre.org/CEM5.pdf'.' In the web page, it says that a simple PCB using etching process can be used as a rain sensor. It is the cheapest form of rain sensor.
3. Temperature sensor: Too much temperature can fade away the crops. In order to avoid the above, we thought of introducing a temperature sensor. The idea about temperature sensor was available from web page 'http://www.engineersgarage.com' electronic-components/lm35-sensor data sheet. In the web page, LM35 is used as the temperature sensor. The features of LM35 are 
  • Sensor gain of 10mV/C
  • Temperature range of 0-100V

Monday, 23 June 2014

New Engineering project topics


SOLAR ENERGY INSTALLATION- FOR BSC
AUDIO AND POWER AMPLIFIER- FOR BSC
BATTERY CHARGERS (CELL PHONE, CAR) – FOR BSC
ALARMS OF DIFFERENT TYPES- FOR BSC
TOUCH ACTIVATED SWITCH AND ALARMS- FOR BSC
AM-FM-SW-TV ACTIVE ANTENNA- FOR BSC
FM TRANSMITTER – FOR BSC
WATER LEVEL INDICATOR WITH ALARM- FOR BSC
AUTO TURN-OFF BATTERY CHARGER- FOR BSC
RAIN ALARM- FOR BSC
REMOTE CONTROL AC LAMP- FOR BSC
DARK AUTOMATED SWITCH- FOR BSC
MOTORCYCLE ALARM – FOR BSC
DC-AC INVERTER WIT 555 TIMER- FOR BSC
BREAK LIGHT FLASHER- FOR BSC
VOLTAGE COMPARATOR- FOR BSC
FUSE MONITORING ALARM- FOR BSC
AUDIO MIXER – FOR BSC
SOLAR CELL PHONE CHARGER- FOR BSC
AUTOMATIC TRICLE CHARGER- FOR BSC
TONE CONTROL- FOR BSC
AUTO DAYLIGHT ALARM- FOR BSC
HIGH AND LOW VOLTAGE CUT-OUT WITH DELAY- FOR BSC
TRANSMITTER ORGAN- FOR BSC
AUTOMATIC OVEN CONTROLLER- FOR BSC
UPS POWER SUPPLY- FOR BSC
SEVEN SEGMENT LED COUNTER – FOR BSC
AUTOMATIC VOLTAGE REGULATOR- FOR BSC
AUTOMATIC VOLTAGE REGULATOR- FOR BSC
GATE ALARM- FOR BSC
HEADPHONE ALARM – FOR BSC
FULL-DUPLEX INTERCOM- FOR BSC
CHRISMAS LIGHT- FOR BSC
FIRE DOOR ALARM- FOR BSC
AUTO FAN SPEED CONTROLLER – FOR BSC
MINIATURE FM TRANSMITTER- FOR BSC
AC LINE CURRENT DETECTOR- FOR BSC
VARIABLE POWER SUPPLY- FOR BSC
ZENER DIODE TESTER- FOR BSC
FM RECEIVER- FOR BSC
ULTRASONIC PEST REPELLER- FOR BSC
POWER SUPPLIERS – FOR BSC
WATER ACTIVATED ALART- FOR BSC
WATER LEVEL INDICATOR WITH ALARM- FOR BSC
POWER FAILURE ALARM- FOR BSC
SELF ACTIVATING POWER SUPPLY- FOR BSC
MICROPHONE MIXER – FOR BSC
EMERGENCY SIREN SIMULATOR- FOR BSC
TRANSFORMERLESS POWER SUPPLY – FOR BSC
DESIGN AND CONSTRUCTION OF A 2000W INVERTER
DESIGN AND CONSTRUCTION OF A D.C TO A.C INVETER SYSTEM
THE CONSTRUCTION OF A 3-PHASE MOTOR OPERATION INDICATOR
CONSTRUCTION OF PVS CONDUIT WIRING SYSTEM OF TWO BEDROOM BUNGALOW
CONSTRUCTION OF A 12 VOLT BATTERY CHARGER
CONSTRUCTION OF AUTOMATIC CHANGE OVER WITH GENERATOR TRIP OFF

Sunday, 22 June 2014

Auto Night Lamp Using High Power LED

Auto Night Lamp Using High Power LEDs is a circuit which turns ON the LED lights interfaced to it at night time and it turns OFF the lights automatically when it is day. Usage of LEDs is growing day by day due to the advantages they provide compared to the conventional filament bulbs or fluorescent lamps. They provide good quality of white light with a better intensity compared to others. They also consume less power compared to their alternatives. These are the advantages which the LEDs encourage us to use them compared to their alternatives.
In this article, we shall see the circuit and the working of turning on or off of high power LEDs with light intensity. The element which is used for sensing light in the circuit is the light dependent resistor. The resistance of the light dependent resistor depends on the light incident on it. If the intensity of light incident on it is more, then the resistance of the circuit decreases. If the intensity of light incident on it decreases, then the resistance of the device increases. We are making use of this property of the light dependent resistor to detect the light and thereby operate the LEDs. We are arranging twenty five light emitting diodes in an array such that five LEDs are in series and five such series LEDs are arranged in parallel.
The transistors are used in saturation mode. They are used as electronic switches in this mode. The transistor BC547 is a general purpose NPN transistor which is used to further switch the LEDs. This is a power transistor with a heat sink. The heat sink helps the transistor to dissipate the generated heat into air so that the transistor can handle higher power loads than it can do without the heat sink.
The entire circuit along with the LEDs is powered by a 12V DC power supply. A battery based DC power supply is usually preferred. However, you can use a ac rectified and regulated power supply.
The LEDs used in the circuit are high powered white LEDs. The intensity of light produced by these LEDs equals an ordinary fluorescent bulb. The lighting produced is sufficient for reading or to do any other daily activity. The circuit can be assembled on a printed circuit board with all the components neatly arranged and the LEDs placed in order. Try to place the LEDs maintaining a distance of about 1 cm between the LEDs so that the the lighting will be well distributed in your room.

Pull Pin Security Alarm System

his circuit helps us to get alerted when anybody picks our pockets or bags. The circuit is very helpful to prevent our goods getting pick pocketed. The circuit is called a pull pin security alarm because it gets activated as soon as the pin is pulled.
The arrangement of the circuit is as follows. The circuit has a pin which is fixed to the pocket and the other end is attached to the circuit. The circuit remains inactive until the wallet is in your pocket as the circuit gets activated when the wallet is pulled from your pocket.
When the wallet is in the pocket, the circuit has the pin attached thereby the circuit remains inactive. Whereas when the wallet is removed from the pocket, the pin gets detached from the circuit thereby the circuit gets activated. When the circuit gets activated, the circuit turns ON the mini loudspeaker. The mini loudspeaker is fed with an alternating signal of audio frequency. This signal vibrates the loud speaker at an audio frequency so that it is well heard to us.

Saturday, 25 January 2014

Single Phasing Monitoring and Prevention System for 3-phase Industrial Loads

    The aim of this project is to construct a single phasing monitor and prevention system using 8-bit microcontroller. Anti-single phasing relays or single phasing preventer are required for critical loads and circuits. These are required because the normal overload protection doesn't trip on time. For large air-conditioning compressors, irrigation pumps these are sometimes, included.

      The purpose of this project is to develop an intelligent system that continuously monitors all the three phase voltages (High voltage AC) and if any of these three phases is disconnected then this system takes the preventive action. The preventive action could be disconnecting the power supply immediately to the load by operating an electromagnetic relay. This system also alerts the user using visual or audible indicators.

        This system consists of three optically isolated high voltage sensors for sensing the presence of high voltage in the respective circuits. One of the voltage sensors is connected to phase line of the supply and the other is connected to neutral line. A micro controller based control system continuously monitors the voltage in all the three phases of the power supply circuit. In ideal conditions all the three phases gets the same voltage. The visual indicators display the health status of all three phases (Red, Yellow and Green). But, when any of the phases gets disconnected then in such situations the micro controller-based system alerts the user about this in the form of visual or audible alerts.


 

Hall Effect Sensor based non-contact tachometer for electrical motors speed measurement


       The purpose of this project is to design and construct a non-contact type of Tachometer. A tachometer(also called a revolution-counter, rev-counter, or RPM gauge) is an instrument that measures the rotation speed of a shaft or disk, as in a motor or other machine. Hall Effect sensors typically use a rotating target attached to a wheel, gearbox or motor. This target may contain magnets, or it may be a toothed wheel. The teeth on the wheel vary the flux density of a magnet inside the sensor head.

        This project consists of a Hall effect sensor connected to a microcontroller unit. The sensor signals from Hall effect sensor are sent to microcontroller for rpm measurement. These measured final values arc displayed on a LCD display connected to microcontroller.





Motor speed monitors and control system using GSM modem

              The purpose of  this project   is  to control   the speed and direction of  DC Motor  using Microcontroller and GSM Modem with password protection.    This uses a PWM  Pulse Width Modulation) technique to control the speed of motor from 0% to 100%. The   speed   of   the  motor   is  measured   using   contact-less   speed  measurement technique.  Speed control is done using PWM (Pulse Width Modulation) method.    User can  send SMS messages   to  control   the  motor   speed  and direction. A GSM modem attached to the control unit handles automatic SMS sending and receiving process.   As this monitoring and controlling can be done by any mobile phone, we provided a security feature by implementing password-based protection. User has to send the password along with the commands to be controlled.

           GSM Modem connected to microcontroller unit is used to control the motor and know the motor live speed. Microcontroller automatically reads the SMS messages stored in the SIM card and takes necessary action like speed control, direction control etc. There will be a particular code that needs to be sent through SMS to set the speed and get the speed from the DC motor  


Features of this project:
1. Remote monitoring and controlling of DC motor.
2. Can be operated from anywhere in the world.
3. Reliable for industrial and domestic needs.
4. Automatic remote speed measurement.


Friday, 17 January 2014

Automatic Plant Irrigation System

Here is a simple project more useful in watering plants automatically without any human interference. We may call it as Automatic plant irrigation system. We know that people do not pour the water on to the plants in their gardens when they go to vacation or often forget to water plants. As a result, there is a chance to get the plants damaged. This project is an excellent solution for such kind of problems.

Block Diagram of Automatic Plant Irrigation System:

Block Diagram of Electronic Plant Watering System
Explanation:
  • Circuit is not that much complicated. We use the basic concept in this circuit i.e. soil have high resistance when it is dry and has very low resistance when it is wet.
  • By using this concept we will make the system work. We insert two probes in the soil in such a way that that they will conduct when the soil is wet and they will not conduct when the soil is dry. So, when the probes do not conduct, system will automatically detect this condition with the help of HEX inverter which will become high when the input is low.
  • HEX inverter will trigger the NE555 Timer and this NE555 timer will trigger another NE555 which is connected to the output of first NE555. Now the second NE555 which is configured as astable multivibrator will help to switch on the Electric valve and as result, it will allow the water to flow to the soil.
  • When the water wet the soil, probes will again conduct and make the output of 7404 low which will make the first NE555 to low and also drive remaining circuit to low. So, automatically it will switch off the valve.
Main Components in Automatic Plant Irrigation System:
Hex Inverter 7404: the main function of the inverter is to give the complemented output for its input i.e. it will give output which is opposite to input. For example, if the input is low to the inverter, then the output will be high. Just like the normal inverter which gives high output when the input is low and gives low output when the input is high. 7404 IC will be having six independent inverters; Operating supply voltage is around 4.75V minimum to 5.5V maximum, normal supply voltage is 5V. They are used in different applications like inverting buffers, drivers, hex inverters etc. 7404 IC will be available in different packages like DIP (dual inline package), QFP (Quad Flat Package) etc. The pin configuration of Hex Inverter 7404 is shown below.
Inverter Pin Configuration

Circuit Diagram of Automatic Plant Irrigation System:

Circuit Diagram of Electronic Watering Plant System
Circuit Explanation:
  • We are all well aware that the plants will die due to lack of water in the soil. Soil will have high resistance when it is dry and it will have very low resistance when soil is wet. We use this simple logic to water the plants and make the circuit work.
  • Two probes which are connected to the circuit are placed into the soil. The two probes will conduct only when soil is wet (resistance is low) and they cannot conduct when soil is dry due to high resistance. The voltage is given to the probes to conduct is given from the battery connected to the circuit.
  • When the soil is dry it will produce large voltage drop due to high resistance. This is sensed by 7404 hex inverter and makes the first NE555 timer trigger which is configured as monostable multivibrator with the help of a electrical signal.
  • When the first NE555 is triggered at pin 2, it will generate the output at pin 3 which is given to the input of second NE555 timer. The second 555 timer is configured as astable multivibrator which got triggered by the first 555 timer and will generate the output and drive the relay which is connected to the electrically operated value through the transistor SK100. You can use a heat sink for SK100 transistor if it is dissipating more heat.
  • The output of second NE555 timer will switch on the transistor SK100 which will drive the relay. Relay which is connected to the input of electrical value and output of value is given to the plant plots through the pipe.
  • When transistor has turned on relay, it will open the valve and water is poured on to the plants pot. When the water content in the soil is increased, the resistance in the soil will get decreased and conduction of the probes will get started which will make the 7404 Inverter to stop the triggering of first 555 timer. Ultimately it will stop the electrical valve which is connected to the relay. Variable resistor (R5) and capacitor (C1) are used to adjust the valve when to we want to conduct the probes.
  • The capacitor C5 (0.01uf) is used to ground, the CV pin of second NE555 timer. C3 will remove the AC noise and allow only DC to the remaining circuit. C4 and R3 will constitute to configure the NE555 in astable multivibrator.
Values of the Components in the Circuit:
  • Capacitor (C4) = 10u 16V.
  • Capacitor (C5) = 0.01u.
  • Resistor (R3) = 27K
  • Resistor (R4) = 27K
  • Diode (D1 and D2) = IN4148
  • Relay = 6V, 150 ohms

Water Level Indicator, water level controller circuit

The Water Level Indicator employs a simple mechanism to detect and indicate the water level in an overhead tank or any other water container. The sensing is done by using a set of nine probes which are placed at nine different levels on the tank walls (with probe9 to probe1 placed in increasing order of height, common probe (i.e. a supply carrying probe) is placed at the base of the tank). The level 9 represents the “tank full” condition while level 1 represents the “tank empty” condition.
When the water-level is below the minimum detectable level (MDL), the seven segment displays is arranged to show the digit 1, indicating that the tank is empty, When the water reaches level1 (but is below level2) the connection between the probes gets completed (through the conducting medium – water) and the base voltage of transistor increases. This causes the base-emitter junction of transistor to get forward biased, this switches transistor from cut-off to conduction mode thus PIN (B0) of microcontroller is pulled to ground hence, the corresponding digit displayed by the seven segment display is 2. The similar mechanism applies to the detection of all the other levels. When the tank is full, all inputs to microcontroller become low and all its outputs go high. This causes the display shows a 9 also in this case a buzzer sound is given, thereby indicating a “tank full” condition.
Most water level indicators are equipped to indicate and detect only a single level. The Water Level Indicator implemented here can indicate up to nine such levels and the microcontroller displays the level number on a seven segment display. So, not only is the circuit capable of cautioning a person that the water tank has been filled up to a certain level, it also indicates that the water level has fallen below the minimum detectable level. This circuit is important in appliances such as the water cooler where there is a danger of motor-burnout when there is no water in the radiator used up also it can be used in fuel level indication.

Water Level Indicator Project Features:

  • Easy installation.
  • Low maintenance.
  • Compact elegant design.
  • The Automatic water level controller ensures no overflows or dry running of pump there by saves electricity and water.
  • Avoid seepage of roofs and walls due to overflowing tanks.
  • Fully automatic, saves man power.
  • Consume very little energy, ideal for continuous operation.
  • Automatic water level controller provides you the flexibility to decide for yourself the water levels for operations of pump set.
  • Shows clear indication of water levels in the overhead tank.

Hardware Description:

Water Level Indicator Project Block Diagram:

Water Level Indicator Block Diagram
Figure 2.1.1 Block diagram

Water Level Indicator Project Circuit Diagram:

Water Level Indicator Schematic Diagram

Water Level Indicator Project Description:

This is the circuit diagram and description for water level indicator.
  • A constant 5v power supply is given to the microcontroller and rest of the circuit from a battery.
  • The tank has 9 conductive type sensors (other types of sensors have been mentioned earlier but in our project only conductive type are used) embedded into it and 8 wires of sensors out of 9 are connected to transistors and the 9th is connected to 5v+ supply.
  • The use of transistor is it acts as inverter (i.e. in on state gives low voltage at output and in non conducting state gives high voltage at its output), all transistors outputs are connected to 1,2,3,4,5,6,7,8 pins (PORTB) of microcontroller.
  • Seven segment display is connected to pin no. 33 to 40 (PORTA). It is connected in common cathode fashion.
    The Output for the 7th level is not only shown in seven segment display but also indicated with a discontinuous buzzer sound.
  • Output for the 8th level (i.e. tank full condition) is not only shown in seven segment display but also indicated with a continuous buzzer sound.

Operation:

The operation of this project is very simple and can be understood easily. In our project “water level indicator” there are 3 main conditions:
  1. There is no water available in the source tank.
  2. Intermediate level i.e. either of 3rd to 7th level.
  3. There is ample amount of water available in the source tank.
So let us discuss on the more about these 3 conditions

CONDITION 1: Water not available

When the tank is empty there is no conductive path between any of the 8 indicating probes and the common probe (which is connected to 5v+ supply) so the transistor base emitter region will not have sufficient biasing voltage hence it remains in cut off region and the output across its collector will be Vc approximately 4.2v. As in this case the microcontroller is used in the active low region (which means it considers 0-2 volts for HIGH and 3-5 volts for LOW) now the output of transistor which is 4.2v approximately will be considered as LOW by the microcontroller and hence the default value given by microcontroller to the seven segment display is 1 which indicates as the tank is empty.

CONDITION 2: Intermediate levels

Now as the water starts filling in the tank a conductive path is established between the sensing probes and the common probe and the corresponding transistors get sufficient biasing at their base, they starts conducting and now the outputs will be Vce (i.e. 1.2v-1.8v) approximately which is given to microcontroller. Here the microcontroller is programmed as a priority encoder which detects the highest priority input and displays corresponding water level in the seven segment display. In this project while the water level reaches the 7th level i.e. last but one level along with display in seven segment a discontinuous buzzer is activated which warns user that tank is going to be full soon.

CONDITION 3: Water full

When the tank becomes full, the top level probe gets the conductive path through water and the corresponding transistor gets into conduction whose output given to microcontroller with this input microcontroller not only displays the level in seven segment display but also activates the continuous buzzer by which user can understand that tank is full and can switch off the motor and save water.

Flow Chart:

Water Level Indicator Flow ChartFigure 4.2.1 Flow chart
Flow chart gives the clear and easy understanding of the project. The process goes on as follows:
The microcontroller checks if the tank is full if the condition is satisfied it indicates the same on display unit and also sounds a buzzer if the condition fails it checks if the tank is filled upto level 7 and this process continues and the corresponding level is indicated in the display unit.

Conclusion and Scope:

Applications of Water Level Indicator:

  • Automatic Water level Controller can be used in Hotels, Factories, Homes Apartments, Commercial Complexes, Drainage, etc., It can be fixed for single phase motor, Single Phase Submersibles, Three Phase motors. (For 3Æ and Single Phase Submersible Starter is necessary) and open well, Bore well and Sump. We can control two motor and two sumps and two overhead tanks by single unit.
  • Automatic water level controller will automatically START the pump set as soon as the water level falls below the predetermined level (usually 1/2 tank) and shall SWITCH OFF the pump set as soon as tank is full.
  • Fuel level indicator in vehicles.
  • Liquid level indicator in the huge containers in the companies.

Schematic of DC Fan Controlled by Temperature Circuit

Fan controlled by temperature circuit 
The circuit exploits the property of Thermistor to operate the DC Fan. Thermistor is a kind of temperature dependent resistor and its resistance varies depending on the temperature in its vicinity. There are two types of Thermistors- NTC and PTC.
Negative temperature coefficient (NTC) Thermistor decreases its resistance when the temperature increases while Positive temperature coefficient (PTC) increases its resistance when the temperature increases. Thermistors are bead like resistors available from 100 ohms to 10K or more values. Here a 4.7K NTC Thermistor is used.IC uA 741 is used as a voltage comparator to switch on the DC fan. Its INV input (pin2) gets an adjustable voltage through VR while its Non-INV (pin3) input gets voltage through a potential divider comprising R1 and the Thermistor. Thus the voltage at pin3 depends on the conductivity of the Thermister.
When the temperature is normal (as set by VR), pin3 gets higher voltage than pin2 and makes the output of IC high as indicated by Red LED. This high output keeps T1 off since its base is positive. DC fan remains off in this condition. When the temperature increases above the value set by VR, resistance of Thermister decreases and the voltage at pin3 decreases. As a result, output of IC becomes low to switch on T1.
A small brush less DC fan (one used in computers) turns on to increase the air circulation. When the temperature returns normal, Fan automatically turns off. Diode 1N4007 is necessary to remove back EMF when T1 turns off.

Cell Phone Detector circuit,

This is a mobile phone sniffer circuit that can detect the signals being used in the GSM (Global System for Mobile Communication) band at about 900 MHz. Since the signals are digitally encoded, it can detect only the signal activity, not the speech or the message contents. A headphone is used to hear the detected signals.

Project Description

The circuit schematic is given in the .rar archive attachment. There are two separate detector units. Every detector unit consists of a dipole antenna, a choke and a diode. The antenna receives the GSM signals in media. Then a small amount of charge is induced in the choke. The diode demodulates the signal and finishes detecting. The diodes must be schottky diodes or germanium diodes. Since the forward voltage of a silisium diode is high, it won’t give a sufficient result in this circuit. LM358 amplifies the received signal. It contains two separate op-amps that are supplied by a common power source. R3 and R7 resistors determine the gain of the amplifiers. When the resistor values are greater than 10M then the noise level increases. If they are small like about 100k, this time it becomes harder to hear the signal.
The PCB file is provided in pdf format. You can apply it to the board by using the ironing method.
R1, R5 : 100K 1/4W Resistor
R2, R6 : 1k 1/4W Resistor
R3, R7 : 8.2M 1/4W Resistor
R4, R8 : 220 Ohm 1/4W Resistor
R9 : 2.2K 1/4W Resistor
D1, D2 : BAT43 Schottky Diode
C1, C2, C4 : 100nF Polyester Capacitor
C3 : 100uF 16V Electrolytic Capacitor
L1, L2 : See Text
U1 : LM358
J1 : 8 Pin Socket
J2 : Stereo JAck
1 × 9V Battery
1 × 9V Battery Socket
1 x LED
1 x On/Off Switch
Figure:1

Figure 1 

The diodes, gain of the amplifiers and the length of the antenna is critical in this circuit. Calculating the length of the antenna is simple. The formulation is given below.
λ=c/f = (300.000km/h)/900MHz =33.3 cm Then; Antenna Length = λ / 2 = 16.6 cm
So there are four pieces of antenna and each one is about 8.3 cm long. The wire type is not critical but its better to choose a fairly thick wire that will not bend too easily. It is a 1.5 mm diameter wire seen in the photo that we used. The two antennas must be positioned perpendicularly.
Figure:2

Figure 2 

The chokes are 10 turn molded chokes. The wire diameter should be about 0.5 – 06 mm and wound around a 5 mm cylindrical object.
Diodes are very critical. You should use one of BAT43, BAT45, AA112, AA116 or AA119. When a silisium diode is used the circuit also works but the detecting area becomes very very narrow.
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