Mini Projects


AUTOMATIC LIGHT CONTROLLER

 Presented By

             R. Jayanth,S. Shathis Kumar, K. Shanjai Anand

 Abstract:
            This circuit controls the switching of the street light or porch light and it will be automated. This circuit of automatic lamp controller using 7806 regulator IC can be used to automate street lights, tube lights or any other house electrical lightning systems. The IC 7806 is a voltage regulator IC that give a steady output voltage against widely fluctuating dc input voltage. For this IC, any voltage that appears in common terminal will be reflected at the output. So when the ground terminal is disconnected, the input is available at the output.

 Circuit Diagram:

 
Specification:

Sr. No.
Component Name
Value
Quantity
1.
IC1
7806
1
2.
Resistor (R1)
1.5K
1
3.
Resistor (R2,R3)
220K
2
4.
Resistor (R4)
1K
1
5.
Variable Resistor (VR1)
470K
1
6.
Capacitor (C1)
1000µF, 40V
1
7.
Diode (D1-D5)
1N4007
5
8.
Zener Diode (ZD1)
8.2V
1
9.
Transistor (T1)
BC557
1
10.
Transistor (T2)
BC547
1
11.
LED (LED1)
White
1
12.
LDR (LDR1)
-
1
13.
Relay (RL1)
12V
1
14.
Transformer (X1)
230/12V
1




Pin Diagram for 7806:


1 - Input
    2 - Ground
   3 - Output
 Design & Working:

            When the common terminal is connected to the ground, the regulator output is equivalent to the rated voltage, and as soon as the terminal is disconnected from the ground, the output increases up to the input voltage. The common terminal is controlled by a transistor, which works as a switch on the terminal. For automatic control of light, a light-dependent resistor (LDR1) is connected to the base of the transistor. In this way, the voltage regulator is able to operate a light bulb automatically as per the ambient light.
To derive the power supply for the circuit, the 50Hz, 230V AC mains is stepped down by transformer X1 to deliver a secondary output of 12V, 250 mA. The secondary output of the transformer is applied to a bridge rectifier comprising diodes D1 through D4, filtered by capacitor C1 and fed to the input terminal of the regulator (IC1). The common terminal (pin 2) of IC1 is connected to the ground line of the circuit through transistor BC557 (T1). The transistor is biased by R2, R3, VR1 and LDR1.

The grounding of IC1 is controlled by transistor T1, while light is sensed by LDR1. Using preset VR1, you can adjust the light-sensing level of transistor T1. The output of IC1 is fed to the base of transistor T2 (through resistor R4 and zener diode ZD1) and relay RL1. LED1 connected across the positive and ground supply lines acts as a power-‘on’ indicator. Normally, the resistance of LDR1 is low during daytime and high during nighttime. During daytime, when light falls on LDR1, pnp transistor T1 conducts.
The common terminal of IC1 connects to the ground and IC1 outputs 6V. As a result, transistor T2 does not conduct and the relay remains de-energized. The light bulb remains ‘off’ as the mains connection is not completed through the relay contacts. During nighttime, when no light falls on LDR1, it offers a high resistance at the base junction of transistor T1. So the bias is greatly reduced and T1 doesn’t conduct. Effectively, this removes the common terminal of IC1 from ground and it directs the full input DC to the output. Transistor T2 conducts and the relay energizes to light up the bulb as mains connection completes through the relay contacts.
As LDR1 is in parallel to VR1+R3 combination, it effectively applies only half of the total resistance of the network formed by R3, VR1 and LDR1 to the junction at T1 in total darkness. In bright light, it greatly reduces the total effective resistance at the junction. The circuit is simple and can be assembled on a small general-purpose PCB. Use a heat-sink for IC1. Make sure that LDR1 and the light bulb are well separated. The circuit can be used for streetlights, tube lights or any other home electrical lighting system that needs to be automated.
Reference:
·     http://www.electronicsforu.com/electronicsforu/lab/ad.asp?url=/EFYLinux/circuit/April2010/CI02_Apr10.pdf&title=Automatic%20Light%20Controller%20Using%207806
-          By M.K. Chandra Mouleeswran
 
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 AUTOMATIC TRAFFIC LIGHT MODEL 

Presented by
                              1. K. ARAVIND       
                                    2. S. DEIVAMANI     
                                    3. K. VENKADESAN
                                    4. G. VENKADESAN

INTRODUCTION

                         A  simple circuit to illustrate the basic principles of traffic signaling is presented here.   A typical road-crossing provided with red yellow and green lights. These lights are stimulated by  LEDs. It is known that the lights of same color  on the opposite roads  will have to be ON or OFF simultaneously . Thus base on LED are connected in series (though they could be wired in parallel ,it is not preferred   because of higher current demand on ICs. ).
                         For the purpose of this model. It has been assumed that red light will be ON for 8 seconds (or 8 units of time ) , the yellow light will be ON for 8 2 seconds and green lights for 10 secs  is 4:1:5. Thus total unit of time add upto 10, and a decade counter can be made use of.
  IC 555

                         The 8-pin 555 timer must be one of the most useful ICs ever made and it is used in many projects. With just a few external components it can be used to build many circuits, not all of them involve timing!
A popular version is the NE555 and this is suitable in most cases where a '555 timer' is specified. The 556 is a dual version of the 555 housed in a 14-pin package, the two timers (A and B) share the same power supply pins. The circuit diagrams on this page show a 555, but they could all be adapted to use one half of a 556.
Low power versions of the 555 are made, such as the ICM7555, but these should only be used when specified (to increase battery life) because their maximum output current of about 20mA (with a 9V supply) is too low for many standard 555 circuits. The ICM7555 has the same pin arrangement as a standard 555.
The circuit symbol for a 555 (and 556) is a box with the pins arranged to suit the circuit diagram: for example 555 pin 8 at the top for the +Vs supply, 555 pin 3 output on the right. Usually just the pin numbers are used and they are not labelled with their function.
The 555 and 556 can be used with a supply voltage (Vs) in the range 4.5 to 15V (18V absolute maximum).
Standard 555 and 556 ICs create a significant 'glitch' on the supply when their output changes state. This is rarely a problem in simple circuits with no other ICs, but in more complex circuits a smoothing capacitor (eg 100µF) should be connected across the +Vs and 0V supply near the 555 or 556. 


 
IC 7490 DECADE COUNRTER               
The 7490 integrated circuit counts the number of pulses arriving at its input.
The number of pulses counted (up to 9) appears in binary form on four pins of the ic.
When the tenth pulse arrives at the input, the binary output is reset to zero (0000) and a single pulse appears at another output pin.
So for ten pulses in there is one pulse out of this pin.
The 7490 therefore divides the frequency of the input by ten.
If this pulse is applied to the input of a second 7490 then this second ic will count the pulses from the first ic.
It will give one pulse out after 100 pulses have been applied to the first ic.
The 7490 can be connected to divide by other values.         
                         
Working  of circuit diagram
                                    For the purpose of this model,it has been assumed that the red light will be `ON` For 8 seconds (or 8 units of time). The yellow light for 2 seconds and green for 10 seconds (i.e) the ratio of timings of red , yellow and green is  4:1:5 . thus the total units of time add up to 10 , and a decade counter can be made use of . table.1,shows the requirements of the lights to remain ‘ON’  at different counts of time .
Table -1
COUNT
R1 ,R3
Y1,Y3
G1,G3
R2,R4
Y2,Y4
G2,G4
 0 to 3
1
0
0
0
0
1
  4
0
1
0
0
0
1
 5 to 8
0
0
1
1
0
0
   9
0
0
1
0
1
0

 Another important reason for this particular ratio of timings is the utilisation of the IC decade counter  7490 in a mode called the bi – quinary mode . the operation of 7490 in this mode is shown in table-2 . for working in this mode , the output  QD(pin 11) has to be connected to the input A (PIN 14)
TABLE – 2
COUNT
Qa
Qb
Qc
Qb
0
0
0
0
0
1
0
0
0
1
2
0
0
1
0
3
0
0
1
1
4
0
1
0
0
5
1
0
0
0
6
1
0
0
1
7
1
0
1
0
8
1
0
1
1
9
1
1
0
0

From a comparison of the tables 1 and 2 . the following relationships can be established.
R1 =A.D         R2 = A.D
Y1=A.D          Y2=A.D
G1=A             G2=A
It is therefore necessary to invert  a and d to get A and  D to get A and D. further from the above relations , it can be derived.
R1 = A.D             R2= A.D
Y1 = A.D             Y2 = A.D
By feeding A and D into a NAND gate , R1 can be obtained . in order to get R1 , the LED’S has to be connected between the output of the NAND gate and +5V line. similarly  Y1, R2 and Y2 can also be obtained
                                   Figure shows the complete circuit diagram . IC1(7490) is wired in astable mode is acting as the clock .the values of Ra , Rb and C1 determines the time period according to the relationship :
                                                                            T =0.693(Ra+2 Rb) C1
The values indicated are a time period of 2 seconds . IC2(7490) id a decade counter wired wired in bi-quinary code . IC3 and IC4 are two 7400(quad NAND gates).two ¼ IC 7400 NAND gates are used as inverter for A and D respectively .
                                                                      The roads can be painted , on a plywood board as in fig .
Fig. the LED’S  R1,Y1,G1 may be mounted on a strip . similarly R2,Y2,G2 etc.,  .may also be mounted on strips . the four strips can now be fixed suitably on the four sides of the road crossing . switch S1, when open , will freeze action for demonstration   

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DRINKING WATER ALARM

 Presented By 
  • ARUNDADHI LAKSHMI.R
  • BHARANI DEVI.K
  • FAUZIA PARVIN.M
  • PRABAVATHY.R


Introduction
The many States supply water for limited duration in a day. Time of water supply is decided by the management and the public does not know the same. In such a situation, this water alarm circuit will save the people from long wait as it will inform them as soon as the water supply starts.

Construction
At the heart of this circuit is a small water sensor. For fabricating this water sensor, you need two foils—an aluminium foil and a plastic foil. You can assemble the sensor by rolling aluminium and plastic foils in the shape of a concentric cylinder. Connect one end of the insulated flexible wire on the aluminium foil and the other end to resistor R2. Now mount this sensor inside the water tap such that water can flow through it uninterrupted. To complete the circuit, connect another wire from the junction of pins 2 and 6 of IC1 to the water pipeline or the water tap itself.

Working
The working of the circuit is simple. Timer 555 is wired as an astable multivibrator. The multivibrator will work only when water flows through the water tap and completes the circuit
connection. It oscillates at about 1 kHz. The output of the timer at pin 3 is connected to loudspeaker LS1 via capacitor C3. As soon as water starts flowing through the tap, the speaker
starts sounding, which indicates resumption of water supply. It remains ‘on’ until you switch off the circuit with switch S1 or remove the sensor from the tap. The circuit works off a 9V
battery supply. The water sensor is inserted into the water tap. Connect the lead coming out from the junction of 555 pins 2 and 6 to the body of the water tap. Use on/off switch S1
to power the circuit with the 9V PP3 battery.


Circuit Diagram





 Apparatus need to prepare this

 ·                     ON-OFF switch
·                     Resistor & capacitor
·                     Speaker
·                     IC's IC LM555
·                     Aluminum foil
·                     and sensor


 REFERENCES:

This project has been refereed from the site:

www.gebooki.com/search/electronics+mini+projects+circuit+diagram



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AUTOMATIC SOIL MOISTURE MONITOR AND CONTROL SYSTEM

Presented By: 

1.      K.venkadesan 
2.      G.vengadesan
                                                                   
ABSTRACT
             
           The aim of our project is to design and construct an Automatic soil  moisture monitor and       control system depending on the moisture content. This project is very useful for agriculture purpose. It saves the water also.

Provides irrigation consultants with a full set of tools to determine and optimize effective irrigation regimes for specific sites and crops.

The project kit permits the duty cycle of an irrigation period to be adjusted to match the absorption dynamics of the moisture. This maximizes water use efficiency – even for micro-irrigation. The sensor is connected to Microcontroller. The sensor is placing in root zone of the plant. It is possible to maintain crops at optimal hydration and monitor excess irrigation. Real-time irrigation control is based on multiple parameters.

The block diagram consists of Sensor, Microcontroller, LED Indication (motor status indication and fault indication), flow sensor and Water Pump. The sensor is placing in plant root zone. The microcontroller is monitor the moisture content through sensor, if moisture content is low it decide to operate the motor. The flow sensor is fixed at the motor pipe and the flow sensor output is given to the microcontroller.

The microcontroller programming (software coding) is developed in C language and compiled using C compiler. The compiler produces the final machine code of the program and it is stored in the Flash memory of micro controller.




EXPLANATION

                           Microcontroller are main part of this project .The                             indicators are connected to micro controller and it indicates the motor status indicator and fault indicator . The relay is also connected to MC level comparator LM324 is to compare the output voltage of sensor 1 and sensor 2 with reference voltage.
In this system we using two sensor and the flow sensor .The sensors are fixed in the sand box and the sensor indicates the dry state or wet state . the flow  sensor are connected in the end of the pipe.


CIRCUIT SPECIFICATION


Soil monitoring and control system is used to check whether the soil is dry or wet position .
In this system the power supply is given +9v to the regulator 7805 which regulates into +5v. micro controller ids the main part of the soil monitoring and control system. micro controller works at +5v supply input supply +9v is given to the c, the filter capacitor is used filter the DC into pulsating DC and the pulsating DC supply  is given to  the IC37805t it is regulator which  converts to pulsating DC supply into +5v ac supply C2is  the noise filter which is used to rectify the noise .
Reset switch is connected to the resistor 4.7k Ω. It is connected in IC2LM324Nis the comparator the two comparator is used there flow sensor is connected at the water outlet from the motor . In this system we are using four LED’S, two indicators motor status ,dry state ,sensor1,sensor2 whether the moisture is wet or dry .

DESIGN WORKING

Microcontroller  is used to controlling the whole process of this system(PIC409pins). In this system the input power supply is given 9v(DC) supply and the first end of the power supply connection is given to sensor and other end of the power supply is given to regulator 7805. Regulator is used to converting 9nDC to 5v AC . The output connection is connected  to noise filter .The noise filter is used to rectify error message in incoming AC supply .

                          In this system comparator is used to compare the output voltage of sensor1 and sensor2 with reference voltage ,which decides the wet and dry conditions. The  one end of the comparator is connected  to the sensor and other end of comparator is connected to +9vsupply. If the soil is in dry condition  the sensor  resistance becomes high, i.e., voltage at  the comparator is >6 output is 0v.
                         If the sand is in wet when the sensor  resistance  is high  voltage lesser than 4 output is 9v. The flow sensor is connected and it finds  whether water flows or not crystal oscillator produced a carrier frequency to operate the hrc . The  motor is connected to pumping purpose and controlled by hrc via relay.LED are used to indicating the sensor ,motor and dry (or) wet
Position.

Reference Books

Programming and Customizing the PIC Microcontroller by  Myke Predko, McGraw-Hill/TAB Electronics
DESIGNING EMBEDDED SYSTEMS WITH PIC MICROCONTROLLERS    by Tim Wilmshurst, University of Derby, UK
PIC Microcontroller Project Book                                                                       By John Iovine
The Digital IC Handbook  By M. S. Morley - TAB Professional and Reference Books, 1988
CMOS Digital Integrated Circuits By Sung-Mo Kang, Yusuf Leblebici - McGraw-Hill Professional


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Salt-Taster

Detects the amount of salt contained in liquid foods

Three-level LED indicator


Circuit diagram:

Salt Taster

Parts:

R1________________470R   1/4W Resistor
R2,R5______________10K   1/4W Resistors
R3,R6_____________220K   1/4W Resistors
R4__________________5K   1/2W Trimmer Cermet
R7________________680R   1/4W Resistor
R8__________________2K2  1/4W Resistor
R9,R10,R11,R12,R13__1K   1/4W Resistors

C1________________100µF   25V Electrolytic Capacitor

D1,D2,D3______3 or 5mm. Red LEDs
D4____________3 or 5mm. Green LED
D5____________3 or 5mm. Yellow LED

IC1_______________LM324 Low Power Quad Op-amp

P1_________________SPST Pushbutton

Probes_________________ (See Text)

B1___________________9V PP3 Battery

Clip for PP3 Battery

Device purpose:

This circuit was designed to detect the approximate percentage of salt contained in a liquid. After careful setting it can be useful to persons needing a quick, rough indication of the salt content in liquid foods for diet purposes etc.

Circuit operation:

IC1A op-amp is wired as a DC differential amplifier and its output voltage increases as the DC resistance measured across the probes decreases. In fact, fresh water has a relatively high DC resistance value that will decrease proportionally as an increasing amount of salt is added.
IC1B, IC1C and IC1D are wired as comparators and drive D5, D4 and D3 in turn, as the voltage at their inverting inputs increases. Therefore, no LED will be on when the salt content of the liquid under test is very low, yellow LED D5 will illuminate when the salt content is low, green LED D4 will illuminate if the salt content is normal and red LED D3 will illuminate if the salt content is high.
D1 and D2 are always on, as their purpose is to provide two reference voltages, thus improving circuit precision. At D2 anode a stable 3.2V supply feeds the non-inverting inputs of the comparators by means of the reference resistor chain R8, R9 and R10. The 1.6V reference voltage available at D1 anode feeds the probes and the set-up trimmer R4.
One of these two red LEDs may be used as a pilot light to show when the device is on.

Probes:

It was found by experiment that a good and cheap probe can be made using a 6.3mm. mono jack plug. The two plug leads are connected to the circuit input by means of a two-wire cable (a piece of screened cable works fine).
The metal body of the jack is formed by two parts of different length, separated by a black plastic ring. You should try to cover the longest part with insulating tape in order to obtain an exposed metal surface of the same length of the tip part, i.e. about 8 to 10mm. starting from the black plastic ring.
In the prototype, three tablespoons of liquid were poured into a cylindrical plastic cap of 55mm. height and 27mm. diameter, then the metal part of the jack probe was immersed in the liquid.

Notes:

  • Wait at least 30 seconds to obtain a reliable reading.
  • Wash and wipe carefully the probe after each test.
  • To setup the circuit and to obtain a more precise reading, you can use a DC voltmeter in the 10V range connected across pin #1 of IC1A and negative supply.
  • Set R4 to obtain a zero reading on the voltmeter when the probe is immersed in fresh water.
  • You may change at will the threshold voltage levels at which the LEDs illuminate by trimming R4. Vary R8 value to change D4 range and R9 value to change D5 range.
  • P1 pushbutton can be substituted by a common SPST switch.
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