Mini Electronics projects

This Book is written for all the people who love innovation. It is the collection of 20 ideas to do some innovative project, to make something new. I believe this Book will be helpful for the students for their mini project. My effort will get success if you get any help like project idea, circuit diagram help from this book. Give your feedback by mailing me...

                                           Adegbecolumbus@gmail.com
                                           @Adegbenkwuda

compact digital soil moisture tester

Here is a simple and compact digital soil moisture tester to check whether the soil is dry or wet. It can also be used to check the dryness or wetness of cotton, woolen and woven fabric

                     

DC-DC Converter     

This simple circuit lets you run a 1W LED from the battery of your car. IC MC34063 is 

used here as a buck converter. It is a monolithic switching regulator sub-system intended 

for use as a DC-DC converter. The device consists of an internal temperature_x0002_compensated reference, a comparator, a controlled duty-cycle oscillator with an active 

current-limit circuit, a driver and a high-current output switch. These functions are 

contained in an 8-pin dual in-line package. Another major advantage of the switching 

regulator is that it allows increased application flexibility of the output voltage

Another circuit 

Conversion of AC to AC is quite simple as in compare to DC to DC converter because it only implies a transformer which converts AC from one voltage level to another voltage level. But conversion of DC to DC is quite tedious regulates voltage to 12 volt. 

work without transformer and more power losses. Here is simple, low-cost, high precision circuit which converts 6-V DC to 12-V DC without using transformer and easy to construct with few component. 

Circuit description of DC to DC conversion 

The circuit of DC to DC conversion is build with a very popular IC LM555 used as multivibrator mood which generate required frequency range from 2 to 10 kHz to drive power transistor T2. Here potentiometer VR1 is used to adjust output frequency given to transistor T2 via resistor R3. A zener diode in this circuit is used as voltage regulator which 

Here Inductor L1 of 100 turns, 24 SWG enameled copper wire wounded on a 40mm dia. toroidial ferrite core and capacitor C5 is employed for energy storage. Transistor T1 is used to control output control with the help of resistor R4 R5.

 

Multipurpose listening device

This circuit can detect very faint, remote sounds 

with a good clarity. It is useful in large conference halls, auditoria, cinema halls, lecture rooms in colleges, etc. The circuit can be housed in a small plastic box and kept in a shirt pocket. It is especially useful for watching TV programmes at a low volume so as not to disturb other family members in the house 

School/College Quiz Buzzer

Manual buzzers used for quiz competitions in schools and colleges create a lot of confusion in identifying the first respondent. Although there are circuits using PCs and discrete ICs, they are either too expensive or limited to only a few number of players

Crystal-Based 50Hz Generator

Here is a simple oscillator circuit that generates 50Hz frequency using a crystal. It produces alternating 50Hz pulses with 50 per cent duty cycle, which can be used in inverter circuits. It comprises a 14-stage counter and oscillator (CD4060), dual J-K flip-flop (CD4027), operational amplifier (LM324) and a few discrete components

                                 

 DC Changeover System with Battery Protection Unit

Emergency lights commonly available in the market come with battery over-charging protection but no discharging protection. Here is a circuit that protects the battery from over-charging as well as over-discharging. The load is powered by the regulator when mains  is  available      and automatically shifts to DC when mains power fails. When mains power resumes, the load is again powered through the regulator and the battery starts charging.

   

DC Motor speed Controler

Here is a simple circuit to control the speed of a DC motor. It can be configured to control the sweep rate of automobiles’ windscreen wiper.

Bedwetting Alarm

Bedwetting is one of the most common childhood problems that can have a significant impact on a child’s health if left unattended. During the night, the parents would not know if the child has urinated and the kid may sleep all night long on a wet bed. Bedwetting alarm provides a very effective solution to this problem. The alarm will sound as soon as the child begins to wet the bed

Accurate Foot-Switch

Certain industrial controls require accurate switching operations. For example, in case of a foot- switch for precise drilling work, even a small error in switching may cause considerable loss. This low-cost but accurate foot-operated switch can prevent that

Remote Control using Wireless Doorbell 

This circuit lets you wirelessly control an appliance from a remote place by using a wireless doorbell. The appliance is triggered by the signal from the transmitter of the wireless doorbell and turns off automatically after the preset time period

Infrared Interruption Counter

Most optical interruption counters make use of a light bulb with light-dependent resistor (LDR) or ordinary phototransistor as the sensor. These interruption counters work satisfactorily in darkness only and cannot be used outdoors because of the chances of false counting due to light sensed from other light sources like sun, light bulb, etc.

IR sensors (infrared LEDs) to make an object-detection circuit

There are various applications of IR sensors such as TV remote controllers, burglar alarms and object counters. Here we have used IR sensors (infrared LEDs) to make an object-detection circuit and also a proximity sensor for path-tracking robots. The basic idea is to transmit the infrared light through an IR LED, which is then reflected by any obstacle ahead and sensed by the receiving LED

Temperature-Tolerance Checking System

Most of instruments and machines used in industries and research laboratories have a temperature-tolerance limit. These can neither be subjected to too high nor too low a temperature for their proper functioning. But they need to function accurately as they are always used in critical applications

Another circuit

(IRF)

infrared (IR) remote controller comprises the transmitter and receiver sections. The range of the transmitter can be increased up to 5 meter by using convex lens. 

Circuit Description of infrared (IR) remote controller Transmitter section: – The transmitter circuit of infrared (IR) remote controller is built around IC 741 (IC1) wired as frequency square wave oscillator. Gate pulse from pin no 6 of IC1 is given to gate of SCR1 to drive IR LED1. Variable resistor VR1 is used to vary the generated frequencies. Receiver Section: – The receiver circuit of infrared (IR) remote controller consist an IC 741, photo transistor (T1) and medium power transistor (T2).

   

PARTS LIST FOR THE ABOVE DIAGRAM

Resistors (all ¼-watt, ± 5% Carbon) 

R1,R2 = 100 KΩ; R3, R5, R8 = 1 KΩ; R4 = 15 Ω; R6 = 22 KΩ; R7 = 10 MΩ; VR1 = 1 MΩ; VR2 = 2.2 MΩ 

Capacitors 

C1, C3, C4 = 0.1 µF; C2 = 1 µF/100V; C5 = 2.2 µF/16V 

Semiconductors 

IC1, IC2 = 741; SCR1 = SN050; T1 = photo transistor; T2 = SL100; D1, D2 = 1N4001 Miscellaneous 

RL1 = 15V, 500Ω Relay; IR LED.

   Simple Key-Operated Gate Locking System

This simple key-operated gate locking system allows only those persons who know the preset code to open the gate. The code is to be entered from the keypad within the preset time to operate the motor fitted in the gate. If anyone trying to open the gate presses a wrong key in the keypad, the system is disabled and, at the same time, sounds an alarm to alert you of an unauthorised

Mains Box Heat Monitor

This simple circuit monitors the mains distribution box constantly and sounds an alarm when it senses a high temperature due to overheating, helping to prevent disasters caused by any sparking in the mains box due to short circuits. It also automatically switches on a bright white LED when the power fails. The LED gives ample light to check the mains box wiring or fuses in darkness. The circuit beeps once when power fails and again when power resumes

                         

  Faulty Car Indicator Alarm

Before taking a turn, either left or right, car drivers need to switch on the car turn indicator lamps so that the approaching vehicle drivers can take precaution accordingly. An accident is likely to occur in case your car turn indicator lamps fail to glow due to some reason or the other. Here is a circuit that sounds an alarm if your turn indicator lamps don't glow, helping you to safeguard against any acciden

1W LED For Automotive Applications

This simple circuit lets you run a 1W LED from the battery of your car. IC MC34063 is used here as a buck converter. It is a monolithic switching regulator sub-system intended for use as a DC-DC converter. The device consists of an internal temperature- compensated reference, a comparator, a controlled duty-cycle oscillator with an active current-limit circuit, a driver and a high-current output switch. These functions are contained in an 8-pin dual in-line package. Another major advantage of the switching regulator is that it allows increased application flexibility of the output voltag

  Play With Robotic Eye (IR Sensor)

There are various applications of IR sensors such as TV remote controllers, burglar alarms and object counters. Here we have used IR sensors (infrared LEDs) to make an object-detection circuit and also a proximity sensor for path-tracking robots. The basic idea is to transmit the infrared light through an IR LED, which is then reflected by any obstacle ahead and sensed by the receiving LED

Handy Tester

For beginners, here’s a low-cost multitester that can be used to test the condition of almost all the electronic components from resistors to ICs. It uses only a few components but can also detect polarity, continuity, logic states and activity of multivibrators

                   Very Useful Free Ebooks On Robotics And It's verious Aspects

1. http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1654&title+=+7+Free+eBooks+On+Instrumentation+Engineering&b_type=new&id=12665 
2. http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1655&title+=+5+Free+eBooks+On+Robust+Control&b_type=new&id=12666
3. http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1640&title+=+9+Free+eBook+On+Electromagnetics%21&b_type=new&id=12598 
4. http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1626&title+=+8+Free+eBooks+On+Assembly+And+Machine+Language+Programming&b_type=new&id=12569
5. http://www.efytimes.com/e1/fullnews.asp?edid=124581
6. http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1626&title+=+8+Free+eBooks+On+Assembly+And+Machine+Language+Programming&b_type=new&id=12569
7. http://www.efytimes.com/e1/fullnews.asp?edid=122400
8. http://www.efytimes.com/e1/fullnews.asp?edid=124022
9. http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1626&title+=+8+Free+eBooks+On+Assembly+And+Machine+Language+Programming&b_type=new&id=12569

                                                      REFERENCE

• http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1622&title+=+6+Free+eBooks+On+Microprocessors+And+System+Design&b_type=new&id=12581 
• http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1636&title+=+15+Free+eBooks+On+Hardware+Design+And+Architecture%21&b_type=new&id=12587 
• http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1640&title+=+9+Free+eBook+On+Electromagnetics%21&b_type=new&id=12598 
• http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=944&a rticle_type=1&id=821&tt=unhot&b_type=new 
• http://www.electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=2 27 
• http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1148&article_type=1&id=991&tt=hot&b_type=new 
• http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=1149&article_type=1&id=992
• 1.http://electronicsforu.com/newelectronics/lab/freecircuitslist.asp?id=1028 
• http://electronicsforu.com/newelectronics/lab/freecircuitslist.asp?id=1026 
• http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=896&article_type=1&id=738&tt=unhot&b_type=new 
• http://electronicsforu.com/electronicsforu/circuitarchives/view_article.asp?sno=892&article_type=1&id=741&tt=unhot&b_type=new 

Things to note before buying resistors...

---

Where & How to Buy Resistors: at the right price, type & quality                                       

Buying resistors may not always be as straightforward as it may seem at first sight - here are some ideas on getting the right product, at the right price, from the right place.

Resistors are needed in virtually every electronic circuit, whether in assemblies for mass production or for a one off for development of for the maker / hobbyist.

Resistors can determine many of the properties for the circuit, and also they are used in large quantities - mass production uses huge quantities.

Whatever the reason for their need, it is important to buy the right resistors and also for a good price. Also the source of supply can be important in some applications.

Accordingly, knowing where to buy resistors and also how best to buy them can present a challenge.

As with any decision, when buying resistors there are several issues to balance.

 Leaded   metal   film       

One of the crucial element of buying resistors is to choose the correct resistor. There are several types of resistor, each with their own advantages and disadvantages:

• Carbon composition:   These resistors are seldom used these days. They find two main uses: the first is for the restoration and repair of vintage radios where they were initially used: secondly carbon composition resistors are ideal for circuits where they need to absorb high transients. As they have a relatively large bulk, they can absorb high transients for short periods. As a result it is still possible to buy these resistors. However, for normal use these resistors are bulky, they have a tendency to vary in value and they generate considerable amounts of noise.                                                                                                                                                                                                                                                                                                                                                                                                                                            
• Carbon film:   Carbon film resistors were the next resistor development. They were much smaller and more stable. Although the noise level was not as high as that of carbon composition resistors, it was still higher than that of more modern resistors like the metal film resistor. It is still possible to buy carbon film resistors from most stockists and distributors.                                                                                                                                                                                                                                                                           
• Metal oxide film :   Metal oxide film resistors axial leaded resistors are made from a thin film of metal oxide that has been deposited into a ceramic rod. The resistor was considered as the successor to the carbon film resistor as its performance was superior but as the metal film resistor was introduced, with a superior level of performance to that of the metal oxide film resistor, its use declined.                                                                                                                                                                                                                                   
• Metal film:   Metal film resistors are the standard leaded format that is used these days. A variety of values and wattages are available. They are low noise and can be obtained to 1% or 2% as standard. Closer tolerance varieties are available.                                                                                                                                                                                                                                                                                                                                                   
• Surface mount resistors:   Surface mount resistors are used in vast quantities for volume manufacture.                                                                                                                                                                                                                                                                                                                                                             
• Wire wound resistors :   Wire wound resistors are typically used where higher power limits are required. Types are available that can be bolted to a chassis or heat sink to remove the heat. Sometimes they may also be used for very close tolerance applications in measuring instruments as they can be very closely trimmed to provide the required resistance, and they are also very stable.                                                                                                                                                                                                                      .. 

Resistor specifications & parameters

When buying resistors it is necessary to closely specify the required resistor. These may seem obvious but there may be a few hints and tips that can help get the most appropriate resistor - some specs to watch out for.

• Resistance value:   The resistance is the obvious specification, and possibly needs little extra explanation                                                                                                                                                                                                                                                                                                                                                  
• Tolerance:   Most resistors these days are manufactured to a high tolerance. Most components used for electronic circuits will have a tolerance of 1 or 2%. However beware of older types which may have a much wider tolerance on them.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
• Power handling:   Care needs to be taken when specifying the power handling. As current is passed through the resistor, heat is obviously dissipated and the temperature rises. They can run quite hot in some applications. As the temperature rises, so they can become less reliable in the long term, or even burn out in the short term. When choosing a resistor to buy for a given application calculate the power dissipation and run it well within its ratings. Many companies that design electronic equipment recommend running them at a maximum of 50 or 60% of their maximum rating. This gives a good margin and ensures the long term reliability is maintained.                                                                                                                                                                                                                                                                            
• Stray inductance:   For some RF applications it is necessary t think of the RF performance of the resistors. Surface mount resistors are good into the microwave region as the fact that they do not have leads and they are small means they have very low levels of inductance. Metal film leaded resistors are OK up to VHF and UHF, but wirewound ones are normally to be avoided above 100kHz or so. There are some specially wound forms of wirewound resistor that have lower levels of inductance, but normally this type should be avoided for RF.                                                                                                                                                                                                                                                                                                                                                                                                                               
• Surge handling :   In some applications it may be necessary for resistors to be able to handle short transient voltage spikes. The old carbon composition resistors are still used for this as they have a large thermal mass and can tolerate the spikes, even if other elements of their performance are not what might be expected these days.                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
• Maximum working voltage:   One element of a resistor specification that may be important when buying resistors for some applications is the maximum working voltage. Today, many resistors only operate at low voltage and therefore this is not an issue, but for others it may be. For higher voltage applications, check on the datasheets whether the voltage expected is within the limits for the resistor. It is wise to have a good margin for this.                                                                                                                                                                                                                                                                                                          

Supplier / distributor choice

In some applications the supplier or distributor of the components is important. For many maker, hobbyist and students, cost and short delivery are two of the key issues and many suppliers are acceptable. For other commercial organisations there may be other issues to consider.

• Timescales:   It is often necessary to consider the timescales when selecting who to buy resistors from. Some suppliers of distributors may be able to deliver very quickly or on a required date. and this is an advantage in many instances
• Cost:   Cost is a major consideration when buying resistors. Particaultly for private individuals this may be one of the most important considerations. Normally quality is good, but this needs to be taken into account especially when prices are low. Normally though quality is very good.
• Wide availability:   In some instances a wide availability of stock is needed and this may be a reason for picking a particular stockist or distributor.
• Traceable stock:  
• Ship to stock: