Engineers Garage

In embedded systems, a simple function rarely exists alone. A simple pushbutton and LEDs controller is useful but if that controller cannot report when a user has pressed a button or share the status its LED indicate, the controllers are not worth their value. Many embedded systems include peripheral devices connected to the microprocessor in…

In this article I will explain a very basic circuit of Clipper using simple components. Clipping circuit is a wave-shaping circuit and is used to either remove or clip a portion of the applied wave in order to control the shape of the output waveform.One of the most basic clipping circuits is the half-wave rectifier. A half-wave rectifier clips either the negative half cycle or the positive half cycle of an alternating waveform, and allows passing of only one half cycle.

This power saving circuit is used to save electricity while ironing. The circuit will switch OFF the iron box when it is not in use. Once the ON time of the circuit is crossed, it will produce an alarm. If we press the Reset button at the time of alarm it will turned OFF the alarm and extend the ON time of the circuit to the next 4 minutes. This circuit will work as a reminder for those who always forget to turn OFF the iron box in this day to day busy life.In this circuit is build around NE 555(IC1), op-amp LM 358 (IC2) and few components. IC1 is designed as a standard monostable multivibrator and its trigger pin 2 is held high by resistor R1.LM 358 is configured as a comparator. Its non-inverting input (pin 3) and the inverting input (pin 2). Inverting pin 2 of IC2 is connected to voltage-divider preset VR1. Using preset VR1 we can vary the reference voltage at pin 2. Buzzer is connected to the output pin 1. Initially output pin 1 of IC2 is low.

The basic aim of this project is to transmit electric power wirelessly.Wireless Power Transfer (WPT) or wireless energy transmission is the transmission of electrical power from a power source to a consuming device without using solid wires or conductors. Wireless transmission is useful to power electrical devices in cases where interconnecting wires are inconvenient, hazardous, or are not possible.

Generally a 12V battery is expected to produce a 12V dc voltage all the time until it gets discharged. Practically, it is not possible and the output voltage of the battery decreases gradually as load connected to it draws current from it. So it is generally considered that if the output voltage of a 12V battery changes from 12V to 9V approximately, it is constant and after the voltage falls below 9V, it is considered to be discharged and need to be charged again. Any inverter designed to use with a 12V battery should be comfortable to produce a constant AC output voltage during the fall of battery voltage from 12V to 9v approximately. My point to say all these is that to monitor a 12V battery, it is sufficient to monitor the battery voltage from 12V to 9V range and a voltage below 9V should give a warning for LOW BATTERY VOLTAGE. Here for the development of the circuit, the 12V to 9V range is divided into 6 parts as 9V, 9.5V, 10V…11.5V. So 6 op amps are used to compare and display the appropriate level of voltage. The circuit is simple. Comparison is done between the two terminals of each op amp and accordingly output is shown. The series of resistors connected at the inverting terminals of each op amp makes a voltage divider and exact comparing voltage is supplied to each op amp.

TRIAC i.e. Triode for Alternating Current is a three terminal semiconductor device for controlling current. The TRIAC is an ideal device to be used for AC switching applications because it can control the current flow over both halves of an alternating cycle. The bi-directionality makes TRIACs very convenient switches for alternating current circuits, also allowing them to control very large power flows with milliampere-scale gate currents. It is possible to view the operation of a TRIAC in terms of two thyristors placed back to back.

There are different techniques to control speed of AC motor. One of the very popular of them is by applying chopped AC waveform – means changing phase angle of applied AC waveform. This method is used in many different devices likeThe firing angle of a thyristor like TRIAC – that gives supply to motor, is delayed to decrease the motor speed or it is fired earlier to increase motor speed. As firing angle is changed, the part of AC waveform applied to motor is chopped more or less. So the average AC voltage applied to motor changes – that changes speed of motor.

The circuit presented here operates a relay for Fixed Timer Interval. So the device or machine connected with relay operates for same time. The device once switched ON, automatically switches OFF after Fixed (set) Time Interval when relay switches OFF. The Time Interval can be varied and it is displayed on 7 Segment Display. This kind of circuits can be used in many applications where it is required to operate any device or machine for Fixed Time Interval. Like·         The Alarm Signal (or Bell) once triggered, remains ON for Fixed Time Interval and then shuts off automatically·         In Manufacturing Industries the Motors have to be rotated for Fixed Time Interval once start button is pressed. It stops automatically when time period is overTime operated relay circuit is build using IC555. To display the time period in seconds 2-digit decade counter is build using CD4026 chip. Another IC555 is used to provide 1 Hz pulse to update time period after every 1 sec.

Children like to watch cartoons movies or any other their favourite show  on the television and do not pay attention on their studies even at the time of examination.  So to keep eye on children we have design a parental control device. When the children in your home hold the remote of the television to on the TV or want to change channel and press any button of the remote then a loud sound would be generated by the device. And these will let you know that your child has  tried to switch on the TV. The main advantage of these circuit is that you can easily do your work without any trouble as it produces loud noise so you can hear the noise while working in the kitchen or while sitting in the nearby room.

The circuit presented here is used to transmit and receive low frequency pulses using IR modulator and demodulator. IR modulator takes low frequency pulses as input. It modulates them on 38 KHz carrier and transmits them through IR LED as 38 KHz IR light. On the demodulator side IR sensor detects (receives) 38 KHz IR light. It demodulates this 38 KHz pulses and recovers transmitted low frequency pulses. One pulse generator is built using IC555 to generate low frequency pulses. IR modulator is also built using IC555 and TSOP1738 IR sensor is used as IR demodulator. 

This is a very easy circuit . This can be employed in automobiles as a sequential indicate light. This circuit is constructed with the help of two ICs first one is a CMOS timer IC i.e. 555 timer and another one is the decade counter IC i.e. CD4017. In this circuit astable mode of the 555 timer IC is been used to trigger the counter. Also few other discrete components are used in the circuit. 

Our governement has made rules that at night times if any vehicle is approaching from opposite side headlights of our vehicle should be dimmed to avoid focusing of . light on the driver in opposite vehicle inorder to avoid accidents . But, we ignore this which is cause for many accidents at night times. 

The circuit which is shown here is too easy circuit. In this circuit IC1 is mounted in a unusual mode. At the time when power resumes, pin 2 of IC1 which is through capacitor C1 is grounded goes low and pin 3 of same IC switches to high. In turn of this pin 4 of IC1 which is a reset pin switches to high state for approximately 10 seconds. When the voltage at C1 reaches to 2/3 of the supplied voltage, capacitor starts discharging and output switches to low, grounding the pin 4 which is a reset pin and hence the fell circuit move out of action.

Ever wondered how those crunch sounds come from the guitars of modern day Rock gods. Well, the answer to this is electronics. So let us go through the history of this “rock” sound. When electric guitars were invented, amplifiers in those days were tube amplifier which unlike today’s amplifiers used triodes or tube valve instead of transistors to amplify signal. The amplifiers in those days were big and bulk. And when they were played at full volume, they produce a “distorted” sound because the guitar signal got too amplified and hence clipped. The great guitarist Jimi Hendrix was the first guitarist to recognise that guitar and the amplifier together can be used as an instrument and started using this distorted sound to produce music. Thus rock music was invented.But tube amplifiers were unreliable, consumed lot of power and were expensive. Thus electronic engineers started to develop circuits which produced the same effect as a fully driven tube amp but were a lot smaller, effective and reliable. This gave birth to distortion pedals with transistors.

555 timer IC is highly used IC in the projects as it is low in price as well as provide high performance. You can find large number of projects on the internet made up of using 555 timer. Here is another simple project made with the help of 555 timer which can offer you hour of enjoyment.The project is made with the help of NE555 timer along with support of some other discrete components. The project which is shown here is clearly a triggering circuit and with the support of variable resistor VR1 in the project timing is adjusted.

Controller is actually a combination of two circuits – driver circuit and Switching circuit. Driver is the actual circuit that drives DC motor and switching circuit decides how DC motor should be driven. So actually, switching circuit is the main circuit that controls the motor. Now there are two parameters of DC motor that can be controlled Speed and Direction.Changing the direction of DC motor is very simple just reverse the supply given to DC motor. For varying speed of motor you have to vary the applied DC voltage. One well known method widely used in industries is Pulse Width Modulated (PWM) speed control of DC motor also known as chopper control.

These circuit cost too less to your pocket as it made up of NE555 IC, buzzer , some resistors and capacitors. These circuit is also a user friendly. As with the help of just by one button pressing you will let other that you are in panicking condition without any difficulty.In these project astable mode of IC NE555 is used. Resistor R1 and R2 along with capacitor C2 used in the circuit so to tune the frequency. In the starting the circuit remain in the disable state. Now when the button is pressed the pin 4 and pin 8 of IC1 gets the high voltage. In turn of these the voltage at pin 2 goes down gradually and voltage at pin 3 starts increased in the same manner. And a situation arrives when the sound comes out from the buzzer. 

Fastest Finger first circuit is basically used in quiz type games where the reaction speed of a participant is significant. The circuit enables us to identify who responded first to the question by triggering a visual and audio indication. The circuit uses a buzzer to produce the audio signal and a seven segment display for visual indication. The display shows the corresponding team number which pressed the buzzer first. The brain of this circuit is an ATMega16 microcontroller which can run at a maximum speed of 16MHz and so there will be no question of clash between any two contestants until and unless their reaction time was same in order of microseconds which is impossible. Continue reading to find out what the circuit components are and how it is assembled as well as put to work.

This circuit will light up different LED’s according to the audio signals which are feed through condenser microphone. When sound intensity is low few LED’s will glow as intensity of sound increases number of LED’s which glow also increases. Important feature of this circuit is we have not use any special running light IC like LB1405. We have made this circuit with the help of seven channel Darlington array IC ULN2003. ULN2003 is a monolithic high voltage and current Darlington transistor array. It contains seven NPN Darlington pair on a single IC. It also have high output voltage with common cathode clamp diode for switching inductive load. And collector current rating of each Darlington pair is 500mA.  Another feature of ULN2003 IC it has 2.7kW series base resistor for each Darlington pair so that it can directly connected to TTL or 5V CMOS device. Read more to find out how this circuit is assembled and how it is made to work.