The document describes a digital analog audio synthesizer project created by three students. The goal was to build an affordable synthesizer using both digital and analog circuits. A microcontroller was used to digitally generate waveforms, which were then sent through analog modulation circuits. Key aspects included affordability, reprogrammability, and customization. The biggest problem encountered was interfacing the keyboard. The synthesizer design included digital oscillators, analog low frequency oscillator, filters, envelope generator, and other circuits. It stayed within budget and provided students experience with both analog and digital circuits.
ELECTRONICS PROJECT REPORT OF HOME AUTOMATION CUM BUILDING SECUIRITYEldhose George
This document summarizes a home security and automation system that uses an intruder detection system and cameras for security, and controls lights, garden watering, and a water pump for automation. The security section uses IR sensors and cameras to detect intruders and monitor areas. The automation section controls lights, garden watering using a solenoid valve, and a water pump for an overhead tank. The system is controlled by a microcontroller and includes circuits for sensors, cameras, relays, and a power supply.
The document describes 70V paging systems and their components. 70V systems use a centralized amplifier with a 70V output to power speakers connected via long runs of wire. This high voltage, low current design minimizes power loss over the wires. The document discusses the benefits of 70V systems and explains their basic design and components, such as the centralized amplifier, speakers, taps, and interface devices. It also covers an alternative self-amplified paging system design that uses individual amplifiers built into each speaker powered by a 24V DC supply.
This document describes a home automation system that allows control of appliances like lights and fans from an Android mobile phone using Bluetooth. The system uses an 8-bit microcontroller with Bluetooth module to wirelessly communicate with the mobile phone. Home appliances are connected to the microcontroller board, which receives on/off commands from a mobile app to control the appliances. Feedback is provided on the device status by lighting LEDs on the microcontroller board. The system provides a low-cost way to automate home devices using a mobile phone over Bluetooth wireless technology.
Automatic Control of Instruments Using Efficient Speech Recognition AlgorithmIJEEE
Matlab straight forward programming interface make it an ideal tool for Hindi Key word Recognition. For the extraction of the feature, Hindi Key word database has been designed by using the Matlab 7.5. The database consists of the eight key words.
Automatic doorbell with object detectionAnurag Alaria
This document describes an automatic doorbell system that uses ultrasonic sensors to detect movement and ring a doorbell. It provides details on the components and circuit design of the transmitter and receiver modules that use ultrasonic waves to detect a person. The system is intended to automatically sense someone's presence and ring the doorbell, saving time and enhancing security compared to a traditional doorbell. The document includes circuit diagrams and descriptions of the main integrated circuits used, including the IC 555 timer and LM324 op-amp. It provides specifications and characteristics for the transistors and other components in the design.
This document describes a home automation project using an Arduino UNO board and a TV remote control. A single remote control is used to operate four appliances or loads connected to a 4-channel relay board. The TSOP1738 IR receiver receives signals from the remote and sends the data to the Arduino. An IRremote library decodes the signals from the numeric keys and power button on the remote. The Arduino then controls the relay board to turn the loads on and off based on the remote control buttons pressed.
Bluetooth Controlled High Power Audio Amplifier- Final PresentaionSagar Mali
This document describes a Bluetooth controlled high power audio amplifier project. The project uses an 8051 microcontroller to control tone, effects, and volume digitally over Bluetooth. The amplifier circuit includes a power supply, preamplifier, digital volume and tone control, power amplifier, Bluetooth module, and microcontroller board. The microcontroller code controls the system and allows interfacing via a computer or Android application over Bluetooth. The project aims to build a cost-effective high power amplifier while gaining experience with microcontrollers and circuit design.
Development of a Low Cost, Reliable & Scalable Home Automation System.imtiyazEEE
The slide is based on construction of a home automation system that will remotely switch ON/OFF any household, industrial or official appliances connected to it, using Arduino UNO, application on a smartphone and visual status of the loads for the feedback.
ELECTRONICS PROJECT REPORT OF HOME AUTOMATION CUM BUILDING SECUIRITYEldhose George
This document summarizes a home security and automation system that uses an intruder detection system and cameras for security, and controls lights, garden watering, and a water pump for automation. The security section uses IR sensors and cameras to detect intruders and monitor areas. The automation section controls lights, garden watering using a solenoid valve, and a water pump for an overhead tank. The system is controlled by a microcontroller and includes circuits for sensors, cameras, relays, and a power supply.
The document describes 70V paging systems and their components. 70V systems use a centralized amplifier with a 70V output to power speakers connected via long runs of wire. This high voltage, low current design minimizes power loss over the wires. The document discusses the benefits of 70V systems and explains their basic design and components, such as the centralized amplifier, speakers, taps, and interface devices. It also covers an alternative self-amplified paging system design that uses individual amplifiers built into each speaker powered by a 24V DC supply.
This document describes a home automation system that allows control of appliances like lights and fans from an Android mobile phone using Bluetooth. The system uses an 8-bit microcontroller with Bluetooth module to wirelessly communicate with the mobile phone. Home appliances are connected to the microcontroller board, which receives on/off commands from a mobile app to control the appliances. Feedback is provided on the device status by lighting LEDs on the microcontroller board. The system provides a low-cost way to automate home devices using a mobile phone over Bluetooth wireless technology.
Automatic Control of Instruments Using Efficient Speech Recognition AlgorithmIJEEE
Matlab straight forward programming interface make it an ideal tool for Hindi Key word Recognition. For the extraction of the feature, Hindi Key word database has been designed by using the Matlab 7.5. The database consists of the eight key words.
Automatic doorbell with object detectionAnurag Alaria
This document describes an automatic doorbell system that uses ultrasonic sensors to detect movement and ring a doorbell. It provides details on the components and circuit design of the transmitter and receiver modules that use ultrasonic waves to detect a person. The system is intended to automatically sense someone's presence and ring the doorbell, saving time and enhancing security compared to a traditional doorbell. The document includes circuit diagrams and descriptions of the main integrated circuits used, including the IC 555 timer and LM324 op-amp. It provides specifications and characteristics for the transistors and other components in the design.
This document describes a home automation project using an Arduino UNO board and a TV remote control. A single remote control is used to operate four appliances or loads connected to a 4-channel relay board. The TSOP1738 IR receiver receives signals from the remote and sends the data to the Arduino. An IRremote library decodes the signals from the numeric keys and power button on the remote. The Arduino then controls the relay board to turn the loads on and off based on the remote control buttons pressed.
Bluetooth Controlled High Power Audio Amplifier- Final PresentaionSagar Mali
This document describes a Bluetooth controlled high power audio amplifier project. The project uses an 8051 microcontroller to control tone, effects, and volume digitally over Bluetooth. The amplifier circuit includes a power supply, preamplifier, digital volume and tone control, power amplifier, Bluetooth module, and microcontroller board. The microcontroller code controls the system and allows interfacing via a computer or Android application over Bluetooth. The project aims to build a cost-effective high power amplifier while gaining experience with microcontrollers and circuit design.
Development of a Low Cost, Reliable & Scalable Home Automation System.imtiyazEEE
The slide is based on construction of a home automation system that will remotely switch ON/OFF any household, industrial or official appliances connected to it, using Arduino UNO, application on a smartphone and visual status of the loads for the feedback.
Adding Remote Controller Functionality To Any StereoEditor IJCATR
Use of stereo has become common in our lives. They are used in cars, TVs, music players etc. And it is essential at least to control their volumes. Suppose there is a stereo amplifier which functions pretty well but it does not have a remote. It would be very annoying if its volume cannot be controlled. So this project is useful as it creates a device which makes use of any existing remote to control the volume. For controlling the volume, we use a volume controller IC. The electronic volume controller IC PT2258 is a digital potentiometer which can be controlled using I2C protocols. It is used to control the attenuation for every combination possible from 0 to -79 dB/step. Universal IR receiver is used to decode the IR codes and the data will be transferred to the Arduino which in turn communicates with the IC PT2258 and controls the volume. The device also consists of two buttons, which are used to synchronize the IR code of the existing remote with the device. So the user will be able to use the device easily.
The document describes the design and implementation of a low-cost wireless home automation system controlled by a smartphone. It discusses:
1) The objectives of designing a cost-effective home automation system using an Arduino and Bluetooth module to control appliances via a smartphone, aimed to help the elderly and handicapped.
2) The experimental setup including components like the Arduino, Bluetooth module, relay board, and smartphone app. Flow charts and diagrams illustrate the system design and operation.
3) Testing results showing the system successfully controlled lights and fans wirelessly via an Android app as intended.
This Presentation is developed by Abhishek Jaiswal(Robotics Workshop Trainer).
It Contains information about Robotics & Automation along with Arduino Understanding. This ppt also has some discussions about Sensors.
Learn from basics and develop till advance.
Cell Phone Controlled Home Automation System using DTMF TechnologyTaufique Sekh
This home appliances control or home automation project uses DTMF decoder circuit to control home and office electrical appliances. Just connect your cell phone headset (headphone) jack to the mobile phone and then mobile will control electrical appliances and electrical equipment through the DTMF key pad of your cell phone. Here for demonstrating, we are controlling an electrical bulb using this circuit project but you can extend this circuit to control many electrical devices with some modifications using4×16 decoder IC.
This project is called ‘Voice Controlled Home Automation project using Arduino’
which enables a user to control the home appliances through voice commands sent to
an Android app i.e AMR voice app.
This document provides an overview and introduction to a digital home automation project using Arduino and Bluetooth. The project aims to develop a home automation system that allows appliances to be remotely controlled via an Android smartphone application. Key components include an Arduino Uno microcontroller, HC-05 Bluetooth module, relays, and an Android app. The system allows electrical appliances like lights and fans to be switched on or off from a smartphone. The Arduino code controls the relays based on commands received over Bluetooth from the Android app.
This document describes a smart door knocker device that uses an Arduino, piezoelectric sensor, servo motor, and other components. The piezoelectric sensor detects knock signals which are processed by the Arduino microcontroller. The microcontroller then actuates the servo motor to unlock the door if the knock signal matches a programmed pattern, allowing authorized users to enter. The document outlines the components, wiring diagrams, programming process, and some troubleshooting for the smart door knocker system.
This document describes a voice-controlled home appliance system using a microcontroller. An Android application sends voice commands via Bluetooth to the microcontroller, which then operates devices like lights and appliances through TRIACs and opto-isolators. The system allows users to remotely control home appliances just by using voice commands from a smartphone, providing convenience and accessibility.
Smart home automation using microcontrollerR.RAJA SHARMA
This document discusses a smart home automation system using a microcontroller. It uses various sensors like a temperature sensor, PIR sensor, ultrasonic sensor, water flow sensor and LDR connected to an Arduino Uno microcontroller. The sensors monitor temperature, detect motion, measure distance, detect water flow and light levels. The Arduino controls and automates home devices and appliances based on sensor readings. It can also connect to a server and mobile through GSM or ethernet for remote monitoring and control of the smart home system.
The presentation discusses designing a home automation system using Arduino that allows controlling electrical appliances like lights and fans via a smartphone. It aims to create a low-cost, user-friendly system especially for elderly and disabled users. The system uses an Arduino board, Bluetooth module, relay board and smartphone app to wirelessly control connected devices. Experimental tests showed the prototype system was effective with satisfactory performance at low cost.
Home Automation System using Arduino and AndroidMuhammad Ayesh
This document provides an overview of a graduation project for a home automation system using Arduino and Android. The system allows a user to control home appliances like garage doors, fans, lights, and water pumps using a smartphone. It discusses the hardware and software components used to implement the system. Key hardware includes sensors for temperature, light, motion, and water level. Motors are used to control appliances. The system is controlled with an Arduino microcontroller and an Android smartphone app. Network connectivity is provided through WiFi to allow remote control via the phone. The document outlines the system design and provides details on implementation, user guide, and future work.
Bluetooth based home appliances controlPROJECTRONICS
This document describes a Bluetooth-based home appliance control system that allows appliances to be operated remotely using a Bluetooth-enabled device like a smartphone. The system uses a microcontroller interfaced with a Bluetooth module to receive commands from a mobile app and control electrical loads accordingly. It consists of a power supply, DTMF decoder to receive signals from Bluetooth, motor driver, solid state relays, and other circuits. The system was designed and tested successfully in the lab to allow remote control of appliances in a way that helps elderly or disabled people. Potential future expansions are also discussed.
This section introduces the basic acoustic resources available on the Music Easel's front panel. It begins with a simple patch using the complex oscillator connected to Gate 1, which can act as a filter or VCA. Signals are then sent to the output section for mixing and effects before monitoring. Additional oscillators and modulation will be covered to expand the instrument's sonic palette.
Raspberry Pi controlled Home AutomationRaiz Maharjan
A project report of Home Automation that allows users to remotely control home appliances using android app, also equipped with live streaming feature.
Home Automation Using Arduino Uno and HC-05Vidhi Shah
Controlling the DC motor (as fan) and Light bulb through HC-05 bluetooth module using the bluetooth terminal app from available on play store. The report attached herewith have a detailed description of the Circuit and the code. Interested ones can do further editings also:)
Students will be able to understand about the various types of signal processors.
Students will be able to choose the signal processors according to the need in studio or live applications.
Students will know about the characteristics of signal processors.
The Handheld Satcom Test Source by WORK Microwave is a portable signal generator capable of producing precise reference signals between 50-180 MHz and 950-2150 MHz. It can be used to test high-frequency converters by generating two signals to measure intermodulation distortion. It is also well-suited for calibrating other test equipment like spectrum analyzers due to its adjustable power levels and ability to store settings internally. Testing confirmed it provides accurate readings when used to verify the measurements of a Deviser S7000 TV analyzer.
The Handheld Satcom Test Source by WORK Microwave allows for precise and certified high-frequency measurements. It can generate signals from 50-180 MHz and 950-2150 MHz with adjustable power levels. It has two independent synthesizers, allowing it to output two signals simultaneously to measure intermodulation distortion. Its rechargeable battery and internal storage of test parameters make it portable and easy to use. The document demonstrates how the Test Source is used to measure parameters of RF converters and calibrate test equipment like the Deviser S7000 TV analyzer, confirming its ability to perform accurate high-frequency measurements.
The document summarizes a test signal generator produced by WORK Microwave called the Handheld Satcom Test Source. It can generate signals from 50-180 MHz and 950-2150 MHz with adjustable power levels and is used to test high-frequency converters and measure intermodulation signals and compression points. The generator has two independent synthesizers, rechargeable batteries, and connects to a computer via USB to control sweeps and measurements through easy-to-use software. It provides a robust and portable solution for precision high-frequency testing.
Adding Remote Controller Functionality To Any StereoEditor IJCATR
Use of stereo has become common in our lives. They are used in cars, TVs, music players etc. And it is essential at least to control their volumes. Suppose there is a stereo amplifier which functions pretty well but it does not have a remote. It would be very annoying if its volume cannot be controlled. So this project is useful as it creates a device which makes use of any existing remote to control the volume. For controlling the volume, we use a volume controller IC. The electronic volume controller IC PT2258 is a digital potentiometer which can be controlled using I2C protocols. It is used to control the attenuation for every combination possible from 0 to -79 dB/step. Universal IR receiver is used to decode the IR codes and the data will be transferred to the Arduino which in turn communicates with the IC PT2258 and controls the volume. The device also consists of two buttons, which are used to synchronize the IR code of the existing remote with the device. So the user will be able to use the device easily.
The document describes the design and implementation of a low-cost wireless home automation system controlled by a smartphone. It discusses:
1) The objectives of designing a cost-effective home automation system using an Arduino and Bluetooth module to control appliances via a smartphone, aimed to help the elderly and handicapped.
2) The experimental setup including components like the Arduino, Bluetooth module, relay board, and smartphone app. Flow charts and diagrams illustrate the system design and operation.
3) Testing results showing the system successfully controlled lights and fans wirelessly via an Android app as intended.
This Presentation is developed by Abhishek Jaiswal(Robotics Workshop Trainer).
It Contains information about Robotics & Automation along with Arduino Understanding. This ppt also has some discussions about Sensors.
Learn from basics and develop till advance.
Cell Phone Controlled Home Automation System using DTMF TechnologyTaufique Sekh
This home appliances control or home automation project uses DTMF decoder circuit to control home and office electrical appliances. Just connect your cell phone headset (headphone) jack to the mobile phone and then mobile will control electrical appliances and electrical equipment through the DTMF key pad of your cell phone. Here for demonstrating, we are controlling an electrical bulb using this circuit project but you can extend this circuit to control many electrical devices with some modifications using4×16 decoder IC.
This project is called ‘Voice Controlled Home Automation project using Arduino’
which enables a user to control the home appliances through voice commands sent to
an Android app i.e AMR voice app.
This document provides an overview and introduction to a digital home automation project using Arduino and Bluetooth. The project aims to develop a home automation system that allows appliances to be remotely controlled via an Android smartphone application. Key components include an Arduino Uno microcontroller, HC-05 Bluetooth module, relays, and an Android app. The system allows electrical appliances like lights and fans to be switched on or off from a smartphone. The Arduino code controls the relays based on commands received over Bluetooth from the Android app.
This document describes a smart door knocker device that uses an Arduino, piezoelectric sensor, servo motor, and other components. The piezoelectric sensor detects knock signals which are processed by the Arduino microcontroller. The microcontroller then actuates the servo motor to unlock the door if the knock signal matches a programmed pattern, allowing authorized users to enter. The document outlines the components, wiring diagrams, programming process, and some troubleshooting for the smart door knocker system.
This document describes a voice-controlled home appliance system using a microcontroller. An Android application sends voice commands via Bluetooth to the microcontroller, which then operates devices like lights and appliances through TRIACs and opto-isolators. The system allows users to remotely control home appliances just by using voice commands from a smartphone, providing convenience and accessibility.
Smart home automation using microcontrollerR.RAJA SHARMA
This document discusses a smart home automation system using a microcontroller. It uses various sensors like a temperature sensor, PIR sensor, ultrasonic sensor, water flow sensor and LDR connected to an Arduino Uno microcontroller. The sensors monitor temperature, detect motion, measure distance, detect water flow and light levels. The Arduino controls and automates home devices and appliances based on sensor readings. It can also connect to a server and mobile through GSM or ethernet for remote monitoring and control of the smart home system.
The presentation discusses designing a home automation system using Arduino that allows controlling electrical appliances like lights and fans via a smartphone. It aims to create a low-cost, user-friendly system especially for elderly and disabled users. The system uses an Arduino board, Bluetooth module, relay board and smartphone app to wirelessly control connected devices. Experimental tests showed the prototype system was effective with satisfactory performance at low cost.
Home Automation System using Arduino and AndroidMuhammad Ayesh
This document provides an overview of a graduation project for a home automation system using Arduino and Android. The system allows a user to control home appliances like garage doors, fans, lights, and water pumps using a smartphone. It discusses the hardware and software components used to implement the system. Key hardware includes sensors for temperature, light, motion, and water level. Motors are used to control appliances. The system is controlled with an Arduino microcontroller and an Android smartphone app. Network connectivity is provided through WiFi to allow remote control via the phone. The document outlines the system design and provides details on implementation, user guide, and future work.
Bluetooth based home appliances controlPROJECTRONICS
This document describes a Bluetooth-based home appliance control system that allows appliances to be operated remotely using a Bluetooth-enabled device like a smartphone. The system uses a microcontroller interfaced with a Bluetooth module to receive commands from a mobile app and control electrical loads accordingly. It consists of a power supply, DTMF decoder to receive signals from Bluetooth, motor driver, solid state relays, and other circuits. The system was designed and tested successfully in the lab to allow remote control of appliances in a way that helps elderly or disabled people. Potential future expansions are also discussed.
This section introduces the basic acoustic resources available on the Music Easel's front panel. It begins with a simple patch using the complex oscillator connected to Gate 1, which can act as a filter or VCA. Signals are then sent to the output section for mixing and effects before monitoring. Additional oscillators and modulation will be covered to expand the instrument's sonic palette.
Raspberry Pi controlled Home AutomationRaiz Maharjan
A project report of Home Automation that allows users to remotely control home appliances using android app, also equipped with live streaming feature.
Home Automation Using Arduino Uno and HC-05Vidhi Shah
Controlling the DC motor (as fan) and Light bulb through HC-05 bluetooth module using the bluetooth terminal app from available on play store. The report attached herewith have a detailed description of the Circuit and the code. Interested ones can do further editings also:)
Students will be able to understand about the various types of signal processors.
Students will be able to choose the signal processors according to the need in studio or live applications.
Students will know about the characteristics of signal processors.
The Handheld Satcom Test Source by WORK Microwave is a portable signal generator capable of producing precise reference signals between 50-180 MHz and 950-2150 MHz. It can be used to test high-frequency converters by generating two signals to measure intermodulation distortion. It is also well-suited for calibrating other test equipment like spectrum analyzers due to its adjustable power levels and ability to store settings internally. Testing confirmed it provides accurate readings when used to verify the measurements of a Deviser S7000 TV analyzer.
The Handheld Satcom Test Source by WORK Microwave allows for precise and certified high-frequency measurements. It can generate signals from 50-180 MHz and 950-2150 MHz with adjustable power levels. It has two independent synthesizers, allowing it to output two signals simultaneously to measure intermodulation distortion. Its rechargeable battery and internal storage of test parameters make it portable and easy to use. The document demonstrates how the Test Source is used to measure parameters of RF converters and calibrate test equipment like the Deviser S7000 TV analyzer, confirming its ability to perform accurate high-frequency measurements.
The document summarizes a test signal generator produced by WORK Microwave called the Handheld Satcom Test Source. It can generate signals from 50-180 MHz and 950-2150 MHz with adjustable power levels and is used to test high-frequency converters and measure intermodulation signals and compression points. The generator has two independent synthesizers, rechargeable batteries, and connects to a computer via USB to control sweeps and measurements through easy-to-use software. It provides a robust and portable solution for precision high-frequency testing.
The document describes a handheld satellite communications test signal generator produced by WORK Microwave. It can generate signals from 50-180 MHz and 950-2150 MHz with precision and calibration certification. The generator allows for precise measurement of parameters for high-frequency converters like intermodulation and 1 dB compression point. It has two independent synthesizers, allowing it to output two signals simultaneously for testing. The generator was used to precisely calibrate a television signal analyzer, confirming its accuracy. It can also be used to test cable runs by sweeping signals and measuring attenuation characteristics.
IRJET- Smart Hand Gloves for Disable PeopleIRJET Journal
1) The document describes a smart glove prototype designed to help disabled people communicate through hand gestures.
2) The glove uses flex sensors on the fingers to detect hand gestures and an Arduino microcontroller to convert the gestures to text or pre-recorded voices.
3) The glove has three modes - displaying gesture status, converting gestures to voices, and controlling home appliances wirelessly through hand gestures.
This document summarizes the WORK Microwave Handheld Satcom Test Source signal generator. It can generate signals from 50-180 MHz and 950-2150 MHz with precision to serve as a reference for measuring complex analog systems. It has two independent synthesizers, allowing it to generate two signals simultaneously for measuring intermodulation of high-frequency converters. Its adjustable output power level from -45 to -5 dBm in 0.5 dB steps enables measuring the 1 dB compression point and conversion gain of converters. The portable generator can operate on its internal battery or via USB, making it a versatile testing device.
The document summarizes a test signal generator produced by WORK Microwave called the Handheld Satcom Test Source. It can generate signals from 50-180 MHz and 950-2150 MHz with precision and is used as a reference for calibrating equipment and testing high-frequency converters. The generator has two independent synthesizers allowing it to output two signals simultaneously for measuring intermodulation. It also allows adjustable power levels for testing parameters like 1 dB compression point and conversion gain of converters. The generator has a rechargeable battery, rugged aluminum housing, and connects to a PC for control via USB without needing additional drivers.
This document discusses sensors and transducers for IoT applications. It begins with defining transducers as devices that convert one physical quantity to another, especially converting a non-electrical quantity to an electrical signal. It classifies and describes different types of transducers and their characteristics. The document then discusses the role of sensors in IoT, including common sensor types used such as temperature, light, motion, and pressure sensors. It outlines how sensors collect environmental data to feed into IoT systems and networks.
The document describes a project to design an instrument that takes measurements from two sensors in a physics lab and calculates the power ratio between them in real-time. The design includes both analog and digital processing components. The analog portion performs a division of the sensor signals, while the digital portion handles data collection, display, and user interface functions using a microcontroller. Through testing, the designers found that software played a larger role than anticipated. While accurate for power meters, the design was not suitable for photon detectors due to their signal characteristics. With further optimization, the instrument could achieve greater accuracy.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research (IJCER) is dedicated to protecting personal information and will make every reasonable effort to handle collected information appropriately. All information collected, as well as related requests, will be handled as carefully and efficiently as possible in accordance with IJCER standards for integrity and objectivity.
The Handheld Satcom Test Source by WORK Microwave is a portable test signal generator designed for precise high-frequency measurements. It can generate signals from 50-180 MHz and 950-2150 MHz with adjustable power levels. The generator has two independent synthesizers allowing it to output two signals simultaneously for measuring intermodulation in high-frequency converters. Its portability and integrated rechargeable battery make it a versatile tool for testing satellite transmission equipment.
The document summarizes a test signal generator called the Handheld Satcom Test Source produced by WORK Microwave. It can generate signals from 50-180 MHz and 950-2150 MHz with precision, making it suitable for calibrating test equipment and measuring parameters of high-frequency converters. The generator has two independent synthesizers allowing it to supply two signals simultaneously for measuring intermodulation. It also allows flexible setting of output levels for measurements like compression point and conversion gain. The generator includes rechargeable batteries, software control, and integrates smoothly with Windows operating systems.
Handicapped Assistance Device for Controlling Electrical Appliances Jamuna R - Assistant Professor,
Abhinai S - UG scholar,
Jhananadhan SP - UG scholar,
Department of ECE,
SNS College of Engineering, Coimbatore, India
Design of an IOT based Online Monitoring Digital StethoscopeIJAAS Team
Acoustic stethoscopes have low sound levels. Digital stethoscope overcomes this issue by amplifying body sounds electronically. As the sound signals are transmitted electronically, it can be wireless and can provide noise reduction. Acoustic stethoscope can be changed into a digital stethoscope by inserting an electric capacity microphone onto its head. Heart sounds received from the microphone are processed, sampled and sound signals are converted analog to digital and sent wirelessly using the Internet of Things(IOT) techniques, so that multiple doctors can do auscultation and monitor conditions of the patient.
This document describes a digital glove system that translates sign language gestures into voice to enable communication between deaf/mute communities and others. The glove uses flex sensors that detect finger bending and sends signals to an Arduino Uno microcontroller. The Arduino compares the signals to pre-programmed gestures and outputs the corresponding word as text on an LCD display and audio from a speaker. The system was able to recognize 32 different words or phrases through unique finger bending patterns detected by the flex sensors. This digital glove provides a low-cost way to facilitate communication for deaf/mute individuals.
Li-Fi stands for Light-Fidelity. Li-Fi is transmission of data using visible light by sending data through an LED light bulb that varies in intensity faster than the human eye can follow. If the LED is on, the photo detector registers a binary one; otherwise it‟s a binary zero. The idea of Li-Fi was introduced by a German physicist, Harald Hass, which he also referred to as “Data
through Illumination”. The term Li-Fi was first used by Haas in his TED Global talk on Visible Light Communication. According to Hass, the light, which he referred to as „DLight‟, can be used to produce data rates higher than 1 Giga bits per second which is much faster than our average broadband connection.
This Project discusses the implementation of the most basic Li-Fi based system to
transmit Sound signal from one device to another through visible light. The purpose is to demonstrate only the working of the simplest model of Li-Fi with no major consideration about the data transfer speed. This model will demonstrate how the notion of one-way communication via visible light works, in which Light emitting diodes (LEDs) are employed as the light sources or Transmitter antennas. the sound is transferred by light and is detected at the receiver without fading.
This document describes the design and testing of a two station aircraft intercom circuit. The circuit uses a summing amplifier to mix audio inputs from the pilot and co-pilot microphones. An audio amplifier then amplifies the mixed signal for the headsets. A comparator circuit ensures the pilot can hear their own voice by comparing the microphone input to a threshold voltage. The author prototypes the circuit on a breadboard, then builds it on stripboard. Extensive testing of each component and the full circuit is described. The completed intercom unit is installed in an aluminum enclosure with controls.
1. EET 4110 SENIOR PROJECT II
__________________________________________________________
DIGITAL ANALOG AUDIO SYNTHESIZER
Ryan Halgren
Shaun Weston
Mindaugas Sanko
Spring 2015
Metropolitan State University of Denver
2. 1 | P a g e - S y n t h e s i z e r
TABLE OF CONTENTS
Executive Summary ..............................................................................................................................2-6
Introduction ...........................................................................................................................................2
Project goal ........................................................................................................................................ 2-3
Problems ................................................................................................................................................3
How it works ...................................................................................................................................... 3-4
Code .......................................................................................................................................................5
Circuits .............................................................................................................................................. 5-6
Conclusion .............................................................................................................................................6
Project Costs ............................................................................................................................................7
Project Plan .............................................................................................................................................8
Appendix ..................................................................................................................................................9
Arduino Code .................................................................................................................................. 9-12
Circuit Details and schematics ...................................................................................................... 12-18
Build and Assembly Pictures ......................................................................................................... 22-24
Resources ...............................................................................................................................................25
Data sheet links .....................................................................................................................................26
Executive Summary
3. 2 | P a g e - S y n t h e s i z e r
Introduction
A synthesizer is an electronic musical instrument that creates musical tones by generating electronic
signals. The generated waveforms can be converted into audible sound using a speaker or headphones.
Synthesizers can either imitate other instruments or generate new timbres that can only be made via
electronic circuitry. There are various methods to generate the signal and various methods to control the
signal as well. The main components of a synthesizer and their purpose are listed below:
1. The Oscillators, which generate the tones.
2. The LFO (Low Frequency Oscillator), which usually modulates either the frequency or gain of
the waveform generated by the oscillators.
3. The Filter, which emphasizes and/or removes certain frequencies.
4. The Envelope Generator, which controls changes in frequency or gain over the duration of the
note.
5. The Amplifier, which controls the overall gain of the synthesizer.
Today nearly all popular music involves a synthesizer and much of it uses the synthesizer as the lead
instrument or as the only instruments. Most genres of music preferred by the younger generations use
synthesizers as the main instrument and they have become the tool of choice for aspiring musicians.
Project goal
The purpose of this project was to build an affordable audio synthesizer that is composed of both
digital and analog circuits. As electrical engineering students we need to be viable in both the digital
and the analog curriculum. With the synthesizer, there are multiple ways in which the analog and
digital aspects can be implemented. For the digital side, we used a reprogrammable microcontroller to
generate the sound waveforms. Using code to design our signals allows for the type of synthesis and
the signals generated by the oscillators to be changed. From the digitally generated analog output of the
microcontroller, the waveform is sent through a series of analog circuits to modulate or augment the
waveform. These circuits include: Low Frequency Oscillator, State Variable Filter, Envelope Generator,
Ring Modulator, Voltage Controlled Amplifier and Bass Control. The signal will then be output to an
audio jack so it can be played through a speakers for the user to hear.
Key aspects that we aimed for in project proposal:
Affordability:
o We were able to stay in budget with spending under $175. We were able to accomplish
building a synthesizer design that is much more affordable to own or to build yourself.
Reprogrammable:
o We were able to use a microcontroller to provide the oscillations. The synthesizer is be
programmable, but the output pin need to be re-wired for some of the different kinds of
synthesis code. This makes it more user friendly for engineers than for the average user.
Customized for the user:
o The microcontroller can be reprogrammed and customized with a small amount of
rewiring. The analog circuits are fixed, but there is room in the enclosure for more
circuits and extra connection pins soldered onto the current circuit boards so that
4. 3 | P a g e - S y n t h e s i z e r
additional modulation circuits can be connected in the future. Also it can take an
external input signal from another synthesizer or instrument and modulate its sound with
the LFO, Filters etc.
Problems
The most difficult tasks and our biggest problem was interfacing the keyboard with the microcontroller
and ensuring that we were able to read all of the keys correctly with the number of analog read inputs
on available. We did not realize when we proposed this project how difficult it was to create a piano
style keyboard to control an electronic musical instrument. For now we have a potentiometer knob to
turn to different positions to control the note.
We wanted to use the Arduino Due for our microcontroller because It has a very high sampling rate,
512kbs of programming memory, a ton of ports and has a built in analog to digital converter so it can
generate a sound with code and give an actual analog output of that function. However, we
encountered issues with the Due that we did not foresee. We wanted the Due to allow frequency
changes when a note was being pressed, but the Due does not allow frequency changes in the input pins
and have a fixed value for each pin. This made us fall behind in building the key interface. To fix this
issue, we decided to go with an external keyboard known as the Midi keyboard. We were not able to
attach it for the presentation since we needed a part that has not arrived yet in order to attach a midi
keyboard. This would have allowed us to have a keyboard interface, but it would be an external plug in
instead of being attached with the synthesizer.
How it Works
The block diagram for our synthesizer design in Figure 1 below shows the parts of the synth and how
the circuits interconnect. The audio signal flow is shown by the black arrows and the orange arrows
represent control voltage signals.
For what we were able to get working by the end of the semester we simply have a potentiometer
connected to the 5 volt pin of the micro controller for our keyboard control voltage to determine the
note being played. From the Microcontroller output pin the signal goes through a basic Audio Amplifier
circuit with a small gain to boost the signal so that it will work correctly with the analog circuits. From
there it goes to the Ring Modulator, which is how the control voltage waveform from the Low
Frequency Oscillator modulates the sound. The LFO waveform is a sinusoidal signal with variable
shape and speed which controls the volume of the signal through amplitude modulation. After the Ring
Modulator the signal goes to the first Voltage Controlled Amplifier to allow the Envelope Generator to
shape and control the gain of the signal. The Envelope Generator is triggered by a voltage pulse from
the micro-controller or from a manual push button connected to the positive voltage rail. Once
triggered the Envelope Generator shapes the a voltage signal to have a rise and fall to it, instead of an
instantaneous change from low to high and high to low. The Voltage Controlled Amplifier allows this
voltage shape to control the rise and fall of the volume of the signal for each time the E.G. is triggered.
5. 4 | P a g e - S y n t h e s i z e r
Figure 1. Synthesizer Flow Chart
The next stage is the State Variable Filter, which allows the user to select and filter out certain
frequencies through High Pass, Low Pass and Band Pass filters. The Bass Volume Control circuit is
fairly simple, it just cuts or boosts the low frequencies (~300Hz and under). The final stage is another
Voltage Controlled Amplifier which reads the voltage through a potentiometer to control the overall
gain of the synthesizer sound.
Code (see Appendix for code and details)
The microcontroller can be reprogrammed with different types of oscillators but the output pins of the
micro controller have to be rewired when the code is changed. We have two versions of oscillator code.
One uses the Pulse Width Modulation output and can be used with most Arduino types. The second is
only compatible with the Arduino Due and uses the digital to analog converter output to generate
programmed waveforms.
Circuits (see Appendix for circuit details and schematics)
Audio Amplifier:
The Audio Amplifier circuit that we decided to use is a very simple amplifier with a gain of only 5 to
try to avoid noise. The design is based on the schematic given on the data sheet an IC. We changed the
value of select passive components to get the gain we desired.
6. 5 | P a g e - S y n t h e s i z e r
Low Frequency Oscillator:
The LFO signal is used as a periodic control to modulate other component’s value. Our LFO modulates
the amplitude of the signal via a four quadrant multiplier (ring modulator). Our LFO design has
multiple waveform outputs to select from including square, saw/triangle, pulse and parabolic. The three
adjustable parameters are speed, shape and mix. The speed is variable from 1Hz to 33Hz.
Ring Modulator:
Allows the Low Frequency Oscillator to control the amplitude of the signal through amplitude
modulation. We used a four quadrant multiplier rather than a two quadrant to eliminate the bleed
through of the LFO into the audio signal. This way the LFO signal is not heard, just the effect of the
LFO on the audio signal is heard.
Envelope generator:
The Envelope Generator is used to help shape the sound, a rise and fall in volume, of each note. The
general form of an envelope filter is an ADSR (Attack, Decay, Sustain, Release). This helps control the
time it takes for the note to rise to its peak volume, how long it will remain at its peak and how long it
will take to return to zero volume once the note is released. Our E.G. design implements the standard
ADSR form and can be triggered manually by a button for use with a continuous signal.
Attack time is the time taken for initial run-up of level from nil to peak, beginning when the key is
first pressed.
Decay time is the time taken for the subsequent run down from the attack level to the designated
sustain level.
Sustain level is the level during the main sequence of the sound's duration, until the key is
released.
Release time is the time taken for the level to decay from the sustain level to zero after the key is
released (2).
Voltage Controlled Amplifier:
The VCA allows a voltage (whether DC or AC signal) to control the gain of the signal being passed
through the amplifier. The effect is a similar sound to the Ring Mod and uses the same
transconductance amplifier input to control the signal. For our first VCA the E.G. creates the shaped
voltage ‘pulse’ to change the volume each time it is triggered. Our second VCA uses a variable DC
voltage to control the volume of the signal.
Filters:
The Type of filter that we decided to use for our synthesizer is a State Variable Filter. It is a cascaded
system which simultaneously outputs a High-Pass, Low-Pass and Band-Pass response using active
filters. We chose this type of design because it allows the operator to rather easily switch between filter
types. The typical design uses three or more operational amplifiers with a summing amplifier and two
integrators. The two resistors in the integrators must remain equal for the filters to vary the cutoff
frequencies in unison while maintaining a stable phase response. This is a very flexible system because
a second order response can be achieved with the HP and LP or a high gain can be achieved by the BP,
depending on the Q value. The cutoff frequency and Q value-(inverse of damping coefficient) are
7. 6 | P a g e - S y n t h e s i z e r
adjustable via two potentiometers. In musical terms adjustable Q value of a filter is known as resonance
of the filter.
Bass Volume Control:
The Bass Volume Control is a frequency selective circuit that give a positive or negative gain in
decibels (boost or cut) at frequencies of 300Hz or less. This controls the bass range of frequencies
without having any effect of the high or treble frequencies.
Power Supply:
We used a +15 volt DC power supply that takes the standard 120v @ 60Hz. We used some 12 volt
regulators to lower the output to +12 volts. We also had to add a load to the 5 volt output of the power
supply to draw current from the +15 volt outputs.
Keyboard & box enclosure: (see Appendix for circuit details)
The box enclosure for the synthesizer is made of oak and plywood. The wood is stained and finished
for a good look and feel. The 15 volt power supply mounted securely inside the wood enclosure with
the plug and switch exposed. The box has rubber feet screwed to the bottom so that it will sit securely
on any surface. 5/8 inch standoff were used to support the circuit boards inside the enclosure.
Conclusion
In completing this project we were able to meet all of the goals we set for ourselves in our senior 1
proposal except for the keyboard interface. We were able to build a reprogrammable musical
synthesizer with a digital oscillator and analog modulation circuits. We stayed under our predicted
budget and built a synthesizer with customizable features that is less than half the cost of any
synthesizer on the market.
As electrical engineering students, it is critical for us to know analog and digital circuits and how they
are inter connected. An audio synthesizer is an excellent project for students to gain experience
applying their knowledge of both circuit types. This project had us programming, designing analog
circuits, building circuits and soldering, building an enclosure box and interfacing with a
microcontroller. The variety, difficulty and amount of work made this project a great challenge.
Because this was a challenging project, we think it was one of the best learning experience of our
academic career. It was incredibly fun designing this synthesizer and we will be continuing to write
new versions of oscillator code and design additional circuits.
8. 7 | P a g e - S y n t h e s i z e r
Project Costs
Parts Quantity Cost per Part Total
LM13700 OTA 2 $2.00 $4.00
TL072 dual op-amp 7 $0.30 $2.10
TL074 quad op-amp 1 $0.40 $0.40
BC547 NPN transistor 5 $0.10 $0.50
7555 Timer 1 $0.45 $0.45
Capacitors (various values) 15 $0.30 $4.50
10K pot linear 2 $1.55 $3.10
100k pot Linear 3 $1.55 $4.65
50k pot linear 1 $1.55 $1.55
500k pot linear 1 $1.00 $1.00
10k pot Logarithmic 5 $0.50 $2.50
100k pot Logarithmic 2 $1.00 $2.00
1M pot Logarithmic 3 $1.00 $3.00
dual gang 10k pot Logarithmic 1 $2.50 $2.50
Resistors (various values) 52 $0.10 $5.20
1/4 inch Audio Jack 1 $2.00 $2.00
7812, 7912 (voltage Regulators) 3 $0.50 $1.50
Switches 3 $1.50 $4.50
Buttons 2 $1.50 $3.00
Ferrite Beads 2 $0.10 $0.20
4n35 Optocoupler 1 $0.50 $0.50
PCB's 2 $8.00 $16.00
+15 volt Power Supply 1 $5.00 $5.00
Arduino Due 1 $50.00 $50.00
Programming Cable 1 $10.00 $10.00
Knobs 15 $1.00 $15.00
1N4148 Diodes 8 $0.10 $0.80
Wires & Solder - $5.00 $5.00
Midi Jack 1 $4.00 $4.00
Rubber Feet 4 $0.50 $2.00
Standoffs 10 $0.20 $2.00
Wood Screws 16 $0.15 $2.40
Wood - $7.00 $7.00
Stain - $4.00 $4.00
Glue - $2.00 $2.00
TOTAL: $174.35
Figure 2. Table of part costs
9. 8 | P a g e - S y n t h e s i z e r
Senoir Project Plan
(Above shows the original project plan, below is the actual time line)
Figure 3. Project Plan vs. Project Outcome
10. 9 | P a g e - S y n t h e s i z e r
Appendix
Synth Basics:
The possible waveform synthesis techniques that our design is capable of are:
Additive synthesis
Wavetable synthesis
Sample-based synthesis
Pulse width modulation synthesis
Development of the microcontroller:
Figure 4. Arduino Due Microcontroller
We currently have two types of code (two types of synthesis) to load onto the Arduino to create the
oscillators. The first version uses C code based on the open-source code for the Auduino (audio-
Arduino) project. The code we found uses grain frequency changes through Pulse Width Modulation to
generate the sound and only uses 1 input pin to read pitch varied by a potentiometer. The sound is
generated by the PWM output of the micro controller. We plan to build off of this code to allow a midi-
controller to be read by the microcontroller to determine the note rather than a potentiometer.
For the second version of the code we wanted to use the Digital to Analog convert output of the
Arduino Due to produce an oscillator. This code produces four different types of oscillator waveforms:
sine wave, square wave, triangle wave and saw tooth wave. The way we constructed this is by first
having a mapped full cycle of each wave. Once we have it mapped out, there is nothing more than
putting it into the Due’s digital to analog convertor to get the output of each wave. The full code is
shown below of how each waveform is getting mapped out, getting selected, and how it is being
outputted.
Code:
PWM Code Preview:
// Analog in 0: Grain 1 pitch
// Analog in 1: Grain 2 decay
// Analog in 2: Grain 1 decay
// Analog in 3: Grain 2 pitch
// Analog in 4: Grain repetition frequency
#include <avr/io.h>
#include <avr/interrupt.h>
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uint16_t syncPhaseAcc;
uint16_t syncPhaseInc;
uint16_t grainPhaseAcc;
uint16_t grainPhaseInc;
uint16_t grainAmp;
uint8_t grainDecay;
uint16_t grain2PhaseAcc;
uint16_t grain2PhaseInc;
uint16_t grain2Amp;
uint8_t grain2Decay;
// Map Analogue channels
#define SYNC_CONTROL (4)
#define GRAIN_FREQ_CONTROL (0)
#define GRAIN_DECAY_CONTROL (2)
#define GRAIN2_FREQ_CONTROL (3)
#define GRAIN2_DECAY_CONTROL (1)
uint16_t mapPentatonic(uint16_t input) { //code has mapped out note scales that are not included in this code preview
uint8_t value = (1023-input) / (1024/53);
return (pentatonicTable[value]);
}
void audioOn() {
#if defined(__AVR_ATmega8__)
// ATmega8 has different registers
TCCR2 = _BV(WGM20) | _BV(COM21) | _BV(CS20);
TIMSK = _BV(TOIE2);
#elif defined(__AVR_ATmega1280__)
TCCR3A = _BV(COM3C1) | _BV(WGM30);
TCCR3B = _BV(CS30);
TIMSK3 = _BV(TOIE3);
#else
// Set up PWM to 31.25kHz, phase accurate
TCCR2A = _BV(COM2B1) | _BV(WGM20);
TCCR2B = _BV(CS20);
TIMSK2 = _BV(TOIE2);
#endif
// Stepped pentatonic mapping: D, E, G, A, B
syncPhaseInc =mapPentatonic(analogRead(SYNC_CONTROL));
grainPhaseInc = mapPhaseInc(analogRead(GRAIN_FREQ_CONTROL)) / 2;
grainDecay = analogRead(GRAIN_DECAY_CONTROL) / 8;
grain2PhaseInc = mapPhaseInc(analogRead(GRAIN2_FREQ_CONTROL)) / 2;
grain2Decay = analogRead(GRAIN2_DECAY_CONTROL) / 4;
}
SIGNAL(PWM_INTERRUPT)
{
uint8_t value;
uint16_t output;
syncPhaseAcc +=syncPhaseInc;
if (syncPhaseAcc < syncPhaseInc){
// Time to start the next grain
grainPhaseAcc = 0;
grainAmp = 0x7fff;
grain2PhaseAcc = 0;
12. 11 | P a g e - S y n t h e s i z e r
grain2Amp = 0x7fff;
LED_PORT ^= 1 << LED_BIT; // Faster than using digitalWrite
}
DAC code:
#include "Waveforms.h"
#include "Arduino.h"
#define oneHzSample 1000000/maxSamplesNum // sample for the 1Hz signal expressed in microseconds
const int wavebutton = 2, octane = 9, key1 = 3, key2 = 4, key3 = 5, key4 = 6, key5 = 7;
volatile int wave1 = 0, octaneChange = 0;
int keyfound = 0, i = 0;
int sample;
void setup()
{
analogWriteResolution(12); // set the analog output resolution to 12 bit (4096 levels)
analogReadResolution(12); // set the analog input resolution to 12 bit
//pinMode (key1, INPUT);
//pinMode (key2, INPUT);
//pinMode (key3, INPUT);
//pinMode (key4, INPUT);
//pinMode (key5, INPUT);
attachInterrupt(wavebutton,wave1Select, RISING); // Interrupt attached to the button connected to pin 3
//attachInterrupt(octane,OctaneSelect, RISING);
}
void loop(){
//while(digitalRead(key1) == HIGH || digitalRead(key2) == HIGH || digitalRead(key3) == HIGH || digitalRead(key4) ==
HIGH || digitalRead(key5) == HIGH )//{
// Read the the potentiometer and map the value between the maximum and the minimum sample available
// 1 Hz is the minimum freq for the complete wave
// 170 Hz is the maximum freq for the complete wave. Measured considering the loop and the analogRead() time
sample = map(analogRead(A0), 0, 4095, 0, oneHzSample);
sample = constrain(sample, 0, oneHzSample);
analogWrite(DAC1, waveformsTable[wave1][i]); // write the selected waveform on DAC1
i++;
if(i == maxSamplesNum) // Reset the counter to repeat the wave
i = 0;
delayMicroseconds(sample); // Hold the sample value for the sample time
//}}
// function hooked to the interrupt on digital pin 3
void wave1Select() {
wave1++;
if(wave1 == 4)
wave1 = 0;}
Waveforms file:
#ifndef _Waveforms_h_
#define _Waveforms_h_
#define maxWaveform 4
#define maxSamplesNum 120
static int waveformsTable[maxWaveform][maxSamplesNum] = {
// Sin wave
{
0x7ff, 0x86a, 0x8d5, 0x93f, 0x9a9, 0xa11, 0xa78, 0xadd, 0xb40, 0xba1,
14. 13 | P a g e - S y n t h e s i z e r
Audio Amplifier:
Our Amplifier desing is based on the simple LM386 audio amplifier circuit given below. We simply
adjusted the resistor values to give us a gain of 5 rather than a gain of 20. With a gain of 20 we thought
we were getting to much noise and decided to lower the gain to 5. This seemed to be just enough to
strengthen the signal from the microcontroller without having to much noticible noise.
Figure 5. Basic LM386 Audio Amplifier Circuit
LFO:
Figure 6. Low Frequency Oscillator Schematic (based on Schmidt Trigger)
15. 14 | P a g e - S y n t h e s i z e r
Our Low Frequency Oscillator Design is based on the standard schmitt trigger and integrator oscillator
core. The first potentiometers in the integrator path allows for the speed to be adjusted. The second
potentiometer, after the two diodes, allows the user to adjust charge versus discharge time. Adjusting
charge to discharge ratio allows the triangle/saw output to be changed from triangle, to sawtooth and
reverse sawtooth waves. The discharge vs charge also has an interesting effect on the pulse output of
the Schmitt trigger. As the ratio is changed, the duty cycle of the pulse is changed and becomes a
variable duty cycle square wave.
Because there is always half of the saw/triangle wave above 0 volts, a comparator referenced to ground
is used to generate a square wave from the output of the integrator. The shape of the square wave is
independent of the charge direction but the adjustment of the charge direction does change the phase of
the square wave.
After the comparator stage is a buffered voltage divider to reduce the square wave to a more suitable
level. This also drives one side of the variable output mixer pot, while the triangle wave from the
integrator drives the other side. The final op-amp is used as a buffer for the output of the variable
mixer.
Integrator Calculations: Fc = 1/(2*pi*R*C) = 1/(2*pi*15kohms*330nf)
Fc = 33Hz
LFO Variable Output Waveforms:
Figure 7. LFO variable waveforms through oscilloscope
16. 15 | P a g e - S y n t h e s i z e r
Ring Modulator/Four Quadrant Multiplier:
Figure 8. Ring Modulator Schematic
Figure 8 shows how and Operational Transconductance Amplifier can be used as a ring modulator or
four-quadrant multiplier. In this circuit zero carrier output is available when the modulation voltage is
at zero volts, but increases when the modulation voltage moves positive or negative relative to zero.
This makes it ideal for use with sinusoidal signals. The carrier output signal is inverted relative to the
carrier input when the modulation voltage is positive. The carrier output is non-inverted compared to
the input when the modulation voltage is negative. The Figure 8 circuit uses values suitable for
operation from dual 15V supplies, but also works well with our 12V supply. The gain is determined by
I-bias which is settable by adjusting the potentiometer R9 on the modulation input. How it basically
works is that the OTA feeds an inverted signal current into the bottom of R7, and simultaneously the
input signal feeds directly into the top of R7. R2 is set so that when the modulation input is tied to the
zero volts common line, the overall gain of the OTA balances the input current of R7, and under this
condition, the circuit gives zero carrier output. The adjustable R9 allows the modulation input to be
changed from a value that causes almost no modulation on the output, to a value that causes excessive
modulation and fold-back of the modulation signal shape on the carrier output waveform.
17. 16 | P a g e - S y n t h e s i z e r
Envelope generator:
Figure 9. Multisim model of ADSR envelope generator circuit
The core of the schematic is based on an original idea by Jonathan Jacky that was published in
Electronics ("Two-chip generator shapes synthesizer's sounds" Electronics #11, September 1980 : 137-
138). Additional contributions to that design made by (Tom G.-EFM, René Schmitz).
The transistor circuit that sees the gate signal before the timer is used as a buffer for the trigger signal
to the timer. The first diode protects the circuit from negative voltages. The other Diodes are used to
dispatch the charge and discharge current of the timing capacitor through the potentiometers. These
potentiometers will control the time/level of Attack, Decay, Sustain and Release. The two op-amps are
used as a simple voltage follower.
How does it work ?
GATE signal is off (0V)
The base of Q1 is at 0V et Q1 is blocked. The base of Q2 is at Vrail/2 and Q2 is conducting. Thus,
pin 4 of the U1 is at 0V and maintains the timer in a quiet stage. Capacitor C3 is discharged and the
output level is 0V.
GATE signal is on (>3V)
When a gate signal occurs (>3V), Q1 comes to a conduction state, the base of Q2 comes to 0V
and Q2 is blocked. Thus pin 4 of U1 is at +Vrail (15V), at the same time a brief pulse is generated
by C1 at the base of Q3, the latter becomes conductive for a few hundredth of second bringing pin 2
(trigger) of U1 to 0V for a brief time. These events trigger the timer. Pin 3 (out) of U1 reaches
15V and capacitor is being charged through D3 and P1 whose value sets the Attack duration.
The voltage at C3 is monitored by pin 6 (threshold) of U1. When this value reaches 2/3 of Vrail that
is 10V, the timer toggles, pin 3 goes to 0Vstopping the charging of C3. Then C3 start discharging
itself through D4, R12 and P2 which value sets the Decay speed, to eventually reach the voltage
18. 17 | P a g e - S y n t h e s i z e r
value set by the voltage divider. This divider is calculated to provide a Sustain voltage ranging from
0V to 10V. This value is held as long as the gate signal is up.
GATE signal returns to 0V (Porte/Gate : 0 V)
The base of Q1 returns to 0V and Q1 is blocked. The base of Q2 is at Vrail/2 and Q2 comes to a
conduction state. C4 starts discharging through D2, R13 and P3. The value of P4 sets the discharge
speed that is the Release duration. Pin 4 of the 7555 is set to 0V and switches the 7555 timer to a
quiet state. (2, Yusynth)
Voltage controlled amplifier:
Figure 10. Multisim model of voltage controlled circuit
Looking at Figure 10 we see how a voltage-controlled amplifier (VCA) can be designed using a
Transconductance Operational Amplifier. The input signal goes to the non-inverting terminal of the
OTA through the 27k resistor which is the current limiting resistor. Then the 33k resistor determines the
peak (overload) amplitude of the output while it loads the high impedance output of the OTA. The
actual output signal is made available at a low-impedance level through the buffer stage through the
4.7k resistor. The voltage for the circuit in figure 10 should be powered by 9V. Here the ID current is
fixed to about 0.8mA through R1 and I-bias is varied with R8 and the external gain control voltage.
While the gain-control voltage is at the -9V I-bias is 0 while there is an overall ‘gain’ of -80dB within
the circuit. Then with the gain-control at +9V I-bias is around 0.8mA with a voltage gain of roughly 1.5
within the circuit. This circuit is a non-inverting amplifier by using the non-inverting pin on the OTA. It
could be used as an amplitude modulator or a two-quadrant multiplier through feeding the carrier signal
19. 18 | P a g e - S y n t h e s i z e r
to the input terminal with the modulation signal to the gain-control input terminal, much like the ring
modulator circuit..
State Variable Filter:
A state variable filter is basically an analog computer that continuously solves a second order
differential equation. The second order response gives the HP and LP filters a roll-off slope of 40dB
per decade or 12dB per octave. The first stage of the filter is the adder/subtractor, which sums the
outputs from the two integrators in the later stages. The state-variable filter has many more variations
than most types of filters. The signal can be applied to either the non-inverting or inverting input of the
first op amp. The gain and Q value can be adjusted by changing the values of several different resistors.
The corner frequencies of the HP and LP filters and the center frequency of the BP can be adjusted by
raising or lowering the values of the integrator resistors. The frequencies are not altered by the gain or
damping coefficient.
Figure 11. State Variable Filter Block Diagram
The component values of the two integrators are set equal to each other to keep the corner frequencies
of the HP and LP filters equal. If these frequencies are not equal then the BP response is widened until
it is very unselective or it becomes attenuated until it is nearly undetectable. Unequal corner
frequencies will also cause change in the phase relationship between the LP and HP. A dual
potentiometer is used to vary the two resistors in unison and maintain the BP response and phase
relationship while changing the corner/center frequencies.
The pass-band gain for the LP and HP filters is very close to unity. The gain of the BP filter is equal to
the Q value, which is inversely proportional to the damping coefficient. The damping coefficient (α) of
the state-variable filter has the same effect as it did for the single op-amp filters. For LP and HP the
damping coefficient of 1.414 gives a Butterworth response, damping of 1.732 gives a Bessel response,
and damping of 0.766 gives a Chebyshev response (3dB peaks). We added an extra stage to the filter to
allow for independently adjustable damping and gain. We set the gain at unity and made the damping
adjustable through a potentiometer. The damping coefficient is determined by the ratio between
potentiometer in the negative feedback loop of the fourth op amp and the two resistors in the larger
feedback loop from the second op amp (see figure 12).
20. 19 | P a g e - S y n t h e s i z e r
Figure 12. State Variable Filter MultiSim Schematic
We chose the values of the capacitors and the dual gang potentiometer in the integrators to be able to
sweep the corner frequency over the entire audible range. We decided to use a standard value of 10k
ohms for the potentiometers and based on the equation Fc = 1/(2*pi*R*C), we calculated that we
needed 0.33uf capacitors to give us the correct frequency range. We also put a 24 ohm stop resistor in
series with the potentiometer and at 10,024 ohms the corner frequency is 48 Hz and at 24 ohms the
corner frequency is 20 kHz.
Filter Calculations
(Note:component names in equationsrefer to Figure 4)
αR = 5k + 20k pot α = damping coefficient R = 10k
α = 25k/10k 5k/10k
α = 2.5 0.5
Q = 1/ α Av(bp) = Q
Q = 0.4 2
R1 = R2= R3= R R6= R5= Rpot
R = 10k ohms C1= C2= C.
Corner/Center frequency => Fc = 1/(2*pi*Rpot*C)
C = 0.33uf
21. 20 | P a g e - S y n t h e s i z e r
Rpot = 24 ohms + 10k ohm pot
Fc = 1/(2*pi*Rpot*C)
Fc(min) = 1/(2*pi*10024*0.33*10^-6)
Fc(min) = 48.11 Hz
Fc(max) = 1/(2*pi*24*0.33*10^-6)
Fc(max) = 20.095 kHz
Band pass filter transfer function:
High pass filter transfer function:
Low pass filter transfer function:
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Figure 13. Simulation of Frequency Response of Filters
It can be seen in figure 13 that the response of the HP an LP filters is of the second order and has a roll
off of 40dB per decade. The BP has a first order roll off of 20dB per decade.
Figure 14. Simulation of Phase Response of Filters
It can be seen in figure 14 that the phase response is stable in the audible range of frequencies.
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Circuit Build:
Figure 15. Circuit Board soldering pictures
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Power Supply:
Figure 16. Power supply with added load on +5 volts
Layout & Enclosure:
Figure 17. Wood enclosure build
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Figure 18. Mounting interior components to enclosures
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Resources
1. Audiono Lo-fi synth for Arduino. http://duino4projects.com/auduino-lo-fi-synth-for-arduino/
2. Dailey, Denton. Operational Amplifiers and Linear Integrated Circuits: Theory and
Application. McGraw-Hill, 1989.
3. Envelope Generator ADSR. Yusynth. jan. 31st, 2009
http://www.yusynth.net/Modular/EN/ADSR/index_old.html.
4. Halgren, Ryan & Khokhar, Hassan. Lab 8: State-Variable Filter. EET 3120, Advanced Analog
Electronics. May 6th 2014
5. http://arduino.cc/
6. Inevitablecraftslab. Midi to Arduino. Instructables. http://www.instructables.com/id/MIDI-TO-
ARDUINO/
7. Marston, Ray. Understanding and Using ‘OTA’ Op-Amp ICs. Nuts &Volts Magazine. May,
2003.
8. Nilson, Riedel. Electric Circuits, 9th Edition. Pearson Education. 2011.
9. RCArduino. Arduino Projects, Libraries and tutorials.
http://rcarduino.blogspot.com/2012/08/adding-audio-to-arduino-projects.html
10. SimpleWaveformGenerator.Arduino tutorials.
http://www.arduino.cc/en/Tutorial/DueSimpleWaveformGenerator
11. Stone, Ken. Modular Synth. Modules. http://www.cgs.synth.net/
12. Supplemental LM13700 Application Examples.
http://www.idea2ic.com/LM13600/SUPPLEMENTAL%20LM13700%20APPLICATION%20E
XAMPLES.html
13. Synthesizer. wikipedia. http://en.wikipedia.org/wiki/Synthesizer
14. Synth Schematics. Envelope Generator ADSR. http://www.schmitzbits.de/adsr.html
15. Texas Instruments. LM386 Low Voltage Audio Power Amplifier. August, 2000.
http://www.ti.com/lit/ds/symlink/lm386.pdf
.