Digital Voice Record and Playback Project

This project is based on ISD2560P IC which allows you to record 60 seconds voice and then playback it with very high quality.

 

 As shown in the schematic, the input soruce is an electret microphone. If a dynamic microphone is used, R2,R3,R4 resistors and C3,C5,C7 capacitors will be omitted and microphone will be connected to the 17 and 18 numbered pins directly. Since it has better frequency response, we choose electret microphone in this project.

 

Controlling the circuit is very simple. Sw1 switches between record and playback modes. Push button B1 is used for start and pause functions. B2 stops the process.

To record voice, first move Sw1 to the record position and then push B1 once. IC will start recording and during this process red LED will bright. One push to B1 pauses and second push continues recording. You can record 60 seconds by this way. To stop recording push B2.

To listen the voice recorded before, move Sw1 to playback position then push B1. During the playback process red LED will bright again. One push to B1 pauses and second push continues playing. To stop playback push B2.

There are some other operating modes for ISD2560P. Mode choice is done by the 7 numbered pin of the IC. For instance if you want to play the voice repeatedly, 7 and 4 numbered pins must be connected to +5V. Another mode is recording and playing only during pushing B1 button. To switch this mode, connect the only 6 numbered pin to +5V.

Supply voltage of the circuit is +9V that is supplied by a 9V battery or 9V AC/DC adapter.But since ISD2560P requires +5V, we use a voltage regulator in our circuit. You can see the supply part of the circuit based on 7805 regulator in the figure.

 

SD2560P IC includes an amplifier to drive a 16 OAmplifier Parthm speaker but the output volume is not sufficiently enough. So instead of a 16 Ohm speaker, an amplifier circuit must be connected to the output. You can see the amplifier part of the circuit based on LM386 in the figure. SP+ and SP- pins must be connected to 14 and 15 numbered pins of ISD2560P. A 100K potentiometer is used to adjust the output volume. If the output of the amplificonnected to a 8 Ohm speaker, then much higher volume will be taken. 

300 Watt MOSFET Real HI-FI Power Amplifier

My passion for excellence progressed over the past 40 years to developing sonically superior amplifiers to the highest possible standards, providing life like sound performance.

I am committed to sharing my experience of the RAS 300 with other enthusiasts sharing my passion for perfection.I designed this minimalist amplifier to be durable, simple to operate while offering high fidelity equivalent to the original sound source and would recommend partnering this amplifier only with other products of outstanding quality.

When I set out to design this amplifier, my aim was to create a product most suitable for the reproduction of complex music and speech signals. Although I placed high emphasis on electrical characteristics, the single most important requirement is achieving an audibly superior sound, vivid spatial imaging and superb tonal clarity.

Although the average listening level is normally less than 10 watts, my design approach was to create an amplifier with ample reserve power, but biasing it for class A at average listening levels reducing cross-over distortion to extremely low levels.

There is not one capacitor in the signal path, improved the accuracy of the tonal characteristics of instruments and voices significantly.
The RAS 300 has almost zero phase distortion far beyond the audio range resulting in perfect resolution and totally un-coloured sound.

Amplifier Specification:
Maximum Output: 240 watts rms into 8 Ohms, 380 watts rms into 4 Ohms
Audio Frequency Linearity: 20 Hz – 20 kHz (+0, -0.2 dB)
Closed Loop Gain: 32 dB
Hum and Noise: -90 dB (input short circuit)
Output Offset Voltage: Less than 13 mV (input short circuit)
Phase Linearity: Less than 13 0 (10 Hz – 20 kHz)
Harmonic Distortion: Less than 0.007% at rated power
IM Distortion: Less than .009% at maximum power

The amplifier consists of two completely separate monaural amplifiers each channel has its own power supply, resulting in zero inter-channel cross talk, a common phenomenon in amplifiers sharing the same power supply.

In order to obtain the full output power each supply transformer should be rated at 40VAC – 0 – 40VAC at 640VA. Unlike many designs relying on the reservoir capacitors to supply peak currents, I prefer to have the raw power available from the transformer resulting in much faster transients.

Although the RAS 300 specifications are moderate, when listening to it you will immediately experience the massive reserve power available and never have any cause of anxiety that something is going to give in that one would when driving many amplifiers loud.

You will hear nothing but reality with no distortion at any level and I guarantee that this amplifier will divulge the best qualities of any equipment connected to it.

Electronically Controlled Security Door Keyboard

The circuit was constructed to provide a simple electronic lock system based on a single integrated circuit and will require a code of seven digits.

• 4022 – a 4-stage CMOS counter with 8 decoded outputs used for binary counter/decoder, divide-by-N counting, frequency division, decade counter/decimal decode display, and counter control/timers due to its features such as standardized symmetrical output characteristics, medium speed operation, parametric ratings (5V, 10V, 15V), 100% tested for quiescent current at 20V, and fully static operation
• BS170 – an N-channel enhancement mode field effect transistor designed to minimize on-state resistance while providing reliable, rugged, and fast switching performance and particularly suited for low voltage, low current application such as power MOSFET gate drivers and small servo motor control due to its features of high saturation current capability, voltage controlled small signal switch, and high density cell design
• BD679 – a monolithic NPN Silicon epibase power Darlington transistor with resistors and diode in a TO 126 plastic package and is typically used for AF applications due to its high current gain

The construction of the circuit is relatively simple since it utilizes a very few components. One important thing to be considered in doing this circuit is the time it will take, after the push button switches are pressed, for the code to reach the main IC. There will be a delay unless all the keys were entered. When the right sequence of code was entered correctly, the output of Q7 will be activated for approximately 4 seconds. This will drive the transistor Q2 which in turn would drive one relay that will open the door or any other circuit attached.

The use of red LED D3 provides a visual indication of the activation of Q2. The code that has been set for the circuit is 1704570, as seen in the diagram. This was made possible by the arrangement of the resistors with their corresponding connections to the switches. The resistors are arranged from points A to G order while the switches are connected to the corresponding resistors in random order. The security code can be changed by altering the connections between the switches and the outputs of the IC1.

In most secured places with the capability of the company to purchase high end equipments, an electronic key operated door is usually installed. This will prohibit the entry of unauthorized persons or verify the entrance of a person by supplying the correct key code. This electronic security door key may also be found on vehicle doors for locking and unlocking purposes. Other establishments that utilize this are jewelry shops, banks, apartments, factories, hotels, prisons, apartments, and homes. They are very reliable since they are convenient to use and can be integrated easily with other circuitries.

12V Lead Acid Battery Discharge Indicator

The circuit was designed to produce an indication before a 12 V lead acid battery would reach the discharged state

• LM723 – a positive NPN standard voltage regulator mainly designed for series regulator applications which can be utilized for both foldback and linear current limiting due to its very low standby current drain circuit
• Trimmer – a miniature variable component used to make fine adjustments to capacitance, inductance or resistance (potentiometers)
• BC547 – NPN small signal transistors designed for general purpose switching and amplification due to its low voltage, low current and three different gain selections

Lead acid batteries are comprised of a Sulphuric acid solution electrolyte, a sponge metallic lead anode and a lead dioxide cathode. Because of the chemical combinations, this heavy metal element is toxic and disposing it improperly would be hazardous to the environment. Mechanically, the lead acid battery is made of a series of identical cells where sets of positive and negative plates comprise each cell. A typical cell is built with more plates in order obtain the needed current output. The positive plates are attached together as well as the negative plates. There are always one or more negative plates than positives because the arrangement of the positive plate is always in between the negative plates. These plates are immersed in an electrolyte of dilute sulphuric acid and distilled water. Sulphuric acid is a very reactive substance of oxygen atoms, sulphur, and hydrogen. The sulphuric acid has the ability to distribute itself very evenly throughout the electrolyte in the battery due to its instability. This will always to an even reaction between all the plates by producing current and voltage. Both plates are turned into lead sulphate by the chemical reaction between the lead dioxide at the positive plates, the spongy lead at the negative plates, and parts of the electrolyte.
The result of all the reaction is a potential difference between the two plates where the positive plate gives up electrons and the negative plate gains them in equal numbers. However, there is a limitation in the length of time for the reaction to produce the cell voltage. The voltage will remain constant without the presence of connection between the two plates. The chemical reaction will be able to continue the electrons to flow through the circuit from the negative plate to the positive in the event that a load is placed between the positive and negative plates. The current produced by the cell is represented by the flow of electrons. The battery will fail to produce any current when the supply of electrons becomes depleted. The cause of this depletion may pertain to the electrolyte being turned mostly into water or the active material on the negative plate has been used up. The efficiency of the battery system depends on the heating levels of the chemical process wherein greater heating means the battery is quickly exhausted.
To protect the batteries for the fear of being destroyed, the circuit provides the detection of discharge. Since the lead acid battery has a voltage of 12 V, it is not allowed to be rated below 10.8 V. otherwise, the LED would light to indicate the voltage drop. Lead acid batteries should never run flat and the maximum recommended discharge is 75% of the total. This signifies that the minimum charge remaining on the battery should be around 25% before recharging. Lead acid batteries should always be regularly charged even on its idle state once it has been filled with electrolyte. Due to its own resistance, the battery is self discharging when not in use. This could lead to a flat discharge even without putting the battery into service. The self discharge rate is a measure of how much the batteries discharge by them and is managed by the metallurgy of the lead used inside and the construction of the battery. The depth of discharge is a measure of how deeply the battery is discharged. The deeper the batteries are discharged, the shorter is their life cycle.
On order to control the discharge of the battery, a stable voltage in a circuit is required to check the voltage. This can done using the IC1 LM723 which is a monolithic integrated circuit programmable voltage regulator, assembled in 14-lead dual in-line ceramic and plastic package. It can provide internal current limiting and an external NPN or PNP pass element may be used when the output current exceeds 150 mA. The specifications are made for remote shutdown and adjustable current limiting. The poles of the battery are connected to the terminal entry of the circuit. The stability voltage around 7.15 V is handled by the pin 6 of the IC as it receives an input voltage larger than 9.5 V. the stability voltage is provided to the pin 5 while pin 4 obtains a part of the input voltage which is checked by the trimmer. The trimmer is meant to be set correctly when installed. IC1 operates as a voltage comparator which compares the value of voltage between pin 4 and pin 5. When the voltage in pin 4 is larger than the voltage in pin 5, the output in pin 9 becomes low. But when the output in pin 9 becomes high, the LED will turn on as a result of the conduction of Q1. The regulation of the circuit requires an external power supply which can be regulated with a value of 10.8 V. the trimmer is also adjusted so that when the LED turns ON, the voltage from the supply will be improved.
The rate of discharge is also affected by storage. A battery should never be stored directly on the ground especially not on the concrete. Using wooden pallets is the best storage method since it will not allow damp paths, will not conduct, and will provide good air circulation. A refreshening charge once every two months or more is recommended by most manufacturers during storage. Thin electrode plates allow a lot of energy to be discharged quickly for a short period of time like in car batteries. Thick electrodes in lead acid batteries can tolerate discharges better than thin but at the expense of producing heavier batteries.
Lead acid batteries are being used in several industries because they are tried and tested, robust, tolerant to abuse and overcharging, low internal impedance, can deliver high currents, wide range of capacities and sizes, supplied worldwide, indefinite shelf life if stored without electrolyte, reliable, and low cost. They are used in equipments like the electrical motors in conventional submarines and nuclear submarines where large lead acid batteries are used; in power failure cases which use lead acid batteries for emergency lighting; in uninterruptable power supplies used for small computer systems, marine applications, electric scooters, and electrified bicycles where backup power supplies for alarm are utilizing gel batteries; in supplying heater voltage in the early radio receivers constructed out of vacuum tubes; in providing large backup power supplies for computer centers and telephone, off-grid household electric power systems, and grid energy storage where wet cell batteries are employed which is designed for deep discharge; in battery electric vehicles like golf carts which use propulsion batteries; in forklifts where batteries are used as counterweights; and in motor vehicles for ignition, lighting, and starting where the current for initiating internal combustion engines are provided by batteries.

Nickel-Cadmium (NiCd) Battery Charger

The circuit diagram shows a regular charger being powered by an AC input source, intended for charging batteries.
This type of rechargeable batteries are usually termed as “NiCd”, which was a brand name of SAFT Corporation and should not pertain generically to nickel-cadmium batteries. Charging NiCd batteries requires constant current source by using a transistor. The BD140 power transistor has the features of high current (max. 1.5 A) and low voltage (max. 80 V). It is generally used for power applications purposes as used in television circuits and hi-fi amplifiers. Two high conductance fast diode 1N4148 applies a direct voltage to the majority-carrier of the transistor while stabilizing the voltage drop across them. Voltage drop can be defined as the reduction in voltage across a conductor where current is flowing. When the switch is closed, the charging current is estimated as 15mA to 45mA which makes it appropriate for rechargeable batteries of 1.5 V and 9 V. For high quality NiCd’s, the charging stops when the battery gets too hot. To obtain the best results, charging should be done in a room temperature or cool place. The discharge rate for NiCd batteries depends on the size.
There are other available types of rechargeable batteries in the market. While NiCd uses nickel oxide hydroxide and metallic cadmium as electrodes, the nickle-metal hydride cell (NiMH) uses hydrogen-absorbing alloy for negative electrode. The Lithium-ion (Li-ion) uses the anode, cathode and electrolyte to function properly.
The disdavantage of NiCd batteries is the severe toxicity and high cost. Inaccurate use of these batteries can lead to damage to itself or to humans.

Digital Voltmeter with 3-Digit Output

The construction of the device uses PIC16F676 for reading analog signal such as voltage, and displaying the 3-digit output by using 7-segment LED.

On the hardware part, the PIC16F676 has 10-bits 8 channels since most of PIC microcontrollers has either 8-bit or 10-bit analog to digital converter module. In this project, only one channel is used for measuring the input voltages while the others pins are used for digital I/O. A voltage divider consisting of R1 & R2 is used for the voltage input. The appropriate display of full scale voltage is being adjusted by VR1 connected in parallel with R2. The analog input will come from the divided input voltage from AN3.
In scan display routine, the digital output RA0-RA2 turns ON/OFF the digits. The 7-segment display is driven by the RC0-RC5 and RA5 and will be decoded by a software using CCS C compiler to programming. The 7-segment code is a converted form of the input voltage on RA3. The interrupt of every 5 ms is set on the timer while scanning all digits around 66 Hz frequencies. This means that for every 5 ms, only one digit is turned ON

1A Power Supply with 0 to 15 Volts Adjustable Output

Terminology

2N3055 – a complementary Silicon Epitaxial-Base planar NPN transistor mounted in Jedec TO-3 metal case for use as power transistor
Bridge Diode – also known as bridge rectifier which has four diodes arranged in a bridge configuration where the output voltage has the same polarity with either polarity of the input voltage
The construction of this power supply circuit is very simple in such a way that the components used are easy to be located while the cost is very cheap. With the biggest provided current at 1 A, the output voltage is adjusted for minimal ripple effect and stabilized in the range of 0 V to 15 V DC. This is made possible by the standard transformer output of 1.5 A with a primary winding voltage of 220 V and secondary voltage of 18 V. The current is being limited by the Zener diode D1 with a rating of 18 V and 1.5 W. The linear potentiometer R2 is responsible for the regulation of current.
The power transistor Q1 is a classic type that would require to be placed in a suitable heatsink to suppress the high heat dissipation during the operation of the circuit. The heat dissipation will be continuous during the presence of the highest current. The bridge diode GR1 will provide full wave rectification from the AC input which will also convert the incoming alternating current (AC) input into direct current (DC) output. One good feature of the bridge diode is maintaining the same polarity of the output regardless of the polarity of the input.

The 15V/1 A power supply may be used to handle home automation control system which can be powered by 12 Vdc. They can be made into power adapter models to support a wide variety of applications such as TFT monitors, broadcasting, laptops, digital cameras, telecommunications, PSP’s, routers, notebooks, guitar effects pedals, KVM extenders, iPod’s, scanners, CCTV’s, printers, cassette players, radios, and other portable applications.

ELECTRONICS STREET LIGHT SWITCH

Circuit Description of Electronics street light switch 

As electronics street light switch is a switching circuit so, for more detail we can divide this circuit into two section i.e. power supply and switching circuit.

In this power supply section the work of step-down transformer is done by register R₁ and further rectification to change into 9.1V dc is by diode D₁ and zener diode ZD₁. The output voltage across zener diode is further filtered by capacitor C₁ and c

 The another section  of street light is switching section built around light-dependent register LDR₁ with the help of transistor T₁ through T₃ and timer IC NE555 (IC₁), where LDR₁ is used as sensor of this switching circuit.As in day time the resistance of LDR₁ remain low but it is reverse in night time i.e. high resistance is offered by LDR₁. For this property of LDR₁ the timer IC used in this circuit is as inverter. So, high input at pin 3 is provided by low input at pin 2 and vice-versa. Lastly, this inverter is used to turn street bulb B₁ on with the help of triac (triac is activated).

The transistor T₁ and T₂  is remain cut-off to make pin 4 and pin 8 of IC₁ low due to light fall on LDR₁ during day time. Due to this transistor T₃ is also cut-off and trigger voltage is not received by IC₁ through pin 2. As a result the output voltage at pin 3 is low which does not activate triac and the street bulb does not glow.

     Automatic street light switch

PARTS LIST

Resistors (all ¼-watt, ~+mn~ 5% Carbon)

R₁ = 10 KΩ/10-watt

R₂ = 33 KΩ

R₃ = 39 KΩ

R₄, R₆, R₇ = 10 KΩ

R₅ = 100 Ω

Capacitors

C₁, C₅ = 0.1 µF

C₂ = 1000 µF/25V

C₃ = 10 µF/25V

C₄ = 0.01 µF

Semiconductors

IC₁ = NE555 timer IC

T₁, T₃ = BC548

T₂ = 2N2222

ZD₁ = 9.1V/0.5V

D₁ = 1N4001

Triac₁ = BT136

LED₁ = RED color

Miscellaneous

LDR₁ = light-dependent resistor

F₁ = Fuse, 5A

B₁ = 100W/ 230V AC

SW₁ = On/off Switch

Bridge Power Audio Amplifier

Here is simple circuit of bridge power audio amplifier used in application requiring more power than is provided by the single LM380 amplifier, the two LM380s can be used in the bridge configuration shown in figure 1. In this arrangement (bridge power audio amplifier) the maximum output voltage swing will be twice that of a single LM380 amplifier; therefore, the power delivered to the load by bridge power audio amplifier will be four times as much. For improved performance, potentiometer R₃ should be used to balance the output offset voltage of the LM380s. Here R₂ C₃ for stability with high-current loads.

 

Resistors (all ¼-watt, ± 5% Carbon)

R₁ =2 MΩ potentiometer

R₂ = 2.7 Ω

R₃ = 1 MΩ

Capacitors

C₁, C₂, C₃ = 0.1 µF

C₄ = 51 pF

Semiconductors

IC₁, IC­₂ = LM380 audio power amplifier

Miscellaneous

8Ω 1-W speaker

Bidirectional Logic Level Converter Circuit

Often, it becomes necessary to interface an existing or new 5V AVR / PIC / MCU project to new devices that use 3.3V logic, like memory cards, sim cards, etc. Described here is a circuit that converts +5V to +3.3V logic or +3.3V to +5V logic. This compact circuit makes it perfect for embedded systems that need to interface with different logic levels. The design is based on 74LCX 245 IC, which is a low voltage bidirectional transceiver with 5V tolerant inputs and outputs, from Fairchild.
The 74LCX245 IC contains eight non-inverting bidirectional buffers with 3-STATE outputs and is intended for bus oriented applications. The device is designed for low voltage (2.5V and 3.3V) VCC applications with capability of interfacing to a 5V signal environment. 74LCX245 IC is fabricated with an advanced CMOS technology to achieve high speed operation while maintaining CMOS low power dissipation
 Schematic of the Logic Level Converter Circuit

 

The presented circuit features improvements that set it apart from other published logic level converter circuits. The improvements include on-board +3.3 low-drop voltage regulator, direction selection jumpers, easy-to-use input/output terminals and power on indicator LED. The circuit can be easily interfaced via standard jumper wires. The whole circuit can be fabricated on a small piece of prototyping board, with the help of an SOIC/SOP/SSOP – to – DIP adapter. Or you can prepare your own SMD printed circuit board for the construction task. In order to configure the circuit as +5V input and +3.3V output, the jumper (JP1) must be set to position A -> B. For configuring the circuit as +3.3V input and +5V output, the jumper (JP1) must be set to position B -> A. The onboard +3.3V can be used to supply power to the connected +3.3V device(s).
Logic Level Converter Features

• 8- non inverting bidirectional buffers
• On-board +3.3V/500mA low-drop fixed voltage regulator
• User only needs to supply dc power to +5V pin
• Power on LED
• Direction selection Jumpers
• Small and compact circuit

IC1 is configured to enable output (OE pin -pin 19 of IC1- pulled down), and the default direction is A -> B (DIR pin -pin 1 of IC1- pulled up by jumper JP1). You can manage the OE and DIR signals by applying the desired logic value to these signals

Lab Note: Prototype was tested with 74LCX245 IC in ‘Thin Shrink Small Outline Package’ (TSSOP). The prototype on the common circuit board was built with the help of a 20-pin TSSOP to DIP adapter.
MOSFET I2C Level Converter Circuit

he above circuit is built with the BSS138 MOSFETs and can be used when you need only the an I2C level converter from 5V to 3.3V or from 3.3V to 5V.

ICSP custom cables and Arduino

As soon as we start getting familiar with the basics of Arduino, we start noticing some interesting components that are not commonly used on the Arduino. One of these things are the ICSP headers. They are those six pins that stick out, organized in a two-row three-column orientation.
As Arduino enthusiasts become familiar with the concept of microcontroller programming, they realize that programming is not as simple as plugging a USB cable into the microcontroller and pressing upload. However, technology is growing and there are already microprocessors that support USB protocol out of the box, yet they still have to be loaded with a specific firmware or program to run in a desired way. The main controller on the Arduino is a microcontroller that has a specific firmware on it in order to receive serial data and be programmed that way through USB. Without this firmware the code found in the Arduino IDE would not be compatible with the microcontroller. It is the ICSP header that allows the microcontroller to receive the firmware or program that does all the advanced functionalities that are desired.
ICSP stands for In Circuit Serial Programming, it is a standard way to program AVR chips. You may be asking what AVR is? AVR is a standard abbreviation used to classify Atmel microcontrollers. Atmel, a company that manufactures microcontrollers, has created a microcontroller (chip) that Arduino uses in its prototyping boards like Arduino UNO, make sense?

 

All this may seem like great knowledge but what can be done with this knowledge and just an Arduino? The webpage by Arduino explains a way to go from an Arduino UNO to an Arduino clone on a breadboard. Very exciting, we can actually create our own Arduino. Looking at all the wires that are required to connect the Arduino to the microcontroller to upload the boot loader, is disappointing and seems like too much. How about if a USB to serial converter cost too much for us? Are we expected to connect these wires every time we want to program this chip? What a hassle. I have a cheap and easy way to program your chip without much effort.
Enough with the learning let’s get our hands working and build a custom ICSP cable to program/bootload an Arduino, an ATMEGA328P (chip used in Arduino UNO) , or any other AVR microcontroller.
Things you will need:

• Arduino0
• IDE cable.
• Bread Board and an Atmega328p or another Arduino
• Jumpers and male headers if you are using a Bread board instead of another Arduino

Step 1: The IDE cable has one side that has a red wire coming to it. Count three pins in from the edge of the ide cable and make a mark, there are two rows so three times two will be six pins altogether. Do this on both sides of the cable.

 

Step 2: Cut the IDE Cable connector at the mark do this also on both sides of the cable. When the cable is cut, there will be more than six wires that are still attached to the connector. Count off six wires from the edge and strip the rest away from the connector
Step 3: This requires to gain some knowledge about ICSP pinouts. ISCP uses six pins to program the microcontroller and instead of spending my time, trying to explain what each pin does here (http://en.wikipedia.org/wiki/Incircuit_serial_programming) is a good Wikipedia article that explains it quite well.
Basically there is a power and ground, a clock signal, two signals for data, and most importantly a reset pin. I spent some time going down into the core of how everything is connected from an Arduino to an Arduino for Bootloading and noticed that there are predetermined pins on AVR microcontrollers for each of those pins on the ICSP connector. When doing a Bootloading/programming from Arduino to Arduino every pin is connected directly from chip to chip, meaning the data is connected directly to the data and so one. Only the reset pin is different, that is what makes this so nice. The programming Arduino sends the reset signal from one of its pins (pin 10 if using ArduinoISP sketch) and it connects to the reset of the programmed chip. In order to get the right configurations all we have to do is peel away the fifth wire on our new cable and solder a jumper to it.

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Step 4: Clean up the connector by adding some heat shrink, plug it into you programming Arduino and you are set to go.
This is the best way to use your Arduino as a programmer. It allows you to use your Arduino for other projects but when you need a program all you have to do it plug in this custom cable. Instead of having 50 Arduinos for all our projects, we have shields that plug in and out making Arduino easy to use, This is a good comparison to an Arduino shield as it allows you to quickly add functionality of your Arduino with not much thought.

Android Password Based Remote Door Opener System Project

Our project aims at remote password based door opener system through an android application. The system tends to make a secure door opening mechanism such that the door only unlocks when a security personnel opens it by entering the right password through an android application.
The authorized personnel needs to be present within Bluetooth range of the door but need not open the door manually. He just needs to enter the right password through his android application in order to unlock the door. This is a useful concept in places where the security needs to open gates quite usually or need to operate a door from a vehicle without needing to get down from it.
The command sending functionality is achieved through an android application. The application provides an interactive user friendly GUI for this purpose. The android application can be operated from any device running on android OS and uses Bluetooth as a medium for sending commands.
As soon as commands are sent through the android device a Bluetooth receiver is used to receive those commands. These commands are then sent to the 8051 microcontroller. The microcontroller processes these commands and then tallies the password to check its correctness. If the right password is encountered it sends command to open the door.
In case of wrong password it sounds a small buzzer.

Sound Activated Switch

Micro Switch 

Consider a situation in a bank or any organization where a sudden invasion by the burglars has taken place. Now all the staff has been handcuffed by the robbers and the main locker room full of valuable resources is at the mercy of the robbers. So is there any way to prevent this theft?? Yes, there is, if any buzzer is connected which can start ringing, alarming the local police or a camera fitted along with a GSM modem that can send the video to the police stations. But still the problem lies in the way to switching on these devices.

Consider another situation, when a person is at his room (in a hostel or a hotel) and a thief tries to enter the room at night when the room is dark and the owner is fast asleep. There needs to be a system for automatic switching on of the light and ringing of the buzzer alarm.

In both these situations, the solution lies in devising a way for automatic operation of a switch and to achieve this, one of the most efficient ways is a Sound Operating switch.

Two ways to design your own sound operated switch

 
Using a audio Amplifier and a timer

A basic sound operating switch can be constructed using an audio amplifier IC, a comparator, a 555 timer operating in monostable mode, a relay and a load. Here the basic idea is to change the output of the timer with input from the microphone, in order to switch on the load. The load can be a incandescent lamp or a LED lamp or a motor.

The audio signal is received by the microphone, which converts the audio signal to electrical signals. The signal is given to the pin2 of comparator IC 741. The other input pin 3 of the comparator is given by the reference voltage set by the potentiometer arrangement.

 

In absence of any audio signal, pin 2 is at logic high and the output of comparator is at logic low, giving a low signal to the trigger pin of the 555 timer. The output of the timer is thus at logic high, keeping the relay at off condition. When a sound is heard the microphone detects it and converts it to electrical signal and the signal is applied to pin2 of the comparator and since this pin is now at logic low, the comparator output is at logic high, triggering a logic high signal to the trigger pin of the timer. The timer output is thus at logic low, driving on the relay, which in turn switches on the load( A bulb) for a time determined by the RC combination.

A Sound Operated Switch using Counter IC

You can use this circuit to operate a Relay through the sound of claps. It is highly sensitive and can detect the sound of the clap from a distance of 1-2 meters. AC loads such as lamps, fans etc can be connected through the relay. This circuit has three sections. A sensitive MIC amplifier, A Toggle switch based on IC CD4017 and a Relay driver. IC CD4017 is a decade counter where the output count number is shown by the corresponding output number pin going high.

Condenser Microphone picks up the sound vibrations and generates minute voltage across its terminals. These feeble signals are amplified by IC1. Resistor R1, R3 and variable resistor VR1 adjust the sensitivity of the amplifier. Resistor R1 set the sensitivity of Mic. The amplified output pulses from IC1 passes to the input of IC2 (CD 4017). Resistor R4 keeps the input (pin14) of IC2 low so as to prevent false triggering. IC2 is a decade counter IC which is wired as a toggle switch. That its outputs 1 and 2 (pins 2 and 3) becomes high and low alternately when the input pin14 receives pulses from IC1.  Pin4 (output4) is connected to the reset pin15 so that further counting will be inhibited. The high output from IC2 passes through the current limiter R6 to the base of switching transistor T1. When T1 conducts, Green LED and the Relay turns on. In the next clap, output pin 2 becomes low to switch off the relay and the Green LED. Red LED indicates the OFF position of the load.

In other words, when we first make a clapping sound, the audio signal gets converted by the microphone to electrical signal and amplified by the operational amplifier, which gives the output pulse. When the counter receives the first pulse the pin 2 goes high and the relay driver is switched on to energize the relay and thus switch on the LED. When we again make a clapping sound, the amplifier IC generates another pulse. This time the pin 2 goes low and pin 3 goes high, causing the red LED to glow. The relay is now switched off and the LED is in off condition.

 

Note: It is better to connect the Microphone directly on the PCB using two pieces of the trimmed leads of resistor or capacitor. If Microphone is connected with wires, sensitivity may be reduced. Enclosing the Microphone in a tube will increase the sensitivity considerably. Adjust VR1 to get maximum sensitivity and range.

Sound Operated switches available in the market

 

It is a sound operated electronic switch kit by Electro Kits. It operates on a 9V battery and uses a electrets microphone. It switches on and off an LED mounted on the kit.

Automatic Voice Activated Switch

 

Its switching time is up to 60seconds and supports loads upto 3A-115V or 5A-12V

 

It is a microprocessor controlled switch operating on 1 or 2 claps. It has a relay power rating of 24VDC/AC 3A. It works on a power supply of 12V dc.

 

It is a 1382313 model number sound operated switch operating on a power of 250W max with a supply voltage of 120V. It works in two modes. In Home mode, it can operate one or two appliances. In the Away mode, it will operate on any noise to switch on the connected appliance.

Smart DC fan

EMI signal line filters

In almost all flats the elevators (lifts) are essential. In high rise buildings there are 2 or 3 or even more lifts. These lifts are major source of electrical energy consumption. Why?

The lifts remain idle for most of the time and it is used during peak hours only like in morning from 6 am to 10 am and in evening from 5 pm to 9 pm. So out of 24 hours a lift is used mostly for 8 – 10 hours. Now the problem is, in a lift there is always a fan and a light that stays on continuously. Even if lift is not in used for longer period of time. Although the ON/OFF switches for fan and light are already given, no body turns it OFF. So the fan and light inside the lift stays ON continuously and makes complete waste of electrical energy. Such a waste of valuable electrical energy in this era is not at all desirable. Today all most all the countries are putting their strong efforts to save maximum electrical energy by all means. In India there is heavy scarcity of conventional energy sources from which electricity is produce. So saving electricity and thus these conventional energy sources is must.

On this thought an idea came into my mind that why not to add a kind of intelligence in lift fan and light so that it remains ON till there is atleast one person in the lift. And when lift is totally empty fan as well as light automatically turns off. So there should be a kind of sensor in the lift that senses person presence and automatically turns ON or OFF light and fan inside it.

So here i am presenting a simple circuit called smart DC fan that senses any person near by and turns on. when there is no any person it turns off automatically. Later on I have given one more circuit that is with a small change in the same circuit so that it can switch on and off 230 V AC light and fan at a time inside lift.

Arduino Due Pinout

 

Input and Output
Digital I/O: pins from 0 to 53
Each of the 54 digital pins on the Due can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 3.3 volts. Each pin can provide (source) a current of 3 mA or 15 mA, depending on the pin, or receive (sink) a current of 6 mA or 9 mA, depending on the pin. They also have an internal pull-up resistor (disconnected by default) of 100 KOhm.
In addition, some pins have specialized functions:
Serial: 0 (RX) and 1 (TX) Serial 1: 19 (RX) and 18 (TX) Serial 2: 17 (RX) and 16 (TX) Serial 3: 15 (RX) and 14 (TX)
Used to receive (RX) and transmit (TX) TTL serial data (with 3.3 V level). Pins 0 and 1 are connected to the corresponding pins of the ATmega16U2 USB-to-TTL Serial chip.
PWM: Pins 2 to 13
Provide 8-bit PWM output with the analogWrite() function. the resolution of the PWM can be changed with the analogWriteResolution() function.
SPI: SPI header (ICSP header on other Arduino boards)
These pins support SPI communication using the SPI library. The SPI pins are broken out on the central 6-pin header, which is physically compatible with the Uno, Leonardo and Mega2560. The SPI header can be used only to communicate with other SPI devices, not for programming the SAM3X with the In-Circuit-Serial-Programming technique. The SPI of the Due has also advanced features that can be used with the Extended SPI methods for Due.
CAN: CANRX and CANTX
These pins support the CAN communication protocol but are not not yet supported by Arduino APIs.
“L” LED: 13
There is a built-in LED connected to digital pin 13. When the pin is HIGH, the LED is on, when the pin is LOW, it’s off. It is also possible to dim the LED because the digital pin 13 is also a PWM outuput.
TWI 1: 20 (SDA) and 21 (SCL) TWI 2: SDA1 and SCL1.
Support TWI communication using the Wire library.
Analog Inputs: pins from A0 to A11
The Due has 12 analog inputs, each of which can provide 12 bits of resolution (i.e. 4096 different values). By default, the resolution of the readings is set at 10 bits, for compatibility with other Arduino boards. It is possible to change the resolution of the ADC with analogReadResolution(). The Due’s analog inputs pins measure from ground to a maximum value of 3.3V. Applying more then 3.3V on the Due’s pins will damage the SAM3X chip. The analogReference() function is ignored on the Due.
The AREF pin is connected to the SAM3X analog reference pin through a resistor bridge. To use the AREF pin, resistor BR1 must be desoldered from the PCB.
DAC1 and DAC2
These pins provides true analog outputs with 12-bits resolution (4096 levels) with the analogWrite() function. These pins can be used to create an audio output using the Audio library.
Other pins on the board: AREF
Reference voltage for the analog inputs. Used with analogReference().
Reset
Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.

Arduino Ethernet Pinout

 

Input and Output
Each of the 14 digital pins on the Ethernet board can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms.
In addition, some pins have specialized functions:
Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data.
External Interrupts: 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details.
PWM: 3, 5, 6, 9, and 10. Provide 8-bit PWM output with the analogWrite() function.
SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication using the SPI library.
LED: 9. There is a built-in LED connected to digital pin 9. When the pin is HIGH value, the LED is on, when the pin is LOW, it’s off. On most other arduino boards, this LED is found on pin 13. It is on pin 9 on the Ethernet board because pin 13 is used as part of the SPI connection.
The Ethernet board has 6 analog inputs, labeled A0 through A5, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from ground to 5 volts, though is it possible to change the upper end of their range using the AREF pin and the analogReference() function. Additionally, some pins have specialized functionality:
TWI: A4 (SDA) and A5 (SCL). Support TWI communication using the Wire library.
There are a couple of other pins on the board:
AREF. Reference voltage for the analog inputs. Used with analogReference().
Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.

Arduino Mega 2560 Pinout

 

Input and Output

Each of the 54 digital pins on the Arduino 2560 Mega can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms.
 In addition, some pins have specialized functions:
Serial: 0 (RX) and 1 (TX); Serial 1: 19 (RX) and 18 (TX); Serial 2: 17 (RX) and 16 (TX); Serial 3: 15 (RX) and 14 (TX).
Used to receive (RX) and transmit (TX) TTL serial data. Pins 0 and 1 are also connected to the corresponding pins of the ATmega16U2 USB-to-TTL Serial chip.
External Interrupts: 2 (interrupt 0), 3 (interrupt 1), 18 (interrupt 5), 19 (interrupt 4), 20 (interrupt 3), and 21 (interrupt 2). These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details.
PWM: 2 to 13 and 44 to 46. Provide 8-bit PWM output with the analogWrite() function. SPI: 50 (MISO), 51 (MOSI), 52 (SCK), 53 (SS). These pins support SPI communication using the SPI library. The SPI pins are also broken out on the ICSP header, which is physically compatible with the Uno, Duemilanove and Diecimila.
LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it’s off.
TWI: 20 (SDA) and 21 (SCL). Support TWI communication using the Wire library. Note that these pins are not in the same location as the TWI pins on the Duemilanove or Diecimila.
The Mega2560 has 16 analog inputs, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from ground to 5 volts, though is it possible to change the upper end of their range using the AREF pin and analogReference() function.
There are a couple of other pins on the board:
AREF. Reference voltage for the analog inputs. Used with analogReference(). Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.

Arduino Uno Pinout

 

Input and Output
Each of the 14 digital pins on the Arduino Uno can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms.
In addition, some pins have specialized functions:

Serial: pins 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data. These pins are connected to the corresponding pins of the ATmega8U2 USB-to-TTL Serial chip.
External Interrupts: pins 2 and 3. These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details.
PWM: 3, 5, 6, 9, 10, and 11. Provide 8-bit PWM output with the analogWrite() function.
SPI: 10 (SS), 11 (MOSI), 12 (MISO), 13 (SCK). These pins support SPI communication using the SPI library.
LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it’s off.
The Uno has 6 analog inputs, labeled A0 through A5, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from ground to 5 volts, though is it possible to change the upper end of their range using the AREF pin and the analogReference() function. Additionally, some pins have specialized functionality:
TWI: A4 or SDA pin and A5 or SCL pin. Support TWI communication using the Wire library.
There are a couple of other pins on the board:
AREF. Reference voltage for the analog inputs. Used with analogReference().
Reset. Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.

Midget Emergency Torch Circuit

Here is a tried and tested design of an ultra-simple emergency torch built around the inexpensive dc-dc converter chip MC34063. Beyond a handful of simple components, a lithium coin cell and a small key fob case no additional parts are needed!
The MC34063 (IC1) is a monolithic control circuit containing the primary functions required for dc−to−dc converters. MC34063 consists of an internal temperature compensated reference, comparator, controlled duty cycle oscillator with an active current limit circuit, driver and high current output switch.
This chip was specifically designed to be incorporated in buck and boost (and voltage−inverting) applications with a minimum number of external components. Here, the IC-MC34063 is used to drive three high-efficiency white LEDs using 3V dc supply available from the built-in CR2032 lithium coin cell.

 In this circuit, designed to drive ultrabright white LEDs at constant current, IC1 (MC34063) compares the external voltage at its pin 5 with an internal reference voltage of 1.2 V in order to stabilize its output. Here, resistor R3 (connected to pin 5 of IC1) sets the operating current of the series-connected white LEDs (LED1-LED3). Note that the circuit can provide a variable intensity by making R3 to be a variable resistor. If R3 is linear then the perceived light intensity will be approximately linearly variable with the variable resistor’s shaft position.