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FUNDAMENTALS BASICS ADVANCED ELECTRONICS PROJECTS Shared Dual Variable Power Supply Stepped Desktop Power Supply Superb Power Controller BTA41 Soft Starter + Soft Stopper (motor) Series Balanced LiFePO4 Charger Series Balanced Li-Ion Charger Sanitizing Machine (simple & eco) Solid State Relay / Switch Swift IR sensor & remote Tester Stepper Motor Tester 555 + A4988

ESSENTIALS The general use and essentials for Make-at-Home projects are listed below with comment as Basic or Important or Optional keyword, which means that, BASIC : very much required and affordable IMPORTANT : having this item is advantageous OPTIONAL : may be purchased later BREAD BOARD : A bread board is used for connecting electronic components of a circuit, quickly. The bread board has holes to insert leads of electronic components and interconnecting them using flexible jumper wires. The bread boards are available in various sizes and their ends have slots and projections for adding more bread boards in cascading. Normally, holes of top two lines and bottom two lines are connected horizontally in parallel, which are useful for connecting power supply. The remaining holes, which are in between the horizontal lines, are divided into two groups, top and bottom from mid-line. Each group have holes with vertical connecting lines for connecting main circuit (or components) (BASIC) A model Bread Board with connecting lines, underneath is shown below. Some bread boards with with various sizes are also shown for reference. ​ PRINTED CIRCUIT BOARD (PCB) : A PCB is used to assemble a circuit, using soldering method. A PCB is made of flat insulating material (FR-4, glass epoxy etc.), contains copper tracks (strips) stick on its surface, as connectors for a circuit, is known as Single sided PCB. Holes are made, wherever required to insert the particular electronic component through it, then solder on other side. The surface of PCB, where pinouts of the components to be inserted are printed is called as Silkscreen side . The other surface, on which the leads of the components are soldered is called Soldering side . ( IMPORTANT) ​ Some PCBs have copper track on both the surfaces, is called Double sided PCB . Some PCBs have insulating material and copper tracks as alternate layers is called multi-layer PCB s. The insulating material selection depends on the di-electric strength required and frequency of the data transfer for the circuit. The thickness and width of the copper track depends upon the current carrying capacity required between in the components in the circuit. ​ Single sided, general purpose PCBs, which are easily available and affordable, are normally used in our Make-at-Home projects. If you want to make a complete project and enclose it aesthetically, then select proper PCB, with required size. ​ Some general purpose PCBs with various sizes and connecting lines (dots and lines) are shown for reference. One custom made PCB (green coloured) is also shown as an example. ​ JUMPER WIRES : Jumper wire means , a small wire (about 15cm to 30cm length), low current capacity (normally used for signal transmission) with black coloured end connections on either end (or sometimes one end only). The end connection may be male type (which has pin projecting out) or female type (which has hole). So, the jumper wires are available with following end connectors 1) Male-Male 2)Female-Male and 3) Female-Female. The jumper wires are frequently used for prototyping and quick testing, by connecting holes of bread board or to external components or other circuits/modules. (BASIC) ​ CONNECTORS : Connectors are used to connect / disconnect single or multiple wiring connections easily and quickly. Various types are used on a circuit board, which depends on number of wire connections and current flow through them. The Berg strips and DC power connectors are highly used in most of the circuits. Some connectors, which are frequently used in the circuits are shown below. (IMPORTANT) RELIMATE CONNECTORS : Relimate connectors are also used for quick connect/disconnect multiple wire connections, mostly for PCB to the electronic component or module. Single or double row pins are used for these connectors and the number of pins varies per row as per requirement. The main advantage with Relimate connectors is, they are polarized, i.e., connects in one direction only, to avoid reverse connection. Some Relimate connectors are shown for reference below. (IMPORTANT) CLIPS : Clips are used to connect / disconnect a wiring connections easily and quickly, while testing a circuit. Various types of clips are used as per requirement. Some clipos, which are frequently used in the circuits are shown below. (IMPORTANT) WIRES : Single or multi-strand copper wires (electrical conducting material) are used for connection between electronic components and power supply connections. The cross-section of copper wire depends on the required current to flow through it, (which is directly proportional). Most of the times the copper wire is covered with insulating material (as a sleeve) like, PVC, PTFE etc. For easy identification of wire connection(s), various coloured sleeved wires are used in the circuit board(s) (BASIC) JUMPER CAPS : Jumper cap ( or shorting jumper) is a small connector with 0.1" (2.54mm) pitch, with rectangular plastic enclosure. A small groove is provided on upper portion, as a grip, for easy removal of jumper cap from a circuit. Jumper caps are used to simply connect or disconnect two pins as per users requirements / settings, which is provided in the circuit. It is also useful to quick testing of a circuit. (BASIC) HEAT SHRINK TUBE : A Heat shrink tube is made up of rubber material, in a tubular form. When a small length of the tube is exposed to small flame (or heat), the diameter of the tube shrinks to lower diameter. So, this is positioned on a soldered joint (or any wire joint), and small heat applied to it, to shrink and fit on the exposed metal joint and protect as insulator. (IMPORTANT) ​ The Heat shrink tubes are available with various diameters, out of which, 3mm and 5mm are very useful for Make_at-Home projects. A small gas lighter or hot air blower, is required to apply heat on the surface of the heat shrink tube. ​ INSULATION TAPE : An insulation tape is used to cover joined wires, especially used for mains supply, to avoid electrical leakage and protect from shock, through the exposed copper (metal) wire. Now-a-days, the insulation tapes are available in various colours also. Having at least one insulation tape is recommended. (BASIC) CELLO TAPE : A Cello tape ( or Cellophane tape ) is easily available and affordable, which is transparent and having glue one side. Due to it's transparency and quick fixing on surfaces, it is very much useful to hold small electronic components in position and insulating from conductors (tracks, wires etc.). The cello tapes are available in various widths, like half-inch, one-inch, 2 inch etc. Select the width to suit your requirement. (IMPORTANT) ​ DOUBLE SIDED TAPE : A double sided foam tape is useful to quickly position some electronic modules / components and its related items together. eg: placing small displays, modules on main PCB. (IMPORTANT) EMERY PAPER : A emery / sand paper is also very useful, to clean the surfaces of PCBs before soldering. It is also useful to clean the leads of electronic components before soldering. A high dense, very fine size emery should be used to avoid, unnecessary scratches on the surface, instead of cleaning. So, select emery paper with grit about 1000. (BASIC) ​ CABLE TIES : A cable tie (nylon zip tie) is useful to tie multiple wires / cables together. A cable tie is wrapped around a group of wires and cables and its free end is pulled though its rectangular opening for locking. By pulling the free end, through the eye on other end, the wrapped cables get tightened and locked automatically. ​ A marking on the cable tie or a label used with wires tie is useful for grouping the wires and identify them easily and their functionality. Now-a-days, cable ties are available in various sizes and colors. You have to select the required size. Using multi-coloured coloured cable ties are also useful to easily identifying the group of wires and purpose. (OPTIONAL) SCREWS & NUTS : Fasteners like small screws / bolts, nuts and washers are also important to fix the PCBs, heat sinks, displays, some bigger size components etc. Most of the times M2.7, M3 and M4 screw set of half-inch or one-inch lenght is used. The higher size fasteners are rarely used. Some times wood screws are also used, if the base or cabinet is made of wood / plywood etc. (IMPORTANT) ANTI-STATIC ENVELOPES : Better to maintain anti-static envelopes to keep the modules / circuits, which will protect them from damage due to static electricity, if any. Keeping the components and circuits at-least in a plastic self-sealing cover is preferable. (OPTIONAL) CONTAINERS/RACKS : To keep the electronic components, modules, circuits etc., suitable containers and racks are required. To assemble the completed circuit also, suitable containers / cabinets are to be selected. (OPTIONAL) WORKING TABLE AND CHAIR : Last but not least, a wooden table and chair is required for keeping the components, circuits, soldering station, power supplies etc., at a reach of hand is appreciated. The table and chair should be comfortable while working with the circuits (ergonically designed, if possible) (OPTIONAL) Seek ADVICE, but use your own COMMON SENSE. – Yiddish Proverb

POWER SUPPLIES The basic power supplies necessary for Make-at-Home projects are listed below with comment as Basic or Important or Optional keyword, which means that, BASIC : very much required and affordable IMPORTANT : having this tool is advantageous OPTIONAL : may be purchased later 1.5V CELL : The 1.5V cells (normally called as battery) are commonly used power supply for house-hold electronic gadgets, like remote controls, wall clocks etc. These batteries are used as single use and cannot recharge. These cells are used as power supply for our Make-at-Home projects and testing voltage references etc. Technically there are two types of 1.5V cells. 1)Carbon-Zinc battery cells, which are highly used and more affordable (BASIC) 2)Alkaline battery cells, which gives more life but little costlier (OPTIONAL) Now-a-days, the 1.5V cells are available in various sizes matches to its capacity (mAH), like AAA, AA, C, D etc. Multiple cell holder in series connection is shown for reference. 9V BATTERY : Basically, a 9V battery made up of 6 number of 1.5 cells connected in series. The 9V batteries are commonly used for house hold gadgets, like radios, multi-meters, electronic circuits etc. These batteries are also single use and cannot recharge, except Lithium-Ion batteries. These batteries are commonly used as power supply for our Make-at-Home projects and testing the circuits. Technically there are three types of 9V batteries like 1.5V cells. 1)Carbon-Zinc battery cells, which are highly used and more affordable (BASIC) 2)Alkaline battery cells, which gives more life but little costlier (OPTIONAL) 3)Li-ion battery, is rechargeable, but costlier (OPTIONAL) Lead-Acid & SLA BATTERIES : (OPTIONAL) Lead-Acid battery is the oldest technology and highly used system of storing electrical energy. The lead plates are used as positive (Plain Lead, Pb) and negative (Lead-Dioxide,PbO2) probes and separated by Sulfuric acid (H 2 SO 4 ) as electrolyte. Each cell can hold approximately 2.1V. So, for getting required voltage, the lead-acid cells are grouped together in series. Thus, by grouping 3 cells for 6V, 6cells for 12V, 12cells for 24V approximately, and so on. ​ Most of the automobiles use Lead Acid batteries. Now-a-days, Sealed Lead Acid (SLA) batteries are available, which is almost maintenance free. 12V SLA batteries are used in some of our Make-at-Home projects. Nickel-Cadmium (Ni-Cd) CELLS / BATTERIES : (OPTIONAL) Ni-Cd cells are normally available at 1.2 Volts and at various ampere hour ratings. They are highly used in AA size, which holds approximately 850mAH. These cells has to be charged at 10 percent of its mAH for about 12 hours for full charging. For higher capacities (mAH), D size Ni-Cd cells are used. ​ A bunch of Ni-Cd cells are connected in series to get more voltage (in multiples of 1.2V), which forms as battery pack. These are highly used in cameras, flashlights, emergency lights, RC toys etc. ​ Now-a-days, the usage of Ni-Cd cells/batteries are reduced, after introduction of Lithium cells. 3V COIN BATTERIES : (OPTIONAL) Normally the 3V coin batteries are used for remotes, clocks etc. These 3V batteries are used for power supply of RTC (Real Time Clock) circuits in our Make-at-Home projects. Lithium-Ion (Li-Ion) CELLS & BATTERIES : (IMPORTANT) The Lithium-Ion cells are available as 3.7V, with varying capacities starting from 1000mAH. The Li-Ion cells are re-chargeable using specific (balancing) charger(s). ​ For more capacity and voltage requirements, the Li-Ion cells are connected in parallel (for more mAH) and series (for more Voltage). A 2P3S pack of 2200mAH cells conneced means, cells are connected as 2 parallel and 3 series, which means 4400mAH (2x2200) capacity with 11.1V (3x3.7). Lithium-Polymer (LiPo) CELLS & BATTERIES : (OPTIONAL) The Lithium Polymer cells are improved from Lithium-Ion cells by replacing the electrolyte made of a special polymer instead of liquid/gel electrolyte, with nominal voltage as 3.7V. The new technology reduces the weight of the cell as well as increases the capacity (mAH), which compared to any rechargeable cells. LiPo cells also packed like Li-Ion batteries to get more power and more voltage as power bank(s). Special balanced chargers has to be used for LiPo cell/battery charging. Due to its high capacity to weight ratio, LiPo batteries are highly used in mobile, electric vehicles, drones etc. Lithium-Iron-Phosphate (LiFePo4) CELLS & BATTERIES : (OPTIONAL) The LiFePO4 cells are made of latest technology, with high capacity to weight ratio, normally available as 3.3 Volts. Other advantages are, available in higher capacities like 6000mAH, high discharge rates, withstand high charging voltage (upto 4.2V) etc. ​ These cells are useful for making power banks using parallel and series for electric vehicles and robots etc. Special balancing chargers are to be used for charging these cells/batteries 5V POWER BANKS : (OPTIONAL) Now-a-days, 5 Volts power banks are in use heavily for backup of cell phones, which uses Li-Ion battery to hold the energy. An internal in-built circuit charges the inner battery to its voltage using 5VDC input and discharges as 5VDC, whenever required. ​ Most of the electronic circuits works on 5VDC, these power banks are useful for our make-at-home projects MAINS SUPPLY : (BASIC) The Mains supply is AC (Alternating Current) and it is normally available to you, in either 220VAC 50Hz or 110VAC 60Hz. Some of the Make-at_home projects use mains power supply directly or step-down to required voltage using transformer or SMPS circuit. The mains power supply is very much essential for soldering, lighting, charging of batteries, power supply for the circuits/gadgets etc. DESKTOP POWER SUPPLY : (IMPORTANT) A desktop power supply working on the Mains supply is essential to test a circuit board. It's working cost is very less, when compared to single use batteries. Having a desktop power supply with various DC output voltages (like 3VDC, 5VDC, 8VDC, 12VDC etc.) is very much needed for Make-at-Home projects. ​ Click here to know, how to make your own All-in-one desktop power supply. SOLAR POWER SUPPLY : (OPTIONAL) Now-a-days, the Solar power supply is gaining usage, due to availability and affordability of solar panels and related equipment. You may charge batteries using the solar power and use the power supply from the batteries, whenever required. ​ Some Make-at-Home Solar power projects are presented by Simple Mechatronics, for your knowledge and practical use. An investment in KNOWLEDGE, pays the best interest. – Benjamin Franklin

Sonar RADAR The Sonar RADAR, is to find any obstacle within a distance range by oscillating Ultrasonic Sensor fitted on a Stepper motor shaft. The distance of obstacle(s) are read by the ATMEGA16 micro-controller for each step of Stepper Motor and the distance is proportionally represented as a ray on GLCD (Graphical Liquid Crystal Display). ​ ATMEAG16 is 40 pin Micro-controller is selected for the project, since GLCD requires more pins for its display system. ATMEAGA16 works on 1MHz default clock frequency, is heart of the system. ​ GLCD (JHD12864E) display used in this project, has good viewing size of pixel size (0.48mm x 0.48 mm) and screen area (66mm X33mm approx.) with 128 x 64 pixel resolution, works on 5VDC supply. It has 20 pins, out of which 2 for power supply, another 2 for back-light LED, on extreme ends. 8 pins are used as data lines and 6 pins for control lines and two pins (3 and 18) are for contrast adjustment. The screen is logically divided into two panes as 64X64 pixels on left side and 64X64 pixels on right side, which makes 128X64 pixels in total. The left side pane is selected using CS1 pin and similarly right side pane is selected using CS2 pin. The data and command to GLCD is transmitted in 8 bit format by selecting RS pin setting high/low. The following two functions are used to write pixels and lines as rays, on the GLCD in source code. GLCD_writePixel ( int x, int y ) GLCD_showRay ( long dist, float xstep ) ​ ​ Working Concept/Description: The circuit shown below should be made on a general purpose PCB, except, Stepper Motor and Ultrasonic sensor (HC-SR04). The Ultrasonic Sensor should be placed above the Stepper motor shaft, using proper wheel and fixing arrangement ( view video ), so that, the ultrasonic sensor, rotates to a particular angle, matching to stepper motor shaft. ​ The ATMEAG16 continuously generates/reads signals and process them in the following order in a while loop: 1) Rotates the Stepper motor in a specified steps. 2) Sends Trigger pulse to Ultrasonic Sensor. 3) Reads the Echo pulse timing 4) Calculates the distance. 5) Draws a line (ray) proportional to the distance. 6) Once the motor rotates required number of steps, then, it rotates in opposite direction, which makes oscillations of ultrasonic sensor. The DC power supply (8V to 12V) is connected to Stepper motor driver. A 5VDC is derived from the same board, which is used as power supply for micro-controller, ultrasonic sensor and GLCD. In case, the board does not have the 5VDC output, then use separate 5VDC supply through IC 7805. ​ Full circuit-diagram is available below: ​Initial Setup and Usage: After assembling the circuit on a PCB, connect 8V to 12V DC power supply to the stepper motor control board and switch ON the power switch SW_1 Then load/burn the SonarRadar.hex file to the Micro-controller (ATMEGA16) using AVR programmer. You may connect Stepper motor, Ultrasonic sensor and GLCD before or after writing HEX file to ATMEGA16. Once you upload and switch ON the power supply to the circuit board, two types of triangular patterns will be displayed for a while, which is a self-test for the GLCD, then the radar system starts. Then, the stepper motor rotates with fixed steps, which changes the angle of ultrasonic sensor direction, for each step. The ATMEGA16, reads the distance using ultrasonic sensor at that angle and a line is drawn like a ray on the GLCD proportional to the calculated distance. ​ In case, the stepper motor is not rotating to the required direction, then change the input and/or output connections of the stepper motor, until it rotates to match the direction of rays drawn on the GLCD. CODING: The code is developed using C language and compiled using AVR studio 4. The code may be uploaded/ written to ATMEGA16 microcontroller (MCU) using any suitable AVR programmer through ISP port as shown in the circuit. All the Variables and functions are named for easy identification of purpose using prefix name for easy identification of the controlling component The user define variables are defined initially in the SonarRadar.C file like, #define STEPPER_DELAY 25 // delay to settle the stepper #define STEPPER_STEPS 3 // number of step signals sent to stepper driver So, the value may be varied as per requirement and recompile using AVRstudio4 (or next version) and upload to ATMEGA16. click the link / attachment to download the file and rename as SonarRadar.HEX , then upload to ATMEAGA16 using any suitable AVR programmer. SonarRadar.HEX For source code (in C-language), (SonarRadar.C) please send message through contact form . The code will be sent to your e-mail. Knowing is not enough; we must apply Willing is not enough; we must do – johaan wolfgang von goethe

About . . . Author SHL... Mr. SHL is a Computer Science Engineering Student and interested in automobiles and automation. ​ ​

Small Robot : 9 Obstacle Avoider # . < < < Previous List All Next > > > . Introduction: An Obstacle Avoider is also a self controlled Robot, which will recognize obstacle (like wall) and avoids collision with the vertical surfaces. Many types of sensors may be used for finding obstacle, like IR distance sensor, Ultrasonic Distance sensor, pressure switches etc. But, using Ultrasonic sensor is simple and reasonable to recognize the obstacle. One Ultrasonic distance sensor is fitted on front side of the Small Robot to measure the distance of obstacle. The distance is read from the ultrasonic sensor by the micro-controller (ATTINY84), then analyzed to take turn accordingly, based on the 4 bit motor control data, through the motor driver IC (L293D) on base board. (refer Small Robot Base Frame for motor control codes). The concept of Obstacle Avoider Robot is to avoid flat vertical obstacles. Basically, the Obstacle Avoider periodically sends an ultrasonic wave and measures the distance of obstacle by the time taken to receive its reflected wave from the obstacle. If the distance measured is less than the set distance value, then takes turn accordingly. Here, the Small Robot is programmed to take a right or left turn, when it founds any obstacle within its set distance, else moves forward continuously. About Obstacle Sensing: Here, the Obstacle Avoider uses one ultrasonic sensor module, HC-SR04 (readily available) to read the presence of obstacle in front of it. The ultrasonic sensor module, consists of a ultrasonic wave generator and ultrasonic wave receiver, with required on-board electronic circuit. The ultrasonic sensor module is available with four pinouts, i.e., Vcc, Ground, Trigger and Echo. The ultrasonic sensor module is connected to 5VDC supply across Vcc and Ground pins. Whenever the Trigger pin goes HIGH ( logic 1 ), for 10 micro-seconds, the ultrasonic wave generator sends ultrasonic waves, about 40 KHz, which is not audible to human ears. Then the ultrasonic wave receiver starts listening for the reflected ultrasonic wave. Then, a high pulse is generated from Echo pin, proportional to the time taken to receive the reflected ultrasonic wave by the ultrasonic wave receiver. The Echo pulse time ( or Time of Flight ) is measured by the micro-controller (ATTINY84) and converted to distance by using suitable formula. If the distance obtained by the formula is less than the set distance (means obstacle is near to the Obstacle Avoider or within critical distance), then, the Obstacle Avoider takes turn accordingly, else moves forward. The Concept of working of Ultrasonic sensor is shown below. As the generated Ultrasonic wave moves in a narrow path, sometimes the ultrasonic sensor module may not recognize thin obstacles (like wires etc.) and obstacles above or below the ultrasonic wave path. The ultrasonic sensor module may not recognize the obstacle with inclined surfaces, as the ultrasonic wave may get diverted its path and the ultrasonic receiver may not receive the reflected ultrasonic wave. To avoid such errors, multiple ultrasonic sensor modules are to be used at various directions. Working of Obstacle Avoider: Two versions of Obstacle Avoider are developed. The first version uses a bracket to hold the ultrasonic sensor module at fixed position. So, to check the obstacles at sides, the Small Robot takes right and left turns, at regular intervals. In the first version, only the ultrasonic sensor module is connected to the control board, using jumper wires. The distance of obstacle is measured continuously by the micro-controller (ATTINY84), then takes turn, if the obstacle is found within the critical distance, else moves forward. In this version, the movement of Small Robot is slow, with intermittent brakes, since it takes small turn at regular intervals, to find obstacles at sides. In the second version, a servo is fitted on the bracket and used to swing the ultrasonic sensor module on its horn. The servo motor is also controlled by the micro-controller (ATTINY84) and set to swing right and left side. So, the obstacle distance is read continuously from right, left and forward. The Small Robot takes turn according to the obstacle found, else moves forward. Here, the searching angle for obstacle is high and movement of the Small Robot is also improved. On the control board, no shorting jumper should be used (existing shorting jumper should be removed, if any). Then, the RED LED glows, when the obstacle is found within critical distance, else YELLOW LED glows. This is simple and very useful indication, to know the working status of ultrasonic sensor module. A button switch, SW1 on control board, is useful to start the Obstacle Avoider, after switching ON the power supply to the Control Board. The SW1 switch should be pressed twice in first version, to search the obstacle in both sides, else the Small Robot will search for obstacle in forward direction only. The complete circuit diagram of Control Board with ATTINY84, is available below. Use separate jumper wires to connect ultrasonic sensor module and servo motor to Control board. Omit servo motor and its connections in first version. Download OA1 HEX file Download OA2 HEX file Contact for Source Code Download file(s) from above link and remove .TXT extension. . < < < Previous Once Small Robot's Base Frame is made, then, various control systems for Small Robot are developed and available for selection, using 'Previous ' and 'Next ' buttons here. Next > > > .

Transistors A transistor is a semiconductor package having combination of three P-type and N-type semiconductors successively and normally used to switching or amplify weak signals in electronic circuits. It usually have three terminals for connection to an external circuit. Transistors are basically classified into two types: 1)Bipolar Junction Transistors (BJT) and sub-classified as NPN and PNP transistors. 2)Field Effect Transistors (FET) and sub-classified as JFET and MOSFET Bi-Polar Transistors: There are two types of bi-polar transistors, which are differentiated by the order of the P-type and N-type semiconductors and named them accordingly. Both the types have different behavior when used in a circuit. Out of three semiconductor layers, the middle one (called as BASE) is very thin layer and controls the flow of the electrons, i.e., current passing though the transistor. Other two semiconductor layers are on either side of the BASE and called as EMITTER and COLLECTOR. The COLLECTOR is the thickest layer in a transitor. Out of three connections of a transistor, input power supply is connected to EMITTER, power output is connected to COLLECTOR and signal is connected to BASE. A small change in current to BASE of a transistor effects, significant change of flow of current through the transistor, i.e., from EMITTER to COLLECTOR. Two different symbols are used for NPN and PNP transistors and the emitter is marked with a arrow pointer, base is at middle and straight line for collector. The direction of arrow pointer also indicates the direction of current flow. NPN Transistor: In the NPN transistor, P-type material is in between two N-type materials. Even though, both the ends are made of N-type semiconductor material, they are not interchangeable, due to difference in doping. Normally the middle P-type layer is very thin and one of the N-type layer is larger than other end. Here larger layer is called as Collector and other end is called as Emitter . The middle thin P-type layer is called as Base . The two voltage sources (VBE and VCE), required for proper working of an NPN transistor is shown here. Very small current flow through the Base (IB) due to VBE, makes the lower PN-junction, forward biased like a diode. Due to this phenomenon, majority of electrons cross the barrier between the Emitter and Collector also, which makes the current flow from Collector to Emitter in high quantity. So, with a small current flow at Base, high current flows between Collector and Emitter. So, the total current flow at Emitter is sum of Current flow through the Base and Collector. For practical use, NPN transistor is configured as either Common Emitter or Common Collector mode. The power source is connected between the Collector and Emitter and signal (low current and voltage input) is applied at Base pin. The effect of signal in both the configurations are shown below. Resistors are to be used to control the current flow through the Collector, Emitter and Base as required, which is dependent on its design parameters (available in data sheets of the particular transistor) PNP Transistor: Where as in the PNP transistor, N-type material is in between two P-type materials. Like NPN, both the ends (P-type) are not interchangeable, due to difference in doping. Here the middle N-type layer is very thin and one of the P-type layer is larger than other end. Here also, larger layer is called as Collector and other end is called as Emitter . The middle thin P-type layer is called as Base . For the PNP transistor also, the two voltage sources (VBE and VCE), required for proper working, as shown here. Very small current flow through the Base (IB) due to VBE, makes the lower PN-junction, forward biased, and due to this phenomenon, majority of electrons cross the barrier between the Emitter and Collector also, which makes the current flow from Emitter to Collector in high quantity. So, with a small current flow at Base, high current flows between Collector and Emitter. So, here also the total current flow at Emitter is sum of Current flow through the Base and Collector. The main difference w.r.t. NPN is, the Emitter should be connected towards positive supply and Collector to negative supply. For practical use, PNP transistors also configured as either Common Emitter or Common Collector mode. The power source is connected between the Collector and Emitter and signal (low current and voltage input) is applied at Base pin. The effect of signal in both the configurations are shown below. Resistors are to be used to control the current flow through the Collector, Emitter and Base as required, which is dependent on its design parameters (available in data sheets of the particular transistor) The NPN and PNP transistors are highly used as signal amplifiers and logic gates. The ratio of current flow at Collector to Base is called Gain of the transistor, which is always greater than 1 (typically 100). Field-Effect Transistor (FET): A Field Effect Transistor (FET), (also called Uni-polar Device / Transistor), is different from normal Bi-polar Junction Transistor (BJT) in construction and working principle. A BJT (eg NPN or PNP) is current controlled device, which responds to current flow through its base. Where as an FET is voltage controlled device, which responds to the voltage at gate pin w.r.t. source pin, so has very input resistance. Due to its construction and working principle, the FET's are classifed as Junction Field Effect Transistors (JFET) and Metal Oxide Semiconductor Filed Effect Transistor (MOSFET). Junction Field-Effect Transistor (JFET): Junction Field Effect Transistor (JFET), are two types based on the semiconductors used for construction. i.e., n-channel JFET and p-channel JFET, which is depending on the main and control semiconductors used for construction. Both the types of JFETs are shown here. A JFET is operated in reverse biased, between the Gate and Source pins for control. So, when the voltage increases at PN-junction, between the Gate and Source, the Reverse-bias reduces / prevents the current flow (ID) through the Drain pin. Higher the reverse bias voltage causes, higher the resistance (i.e., lower the current) between the source to drain. The working system of n-channel JFET is shown here. The polarity of power supply is reversed for p-channel JFET. Metal Oxide Semicondictor Field-Effect Transistor (MOSFET): Metal Oxide Semicondictor Field Effect Transistor (MOSFET ) is also called as Insulated Gate Field Effect Transistor (IGFET ). The MOSFET does not have PN-junction like JFET, but controlled by P type or N type channel The channel is controlled by a Silicon Dioxide (SiO2) layer. The MOSFET is sub-divided into Depletion type MOSFET (D-MOSFET) and Enhancement type MOSFET (E-MOSFET). The working principle and differences of D-MOSFET and E-MOSFET are explained below. Depletion type MOSFET (D-MOSFET): The D-MOSFET, either n-type or p-type semi-conducting material, is diffused to source and drain, which is connected by a narrow channel of same material. The remaining gap is filled with the opposite (p-type or n-type) semi-conductor. A Silicon-dioxide layer is used at the channel area, which is connected to the gate. When the gate is connected in reverse biased w.r.t. source, the width of the channel near gate (which is connected to SiO2), increases and reduces the flow of current between source and drain. So, the current flow between source to drain is inversely proportional to gate voltage. In case, the gate is connected in forward biased w.r.t. source, then the width of the channel increases and more current flows from source to drain, which is called as enhancement mode and it is very rarely used on D-MOSFET. Enhansement type MOSFET (E-MOSFET): The E-MOSFET, either n-type or p-type semi-conducting material, is diffused to source and drain and there is no connection between them, except a Silicon Dioxide (SiO2) layer connected to the gate pin. The gap is filled with the opposite (p-type or n-type) semi-conductor. When the gate is connected in forward biased w.r.t. source, a channel is created to connected the semiconductors of source and drain, which allows current flow between the source and drain. The width of the channel near gate (which is connected to SiO2), increases with more forward biased voltage, which in turn increases the flow of current between source and drain. So, the current flow between source to drain is directly proportional to gate voltage. Transistor Packages: Transistors are available in various packages, depends on current flow, maxiumum power and response speed (in MHz). Some of the commonly available packages are listed here. TO-3, TO-18, TO-92, TO-220, TO-220AB, TO-226, SOT-32 etc. ​ Transistor Revolution is origin for Modern electronics, Micro-controllers and Computers. – Simple Mechatronics

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Capacitors: Capacitor is also called as Condenser in electronic circuits. The characteristics of a capacitor is measured in terms of Capacitance, which is the Quantity of Charge stored in a capacitor. The units of Capacitance is Farads in S.I. system. One unit of Farad is very high for all practical purposes. So, microfarads , nanofarads , picofadas are used in the circuits. Capacitance: A capacitor contains two electrical conductos separated by a dielectric medium. Conductor of a capacitor may be a thin metallic foil or thin metal bead or an electrolyte. The nonconducting dielectric commonly used may be glass or ceramic or plastic film or paper or mica, air etc. The capacity of Capacitor increases with decrease in the gap between the conductors and increase of the area of conductors Fixed value Disc Capacitors: Some disc capacitors are marked their capacitance in pico Farads (pF) in three digit coded form. The first two digits indicates value and third digit indicates number of zeroes followed. Refer examples shown below. Fixed or Disc Capacitor does not have any polarity. The two pins may be connected to either positive and negative lines of the power supply or electronic signal. The capacitance value or code is printed on its surface. Maximum voltage it withstands are printed on some capacitors. The maximum value of these capacitors are 1 micro Farad and are available in lower fractions like nano Farads and Pico Farads Fixed value Polarized Capacitors: Polarized Capacitor contains negative terminal marked on its surface. i.e., a black band with negative (-) symbol. For new capacitors the negative terminal is kept shorter than positive terminal. These are mostly electrolytic (conducting material) capacitors. ​ The capacitance of these capacitors are normally starts from 1 micro Farad and available up to 10,000 micro Farads. The capacitance value and maximum voltage it withstands are printed on its surface. ​ Care should be taken while connecting a Polarized Capacitor to avoid damage. i.e. positive terminal of capacitor should be connected to positive supply line and negative terminal of capacitor should be connected to negative supply line only. Variable value Capacitors: Variable Capacitor can vary its capacitance by changing the conductor area by moving the conducting plates, normally by rotation. These capacitors normally have air as dielectric medium and its capacitance ranges in pico Farads. A tank circuit shown here, contains a capacitor and an inductor (coil) which generates frequency depending on the values of capacitance and inductance. A transistor is used to maintain the frequency with proper amplitude. These capacitors are mainly used in tank circuits, which generates oscillations and are used in radio (high frequency) circuits, for tuning the required frequency. Capacitors in DC circuits: Capacitors in DC circuits: Capacitors are used as temporary storage medium in DC (Direct Current) circuits. But, the charge across the conductors leaks through the dielectric medium after sometime. The leakage is high initially and slows down after some time. ​ A capacitor is used as filter in rectifier circuits to reduce the ripples of unregulated voltage, there by generate study voltage. Initially a capacitor charges quickly then slows down the charging rate and matches to the source voltage (i.e., saturation level). Similarly, on discharge, the discharge rate is very high initially, then slows down and reaches to zero level (total discharge). Capacitors in AC circuits: Capacitor in AC circuits behaves differently than DC circuits. A change in voltage on conductor of one side of the capacitor effects on conductor of other side of the capacitor. The output signal is reversed to the input signal polarity. So, AC signal will be transferred in series using capacitor where as DC component will be blocked across the capacitor. High frequencies and/or high capacitance makes easy passage of AC signal through the capacitor. The resistance offered in AC signal across a capacitor is called Impedence marked as Z . So, DC is considered as lowest frequency (almost zero frequency), therefore, the Impedence is highest (tends infinity) for DC signal. Capacitors in PARALLEL connection: If multiple Capacitors are connected in parallel in electronic circuits, the resultant capacitance is equal to sum of each capacitance in the circuit. So, the Resultant Capacitance is always more than any capacitance in parallel connection in the circuit. Capacitors in SERIES connection: If multiple capacitors are connected in series in a circuit, the resultant capacitance depends on the gap between the conductors of each capacitor. So, the Resultant gap is equal to sum of gaps between each capacitor in series. So, in terms of capacitance, inverse resultant capacitance is equal to sum of inverse capacitance of each capacitor in series. The Resultant Capacitance is always less than any capacitance value of any capacitor in the series connection in the circuit. SUPER CAPACITORS: Super Capacitor is a capacitor with high-capacitance than electrolytic capacitor. It works as a low time storage battery. But, its storage voltage (normally available up to 5V) is very less comparative to normal capacitor. ​ The units used for Super Capacitors are in Farads and normally available in 1Farad or more.

microcontroller - COMMUNICATIONS Micro controller Communication means, communicating the internal data or status of a micro controller to external world through its pins as voltage or reading the voltage from its external pins and saving it its registers for further processing as per its program. The communication happens so many ways with micro-controller. We will discuss the concepts of micro controller communication one-by-one. ​ All the Communcation process, values and direction is dependent on the bit(s) set in the related registers of the micro-controller. These bit(s) may be varied by the program code as per your requirement. Analog Communication: In micro controllers, using Analog comminication is limited. But, the human world works on analog values, the micro controllers are provided with ADC (Analog to Digital Converter) and DAC (Digital to Analog Converter) features. ​ The ADC converts the analog value (input voltage) to suiable digital form and saves in its registers for further processing as per the program. ​ The DAC converts the digital value set in its register to suiable analog value (output voltage) for further external equipment control or display. ​ The processing and features about ADC/DAC are discussed seperately and press here for ADC/DAC concepts. Digital Communication : ​ The digital communication mainly works on logic 0 and logic 1 as either input or output. Normally voltage level towards ground level or zero volts is considered as Logic 0. Where as for Logic 1, voltage towards 5VDC as TTL (Transistor Transistor Logic) or some times 3.3V or Vcc are considered for most of the micro controllers. ​ One or multi bit Status: The highly used coomunication is one or more bit(s) status input or output. This is achieved by setting the required bits in the data direction register(s). By setting 1 or 0 in the data direction register, the pins connected to the register, reads input logic from the specified pin or sends output logic to the specified pin. Generally, any pin may be programmed as input or output pin, except for special purpose pins indicated in the data sheet(s). ​ This communication is useful to read one or more button status or status from other electronic equipment or drive one or more LEDs or any other digital devices like displays etc. Parallel Data Communication : The parallel communication is reading or writing a number of data bits simultaneously. Normally, EIGHT number of bits (named as BYTE, identified using ASCII) are used for transmission. Normally, a clock pulse is also sent with the 8 bit data to validate the data on transmission. ​ Serial Data Communication: Serial Communication is highly used in micro-controller projects. The main advantage with Serial Communication is, it uses less number of conductors (wires) for data transmission when compared to parallel data communication and long distance data transmission is also possible with serial communication. ​ The main disadvantage with the serial communication is all the data bits has to be transmitted through single wire sequentially, which takes much time compared to parallel data transmission. ​ Univeral Serial Data Communication: USART (Universal Synchronuous Asynchronous Receiver and Transmitter) or UART (Universal Asynchronous Receiver and Transmitter) are common and Universal serial data communication method used in most of the micro-controllers. ​ The parallel data is converted to serial bits and transmitted through Transmitter pin or the serial data is received from Receiver pin and converted to parallel data in USART/UART communication. ​ In synchronous method, a clock is generated by the master processor and slave(s) transimit or receive the serial data using the clock. Where as in Asynchronous method, all the processors generate their own clock matching to same frequency and data is transmitted and received using their clock frequency by eliminating the transimission of clock connection to all the processors. ​ The registers in the micro-controllers may be set for Full-Duplex (Transmit or Receive simultaneously) or Half-Duplex ( Only Transmit or Receive at-a-time) or Simplex (Uni-direction, either Transmit or Receive) as per the requirement and feature(s) supported by the micro-controller. ​ The USART/UART communication is normally used to connect to PC (personal Computer) through COM port using Voltage level managing board as interface. ​ SPI Communication: ​ SPI (Serial Peripheral Interface ) uses three wires for communication (MOSI MISO and SCK). The data direction will be controlled by the master processor, which also generates clock pulses for accuracy of communication. The slave processor on the other hand communcates with the master synchronising the clock from the master. This is a full-duplex (two way) stable communication. MOSI = Master Out Slave In, means data is transferred from master to slave processor. MISO = Master In Slave Out, means data is transferred from slave to master processor. SCK = Serial Clock, is generated by the master processor for stable and accurate communication SS = Slave Select, the slave select pin for selecting as master or slave using hardware or software. A single master processor may be connected to multiple slaves and control them selecting the SS pin of slave processor. ​ Two Wire Communication: ​ Most of the micro controllers support the Two Wire communication, which is well known as Inter Integrated Circuit or TWI or IIC or I2C (pronouced as I squared C ) communication. Only two wires (SDA and SCK ) are used for communication with multiple devices like micro-controllers, sensors , EEPROMs, ADC ICs, DAC ICs and other ICs which support IIC. ​ All the devices will be connected to the same bus (two wires) and identified by their IDs marked inside the chip by hardware or software. A standard protocal will be followed to access / communicate with each device using master and slave concept. ​ The ICs marked as slave works as slave only, where as other ICs and micro-controllers may work as either master or slave as per its programming. ​ Univeral Serial Bus (USB) Communication: ​ Some micro-controllers support USB communcation, which is very useful for data transfer or data backup from / to devices like pen-drives and connecting external gadgets like keyboard/mouse etc. ​ Four wires are used from USB connection. Two wires are for power supply (+5V and Ground) and Two wires for Data transmission (D+ and D-). So, the micro controller which supports USB marked with D+ and D- pins. ​ Various data transmission speeds are available, for USB data transfer, depending on the versions. They are Low speed 1.5Mbps or Full speed 12Mbps in USB version 1; High speed 480 Mbps in USB version 2; more than 4.8 Mbps and upto 6Mbps in USB version 3. ​ Most of the micro-controllers support USB version 1 speeds only which are useful HID ( Human Interfac Devices ) interfacing, like keyboard, mouse, sensors etc. ​ All the USB devices uses standand individual protocols. The micro-controller used in a project has to support and communicate with the devices using the proper protocols. ​ SUMMARY: ​ The type of communication is used based on the requirement , speed and type of interface avaialble on the sensor / device, that is to be controlled or communicated. The micro-controller has to be selected accordingly. GOOD LUCK TO YOU.

Transformers A transformer works on mutual inductance using AC (Alternating Current) power supply as input to step-up or step-down the output voltage. The input and output coils for mutual inductance are normally connected by a soft iron core. Basics of Transformer: A transformer mainly consists of a core made up of steel laminations for magnetic connection between two coils . Where as, a coil is considered as multiple insulated conducting wires (generally made of copper) wound on the ferrous core. Out of two coils, the coil, which is connected to input AC power supply is called as Primary coil and the other coil, which is generating the AC power due to mutual inductance is called Secondary Coil . Transformers are available with various types of constructions. Various shapes of ferrous cores are designed for least leakage of magnetic flux. The ferrous core is generally made of laminated sheets with insulation in between them to have least eddy current losses. Ferrite core is used for high permeability, which is required, when the frequency of AC input power supply is high. Some times both primary and secondary coils are wound one on another with high electrical insulation in between them. Basic Transformer Formulae: For any transformer, the total power conversion is constant, which mainly depends on the primary coil, secondary coil and core. ​ So, theoretically, Input Power = Output Power, ignoring winding losses, eddy current losses etc. i.e., Vin X Iin = Vout X Iout considering all losses together, the efficiency of transformer is ratio of Output power to Input Power, which varies from 80% to 95% approximately. ​ Similarly, the output voltage depends on the input voltage and ratio of number turns of secondary coil to primary coil. i.e., Output Voltage / Number of Secondary turns = Input Voltage / Number of Primary turns Vout / Nout = Vin / Nin or in other words, Vsecondary / Vprimary = Nsecondary / Nprimary The above ratio is called Transformer ratio or Transformation ratio , which is denoted by r . The main points to be notes for a transformer are , 1 ) It works on AC (Alternating Current) power supply only. 2) It works on mutual inductance between two coils (input and output). 3) A Ferrous (or Ferrite) core is used as a medium to transfer magnetic connection between the two coils. 4) The two coils are electrically isolated from each other 5) The output voltage and current depends on input voltage, current and number of turns of primary and secondary coils. Types of Transformers: So many Varieties of transformers are used, depending on the necessity of output, core type, cooling system etc. Some of the types are listed below. 1) Step-Down Transformers: Step-down transformers are highly used in electrical and electronic circuits. A step-down transformer reduces (steps-down) the output voltage w.r.t. input voltage. i.e., The output voltage available at secondary coil is less than the voltage available at primary coil. As the total power of a transformer is fixed, the current in output (i.e., at secondary coil) increases. ​ A Step-down transformer ( mains AC supply to 9VAC) is shown here, which is normally used in electronic circuits. 2) Step-Up Transformers: Step-up transformers are used, when more output AC voltage is required, w.r.t. input AC voltage. So, the output voltage available at secondary coil is more than the input voltage applied at primary coil. ​ As the total power of a transformer is fixed, the current in output (i.e., at secondary coil) decreases w.r.t. input current. 3) Multiple Voltage Output Transformers: Some transformers have single primary (input) coil and multiple secondary (output) coils. The output coils may not have interconnection to have separate and individual voltages or connected in series. Most of the transformers used in electronics circuits are center tapped transformers. These transformers are used in power supplies for single or different circuit boards, with various required voltages, from mains. 4) Constant Output Voltage Transformers: Some transformers have multiple input connections on primary coil and single (or sometimes more) secondary coil as output. The input tappings are manipulated using a circuit to have fixed output voltage. This type of transformers are normally used in stabilizers, to have fixed AC output voltage, when AC input voltage is fluctuating. 5) Variable Output Transformers: The Variable transformer have single coil wound on a ferrous core. The input power supply is connected across the coil at a suitable number of turns. The output voltage is obtained by having movable tapping point on the coil (using a spring loaded brush). ​ As the Ferrous core is in a circular shape, the movable brush contact is rotating, which is connected by arm to the central axis of the circular core. So, the output voltage is obtained based on the number turns contacted to movable brush, by rotating the central shaft. Transformer Cooling: The transformers used for low power, which are normally step-down transformers, used for power supply to electronics circuits are air cooled. ​ For the transformers used for high power and continuous duty cycle are oil cooled, where the transformer core and coils are submerged in an insulated oil in an enclosure. The oil in the enclosure, gets circulated to atmosphere for heat transfer.