How to design a constant or Variable power supply using LM 2576 ...

               The LM2576 series of regulators from National Semiconductor are low-cost integrated circuits that provide all the active functions for a step-down (buck) switching regulator. The ICs are capable of driving a 3A load with excellent line and load regulation. The devices are available in both adjustable output and in fixed output voltage versions (3.3V, 5V, 12V and 15V).

               The LM2576 requires only a minimum number of external components. A standard series of inductors optimized for use with the IC are available from several different manufacturers. Because of the high efficiency of the switching regulator, the required size of the heat sink will be small and in some cases no heat sink is required.

                The regulator will work with a wide input voltage range: up to 40V for the low voltage and up to 60V for the high voltage (HV) version. Other features: external TTL shutdown capability with 50 µA standby current, cycle-by-cycle current limiting and thermal shutdown for full protection under fault conditions.

The LM2576 is available in both surface mount (TO-263 5-Lead) and TO-220 package. LM2576 datasheet (PDF).

5V/3A step-down switching regulator schematic

The schematic above is simple, easy to build and cost effective, producing 5V from a 7V-40V unregulated supply with a maximum output current of 3A. When using the LM2576HVT-5V version the input voltage can be as high as 70V.

Parts list:

• IC1: LM2576T-5V or LM2576HVT-5V (National Semiconductor)
• L1: 100µH (415-0930, 67127000, PE-92108, RL2444)
• D1: 1N5822 (Schottky Barrier Rectifier diode)
• C1: 100µF/75V (Aluminum electrolytic capacitor)
• C2: 100µF/75V (Aluminum electrolytic capacitor)

1.2-50V/3A variable output step-down switching regulator:

Using the LM2576HVT-ADJ or LM2576HVS-ADJ adjustable version we can build a simple switching regulator with a 1.2-50V, 3A variable output from a 55V unregulated power supply. The maximum output current is 3A.

Parts list: IC1: LM2576HVT-ADJ or LM2576HVS-ADJ L1: 150µH (67127060, PE-53115 or RL2445) D1: 1N5822 (Schottky diode) C1: 100µF/75V (electrolytic capacitor) C2: 2200µF/75V (electrolytic capacitor) R1: 47K potentiometer R2: 1.2K resistor

How to make simple H-Bridge from Mosfet ...

                     

                 Hi friends... in this tutorial we are going to learn how to make a simple H-Bridge using Mosfet.H-Bridge like L293D. L293D are easy to use but the limitation is more, they support only limited range of voltage and current , but if we use  Mosfet for H-Bridge we are full-flexed to use the circuit to wide range of voltage and current . 

                  In this tutorial we use IRF 540 and IRF 9540 (n - Mos and p -Mos) , they have high current  and voltage rating , you may use other Mosfet for your requirements and pc817 is the optocoupler for interfacing the circuit with micro controller and to switch the Mosfet correctly . if you don't use the optocoupler , then the High side Mosfet always be on and make the circuit prevent from working correctly.

• Low-side MOSFETs are always N-channel ones, while on the high-side is P-channel . 
• In this circuit, a high-side MOSFET(IRF9540) and a low-side MOSFET(IRF540) are combined to provide a clean digital logic output. 
• If the input C is HIGH and  the input D is LOW. The output is A is + VCC (12V) of  high-side element and the  output B is GND (0V) of  low-side element.
• If the input D is HIGH and  the input C is LOW. The output is B is + VCC (12V) of  high-side element and the  output A is GND (0V) of  low-side element.

Notes on Nuts and Bolts

            A screw thread is a helical groove on a shaft. When used for delivering power, it is called a drive screw. Drive screws aren't really all that efficient, as they loose a significant amount of power to friction. However, this friction can be put to use in the case of threaded fasteners. You might say that a drive screw is an inclined plane wrapped around a post, while a fastener is a wedge wrapped around a post.

Bolt Terms:

A 1/2-13UNC-2A-3 bolt, with a 2" thread and a 1" shank.

               As nuts and bolts are not perfectly rigid, but stretch slightly under load, the distribution of stress on the threads is not uniform. In fact, on a theoretically infinitely long bolt, the first thread takes a third of the load, the first three threads take three-quarters of the load, and the first six threads take essentially the whole load. Beyond the first six threads, the remaining threads are under essentially no load at all. Therefore, a nut or bolt with six threads acts very much like an infinitely long nut or bolt (and it's a lot cheaper).

Stress on bolt threads. Note how the majority of the stress is on the first thread to the left. Image from Spiralock.		Thread	%	%Sum
		1	34%	34%
		2	23%	55%
		3	16%	71%
		4	11%	82%
		5	9%	91%
		6	7%	98%

           There is little point in having more than six threads in anything. Nuts with National Coarse threads typically have 5 threads in them, whereas nuts with National Fine threads have about 8 threads. Nuts are usually stronger than the bolts they are on, which is to say that the bolt will usually break before the nut strips.
           It is often said that two threads must be exposed above a nut. The reason for this is that the first two threads of a bolt are often poorly formed, and may not engage the nut properly. If they're not doing their share, the other threads in the nut will be overloaded, and the nut may strip.

Source : Gizmology

What is a constant power load , Constant current load and Constant resistance load ???

Constant resistance load:

           In a constant resistance load the current will go down in proportion to the voltage drop as the resistance is fixed and the load must follow ohms law. Heaters approximate this type of load.

Constant current load:

        In a constant current load the load will dynamically adjust its resistance as the voltage drops to keep the current constant. Thus as the battery voltage drops so will the equivalent resistance of the load. Older linear regulators using a pass transistor to deliver constant voltage to a fixed load powering electronics are this kind of load.

Constant power load:

        In a constant power load, the dynamic resistance is adjusted to increase the current inversely to the load voltage. as the voltage rises or falls, then the product of voltage and current in the load is power which is constant. This is done to keep the power dissipated in the load constant as the voltage drops. Electronics devices with SMPS approximate this type of load as they generally employ regulators to generate a constant voltage and when then runs the electronics.

Real loads usually approximate one of the three types of load. Electrical engineers have as one of their tools electronics loads which can be programmed to emulate the load types above.

Source : Quora

What’s the Difference Between Sleep and Hibernate ?

Sleep Mode

Sleep mode is a power-saving state that is similar to pausing a DVD movie. All actions on the computer are stopped and any open documents and applications are put in memory. You can quickly resume normal, full-power operation within a few seconds. Sleep mode is basically the same thing as “Standby” mode.

The Sleep mode is useful if you want to stop working for a short period of time. The computer doesn’t use much power in Sleep mode.

Hibernate

The Hibernate mode saves your open documents and running applications to your hard disk and shuts down the computer, which means once your computer is in Hibernate mode, it uses zero power. Once the computer is powered back on, it will resume everything where you left off.

Use this mode if you won’t be using the laptop for an extended period of time, and you don’t want to close your documents.

Source : Howtogeek

Difference between USART, UART, RS232, USB, SPI, I2C, TTL ...

UART - Universal Asynchronous Receiver Transmitter:

• It is one of the most used serial protocols.
• Most controllers have a hardware UART on board.
• It uses a single data line for transmitting and one for receiving data.
• Most often 8-bit data is transferred, as follows: 1 start bit(low level), 8 data bits and 1 or 2 stop bit(high level).
• The low level start bit and high level stop bit mean that there's always a high to low transition to start the communication.That's what describes UART.
• No voltage level, so you can have it at 3.3 V or 5 V, whichever your microcontroller uses.
• Note that the microcontrollers which want to communicate via UART have to agree on the transmission speed, the bit-rate, as they only have the start bit's falling edge to synchronize.That's called asynchronous communication.
• For long distance communication (That doesn't have to be hundreds of meters) the 5 V UART is not very reliable, that's why it's converted to a higher voltage, typically +12 V for a "0" and -12 V for a "1".
• The data format remains the same. Then you have RS-232 (which you actually should call EIA-232, but nobody does.)
• The timing dependency is one of the big drawbacks of UART, and the solution is USART, for Universal Synchronous/Asynchronous Receiver Transmitter.

USART - Universal Synchronous/Asynchronous Receiver Transmitter:

• This can do UART, but also a synchronous protocol.
• In synchronous there's not only data, but also a clock transmitted.
• With each bit a clock pulse tells the receiver it should latch that bit.
• Synchronous protocols either need a higher bandwidth, like in the case of Manchester encoding, or an extra wire for the clock, like SPI and I2C.

SPI - Serial Peripheral Interface:

• It is another very simple serial protocol.
• A master sends a clock signal, and upon each clock pulse it shifts one bit out to the slave, and one bit in, coming from the slave.
• Signal names are therefore SCK for clock, MOSI for Master Out Slave In, and MISO for Master In Slave Out.
• By using SS (Slave Select) signals the master can control more than 1 slave on the bus.
• There are two ways to connect multiple slave devices to one master, one is mentioned above i.e. using slave select, and other is daisy chaining, it uses less hardware pins(select lines), but software gets complicated.

I2C - Inter-Integrated Circuit (pronounced "I squared C"):

•  It is also a synchronous protocol, and it's the first we see which has some "intelligence" in it; the other ones dumbly shifted bits in and out, and that was that. I2C uses only 2 wires, one for the clock (SCL) and one for the data (SDA). 
• That means that master and slave send data over the same wire, again controlled by the master who creates the clock signal.
• I2C doesn't use separate Slave Selects to select a particular device, but has addressing.
• The first byte sent by the master holds a 7 bit address (so that you can use 127 devices on the bus) and a read/write bit, indicating whether the next byte(s) will also come from the master of should come from the slave.
• After each byte receiver must send a "0" to acknowledge the reception of the byte, which the master latches with a 9th clock pulse. If the master wants to write a byte the same process repeats: the master puts bit after bit on the bus and each time gives a clock pulse to signal that the data is ready to be read.
• If the master wants to receive data it only generates the clock pulses. The slave has to take care that the next bit is ready when the clock pulse is given.
• This protocol is patented by NXP(formerly Phillips), to save licensing cost, Atmel using the word TWI(2-wire interface) which exactly same as I2C, so any AVR device will not have I2C but it will have TWI.
• Two or more signals on the same wire may cause conflicts, and you would have a problem if one device sends a "1" while the other sends a "0".Therefore the bus is wired-OR'd: two resistors pull the bus to a high level, and the devices only send low levels.If they want to send a high level they simply release the bus.

TTL - Transistor Transistor Logic:

• It is not a protocol. It's an older technology for digital logic, but the name is often used to refer to the 5 V supply voltage, often incorrectly referring to what should be called UART.

Source : Electrical Engineering Stack Exchange 

Make your Simple Boost Converter using Arduino ...

                                   Hi... Friends... In this tutorial we are going to see how to make a simple boost converter of output Voltage of 70-80 Voltage with an input of 10 - 15 V ,

Components :

 Inductor                  : 100uH
 Capacitor (Input)    : 25V, 1000uF
 Capacitor (Output) : 100V , 470uF
  Mosfet                   : IRF540
  Diode                    : 1N4007

What is Harmonics, Inter-harmonics, and Sub-harmonics ...???

Harmonics: A sinusoidal component of a periodic wave having a frequency that is an integer multiple of the fundamental frequency.

Inter-harmonics: Components with frequencies between two consecutive harmonics or those components whose frequencies are not integer multiples of the fundamental power frequency.

Sub-harmonics: A special subset of interharmonics that have frequency values that are less than that of the fundamental frequency.

Table below illustrate their usage with examples for a 50Hz system.