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Power Supply Circuits
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- Category: Blog
- Published on Wednesday, 20 April 2022 07:12
- Written by Chia Choon Wha
- Hits: 5130
There are three major kinds of power supplies: unregulated (also called brute force), linear regulated, and switching. The fourth type of power supply circuit called the ripple-regulated, is a hybrid between the “brute force” and “switching” designs, and merits a subsection to itself.
Unregulated
An unregulated power supply is the most rudimentary type, consisting of a transformer, rectifier, and low-pass filter. These power supplies typically exhibit a lot of ripple voltage (i.e. rapidly-varying instability) and other AC “noise” superimposed on the DC power. If the input voltage varies, the output voltage will vary by a proportional amount. The advantage of an unregulated supply is that it’s cheap, simple, and efficient.
Linear regulated
A linear regulated supply is simply a “brute force” (unregulated) power supply followed by a transistor circuit operating in its “active,” or “linear” mode, hence the name linear regulator. (Obvious in retrospect, isn’t it?) A typical linear regulator is designed to output a fixed voltage for a wide range of input voltages, and it simply drops any excess input voltage to allow a maximum output voltage to the load. This excess voltage drop results in significant power dissipation in the form of heat. If the input voltage gets too low, the transistor circuit will lose regulation, meaning that it will fail to keep the voltage steady. It can only drop excess voltage, not make up for a deficiency in voltage from the brute force section of the circuit. Therefore, you have to keep the input voltage at least 1 to 3 volts higher than the desired output, depending on the regulator type. This means the power equivalent of at least 1 to 3 volts multiplied by the full load current will be dissipated by the regulator circuit, generating a lot of heat. This makes linear regulated power supplies rather inefficient. Also, to get rid of all that heat they have to use large heat sinks which make them large, heavy, and expensive.
Switching
A switching regulated power supply (“switcher”) is an effort to realize the advantages of both brute force and linear regulated designs (small, efficient, and cheap, but also “clean,” stable output voltage). Switching power supplies work on the principle of rectifying the incoming AC power line voltage into DC, re-converting it into high-frequency square-wave AC through transistors operated as on/off switches, stepping that AC voltage up or down by using a lightweight transformer, then rectifying the transformer’s AC output into DC and filtering for final output. Voltage regulation is achieved by altering the “duty cycle” of the DC-to-AC inversion on the transformer’s primary side. In addition to lighter weight because of a smaller transformer core, switchers have another tremendous advantage over the prior two designs: this type of power supply can be made so totally independent of the input voltage that it can work on any electric power system in the world; these are called “universal” power supplies.
The downside of switchers is that they are more complex, and due to their operation they tend to generate a lot of high-frequency AC “noise” on the power line. Most switchers also have significant ripple voltage on their outputs. With the cheaper types, this noise and ripple can be as bad as for unregulated power supply; such low-end switchers aren’t worthless, because they still provide a stable average output voltage, and there’s the “universal” input capability. Expensive switchers are ripple-free and have noise nearly as low as for some a linear type; these switchers tend to be as expensive as linear supplies. The reason to use an expensive switcher instead of a good linear is if you need universal power system compatibility or high efficiency. High efficiency, light weight, and small size are the reasons switching power supplies are almost universally used for powering digital computer circuitry.
Ripple regulated
A ripple-regulated power supply is an alternative to the linear regulated design scheme: a “brute force” power supply (transformer, rectifier, filter) constitutes the “front end” of the circuit, but a transistor operated strictly in it’s on/off (saturation/cutoff) modes transfers DC power to a large capacitor as needed to maintain the output voltage between a high and a low setpoint. As in switchers, the transistor in a ripple regulator never passes current while in its “active,” or “linear,” mode for any substantial length of time, meaning that very little energy will be wasted in the form of heat.
However, the biggest drawback to this regulatory scheme is the necessary presence of some ripple voltage on the output, as the DC voltage varies between the two voltage control setpoints. Also, this ripple voltage varies in frequency depending on load current, which makes the final filtering of the DC power more difficult. Ripple regulator circuits tend to be quite a bit simpler than switcher circuitry, and they need not handle the high power line voltages that switcher transistors must handle, making them safer to work on.
Choosing the right microcontrollers
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- Category: Blog
- Published on Thursday, 14 February 2013 09:25
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Embedded processors span the range from simple 8-bit microcontrollers like those at the heart of childrens toys, to powerful custom 64-bit microprocessors and specialized DSPs and network processors. Some of the products that include these chips run a short assembly program from ROM with no operating system; many more run real-time operating systems and complex multithreaded C++programs; and its also increasingly common to find variants of desktop-lite operating systems based on Linux and Windows controlling more powerful devices that are still clearly embedded systems.
If an application does not have very high demands on processing power, and is of relatively small size, then it can make sense to consider an 8-bit microcontroller. 8-bit microcontrollers should typically be considered for applications that are dedicated to just doing one job, with a limited user interface and little data processing.
8-bit microcontrollers
8-bit microcontrollers come in all sizes from small 6-pin devices to chips with 64 pins. They have flash sizes ranging from 512 bytes to 256KB, SRAM sizes from 32 to 8KB, or more, and EEPROM from 0 to 4K, or more. A minimal system can be as simple as a single chip, with a bypass capacitor on the power supply rail.
The three most popular lines of 8-bit microcontrollers are the 8051 series, the PIC series from Microchip, and the AVR series from Atmel, now part of Microchip.
16-bit microcontrollers
16-bit microcontrollers are the next step up from 8-bit, while still sharing many of the same attributes. They are faster, support even more peripherals, and generally offer more memory, both flash and SRAM.
In addition to more IO pins, most of them also have hardware multipliers that are significantly faster, and use less program memory, compared to pure software implementations.It is easy to find devices that have both ADC’s and DAC’s, or devices with capacitive touch sensors, segmented LCD drivers and Ethernet.
Internally, these devices also have hardware blocks typically not found in lower end devices. These include encryption engines, Operational or Programmable Gain Amplifiers, and DMA controllers.
16-bit microcontrollers can be found from various manufacturers such as Microchip (dsPIC33 is a popular choice), NXP, Infineon, Cypress, and the TI MSP430 series.
32-bit microcontrollers
16-bit microcontrollers
16-bit microcontrollers are the next step up from 8-bit, while still sharing many of the same attributes. They are faster, support even more peripherals, and generally offer more memory, both flash and SRAM.
In addition to more IO pins, most of them also have hardware multipliers that are significantly faster, and use less program memory, compared to pure software implementations.It is easy to find devices that have both ADC’s and DAC’s, or devices with capacitive touch sensors, segmented LCD drivers and Ethernet.
Internally, these devices also have hardware blocks typically not found in lower end devices. These include encryption engines, Operational or Programmable Gain Amplifiers, and DMA controllers.
16-bit microcontrollers can be found from various manufacturers such as Microchip (dsPIC33 is a popular choice), NXP, Infineon, Cypress, and the TI MSP430 series.
32-bit microcontrollers
32-bit microcontrollers are powerful devices with microprocessor-like features. Some of the advanced features include instruction pipelining, branch prediction, Nested Vectored Interrupts (NVI), Floating Point Units (FPU), memory protection, and on-board debuggers.32-bit microcontrollers support Real Time Operating Systems (RTOS) that, in turn, provide multitasking capabilities.
Two prominent vendors of ARM-based chips are Atmel with their SAM device line, and STMicroelectronics with their STM32 line of products.In general, the STM32 devices offer more choices, and should be given top consideration when designing in an embedded 32-bit microcontroller.
Two prominent vendors of ARM-based chips are Atmel with their SAM device line, and STMicroelectronics with their STM32 line of products.In general, the STM32 devices offer more choices, and should be given top consideration when designing in an embedded 32-bit microcontroller.
10 Steps to Selecting a Microcontroller
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- Category: Blog
- Published on Thursday, 14 February 2013 09:00
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Selecting the right microcontroller for a product can be a daunting task. Not only are there a number of technical features to consider, there are also business case issues such as cost and lead-times that can cripple a project. At the start of a project there is a great temptation to jump in and start selecting a microcontroller before the details of the system has been hashed out. This is of course a bad idea. Before any thought is given to the microcontroller, the hardware and software engineers should work out the high levels of the system, block diagram and flowchart them and only then is there enough information to start making a rational decision on microcontroller selection. When that point is reached, there are 10 easy steps that can be followed to ensure that the right choice is made.
Step 1: Make a list of required hardware interfaces
Using the general hardware block diagram, make a list of all the external interfaces that the microcontroller will need to support. There are two general types of interfaces that need to be listed. The first are communication interfaces. These are peripherals such as USB, I2C, SPI, UART, and so on. Make a special note if the application requires USB or some form of Ethernet. These interfaces greatly affect how much program space the microcontroller will need to support. The second type of interface is digital inputs and outputs, analog to digital inputs, PWM’s, etc. These two interface types will dictate the number of pins that will be required by the microcontroller. Figure 1 shows a generic example of a block diagram with the i/o requirements listed.
Figure 1 – List of Hardware Features
Figure 1 – List of Hardware Features
Step 2: Examine the software architecture
The software architecture and requirements can greatly affect the selection of a microcontroller. How heavy or how light the processing requirements will determine whether you go with an 80 MHz DSP or an 8 MHz 8051. Just like with the hardware, make notes of any requirements that will be important. For example, do any of the algorithms require floating point mathematics? Are there any high frequency control loops or sensors? Estimate how long and how often each task will need to run. Get an order of magnitude feel for how much processing power will be needed. The amount of computing power required will be one of the biggest requirements for the architecture and frequency of the microcontroller.
Step 3: Select the architecture
Using the information from steps 1 and 2 an engineer should be able to start getting an idea of the architecture that will be needed. Can the application get by with eight bit architectures? How about 16 bits? Does it require a 32-bit Arm core? Between the application and the required software algorithms these questions will start to converge on a solution. Don’t forget to keep in mind possible future requirements and feature creep. Just because you could currently get by with an 8 bit microcontroller doesn’t mean you shouldn’t consider a 16 bit microcontroller for future features or even for ease of use. Don’t forget that microcontroller selection can be an iterative process. You may select a 16-bit part in this step but then in a later step find that a 32 bit Arm part works better. This step is simply to start getting an engineer to look in the right direction.
Step 4: Identify Memory Needs
Flash and RAM are two very critical components of any microcontrollers. Making sure that you don’t run out of program space or variable space is undoubtedly of highest priority. It is far easier to select a part with too much of these features than not enough. Getting to the end of a design and discovering that you need 110% or that features need to be cut just isn’t going to fly. After all, you can always start with more and then later move to a more constrained part within the same chip family. Using the software architecture and the communication peripherals included in the application, an engineer can estimate how much flash and RAM will be required for the application. Don’t forget to leave room for feature creep and the next versions! It will save many headaches in the future.
Step 5: Start searching for microcontrollers
Now that there is a better idea of what the required features of the microcontroller will be the search can begin! One place that can be a good place to start is with a microcontroller supplier such as Arrow, Avnet, Future Electronics or similar. Talk with an FAE about your application and requirements and often times they can direct you to a new part that is cutting edge and meets the requirements. Just keep in mind that they might have pressure on them at that time to push a certain family of microcontrollers!
The next best place to start is with a silicon provider that you are already familiar with. For example, if you have used Microchip parts in the past and had a good experience with them, then start at their website. Most silicon providers have a search engine that allows you to enter your peripheral sets, I/O and power requirements and it will narrow down the list of parts that match the criteria. From that list the engineer can then move forward towards selecting a microcontroller.
Step 6: Examine Costs and Power Constraints
At this point the selection process has revealed a number of potential candidates. This is a great time to examine the power requirements and cost of the part. If the device will be powered from a battery and mobile, then making sure the parts are low-power is absolutely precarious. If it doesn’t meet power requirements then keep weeding the list down until you have a select few. Don’t forget to examine the piece price of the processor either. While prices have steadily been approaching $1 in volume for many parts, if it is highly specialized or a high-end processing machine then price might be critical. Don’t forget about this key element.
Step 7: Check part availability
With the list of potential parts in hand, now is a good time to start checking on how available the part is. Some of the things to keep in mind are what the lead times for the part? Are they kept in stock at multiple distributors or is there 6 – 12 week lead time? What are your requirements for availability? You don’t want to get stuck with a large order and have to wait three months to be able to fill it. Then there is a question of how new the part is and whether it will be around for the duration of your product life cycle. If your product will be around for 10 years then you need to find a part that the manufacturer guarantees will still be built in 10 years.
Step 8: Select a development kit
One of the best parts of selecting a new microcontroller is finding a development kit to play with and learn the inner working of the controller. Once an engineer has settled their heart on the part they want to use they should research what development kits are available. If a development kit isn’t available then the selected part is most likely not a good choice and they should go back a few steps and find a better part. Most development kits today cost under $100. Paying any more than that (unless it is designed to work with multiple processor modules) is just too much. Another part may be a better choice.
Step 9: Investigate compilers and tools
The selection of the development kit nearly solidifies the choice of microcontroller. The last consideration is to examine the compiler and tools that are available. Most microcontrollers have a number of choices for compilers, example code and debugging tools. It is important to make sure that all the necessary tools are available for the part. Without the right tools the development process could become tedious and expensive.
Step 10: Start Experimenting
Even with the selection a microcontroller nothing is set in stone. Usually the development kit arrives long before the first prototyped hardware. Take advantage by building up test circuits and interfacing them to the microcontroller. Choose high risk parts and get them working on the development kit. It may be that you discover the part you thought would work great has some unforeseen issue that would force a different microcontroller to be selected. In any event, early experimentation will ensure that you made the right choice and that if a change is necessary, the impact will be minimal!
Credit: Jacob Beningo January 12, 2014
Jacob Beningo is an embedded systems consultant and lecturer who specializes in the design of resource constrained and low energy devices. He works with companies to decrease costs and time to market while maintaining a quality and robust product. He is an avid tweeter, a tip and trick guru, a homebrew connoisseur and a fan of pineapple! Feel free to contact him on his website.
Top Embedded Projects Ideas for Engineering Students
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- Category: Blog
- Published on Thursday, 14 February 2013 08:26
- Hits: 12357
Embedded system
An embedded system is designed to perform one function with real-time applications. Embedded systems are found in simple devices like calculators, microwave & television remote controls and also in more complicated devices such as a home security and neighborhood traffic control systems. Many Talented people can take the advantages of simple embedded systems and turn them into a more integrated system for controlling other devices.
So, Now-a-days many engineering students are showing lot of interest to improve their practical knowledge in embedded systems in early stage by doing the embedded systems projects in their final year. Generally we use 8051 Microcontroller or PIC Microcontroller based projects as they serve as good reference for final year electronics engineering projects. Here we are giving best and latest list of projects on embedded systems.
8051 Microcontroller Projects
A microcontroller is an integrated circuit or a chip with a processor and other support devices like program memory, data memory, I/O ports, serial communication interface etc integrated together. 8051 is the most popular and widely use microcontroller. So, many engineering students show lot of interest in doing the 8051 Microcontroller projects.
Here is the list of embedded systems projects ideas:
- Propeller display of Time / Message
- Vehicle Tracking By GPS – GSM
- Auto Intensity Control of Street Lights
- Auto Metro Train to Shuttle Between Stations
- Auto Power Supply Control from 4 Different Sources: Solar, Mains, Generator & Inverter to Ensure No Break Power
- Automatic Bell System for Institutions
- Automatic Dialing to Any Telephone Using I2C Protocol on Detecting Burglary
- Automatic irrigation System on Sensing Soil Moisture Content
- Automatic Surveillance Camera Panning System from PC
- Automatic Wireless Health Monitoring System in Hospitals for Patients
- Beacon Flasher Using Microcontroller
- Bidirectional Rotation of an Induction Motor with a Remote Control Device
- BLDC Motor Speed Control with RPM Display
- Cell Phone Based DTMF Controlled Garage Door Opening System
- Cell Phone Controlled Robotic Vehicle
- Closed Loop Control for a Brushless DC Motor to Run at the Exactly Entered Speed
- Cyclo Converter Using Thyristors
- Density Based Traffic Signal System
- Detecting Power Grid Synchronization Failure on Sensing Frequency or Voltage Beyond Acceptable Range
- Discotheque Light Stroboscopic Flasher
- Dish Positioning Control by IR Remote
- Display of Dialed Telephone Numbers on Seven Segment Displays
- Distance Measurement by Ultrasonic Sensor
- DTMF Based Load Control System
- FACTs (flexible ac transmission) by TSR
- FACTs by SVC (flexible ac transmission)
- Fire Fighting Robotic Vehicle
- Flash Flood Intimation Over GSM Network
- Four Quadrant DC Motor Speed Control with Microcontroller
- GSM Based Energy Meter Reading with Load Control
- GSM Based Monthly Energy Meter Billing via SMS
- Industrial Battery Charger by Thyristor Firing Angle Control
- Industrial Power Control by Integral Cycle Switching without Generating Harmonics
- Integrated Energy Management System Based on GSM Protocol with Acknowledgement Feature
- IR Controlled Robotic Vehicle
- IR Obstacle Detection to Actuate Load
- Lamp Life Extender by ZVS (Zero Voltage Switching)
- Life Cycle Testing of Electrical Loads by Down Counter
- Microcontroller Based Line Following Robotic Vehicle
- Design and Implementation of Metal Detector Robotic Vehicle
- Automatic Door Opening System with Movement Sense
- Networking of Multiple Microcontrollers
- Microcontroller based Non Contact Tachometer
- Object Counter with 7 Segment Display using Microcontroller
- Object Detection using Ultrasonic Sensor
- Obstacle Avoidance Robotic Vehicle
- Optimum Energy Management System
- Parallel Telephone Lines with Security System
- Password Based Circuit Breaker
- PC Based Electrical Load Control
- PC Controlled Scrolling Message Display for Notice Board
- Pick N Place with Soft Catching Gripper
- Portable Programmable Medication Reminder
- Power Saver for Industries & Commercial Establishments
- Pre Stampede Monitoring and Alarm System
- Precise Digital Temperature Control
- Precise Illumination Control of Lamp
- Predefined Speed Control of BLDC Motor
- Programmable Energy Meter for Electrical Load Survey
- Programmable Load Shedding Time Management for Utility Department
- Programmable Switching Control for Industrial Automation in Repetitive Nature of Work
- Railway Level Crossing Gate Control through SMS by the Station Master or the Driver
- Railway Track Security System
- Remote Jamming Device
- RF Based Home Automation System
- RF Controlled Robotic Vehicle With Laser Beam Arrangement
- RFID based attendance system
- RFID Based Passport Details
- RFID security access control system
- SCADA (Supervisory Control & Data Acquisition) for Remote Industrial Plant
- Secret Code Enabled Secure Communication Using RF Technology
- Security System Using Smartcard Technology
- Security System With User Changeable Password
- Sine Pulse Width Modulation (spwm)
- Solar Powered Auto irrigation System
- Solar Powered LED Street Light with Auto Intensity Control
- Speed Checker to Detect Rash Driving on Highways
- Speed Control Unit Designed for a DC Motor
- Speed Synchronization of Multiple Motors in Industries
- Stamp Value Calculator for Postage Needs
- Sun Tracking Solar Panel
- SVPWM Space Vector Pulse Width Modulation
- Synchronized Traffic Signals
- Tampered Energy Meter Information Conveyed to Concerned Authority by Wireless Communication
- Theft Intimation of the Vehicle Over SMS to Owner Who Can Stop the Engine Remotely
- Three Phase Solid State Relay with ZVS
- Thyristor Controlled Power for Induction Motor
- Thyristor Power Control by IR Remote
- Touch Screen Based Home Automation System
- Touch Screen Based Industrial Load Switching
- Touch Screen Based Remote Controlled Robotic Vehicle for Stores Management
- TV Remote Operated Domestic Appliances Control
- Ultra Fast Acting Electronic Circuit Breaker
- Underground Cable Fault Distance Locator
- Unique Office Communication System Using RF
- Using TV Remote as a Cordless Mouse for the Computer
- War Field Spying Robot with Night Vision Wireless Camera
- Wireless Electronic Notice Board Using GSM
- Wireless message Communication Between Two Computers
PIC Microcontroller Based Embedded Projects
PIC Microcontroller is another type of microcontroller which is widely used in many electronics projects by the engineering students. Following is the list of few PIC Microcontroller Projects for final year engineering students.
- Density Based Traffic Signal System Using PIC Microcontroller
- GSM Based Energy Meter Reading With Load Control Using PIC Microcontroller
- Portable Programmable Medication Reminder Using PIC Microcontroller
- Pre Stampede Monitoring and Alarm System Using PIC Microcontroller
- RFID Based Device Control and Authentication Using PIC Microcontroller
- Solar Energy Measurement System
- Speed Synchronization of Multiple Motors in Industries Using PIC Microcontroller
- Street Light that Glows on Detecting Vehicle Movement
- Synchronized Traffic Signals at Various Junctions Using PIC Microcontroller
- Theft Intimation of Vehicle Over SMS to Owner Who Can Stop the Engine Remotely
- PIC Based TV Remote as a Cordless Mouse for the Computer
- Detecting Power Theft prior to feeding energy Meter and Intimating to Control Room by GSM
- Speed Control Unit Designed for a DC Motor using PIC Microcontroller
- Auto Intensity Control of Street Lights using PIC Microcontroller
- Networking of Multiple Street Junction Signals for Better Traffic Management
- Vehicle Movement Sensed LED Street Light with Idle Time Dimming
- Cordless Mouse Features by TV Remote Using PIC Microcontroller
- Measuring Solar Photovoltaic Power
- Medication Reminder using PIC Microcontroller
- PIC Controlled Dynamic Time Based City Traffic Signal
- Using TV Remote as a Cordless Mouse for the Computer using PIC Microcontroller
- Pre Stampede Monitoring and Alarm System using PIC Microcontroller
- Portable Programmable Medication Reminder using PIC Microcontroller
- Speed Synchronization of Multiple Motors In Industries using PIC Microcontroller
- Synchronized Traffic Signals at Various Junctions using PIC Microcontroller
- Energy Meter Billing with Load Control over GSM with User Programmable Number Features by PIC Microcontroller
- Solar Energy Measurement System
- Density based Traffic Signal System using PIC Microcontroller
- RFID Based Device Control and Authentication using PIC Microcontroller
- Street Light that Glows on Detecting Vehicle Movement
- Vehicle Theft Intimation to the Owner on his Cell Phone by GSM with User Programmable Number Features using PIC Microcontroller.
These are the few embedded systems projects ideas for engineering students. Get the abstract, block diagram & output video details for above mentioned embedded projects ideas by clicking on buy embedded systems projects.
