Sunday, August 29, 2010

Green Energy Home - Turn Green to Save Money and Earth

By Jerry T Eliszewski
As the issue of global warming is boiling up on world level, the optimistic generation has started finding its own ways to save our planet. A green energy home is one of those alternatives that are being used to fight with global warming. A green energy home doesn't mean that its is made of grass, trees and plants rather the home is energy efficient that utilizes renewable sources of energy mainly from wind and sun. At homes, the tow sources of energy usually used for basic home needs such generating electricity and to get hot water.
With the advancement in technology, now you can easily get solar panels and wind turbines. Once you start using green energy home, you can reduce your electricity bills and carbon print from our earth. Technology of making your own green home is easily available in bits and pieces and you can use these to construct your own devices to create energy. The most commonly used devices to create green energy are windmills and solar panels. Passive solar energy is another good alternate to get hot water and keep your room warm during winters.
You can buy wind turbines, wind mills or solar panels however; you might need to pay hefty amount for them. Therefore, you can pick your tools and start preparing solar panels and windmills yourself so that you can get your green energy home without paying much of your amount. You might be thinking of hiring a professional to make these devices. Of course, you can if your budget allows you to do so. But if you want to save money, there is no need to hire a professional just search for DIY instruction manual on the internet. These manuals will provide you the information on making passive water heaters or other electrical systems right from the scratch.
If you're building a new house with implementation of the concept of green energy home, take advantage in building its footprint and keep the sides of the house towards south as your house will get best conditions for heating as well as cooling. To you're your green energy home full of passive solar energy, you should use heat retentive stones and bricks to make your home and afterward install high efficiency windows.
Your prospective home should have a windmill installed on its potion, roof or any other open area where supply is wind is continuous. The energy you'll get with windmill is very efficient and free from any kind of noise pollution. If your new house is located near a stream or a river you can integrate a hydroelectric generator in your green energy home. The energy will depend upon the flow of river or stream therefore, till the time water is flowing you can be sure of electricity.
You can save our by converting your home into green energy home by utilizing renewable sources of energy. Besides saving our planet you'd also save money on electricity bills as well.
To find out how you can get FREE electricity for your home, read more at

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Saturday, August 28, 2010

Feedback control

         หลายคนคงเคยสงสัยว่าเมื่อเราได้แบบจำลองทางคณิตศาสตร์ของระบบหนึ่งๆมาแล้วนอกจากจะนำสมการนั้นไปทำการ simmulation แล้วนั้นมันจะไปอยู่ส่วนไหนของ Feedback control หรือไปอยู่ใน IC ตัวไหนของ Hardware ในหัวข้อนี้เราจะมาพูดถึงในส่วนนี้ อันดับแรกเราจะนำแบบจำลองทางคณิตศาสตร์ไปหาค่าอัตราการขยายของตัวควบคุม(Feedback Gain K) โดยใช้กฎการควบคุม u=-kx (สมมุติว่าเราหาโมเดลได้อย่างสมบูรณ์) เราก็จะได้ค่า k มาเท่ากับจำนวน Statae ของระบบ ส่วน State x เราจำเป็นที่จะต้องวัดทุกตัวตามสมการ แต่ในบางกรณีเราก็ไม่สามารถวัดได้ เพราะตัวตรวจรู้อาจจะแพงหรือใช้งานยาก เราก็เลยมีวิธีๆ หนึ่ง เรียกว่าตัวประมาณสเตท สมการประมาณสเตทสิ่งที่มันต้องการคือ แบบจำลองทางคณิตศาสตร์ และ สเตทที่วัดได้(กรณีที่เช็คแล้วว่าระบบสามารถสังเกตได้) ซึ่งสมการนี้จะอยู่ในรูปของสมการเชิงอนุพันธ์ เราก็จะเอาสมการเชิงอนุพันธ์นี้แหละครับไปเขียนใน IC เช่นที่ผมเคยทำคือเขียนใน Micro controller PIC18f4431 โดยทำการ Discrete ระบบเสียก่อน ก็จะทำให้เกิดสมการที่มีตัวแปร ค่าของ สเตทในอดีต และค่าของสเตท ปัจจุบันเข้ามาเกี่ยวของแล้ว Output ที่ได้ก็จะเป็นสเตทที่เราไม่สามารถวัดได้นั้นเอง ดังนั้นก็จะเห็นได้ว่าเราก็สามารถนำแบบจำลองทางคณิตศาสตร์ที่อยู่ในรูปของสมการทางคณิตศาสตร์ มาใช้งานจริงได้

Friday, August 27, 2010

Kalman Filter Tutorial

By Bill Goo
The kalman filter is a time series estimation algorithm that is mainly used combined with maximum likelihood approach to estimate parameters for given data. Compared with pure maximum likelihood, which typically assumes that the data series is observed without errors, and obtains the state variables by inversion, Kalman filter assumes that all data is observed with measurement errors, which is one of the big reasons why it becomes more and more popular in economics and finance, as many models in these fields depend on data that are either non-observable, for example, bond prices are observable but interest rates are not; energy future prices are easily observed but underlying assets are not, etc.; or subject to noise, such as due to bid-ask spreads.
There are two basic equations of a Kalman filter: the measurement equation and the transition equation, as the names suggest, the measurement equation relates an unobserved variable (such as interest rates) to an observable variable (such as bond prices), and the transition equation allows the unobserved variable to change over time, for example, interest rates follow a Cox Ingersoll Ross (CIR) process. Essentially Kalman filter is a recursive algorithm, it starts with initial values for the state variables and a measure of the certainty of the guess, and then use these initial values to predict the value of the measurement equation, since the variables in the measurement equation are observed, we can calculate the prediction error, together with a kalman gain factor, to update the values in the transition equation, repeat the process for the next time period and finally we are able to estimate the parameters values by maximum likelihood.
The following steps outline the specific procedures of a kalman filter example:
Step 1: writing down the measurement equation and transition equation, initializing the state vector;
Step 2: forecasting the measurement equation given the initial values;
Step 3: updating the inference about the state vector incorporating kalman gain matrix and the prediction error;
Step 4: forecasting the state vector of the next time period conditioning on the updated values of the previous period;
Step 5: calculating the log-likelihood function under a certain distribution assumption and maximize the log-likelihood, usually a Gaussian distribution is applied.
For a detailed Kalman Filter tutorial case please visit Kalman-filter example.
Bill Goo is a quantitative researcher with specialization in derivative pricing, quantitative risk analysis and trading strategies - he kindly invites you to visit his blog - Quant finance for the latest development of financial engineering industry.

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USB to RS232 Converters - An Introduction

USB to RS232 Converters - An Introduction
By Daniel Lorenz

Many people are familiar these days with the use of universal serial bus [USB] ports on their desktop, laptop and notebook computers. The widely used USB 2.0 specification supports a 480 Mbps transfer rate and is popular because computer users can easily connect a wide range of consumer electronics devices and computer peripherals to their computers without having to configure 'dip switches' or install dedicated interface boards.
Although the 'plug'n'play' functionality of USB is its greatest benefit over older and cumbersome ways of connecting and configuring devices, there are still devices that do not support (or physically have installed) USB ports, but do possess RS232 serial ports.
Here is where USB to RS232 converters have a role to fulfill by connecting computer and RS232 peripheral together.
However, there's more to successfully connecting, for example, an RS232-enabled GPS phone to a computer's USB port, than just manufacturing an appropriate cable. Sophisticated converter electronics plus operating system dependent device driver software are, in addition to the cable itself, what make up a reliable USB to RS-232 converter.
The reason for this complexity lies partly in how software engineers and application programmers have interpreted and coded for the RS232 specification over the years.
The complete details are beyond the scope of this article but in essence the fact that the RS232 specification defines only the interface, and not the protocol to be used, has given implementers a lot of freedom.
Bottom line: application or operating system device driver ways of communicating with RS232 ports introduced a 'flexibility' which does not appear in the more inflexible USB interface specification.
This means that communicating with RS232 via a USB port introduces the requirement for RS232-style UART device driver emulations. So we now have two device drivers involved over a USB Bus with the potential for timing conflicts that can interrupt and delay RS232 communications.
On the hardwire side, there are known issues with various RS232 line driver chips that can result in RS232 input port behavior outside of the original specification.
Another problem that can show up in cheap USB to RS232 adapters is an inability to perform the hardware flow control required by some (but no all) applications.
Of course, identifying which applications use software flow control and which use hardware flow control is often beyond the knowledge of the converter manufacturer. And the application itself may make irregular and unclear use of hardware flow control.
The lesson here is to pay careful attention to how the USB to Serial converter handles application timing, RS232 signaling and hardware flow control. This is particularly important in industrial automation scenarios, although don't be surprised to also experience irregular issues with poorly designed converters in office computing locations.
In contrast, the leading USB to RS232 converter manufacturers use well regarded processor chips in their top end products, such as those from FTDI Semiconductors. They also provide simple to install device drivers supporting popular operating systems such as Windows (including Windows 7 and Vista), Linux and Mac.
Visit to find out more about RS232 to RS485 converter products, free Tools and Diagnostic software.
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Interfacing a Microcontroller With a PC Using RS232 and the PC Serial Port

By Sidney Kantor
Serial Communication
Serial communication is a technique of transmitting data between two pieces of hardware. The smallest piece of data that is transmitted is the byte. A byte is made up of 8 bits. When data is transmitted between two pieces of hardware, the bits are sent one at a time. The hardware sends these bits by sending varying voltages across the wires connecting the devices. The sender and the receiver agree on how often a bit (or voltage level) will be sent.
How often a bit will be sent is referred to as baud rate or bits per second (bps). Then with the help of very precise clocks they can send a series of voltage levels between each other and then reassmble these voltage levels into bytes.
The Problem Communicating Between a PC and a Microcontroller
The RS232 serial port on a PC uses +3 to +25 volts to signify a logic level of 0, and -3 to -25 volts to signify a logic level of 1.
Most microcontrollers use TTL / CMOS logic levels which use 0 to some threshold voltage to signify a logic level of 0, and some threshold voltage to 5 volts to signify a logic level of 1.
In order for the PC and a microcontroller to successfully communicate some logic level translation is necessary.
Using a TTL / CMOS To RS232 Converter
There are many companies that manufacture modules that take care of the required logic level translation. The TTL / CMOS To RS232 Converter is one such module. Typically, these modules connect to the RS232 port on the PC and connect to the microcontroller's transmit and receive pins. Supply 5 volts and ground and you are ready to communicate.
Applications Ideas
Once you have your microcontroller communicating with your PC it opens up all kinds of possible applications ranging from data loggers, pc based oscilloscopes, controlling your pc from your microcontroller, controlling your microcontroller from your pc, etc.
For more information please visit
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