WEKA and me: Another love and hatred relationship

While working on machine learning projects, I am quite picky and I like to do implement the algorithms by my own. On the other hand, if there are approaching deadlines or the algorithms are rather hard to implement, open source packages are usually the way to go. Since it contains many popular algorithms I use WEKA a lot when I am lazy. It is quite good and definitely a nice starting point for having a feeling with the algorithms for starters. On the other hand, I most of the times don't know what is going inside (I am not very much interested into tracing the JAVA source) and interfacing to Matlab or C is sometimes annoying. Still much better compared to SPIDER or Classification Toolbox.

Technical Tips on Brushless DC Motor Control

Brushless DC motors are getting more and more popular. I believe in near future, they will replace most of the brushed DC motors in mechatronics applications. Unfortunately, it is not very easy to find resources on the net for PWM control of brushless DC motors with microcontrollers and new driver integrated circuits. The best resource I found so far is the technical tips from Hitachi Power Semiconductors Division:

http://www.pi.hitachi.co.jp/pse/product/IC/tips/index.html

AD7329: SPI analog to digital converter with +-10 V range

Nowadays most of the microcontrollers come with onboard ADC's. Even though specifications state they have up to 12 bit resolutions since the voltage range they operate in is most between 0-3.3V's, most of the accuracy is lost to noise. External ADC chips working with higher input voltage ranges can be a solution for this problem. Lately, I integrated and AD7329 8 channel SPI ADC chip from Analog Devices to a PIC microcontroller. The results were much better than I expected. I increased my accuracy by a factor of 16 (2^4) mainly due to the increased voltage range ( +-10 V) and also better AD converter. SPI communication with the PIC is easy to establish and requires only 4 lines. Due to the speed of A2D conversion it is good to drive the analog inputs of the chips with some high bandwidth opamps.

http://www.national.com/mpf/LM/LM324.html

LM324: Low Power Quad Opamp

Old LM444's don't come in TSSOP packages (they come in SOIC packages). If you want to squeeze the most number of IC's in the smallest circuit area, TSSOP's are the way to go. Therefore I found a replacement for LM444 coming in TSSOP packages with more or less same performance specifications: LM124 family.

http://www.national.com/mpf/LM/LM324.html

Nice Book on Circuit Design

For my research, I needed to design a mixed signal circuit containing digital microcontrollers with high frequency oscillators, analog signals and power electronics. I thought that noise would be a big problem in this circuit and realized that in many circuits courses I took, the profs did not give that many hints on how to design these kind of circuits. Before starting, I decided to read a book on the subject. I read Tim Williams' The Circuit Designer's Companion. It was a really nice book which can be read easily but giving great insight for circuit design. Highly recommended.

Kepco Power Supplies: Crocodiles of the Electromechanical Labs

After a long break, I am adding a new article to my blog (actually just another small mental note to help me keep forgetting things). Lab equipment evolves very fast in most of the technial fields. Most of the stuff which were the top notch equipment of any lab 20 years ago, is mainly obsolete today. The trend is much faster in embedded system related laboratories. On the other hand, at work I am using Kepco Bipolar power supplies. They look archaic but they do their work flawlessly and they are extremely robust. When I read PhD thesis that are from early 80'ies, I see them present in the experimental setups. Even their physical appearance is the same. They are like the crocodiles in the nature, achieved perfection in one area and existing practically forever.

Embedded Microprocessor Benchmarks

Internet is full with benchmarks on the personal computer microprocessor performance. On the other hand, if you are dealing with microcontrollers in the embedded systems realm, it is really hard to find some benchmark information comparing different brands and models. Recently, I learned that there exist an Embedded Microprocessor Benchmark Consortium (EEMBC) which provides some tools for benchmarking and publishes some benchmark results for the frequently used microprocessors. I know that speed is just one factor for selecting a microcontroller besides I/O options, power consumption, ease of use but it is worth looking to this site for some ballpark figures.