Turn-key PCB assembly services in prototype quantities or low-volume to mid-volume production runs
Turn-key PCB assembly services in prototype quantities or low-volume to mid-volume production runs

USB types and architecture

USB (Universal Serial Bus) – is type of serial communication interface since January 15, 1996 when first USB-1.0 specification came up to day light. There were several organizations behind USB creation like Compaq, DEC, IBM, Intel, Microsoft, NEC, and Northern Telecom. There are several modifications of USB, but most common for microcontrollers are Low Speed (LS, 1.5Mb/s) and Full Speed (FS, 12Mb/s). Probably everyone knows USB because of widely used Flash memory cards, various devices that connect to personal computer via USB port like printers, cameras, scanners, media players. Today USB 1.0 is almost left behind as there is common USB 2.0 standard used which theoretical speed reaches up to 480Mb/s. Historical timeline of USB evolution: 1996 – USB-1.0 – up to 12Mbit/s (LS and FS) – Initial version; 1998 – USB-1.1 – up to 12Mbit/s (LS and FS) – Updated version; 2000 – USB-2.0 – up to 480Mbit/s (LS, FS and HS) – Increased speed and added miniUSB; 2004 – Wireless USB- up to 480Mbit/s – Wireless connection; 2008? – USB 3 – up to 4.8Gbit/s – on the horizon. It is amazing how technology evolves – just imagine few years ago we were exchanging information by using 3.5″…

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Single supply operation amplifiers versus dual supply

We used to see dual supply ideal operational amplifiers (Op Amps), what means that Op Amps are powered from dual supplies with equal magnitude and opposing polarity. The center tap is connected to the ground which serves as a center of the supply voltage. Single supply operational amplifiers are powered with single polarity voltage. In this case you loose convenient ground reference that split supply op amps have. In this case you must ensure that signal swings between correct voltages (eg. VCC and GND). Input sources connected to ground are actually connected to a supply rail in single-supply systems. This is analogous to connecting a dual-supply input to the minus power rail. This requirement for biasing the op amp inputs to achieve the desired output voltage swing complicates single-supply designs.

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Connection sockets and headers used in embedded projects

Probably everybody gets confused each time when considering what connectors to use in electronic projects. There are so many connector types and technologies that can be chosen. So what connectors is the best choice, or there is no single answer? Before answer these questions lets go through several points. First of all why do we need connectors? There is no problem to solder all components and wires together without ability to loosen or wear out. But in fact there are much more advantages of using connectors comparing to reliability of connection. Connectors make it easier to assemble electronics products; Allows easier to repair devices with ability quickly to replace faulty parts; Easier to upgrade old components or blocks with newer ones; Ads flexibility to design. Probably most common connector used by embedded electronics hobbyists are 0.100″ spaced pins as its step is same as of widely used DIP chips and prototyping breadboards.

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Contact lenses with circuits for superhuman vision

Can you imagine having screen directly on your eye like movie characters from the Terminator or Bionic Woman? Maybe not for having virtual crosshairs or zoom in on far-off scenes, but for more practical use like having virtual displays for visual aids to help vision-impaired people, holographic driving control panels and even as a way to surf the Web on the go. The device to make this happen may be familiar. Engineers at the University of Washington have for the first time used manufacturing techniques at microscopic scales to combine a flexible, biologically safe contact lens with an imprinted electronic circuit and lights. There are many possible uses for virtual displays. Drivers or pilots could see a vehicle’s speed projected onto the windshield. Video-game companies could use the contact lenses to completely immerse players in a virtual world without restricting their range of motion. And for communications, people on the go could surf the Internet on a midair virtual display screen that only they would be able to see. The prototype device contains an electric circuit as well as red light-emitting diodes for a display, though it does not yet light up. The lenses were tested on rabbits for up…

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Batteries and cell characteristics

Batteries are cheap, small and relatively safe way of having portable energy source. There are many types of batteries with different characteristics and uses. Probably many of you heard terms battery and cell referring to the same. But from technical perspective these are different things – cell is a single unit which houses a single chemical reaction and produces electricity, while battery is a pack of cells. Nominal cell voltage and battery voltage For instance single AA battery can be called a cell because this is a single unit where single chemical reaction generates voltage of 1.5V, but car lead-acid battery have six cells producing 2.0V each while all battery produces 12V. So first important thing to remember that single cell can produce specific nominal cell voltage that depends on chemical reaction, while battery voltage is a combined voltage of multiple cells connected in series (or parallel).

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Surface Mount Soldering with inexpensive equipment

This is an excellent video about SMD soldering using cheap and straightforward equipment that most electronics hobbyist can find at home. This 9 min video tutorial prepared by CuriousInventor includes up-close shots of fine pitch soldering such SMD elements as 603 resistors, PLCC< 44 pin QFP, 208 pins fine-pitch QFP. Also, there are few SMD desoldering tips disclosed.

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AVR internal oscillator jitter research

If you go to AVR site and open an AVR application note AVR053, you will notice that there are different RC oscillators installed into AVR chips during history. In the table, you can see tunable oscillator versions and their features. Simply speaking each new version of oscillator introduces better features and improvements. But is it truth? ChaN has made exciting research on this oscillator version. He simply tested output signal with fixed width and measured timing fluctuations of it. And he found out, that RC generator frequency slowly fluctuates during the time. Of course, RC oscillator fluctuations are not a problem as this type of clock source isn’t considered to be stable. In time critical applications it is better to use crystals. But the most exciting thing is that newer versions of tunable oscillators were generating much more jitter than older ones. In the picture, you can see that chips introduced 2-3 years ago show almost no noticeable jitter, while new ones give about 0.5% maximum. It seems that significant fluctuation appeared from 4.0 RC oscillator version. It is hard to tell the reason why it is so. Probably it is a result of some efficiency improvements, that resulted in…

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