The term Biosignal refers to all the signals that are being generated in the human body or any other living organism or more specifically it is used to represent all those signals from living organisms that are monitored to obtain certain useful information. Primarily, the term refers to signals that are electrical in nature but, some non-electric signals are monitored as well.

Typically, the changes in potential difference across a certain tissue in the body are measured in case of bio-electric signals. Let us have a look at few of the properties of biosignals generated by the human body that are analysed to obtain information:

• In case of Electroencephalography, the activity of the human brain is monitored. Usually, at a synapse (junctions between the cells of the nervous system), flow of ions takes place. This results in the formation of various signals that are used by the body to transfer information. The voltage variations that are caused by these signals are recorded and thus, the activity of the brain is measured.

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Digital signal processing is the technique used to analyse various digital signals and obtain information form the same. It is also used for transfer of information from one place to another and also involves conversion in between analogue and digital signals.

It finds its application in various areas ranging from broadcasting to medicine.

Let us have a look at some of the applications of the same.

Biomedical Applications: DSP is used extensively in the field of biomedicine. In it, the various signals that are generated by the different organs in the human body are measured in order to find information regarding the health of the same. For example, in case of electrocardiograms, the electric signals generated by the heart are measured. Similarly, the activity of the brain is monitored by electroencephalograms.

Automatic Control: These days, many gadgets are available that can perform their tasks automatically. These devices contain various components that can take inputs depending on the surrounding conditions. These are conveyed to the control unit of the device where they are processed and the necessary action is taken. For example, a device like the thermostat increases its resistance in proportion to temperature. This can be used to stem the current in a machine whenever the temperature rises. Read the rest of this entry »

These are devices that are used in electronic circuits to make reconfiguration of the same possible. The logical gates that are normally used perform a fixed function however, the Programmable Logic Devices (PLD) does not perform any predefined task when they are manufactured and need to be programmed before they can be used.
Before the introduction of PLDs, ROM (Read Only Memories) was used. EPROM that was available could be programmed by using any standard hardware for that device and hence, did not require any other peripheral hardware. Another advantage of ROMs is that a particular binary code stored in it could be obtained on any of the n output lines that were available in it. Thus, they can be programmed in any way one wishes to. However, ROMs have some disadvantages when they are used as PLDs. They do not produce the outputs as quickly as other devices; they are not very dependable as far as asynchronous inputs are concerned, they require more amount of power etc.

The first PLD was the programmable logic array that was developed from ROAM (Read Only Associative Memory) by modification of one of its metal layers and had 17 inputs and 18 outputs. Read the rest of this entry »

Biomedical devices are those electrical devices that are used in medicine to carry out various tests on the human body. A lot of research has been performed in this field and as a result, these devices have become indispensable as far as medicine is concerned.

Let us have a look at some of the tasks that are performed by making use of these devices:

• For diagnosis of various diseases or abnormalities.
• In prevention of these diseases, their cure, mitigation etc.
• In many cases, some parts of the human body malfunction and are no longer able to perform their respective tasks. In such cases, these devices may be used as a replacement for those body parts. For example, a pace maker is used for a person who has a weak heart.

Based on the type of function that they perform and on other characteristics, these devices have been classified into the following three types:

• The devices in the first class relatively cause less amount of harm to the user and have been designed using simple techniques. These devices include ordinary items such as surgical gloves, tongue depressors, other hand held instruments used in surgery etc.

• The devices that belong to the second class have certain specialised applications and controls. It may be required to maintain certain standards in these devices during their manufacture as they can potentially harm the user if they are not used correctly. These devices include surgical drapes, wheel chairs with electric power, X-ray machines etc.

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Processing of audio signals is one of the most important and widely used applications of digital signals processing. It is being used in many fields such as communication, broadcasting of audio signals for radios, television etc. It primarily includes analysis of audio signals that fall in the human hearing frequency by mathematical. The audio signals that fall in the human auditory range depends both on physical and psychological factors. A separate branch has been introduced to study the same and is called psychoacoustics.

Wherever signals are concerned, one has to deal with two different types viz. digital and analogue. The techniques that are used in order to deal with these two types of audio signals are different. In case of analogue audio signals, the pressure transformations are usually represented electrically in the form of voltage levels.

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Despite the fact that USB is live for more than 10 years - electronic amateurs move towards it relatively slowly. Probably main reasons are that many electronics work with relatively old computers where RS232 port is actively used. Even me when buying new PC I was looking that motherboard was equipped with at least one COM port. But situation is more complicated with Laptops where COM or LPT ports are not used anymore due to limited space and other reasons. The only way is to adapt to USB in one way or another.

One of temporary solutions may be using USB to RS232 adapters. But again this is only emulation of COM port and not all programs may understand it correctly like PonyProg doesn’t work with virtual COM ports.

Today companies producing electronics components have been pushing lots of types of USB chips to market. In order not to get lost there is some classification made. So USB chips may be classified as follows:

• Microcontrollers with build in USB interface;
• Microcontrollers with USB emulated program;
• USB converters or USB bridges;
• Hub controllers;
• Host controllers;
• Dual role controllers, OTG (On-The-Go);
• USB transceivers, USB switches

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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″ 1.44Mbytes Floppy diskettes, now 4GB Flash isn’t enough. Same is with data transfer speed. Amount of digital information grows incredibly fast and everything has to go through some wires or wireless - who wants to wait for a long time while 4GB video will be transferred from camera to hard drive. I don’t :). Read the rest of this entry »

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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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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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 to 20 minutes and the animals showed no adverse effects. Read the rest of this entry »