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.

Continue reading

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).

Continue reading

Bi-color LED indication

Bi-color LEDs are same LEDs as uni-color just there are more than one LED housed in one package. Bi-color LEDs may have two or three leads depending on intentional connection method. Three lead LEDs have common cathode lead to which both LEDs are connected internally.   In order to tun one of the LEDs or both at the same time connect cathode to ground via current limiting resistor which value is equal to one LED required limiting. Of course you can connect current limiting resistors to each of anodes and control current individually. Then you can apply power to one of anodes or both at same time to have bi-color amber illumination. Two leads bi-color LEDs have two LEDs connected in parallel but in opposite sides. One LEDs anode is connected o another LEDS cathode and other lead same way. So by applying power you will be able to light only one LED. For instance if you connect to microcontroller you will need to use two microcontroller pins to control both LEDs.   So you cant turn on both LEDs at once without specific technique like dynamic switching both LEDs in high speed that would make effect of both LEDs…

Continue reading

Using NVRAM in embedded projects

NVRAM(Non-Volatile Random Access Memory) is one of non-volatile memory selections. This may be alternative to EEPROM back up memory. NVRAM chips can be used for nonvolatile memory storage with many benefits comparing to EEPROM. Main benefit is that NVRAM chips work like static RAM. Actually they are RAM just they contain lithium cell battery for retaining RAM contents when main power is switched off. The backup memory can store contents as long as battery provides power. NVRAM chips doesn’t require much power, backup can be guaranteed for up to ten years. For instance lets take Dallas NVRAM chip DS1225.   It contains 64k(8k x 8) of RAM memory.

Continue reading

How does RFID tag technology works

RFID introduction RFID taging technology is successfully used among us, but we don’t notice them always and do not think about them as they are not noticeable because we do not have directly to take any actions to transfer or read any information from RFID tags. But probably everyone notices in big supermarkets, book stores two parallel frame antenas and thicker labels on products you buy, or maybe you have RFID entrance card at your work. So lets see how this technology works. RFID is so called Radio Frequency Identification system which consists of two main parts: transmitter and receiver. The labels, access cards and even passports in some countries they have RFID transponders integrated. These transponders are called “tags”. Each tag has information programmed in it. This information can be read by reader via Radio Frequency link. Tags can be very miniature like thicker paper sheets. Simplest ones have only antena and diode. These tags only reflect signals incoming from transmitters. These are tags that are used in supermarkets and other places for securing goods from stealing. If signal is reflected, alarm is triggered. When tag is scanned by seller, it is simply electrically destroyed so it won’t trigger…

Continue reading

Easy way to measure motor torque

Motor torque (momentum) is one of the motor ratings which is used to indicate rotary motor force produced on its output shaft. Motor torque rating is usually captured at the point when the motor is stalled. The torque measurement unit is (Nm) in the metric system or (ft-lbs) in the US system. But the principle is the same torque is a multiplication of lever length (r) and force(F) applied to lever: Ï„=r x F So there is a simple experiment on how to measure motor torque quite accurately without any fancy measuring tools. All you need is a motor of which torque will be measured, a nominal power supply of motor, thread long enough, a mass of known weight, ruler and a table or other lifted surface where the motor will be fixed.

Continue reading

Testing pulse transformer with an oscilloscope

Pulse transformers are little different from regular AC transformers. In AC transformers magnetic flux alternates between negative and positive values in core while in pulse transformers magnetic flux is unipolar. Pulse transformers are used in TV, computer power supplies. If you need to test pulse transformer it may be almost impossible to do this with ohmmeter even digital one because windings of impulse transformer have very low active resistance except high voltage ones. One way to test is to measure inductance of windings and compare them to values in specifications, but not everyone has ability to measure inductance and not always you have transformed specifications near by. So there is another way to test pulse transformers which may be acceptable to almost everyone radio-hobbyist. By using low frequency generator which works at resonance frequency of contour which consists of external capacitor and pulse transformer winding.  

Continue reading