Electrifying Electronix

PCB from LION circuit

http://www.voicendata.com/inventor-of-iot-to-be-part-of-nasscoms-design-engineering-summit/

Microcontroller

A microcontroller (sometimes abbreviated µC, uC or MCU) is a small computer on a single integrated circuit containing a processor core, memory, and programmable input/output peripherals. Program memory in the form of NOR flash or OTP ROM is also often included on chip, as well as a typically small amount of RAM. Microcontrollers are designed for embedded applications, in contrast to the microprocessors used in personal computers or other general purpose applications.

Microcontrollers are used in automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls, office machines, appliances, power tools, toys and other embedded systems. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes.
Mixed signal microcontrollers are common, integrating analog components needed to control non-digital electronic systems.

Some microcontrollers may use four-bit words and operate at clock rate frequencies as low as 4 kHz, for low power consumption (milliwatts or microwatts). They will generally have the ability to retain functionality while waiting for an event such as a button press or other interrupt; power consumption while sleeping (CPU clock and most peripherals off) may be just nanowatts, making many of them well suited for long lasting battery applications.

Other microcontrollers may serve performance-critical roles, where they may need to act more like a digital signal processor (DSP), with higher clock speeds and power consumption.

FDMA, TDMA & CDMA :-


Frequency Division Multiple Access (FDMA) :

Each user transmits with no limitations in time, but using only a
portion of the whole available frequency bandwidth.

Different users are separated in the frequency domain.




Time Division Multiple Access (TDMA):

Each user is allowed to transmit only within specified time
intervals (Time Slots). Different users transmit in differents Time
Slots.

When users transmit, they occupy the whole frequency bandwidth
(separation among users is performed in the time domain).




Code Division Multiplexing Access (CDMA) :

In CDMA each user is assigned a unique code sequence (spreading
code), which it uses to encode its data signal.

The receiver, knowing the code sequence of the user, decodes the
received signal and recovers the original data.

The bandwidth of the coded data signal is chosen to be much larger than the bandwidth of the original data signal, that is, the encoding process enlarges (spreads) the spectrum of the data signal.

CDMA is based on spread-spectrum modulation.

GSM vs CDMA

GSM (Global System for Mobile Communication) and CDMA (Code Division Multiple Access) are two dominant technologies for mobile communication. These two technologies differ in the way calls and data travel over the mobile phone networks take place. On comparing both the technologies GSM has some limitation when the call quality is concerned but still has more flexibility and an easy implementation relative to the CDMA technology. The major difference between the two lies in terms of the technology they use, security factors, their global reach and the data transfer speeds.

1. Technology

The CDMA is based on spread spectrum technology which makes the optimal use of available bandwidth. It allows each user to transmit over the entire frequency spectrum all the time. On the other hand GSM operates on the wedge spectrum called a carrier. This carrier is divided into a number of time slots and each user is assigned a different time slot so that until the ongoing call is finished, no other subscriber can have access to this. GSM uses both Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) for user and cell separation. TDMA provides multiuser access by chopping up the channel into different time slices and FDMA provides multiuser access by separating the used frequencies.

2. Security

More security is provided in CDMA technology as compared with the GSM technology as encryption is inbuilt in the CDMA. A unique code is provided to every user and all the conversation between two users are encoded ensuring a greater level of security for CDMA users. The signal cannot be detected easily in CDMA as compared to the signals of GSM, which are concentrated in the narrow bandwidth. Therefore, the CDMA phone calls are more secure than the GSM calls. In terms of encryption the GSM technology has to be upgraded so as to make it operate more securely.

3. Spectrum Frequencies

The CDMA network operates in the frequency spectrum of CDMA 850 MHz and 1900 MHz while the GSM network operates in the frequency spectrum of GSM 850 MHz and 1900 MHz.

4. Global Reach

GSM is in use over 80% of the world’s mobile networks in over 210 countries as compared to CDMA. CDMA is almost exclusively used in United States and some parts of Canada and Japan. As the European Union permissions GSM use, so CDMA is not supported in Europe. In North America, especially in rural areas, more coverage is offered by CDMA as compared to GSM. As GSM is an international standard, so it’s better to use GSM in international roaming. GSM is in use by 76% of users as compared to CDMA which is in use by 24% users.

5. Data Transfer Rate

CDMA has faster data rate as compared to GSM as EVDO data transfer technology is used in CDMA which offers a maximum download speed of 2 mbps. EVDO ready mobile phones are required to use this technology. GSM uses EDGE data transfer technology that has a maximum download speed of 384 kbps which is slower as compared to CDMA. For browsing the web, to watch videos and to download music, CDMA is better choice as compared to GSM. So CDMA is known to cover more area with fewer towers.

6. Radiation Exposure

GSM phones emit continuous wave pulses, so there is a large need to reduce the exposures to electromagnetic fields focused on cell phones with “continuous wave pulses”. On the other hand CDMA cell phones do not produce these pulses. GSM phones emit about 28 times more radiation on average as compared to CDMA phones. Moreover, GSM phones are more biologically reactive as compared to CDMA.

Resistor

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.
The current through a resistor is in direct proportion to the voltage across the resistor's terminals. This relationship is represented by Ohm's law:

where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms.
The ratio of the voltage applied across a resistor's terminals to the intensity of current in the circuit is called its resistance, and this can be assumed to be a constant (independent of the voltage) for ordinary resistors working within their ratings.

LED

Light-emitting diode :

When a light-emitting diode is forward-biased (switched on), electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor.
LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved physical robustness, smaller size, and faster switching. LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output.