BATTERY TESTER CIRCUITS........

Battery Tester Project Using LM3914 IC

This objective of this project is to design and build a battery tester that is able to test various types of dry cell and rechargable battery with a voltage of less than 2V. Configured as a bar graph battery level indicator, the LM3914 IC from National Semiconductor senses the voltage levels of the battery under test and drives the 10 LEDs to ON or OFF based on the voltage that is detected. The current driving the LEDs is regulated by using the external resistor R1 and hence limiting resistors are not required.

The schematic shows the simple connections where the reference voltage at pin 8 of U1 can be adjusted by adjusting the variable resistor VR1. The voltage at pin 8 will set the maximum scale of the LED. In testing dry cellbattery of 1.5V, set the voltage at pin 8 to 2.0V. Each of the LED will thus represent 200mV when lighted up.

 

If testing of rechargable battery such as NiCd or NiMH is required, set the reference voltage to a lower value such as 1.5Vas the typical voltage of a rechargable battery is approximately 1.2V.

When testing the battery, take note of the polarity of the probe to the terminals of the battery. T1 is to be placed on the positive terminal and T2 the negative terminal of the battery.

Parts List

The parts list of the project is as shown below.

 

GSM (Global System for Mobile Communications)

GSM (Global System for Mobile Communications) is a Digital Wireless Technologyused for cell phone in the world that is, it is a cellular technology used for transmitting mobile voice and data services. It was developed by the European companies.

Features Of GSM

• It is 2G Technology
• GSM is a circuit-switched technology
• Uses GMSK [Gaussian Minimum Shift Keying] Modulation
• It supports FDMA & TDMA
• It uses SIM card so u can easily switch your SIM card between phones
• International roaming is easier on a GSM network
• In GSM every user requires a separate frequency channel for communication
• GSM accounts for 80% of total mobile phone technologies market

• The Frequency Band(range) in GSMThe frequency of the carrier is very important, because it determines the Size, power, efficiency of your mobile phones.

• It supports FDMA & TDMA as Multiple Access Techniques

SRC:HERE

Digital Microwave Communications

Microwave is a kind of electromagnetic wave. In a broad sense, the microwave frequency range is from 300 MHz to 300 GHz. But In microwave communication, the frequency range is generally from 3 GHz to 30 GHz.

Concept of Digital Microwave Communication

Digital microwave communication is a way of transmitting digital information in atmosphere through microwave or radio frequency (RF).

Microwave communication refers to the communication that use microwave as carrier.

Digital microwave communication refers to the microwave communication that adopts the digital modulation.

The baseband signal is modulated to intermediate frequency (IF) first . Then the intermediate frequency is converted into the microwave frequency.

The baseband signal can also be modulated directly to microwave frequency, but only phase shift keying (PSK) modulation method is applicable.

Src:Here