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Interview Questions Part 2

1. What are the drawbacks of Walsh codes?Walsh codes have the following drawbacks:

1. the codes do not have a single, narrow autocorrelation peak.
2. The spreading is not over the whole bandwidth; instead the energy is spread over a number of discrete frequency components.
3. Although the full sequence cross correlation is identically zero, this does not hold for a partial sequence cross correlation function. Thus advantage of using orthogonal codes is lost.
4. Orthogonally is also affected by channel properties like multi path. 2. Explain radio environment in building.Building penetration: Building penetration depends on the material used for construction and architecture used. This varies building to building and is based on building construction.
Building Height Effect: The signal strength is always higher at top floor and generally floor gain height is about 2.7dB/floor which is not dependent on building construction.
Building Floor Reception: The signal isolation between floors i…

Interview Question Part 1

1. What is Electronic? The study and use of electrical devices that operate by controlling the flow of electrons or other electrically charged particles.
2. What is communication? Communication means transferring a signal from the transmitter which passes through a medium then the output is obtained at the receiver. (or)communication says as transferring of message from one place to another place called communication.
3. Different types of communications? Explain. Analog and digital communication.
As a technology, analog is the process of taking an audio or video signal (the human voice) and translating it into electronic pulses. Digital on the other hand is breaking the signal into a binary format where the audio or video data is represented by a series of "1"s and "0"s.
Digital signals are immune to noise, quality of transmission and reception is good, components used in digital communication can be produced with high precision and power consumption is also very le…

Temperature Controlled DC Fan using Microcontroller

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A Temperature Controlled DC Fan is a system which automatically turns on a DC Fan when the ambient temperature increases above a certain limit. Generally, electronic devices produce more heat. So this heat should be reduced in order to protect the device. There are many ways to reduce this heat. One way is to switch on the fan spontaneously. This article describes two such circuits that automatically, switches the fan when it detects the temperature inside the device greater than its threshold value. 
Circuit 1 Temperature Controlled DC Fan using 8051 Circuit Diagram



Principle The project works on the principle of Analog to Digital Conversion. The Analog data from the LM35 temperature sensor is given to the analog to digital converter ADC0804. The analog output of the temperature sensor will vary at 10mV per degree Celsius. ADC0804 is an 8-bit ADC. For a reference voltage of 5V, we’ll get a resolution of 5V/28 = 20mV. Which means, this is the minimum change in the analog value from the sen…

Water Level Indicator Mini Project

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The Water Level Indicator employs a simple mechanism to detect and indicate the water level in an overhead tank or any other water container. The sensing is done by using a set of nine probes which are placed at nine different levels on the tank walls (with probe 9 to probe 1 placed in increasing order of height, common probe (i.e. a supply carrying probe) is placed at the base of the tank). The level 8 represents the “tank full” condition while level 0 represents the “tank empty” condition. When the water-level is below the minimum detectable level (MDL), the seven segment display is arranged to show the digit 0, indicating that the tank is empty, when the water reaches level1 (but is below level2) the connection between the probes gets completed (through the conducting medium – water) and the base voltage of transistor increases. This causes the base-emitter junction of transistor to get forward biased, this switches transistor from cut-off to conduction mode thus PIN (B7) o…

741 operational amplifier

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An operational amplifier (often op-amp or opamp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output.[1] In this configuration, an op-amp produces an output potential (relative to circuit ground) that is typically hundreds of thousands of times larger than the potential difference between its input terminals. Operational amplifiers had their origins in analog computers, where they were used to perform mathematical operations in many linear, non-linear and frequency-dependent circuits. The popularity of the op-amp as a building block in analog circuits is due to its versatility. Due to negative feedback, the characteristics of an op-amp circuit, its gain, input and output impedancebandwidth etc. are determined by external components and have little dependence on temperature coefficients or manufacturing variations in the op-amp itself.
Operation[edit] An op-amp without negative feedback (a comparator) The amplifier's …