Applications of Basic Electronics Components Nur Liyana Tajul Lile

Half-wave rectifier circuit. rectification is the conversion of alternating current (AC) to direct current (DC)

Half-wave rectification is insufficient for most power applications. The harmonic content of the rectifier's output waveform is very large difficult to filter. half of the rectifier capacity is unused As the AC power source only supplies power to the load one half every full cycle http://www.allaboutcircuits.com

Half-wave rectification is, however, a very simple way to reduce power to a resistive load. Some two-position lamp dimmer switches apply full AC power to the lamp filament for “full” brightness and then half-wave rectify it for a lesser light output. http://www.allaboutcircuits.com

Half-wave rectifier application: Two level lamp dimmer. http://www.allaboutcircuits.com

In the “Dim” switch position, the incandescent lamp receives approximately one-half the power it would normally receive operating on full-wave AC. the half-wave rectified power pulses far more rapidly than the filament has time to heat up and cool down the lamp does not blink (on/off) its filament operates at a lesser temperature than normal less light output. http://www.allaboutcircuits.com

This principle of “pulsing” power rapidly to a slow-responding load device to control the electrical power sent to it Since the diode is either fully conducting or fully non-conducting at any given time, it dissipates little heat energy while controlling load power, very energy-efficient. http://www.allaboutcircuits.com

Clipper A practical application of a clipper is to prevent an amplified speech signal from overdriving a radio transmitter Over driving the transmitter generates spurious radio signals interference with other stations. A sine wave may be squared up by overdriving a clipper The clipper is a protective measure. http://www.allaboutcircuits.com

Clipper prevents over driving radio transmitter http://www.allaboutcircuits.com

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Over-Temperature sensing circuit To determine when the temperature reaches a certain critical value. The circuit consist of a Wheatstone bridge with op-amp used to detect when the bridge is balanced Thermistor (R1) is a temperature-sensing resistor with a negative temperature coefficient (resistance decreases as temperature increases)

At normal temperature (below critical), R1 is greater than R2 Potentiometer R2 is set to a value equal to the resistance of the thermistor at the critical temperature At normal temperature (below critical), R1 is greater than R2 Unbalanced condition that drives the op-amp to its low saturated output level Transistor Q1 off. As temperature increases, resistance of thermistor decreases When temperature reaches critical value, R1=R2, bridged becomes balanced. At this point op-amp switches to its high saturated output level, turning Q1 on Energizes the relay Activate alarm An apropriate response to over-temperature condition.

Analog-to-Digital Conversion Common interfacing process when linear analog system must provide inputs to digital system. The simultaneous, flash method of A/D conversion uses parallel comparators to compare linear input signal with various reference voltages develop by a voltage divider When input voltage exceeds the reference voltage for a given comparator, High level is produced at comparator output Figure below shows analog to digital converter Produces 3 digit binary numbers on its output Requires 7 comparators (2n-1) n-digit binary

Used large no of comparators Priority encoder is a digital device produces a binary number on its output representing the highest value input

Electronics, By D. I. Crecraft, David Gorham

Electronics, By D. I. Crecraft, David Gorham

The ADC is fixed at 10 bits of binary data output, To measure the height of water in a 40- foot tall storage tank using an instrument with a 10-bit ADC. 0 feet of water in the tank corresponds to 0% of measurement 40 feet of water in the tank corresponds to 100% of measurement. The ADC is fixed at 10 bits of binary data output, it will interpret the tank level as one out of 1024 possible states. http://www.allaboutcircuits.com

physical water level in each step of the ADC divide the 40 feet of measurement span by the number of steps in the 0-to-1024 range of possibilities, which is 1023 (2n-1). obtain 0.039101 feet per step.

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Controlling a fan with a thermistor Thermistor can be used for the fan to come on above a specific temperature. The diagram below is a circuit which uses an op amp as a comparator with an output which goes high when pin 5 goes higher than pin 6. http://www.bcae1.com/

The temperature and voltage on the potentiometer can be changed. Voltage can be changed based on the potentiometer This controls the reference voltage on the negative input of the op amp. Setting it lower makes the fan come on at cooler temperatures. http://www.bcae1.com/

Thermometer is used to change the relative temperature When the conditions are right, the relay will engage and the fan will run. http://www.bcae1.com/

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Bipolar Junction Transistor Transistor switch

Used as a switch to turn the LED on and off Square wave input voltage with a period of 2s is applied to the input. When square wave is at 0V, transistor in cutoff. No Ic LED does not emit light When square wave goes to its high level, transistor saturates Forward bias the LED Ic through LED Emits light LED is on for 1 second and off for 1 second

References http://www.allaboutcircuits.com http://www.bcae1.com/ http://www.citycollegiate.com/wheatstone _bridge.htm Electronics, By D. I. Crecraft, David Gorham

In group of 5, select three electronics components and explain their applications.