In today’s world, we use many electrical circuits to carry out basic and complex tasks. Some tasks are such that we expect an electronic system to automatically complete without manual interference.
Take a simple example:
When there is someone prowling in the dead of the night in a bank, we would expect an electronic system to automatically detect the presence of an intruder and respond by flashing security lights or sounding an alarm.
So, we have two important words here:
Hence, to automatically detect a change in the environment and respond to this stimulus, electronic systems make use of devices known as transducers.
Any electronic system can be considered to consist three basic parts:
- Input transducers/ sensors.
- Output transducers.
Now we’ll be explaining what each part does and their examples:
|Part||What it does||Example|
|Input transducers/ sensors.||input transducers detect changes in the environment||Light dependent resistors, thermistors, microphones, sensors etc.|
|Processors.||Processors decide on what actions to take||CPU in a computer|
|Output transducers.||Output transducers convert the electrical energy supplied by the processor into another form to give an output||Light emitting diodes, buzzers, motors, heaters, relays etc.|
|Light dependent resistors (LDR)|
|What is a LDR?||A LDR is a type of ‘variable resistor’ whose resistance depends on the amount of light falling on it.|
|How does an LDR work?||An LDR is made up of a material which does not conduct electricity too well (such as graphite). In the dark, a LDR has an extremely huge resistance. However, when light is shone on the LDR, its resistance decreases, letting electric currents flow through it.|
|Uses of LDRs||LDRs are used in burglar alarm systems and systems involving security lights.
LDRs are also used in some digital clocks.
|What is a thermistor?||Thermistor is another type of resistor, whose resistance depends on its environment. (In this case, the resistance depends on the surrounding temperature.)|
|How does a thermistor work?||For some thermistors, the resistance decreases as the temperature increases.
For other thermistors the resistance increases as the temperature increases
|Uses of thermistors||Some thermistors are used in circuits designed to prevent overheating.
Thermistors are also used in temperature probes
Thermistors can also be used to switch a relay.
|What is a relay?||A relay is a type of switch that works using an electromagnet.|
|How does a relay work?||When relay is used there are two circuits:
1. The electromagnet coil of the relay is in one circuit
2. The switch is in another circuit.
When a current flows through the relay coil in the first circuit it becomes magnetised. It pulls on the switch in the second circuit, causing it to close and allowing a current to flow in the second circuit.
The second circuit often involves a large voltage which would be risky for an operator to switch or which could not be switched by a normal electronic circuit.
|Uses of relays||Relays are often used to switch the mains supplies in houses
Relays are also used in electric bell/alarms
|Light Emitting Diode (LED)|
|What is an LED?||A LED is a diode made from the semiconductor gallium arsenide phosphide.
(A diode is a component that allows electric current to flow in one direction only.)
|How does an LED work?||When a current passes through a LED, it gives out coloured light.
Note: If the voltage passes 5V, a lot of damage can be caused (Be careful!)
|Uses of LEDs||LEDs are used in indicator lamps on computers, and electrical component such as radios.
Many clocks, calculators, video recorders and measuring instruments have seven-segment LED numerical displays.
LEDs are also used in traffic lights.
A diode is a component that allows electric current to flow in one direction only.
A diode is a non-ohmic conductor. It is useful for converting alternating current (which varies back and forth) into direct current (which flows in one direction only).
This process is known as a rectification and the diode acts as a rectifier.
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