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Power supplies

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Batteries are the most common source of power used for electrical circuits in schools. They come in a variety of sizes, which can be combined in series battery holders. This allows the voltage produced to be equal to the sum of the batteries used: eg 3 x 1.5 V AA batteries would produce a voltage of 4.5V.

Batteries and Voltage

Battery Voltage
AAA 1.5V
AA 1.5V
C 1.5V
D 1.5V
PP3 9V

When choosing a battery, the following should be considered:

· The power requirements of the circuit.

· The battery life needed, measured in milliamp hours.

· The size, shape and weight of the battery.

· The cost of the battery.

· Sustainability: could rechargeable batteries be used?

· Battery disposal: how will the battery be disposed of at the end of its working life?

As an alternative to batteries, external power supplies can be used with low-voltage regulators (such as L7805 and 78L05). Their use is often limited by cost, the need to be attached to the external power supply and the power requirements of the circuit.

Standard symbols guide

The standard symbols for the key components used in electronic circuits are shown in the table below.

Electronic circuit symbols

Cell Light-emitting diode (LED) Push-to-make switch Diode Bell Voltage rails
Battery Flashing LED Push-to-break switch Thyristor Microphone Earth
Resistor Bi-colour LED Single-pole single-throw switch NPN transistor Buzzer 555 timer IC
Variable resistor Tri-colour LED Single-pole double-throw switch Field effect transistor (FET) Loud-speaker Operational amplifier (op-amp)
Potent-iometer Photo transistor Capacitor AND gate Lamp Voltage regulator
Thermistor Opto-isolator Electrolytic capacitor OR gate Motor Crossing of conductors
Light-dependent resistor (LDR) Ammeter Piezo crystal oscillator NOT gate Voltmeter Joined conductors

 


 

Test Bite

Начало формы

What does IC stand for?

Individual circuit
Integrated circuit
Integrated chip


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