Power supplies

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

Дата добавления: 2015-10-26