Electronics 4

Act 4

• Sensors
• Breadboard
• Transistor

There are 3 types of sensors used in D&T.

• LDR: Light Dependent Resistor Use in light sensing circuit
• Thermistor Use in temperature sensing circuit
• Moisture Sensor.: Used in moisture sensing circuit

LDR. how it works

• LDR is a light dependent resistor where its resistance varies with the amount of light it received.
• Due to this property, it is used in a light sensing circuit.

Questions

1. List the types of sensors used to detect light.

How to use a breadboard.

Transistor

• A Transistor is an electronic component that acts as a switch or amplifier.
• It comes in a package with three terminals.

• There arte 2 types of Transistor NPN or PNP.
• NPN are commonly used in our syllabus. In D&T we are only interested to see NPN transistor as an electronic switch.
• For a NPN transistor, it consist of 3 terminals. Collector, Emitter and Base.
• Click here to see how a transistor works as a switch.
• A small current flowing to the base of the transistor to emitter will cause the transistor to switch on.
• When the transistor is switched on, larger current will then be able to flow from collector to emitter.
• A transistor works by controlling the current going to base hence switching the transistor on or off. unlike a physical switch, a transistor can only be turn on or off by electrical means.