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Knowledge Domain: Electrical Simple Unit: Connections Skill: Building and Using a Continuity Tester Tools and Parts Required: 1) Soldering iron 2) Solder 3) Stranded wire 4) Solid-core wire 5)Needle-nose pliers 6) Wire cutters 7) Wire strippers 8) Heat shrink tubing 9) Epoxy 10) 5mm super red diffused LED (digikey: 67-1648-ND) Introduction This skill is an introduction to basic circuit theory.First, you must understand that electricity only flows in a closed circuit. A closed circuit is a loop of materials that will conduct electricity. An open circuit is a loop that will not conductelectricity. A continuity tester helps to determine if a circuit is closed or open. Testing circuits is an essential skill for troubleshooting. A functioning continuity tester indicates continuity,sometimes called connectivity. The LED on the continuity tester will light when the test leads are connected to two points that are connected electrically. The LED will not light if the two points are notconnected electrically. Example Below is a picture of a simple continuity tester. The circuit includes a battery, a light emitting diode (also called an LED), and a resistor in series.

11) 200 ohmresistor (digikey: P200BACT-ND) 12) Perfboard or PCB (digikey: 3405K-ND) 13) 2 Alligator Clips (digikey: 3141033-ND) 14) Battery holder (for 2 AAA batteries) (digikey: BC 2AAAW-ND) 15) 2 AAA batteries16) Sandpaper (optional)

Identification and Diagnosis Before Assembling the Continuity Tester Be aware of the following items as you build your continuity tester • Polarity. Some electricalcomponents are polarized. Polarized components have a negative end and a positive end. Polarized components will only function when placed in the circuit in the correct direction. In the continuity tester,the batteries and the LED are both polarized. The resistor is not polarized. o The battery holder has markings that indicate the positive end (+) and the negative end (-). Verify the direction of the...