Make a simple component and continuity tester. This is used to test circuits and electronic components to see if they work.

Step 1: What You Will Need

What you will need

1 x 3 by 8 holes strip board
1 x 390ohm resistor
1 x LED (any colour)
Soldering Iron (with solder of course)
2 x Crocodile/Aligator clips
1 x PP3 Battery Connecter (I took my from an old PP3 battery)
Coloured wire eg. green&red/blue&red etc.
3-5 mm drill bit to break copper in the board

Step 2: Building the Circuit

Start by breaking the copper as I have done in the picture. Then place and solder the positive wires with the battery clip and the crocodile/alligator clips on the strip with the broken tracks as I have done. Then start by placing the 390ohm resistor leaving a break in the copper between the two leads on the broken track (next to the battery clip) and solder it in. Then place the LED on the broken track (the positive way around and next to the crocodile clip) and solder it in leaving a break in the copper between the two leads.

Step 3: Connect It Up

All thats left to do now is connect it up to a 9v PP3 battery and connect the clips to a component or circuit you are going to test. If you are testing an LED both LEDs will light up brightly. *Note if you are testing a capacitor remember to connect it with the correct polarity or you risk your capacitors life.

Resistors
LED bright for low resistance, less than about 1k.
LED dim for medium resistance, a few k.
LED off for high resistance, more than about 10k.

Diodes
LED bright with red lead to anode and black lead to cathode (stripe).
LED off with black lead to anode and red lead to cathode (stripe).

Zener Diodes
LED bright with red lead to anode and black lead to cathode (stripe).
LED dim with black lead to anode and red lead to cathode (stripe) if the zener diode voltage is less than about 7V.
LED off with black lead to anode and red lead to cathode (stripe) if the zener diode voltage is greater than about 7V

Transistors
For each pair of transistor leads connect the tester leads first one way, then the other way.
These are the results for an NPN transistor in good condition:
CE pair: LED off both ways.
BC pair: LED bright with red lead on B, LED off the other way.
BE pair: LED bright with red lead on B, LED off the other way.

These are the results for a PNP transistor in good condition:
CE pair: LED off both ways.
BC pair: LED bright with black lead on B, LED off the other way.
BE pair: LED bright with black lead on B, LED off the other way.