This is a simple continuity tester that you can use for checking if components work or to check for shorts on a PCB. Its really cheap and free if you don't solder it together because you can take the components of when ever you want. My friend got me to make him one when he was trying to figure out what the wires in his ceiling lead to wile re-wiring.

The version I made is a simple no solder circuit on a piece of cardboard but I've included a PCB version for etching. You can also solder the cardboard. I'll explain both ways.

Step 1: Your Materials

You will need:

- 9v battery

- 9v battery clip

- LED

- Resistor (100 ohms or above, i used a 320 omh resistor)

- Cardboard / PCB

- Crocodile Clips / Banana Plug connectors

- Wire

- Soldering Iron (optional)

- Solder (optional)

- Wire stripper (optional)

Step 2: Make the Holes in the Cardboard / Drill PCB

Cardboard: Line up your components as shown and use a pencil or pin to make holes in the cardboard, you might want to label the holes as shown. There's an extra 2 holes to thread the wire around a corner (shown in the next step)

PCB: Drill the holes in your PCB after etching it or having it made.

Step 3: Inset the Components

Cardboard: Put the components in the holes you made earlier and as i mentioned earlier thread the wire along the corner to prevent it pulling.

PCB: Insert the components in the PCB as shown in the assembly diagram.

Step 4: Twist the Components Together / Solder

Cardboard: Twist the component legs together and the wires together as shown (you may need your wire stripper to expose more of the core to wrap around.) You can solder over the joints if you wish. If you don't solder over like me, make sure that the legs and wires are twisted around properly now otherwise they'll keep coming lose and be a pain when you try to use it. Don't forget to connect the clips to the wires.

PCB: Solder your components onto the board and cut the legs short. A good joint is shiny and touches the board, you want to avoid cold joints where the board was too cold before the solder was applied so it isn't holding it down properly - this will lead to a poor connection that could be mistaken for a bad component or connection during usage. You can usually tell by looking at the joint or seeing if it moves when you try to push it after its cooled. Don't forget to connect the clips to the wires.

Step 5: Use It!

Connect the crocodile clips / connectors to the component or the track and see if the LED lights up, if the LED doesn't light up with no component between it, check your soldering / twisting, if that's okay then you may have used a resistor with a value too high or your LED doesn't work. If you're testing a polarity sensitive component, be sure to connect the component correctly to the positive and negative sides.

PCB / Strip-board / pref-board tracks:

LED On: good connection with no breaks

LED Off: no connection or if testing through components - resistance is too high.

If the following doesn't happen for your component, it may be broken or the currents too low

Resistor:

LED Bright: low value, few ohms

LED Dim: few thousand oms

LED Off: over 10K ohms

Diode:

LED On: Positive clip to positive side and negative clip to negative side

LED Off: Positive clip to negative side and negative clip to positive side

LED (not lamp)

LED On: Positive clip to positive side and negative clip to negative side

LED Off: Positive clip to negative side and negative clip to positive side / Doesn't work

Transistors:

B = base, C = collector, E = emitter. (you can figure it out by testing or just look it up)

NPN transistor:

CE pair: LED off both ways.

BC & BE pairs: LED bright with red lead on B, LED off the other way.

PNP transistor:

CE pair: LED off both ways.

BC & BE pairs: LED bright with black lead on B, LED off the other way.

The PCBs shown above are from guitar pedals, a MXR Phase 90 and a Silicone Fuzz Face that my friend etched for me. If you're interested in making them they can be found here:

http://www.generalguitargadgets.com/how-to-build-i...

No prizes for guessing what company the bit of cardboard or battery is from