How to Make a Continuity Tester

I have two multimeters; one which gives a reading but no audible beep when the contacts are made, and the other multimeter which is broken but works for continuity testing, however doesn't always beep if the level it reads isn't quite high enough.

I wanted something more reliable!

A continuity tester is a gadget that literally tests "continuity" or continuence, in other words, you use one to check where traces lead to on printed circuit boards.

There are several guides on YouTube and Instructables, however they all seem to use 3v battery (as run an LED to show when continuity is present) or more, if move voltage, then they use a resistor to stop the LED from frying. Ok, 3v is probably ok for most work, however if you are prodding about with finding traces on microchips, it isn't always a good idea to have 3v running through parts of a board.

My method is different because it only uses 1.5v to achieve a similar result; less voltage = safer for a motherboard. 

The result I think looks quite professional, a light on one of the ends of the gadget illuminates, at a place you are looking at anyway (ie the tip); and made using the following:

2 x pens
1 x light from a GameBoy light unit
Some thick single core wire (for the probes)
Black electrical tape
1 x AAA battery
About 60cm of flexible wire

Scissors
Soldering iron and solder
Flux (so you can solder to the battery terminals)
Glue / hot glue

What pens you use are entirely down to what you have available; what you want are clear ones so when the light is installed, you will see it shining. Most disposible pens seem to be almost exactly the same circumference as an AAA battery, which is handy.

Step one: find two similar pens

Step two: disassemble

The looks of the pens you use may look different, however most have a screwable tip and end

 

You can cut the pen down so it ends up the same size as it was by reducing the length taking the size of the AAA battery into account, or just cut in half, as I did

The light was from a similar GameBoy light unit. They are rated as 3v however work fine at 1.5v (at least, mine do).

Remove the lights from the GameBoy unit, and start wiring to the pen. What you want is, to put it simply:

piece of rigid wire (eg single strand wire
>
light
>
one end of battery terminal
> 
other end of battery connected to a 60cm or longer wire for the other pen

To solder to battery terminals, apply a little flux, then the solder will attach fine

The pen I used had a rubber base to it, so I trimmed that down to get a clear window for the light to shine through - if your pen is just clear all the way through, you don't need to do anything.

Then, using some electrical tape, tape the battery to the pen, then solder the 60cm wire to the other battery end and tape that battery end to the other end of the pen, when the wire has been fed through the end of the pen.

You can easily unravel the electrical tape in the future to change the battery if you need to.

Firstly, test the wire makes contact and the light works fine, before making the housing for the long wire (pen #2).

The 

This time, just solder a thick wire / single strand wire, as per the other pen, and attach through the pen tip, using glue/hot glue to maintain it in place.

Wrap in electrical tape as before. 

Then, by touching the tips together, you should have a working, and cheap to make continuity tester!

There is no need for an on/off switch as by definition, the circuit is off until the continuity is met in which case the light comes on; off when off!

The result looks very attractive, and feels nice in your hands, as by definition, they are based on pens.


For other modding projects, especially in regards to modding video gaming consoles, please visit my website:  www.bacman.co.uk/home