Instructables
This is a simple continuity tester using a green L.E.D and two button cells. It is built into a clear ball point pen body.
 
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Step 1: Description

Electronic circuits are built by connecting components together. This connection might be direct, as when you twist the leads of two components together. Or it might be using a length of wire, or via a trace on a circuit board.

In any case, it is essential that some points are connected together, and equally essential that some other points are NOT connected together. A continuity tester enables you to quickly check whether points intended to be connected are really so, and that points intended to be isolated are also really so. Such a check is usually performed on a circuit board before any components have been loaded into it.

The technician's instrument of choice, the multimeter, is not really suited for a quick check. It gives you a reading, which then has to be interpreted. However, some meters do have a "continuity" position with a beeper for this purpose.

I have here attempted to provide instructions to make a small intrument with visual indication of continuity, suitable for checking continuity of conductors, low value resistors and high value capacitors. It is not suitable for checking semiconductor devices. It might be possible, depending upon your LED, to check diodes with it.
thegrendel1 year ago
An interesting and elegant project.
You might want to consider adding a current-limiting resistor,
say 220 ohm or so, otherwise you'll be replacing burned-out
LEDs every so often.
I guess the V= 2 x1.5 cells =3V
The best thing to build this project or any other project is to use a schematic diagram; I personally will have lots of problems trying to build a project without a schematic, it is difficult to follow on these instructions
Nice I like the < 3 volt design to keep from killing ICs when looking for bad traces on a motherboard.
markee24 years ago
you are very creative in using a ball pen casing as a holder of your circuit
actually i copied your idea and made my friend one. initially it worked but
 i found some problem when testing continuity that involves high resistance wiring. The led doesn't light at all.

fortunately i found a solution when i found this circuit from
http://www.simple-electronics.com/2009/10/wire-continuity-tester-by-transistor.html


simple wire contuinity tester.JPG
This is great. I got a tester a while back, and the thing didn't even work. Not even a light inside. I'm going to use the casing for this.
awesome. i like the size of that project. i did something similar with a old remote control and added a piezo for sound. works great.
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