In this instructable you will be able to make a continuity tester for less than 50 cents


In electronics a continuity tester is a very crucial tool. It helps you to troubleshoot your circuit and find faults in it.

The basic idea is that the device consists of two probes which when come on contact make a buzzing sound.

While troubleshooting a circuit the probes are touched to the two contacts which needs to be tested, if they are connected the continuity sensor makes a buzzing sound.

Most multimeters are equipped with a continuity tester but some are too slow or you can make one if you don't have a multimeter on don't like to carry one always


The materials you would be requiring for this build are very cheap and would cost you about 50cents to 1$ depending on the place you live and the place you buy them from.

The materials you would require are:
1. AAA Battery
2. Buzzer (preferably small)
3. One male-to-male jumper ( or you can use headers or pins)
4. An old thick sketch pen ( of course you can buy a new one if you don't have one)
5. Any pen
6. Some wire

The tools you would require

1. Soldering iron
2. Hot glue or any other adhesive
3. Wire strippers or scissors
4. Solder
5. Sandpaper(100 grit)


The circuit is the simplest that can be. It is very similar to the basic light bulb circuit that everyone tried in their childhood.

The only difficult part is that you will have to sand the battery contacts before you can solder wires to them.

Also check the polarity of the buzzer. The longer leg is the positive end and the shorter one is the negative end.


For making the body the first thing you need to do is to clean out the pen. Open the pen and pull out the refill and the tip with pliers. Then you can stuff everything in the pen.

The pins or one end of the male to male jumper will become one of the probe and the second end or the second pin will become the second probe.


After you have fit in everything and one probe is poking out of the pen and you have tested the circuitry by touching the 2 probes, using hot glue secure every thing including the pin or the male to male connector.

The next thing is to poke a hole through the cap you had taken out and thread the other probe through it.

Secure the cap back on and test your circuit.


For the second probe take an old pen and remove the back cover and pull the refill, poke a hole and pass the wire hanging out of your first probe through the hole.

Solder the other end of the male to male connector and then secure it with hot glue at the tip of the pen.


Touch the two probes and you should hear a beeping sound.

If you don't hear the beeping sound then the circuitry is not working the most common problem being that the connection from the battery is broken.
Great Instructable! Hope you come up with more of them the future! ;)
Awesome idea. I too like making my projects out of recycled stuff i find, good stuff man :) <br><br>(i know this project was meant for simplicity and to be made cheap, but you may want to be weary of having the battery and piezo element directly inline with the continuity checker; as this may wreak havoc on the components you check. Might be a good idea to use a seperate (low power) component to open a path between the battery and piezo[ transistor / op amp etc]. Just food for thought)
Thanks for your valuable input while your point is good about the amplification and separation of the components.<br><br>also to tell you I have tried making the same thing with a 2N2222 transistor but it only reduced the efficiency and I had to change the battery more frequently, because the transistor required a voltage of 0.7 volts to open the circuit which would not be available when using only a 1.5v battery.<br>If I would have used a higher voltage like 5v I would have added an op amp or a transistor also.<br>I agree a lot more sophistication can be added which brings its own complexity but for the majority of beginners viewing this instructable the idea was simplicity.<br><br>let's keep in touch and keep learning
Quiescent current of a 2n2222 shouldn't be noticeable, maybe a few micro amps, set up properly it should not be reason to change battery often. <br><br>The 0.7V shouldn't be an issue (with proper set up). Dont think of it as your losing half of your battery voltage just to get over the knee voltage. Similiar to how a phone runs off a single 3.7 volt battery [ theres a screen, a transmitter, a receiver, a speaker, a mic, etc all &quot;totaled&quot; much more than 3.7V] , you should be able to power multiple 1.5 or less volt components off that battery (since the current draw of saturating the base of the 2n2222 would not be enough to really take much away from your piezo.) <br><br>(i only say this because you stated you had issues achieving the &quot;transistorized&quot; result. I do understand the whole &quot;simplicity for begginer viewers&quot; you got going. It would just be a shame for a beginner to probe something sensitive with this and make more of a mess haha. anyways i guess you dont learn without breaking stuff as a begginer. ) <br><br>Kudos on the project my freind.
Ian I am very thankful fur your keen interest and valuable comments. You see, incidentally I have tried the same thing with a 2n2222 but the when with repeated use the battery voltage reduces to below 0.7 volts the device stops functioning while without the transistor it keeps working. Also the sensitivity or efficiency of the device does not increase.<br>However taking your input I will try it again and communicate it to you. Can you send me your mail ID. But I will be able to do it only after 25th of March as my school final exams are on and my mom will not let me touch electronics till then :(<br>My hypothesis is that the 2n2222 can handle up to 800 ma but if while probing the circuit then probes come in direct contact with the high amperage then the transistor may heat up or even die. Another thing being that if the resistance inc the device stops functioning thus making no difference and defeating the job of the device. I will check this all out in my further 'research' tries. Thank you for agreeing about the valuable simplicity this device brings in and will like to protect that but also will keep researching.<br><br>Your inputs are interesting and good do keep in touch and writing.
<p>I appreciate your simple circuit. So many continuity testers seem to add layers of transistorized electronics. It always seemed to me a simple bulb or buzzer is all that is needed to show the presence of an electrical path. </p>
Phil I appreciate your thought of simplicity. There can be many ways with which one can make the same thing with complex circuit and components. I always try to put purpose ahead of the internals. Because there is no point in making a very complex thing that does a simple job which can be done by a simple thing also.<br><br>FYI you can read my comment below relating to the same<br>THANKS

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