Breadboard Fuse




Introduction: Breadboard Fuse

Isn't it annoying when all of the sudden the TV turns off with a loud bang and you're sitting in the dark living room?
Man, now you have to get up and switch the circuit breaker back on.
But did you ever think of the fact, that this could have ended in your house burning down as well ?
Circuit breakers and fuses are often times necessary in households, but also in breadboard electronics.

I usually put my circuits together on a breadboard at least once to try them out. As a power supply I usually use lead batteries, as they have the huge advantage of being able to supply several amps at once.

This comes in handy, especially when experimenting with Audio Amps and MOSFETs in fast switching appliances.
But in case you ever wire something incorrectly and short your circuit out, these power supplies won't forgive any mistake. My mistakes usually end up with smoke, molten insulation and me swearing.

Now you could argue that I have to double-check, or step down in amperage, but I found a simple and super cheap way of limiting the shortcircuit-amperage on my breadboard for free!

A fuse in Electronics is usually a piece of metal with encasing, which starts melting at a certain amperage and thus interrupts the circuit. They also are a pain to replace and to integrate them on your breadboard.

Step 1: Build Your Own

So what I came up with is taking a mechanical pencil and take out the lead. Because in fact, nowadays there isn't any lead in your pencils, but graphite.
Graphite is just pure Carbon, non-toxic, cheap and it has the property to conduct more electricity the hotter it gets.
And as the graphite in your pencil is fairly thin, it will just shatter into tiny parts when touched to the contacts of a high amp battery, because it's resistance decreases rapidly in a short circuit situation and it gets extremely hot within milliseconds. Now don't worry, it also cools down that fast.

You will only need
a mechanical Pencil
A Croco Clip
Your powersource & a breadboard

Step 2: Find a Mechanical Pencil

Just find a mechanical pencil (I use a #2, your fuses maximum amperage will depend upon the thickness) and take out a lead.
Break it in half. Be careful, as it shatters really easy.

Step 3: Connect to Your Breadboards Supply Lines

All you need to do is have the connection to one of your batteries contacts run through the graphite.
Push them into two neighboring contact lanes. Be sure to push straight down, or they will break.
I usually connect the top parts with a croco clip. Don' waste your time trying to solder it to .. anything. Graphite doesn't solder well.
Connect battery--fuse--supply lane and you're good to go.

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    2 Discussions


    5 years ago

    Thank you very much :)

    Oh wow I love the idea of being able to easily test our circuit, and so cheap to do! Thanks for sharing your awesome idea! Welcome to instructables!