Big Clive Examines ‘Things you should know about fuses.’

Big Clive takes a look at the construction, design, and application of a few different fuse types including ‘automotive’ (blade) fuses, passive fuses, and industrial fuses, among others. It’s a lengthy video (27 minutes!) but captivating, and I won’t spoil the 15kV expulsion fuse design.


This was supposed to be a short video, but that didn’t happen.
In summary:-

A fuse is designed to be the weakest point in a circuit so that it fails first and breaks the circuit protecting other components and cables.

A 1A fuse does not blow at 1A. It will blow quickly at very high fault currents, but take progressively longer to open the circuit as the current is lowered to nearer its rating.

Glass fuses are only rated to break a low fault current.
Ceramic sand filled fuses can break much higher fault current.

Time delay or slow blow fuses (T) can withstand surges.
Quick blow or fast blow fuses (F) will blow faster in a fault.
Semiconductor fuses (FF) are very sensitive and expensive.

The voltage rating of a fuse indicates its ability to work safely up to that voltage. 3A is 3A so a 250V fuse will work fine on 12V.

If a slow blow is replaced with a quick blow fuse it may keep blowing intermittently. It’s not uncommon for less aware people to replace an anti-surge fuse with the quick blow one they had handy. Then when the fuse blows again the person changing it may replace it with another quick blow because that was what was fitted. Assess the type of load and make an informed decision.

Never short out fuses. People who get over-confident in their fuse-shorting repair skills usually learn the hard way when they bypass too many and cables start going on fire or the last one they put in blows up in their hand causing a shock and burn.
Wrapping fuses in tin foil or adding external wire can end badly due to the unconstrained nature of the fault breaking element. If you create/use a fuse that has a higher current handling ability than the thinnest cable in the circuit, then that cable may go on fire along its full length and cause significant damage to its surroundings.

HRC (High Rupturing Capacity) fuses have the fuse wire running through a fine powder that quenches the arc quickly and forms a solid glass-like substance internally in the process.

Industrial multimeters use HRC fuses so they can break the circuit safely if accidentally applied across a high current supply while in current measuring mode, or if another inappropriate range causes failure. I know they’re expensive, but you must replace them with the correct type of fuse to avoid a scenario where the meter literally explodes in your hands causing shock and burns.

Electronic PTC (Positive Temperature Coefficient) fuses are ideal in many low voltage electronic applications. They work by going high resistance when they get hot and will reset when the power is turned off for a while.

If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-

Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here:

Join Adafruit on Mastodon

Adafruit is on Mastodon, join in!

Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.

Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.

Join us every Wednesday night at 8pm ET for Ask an Engineer!

Join over 36,000+ makers on Adafruit’s Discord channels and be part of the community!

CircuitPython – The easiest way to program microcontrollers –

Maker Business — “Packaging” chips in the US

Wearables — Enclosures help fight body humidity in costumes

Electronics — Transformers: More than meets the eye!

Python for Microcontrollers — Python on Microcontrollers Newsletter: Silicon Labs introduces CircuitPython support, and more! #CircuitPython #Python #micropython @ThePSF @Raspberry_Pi

Adafruit IoT Monthly — Guardian Robot, Weather-wise Umbrella Stand, and more!

Microsoft MakeCode — MakeCode Thank You!

EYE on NPI — Maxim’s Himalaya uSLIC Step-Down Power Module #EyeOnNPI @maximintegrated @digikey

New Products – Adafruit Industries – Makers, hackers, artists, designers and engineers! — #NewProds 7/19/23 Feat. Adafruit Matrix Portal S3 CircuitPython Powered Internet Display!

Get the only spam-free daily newsletter about wearables, running a "maker business", electronic tips and more! Subscribe at !

1 Comment

  1. You forgot the best fuse diagram!

    (BTW, it’s a complete joke ^^ Don’t use those!)

Sorry, the comment form is closed at this time.