In late 90s, I found a schematic of a resetteable fuse made with an thyristor. That was not automatically resetteable but instead when triggered, you had to push a button to rearm it. I built that circuit (and I remember using a potentiometer to make it adjustable) and used it as the fuse at the ouput of my homemade bench variable power supply. However, I remember it being not reliable at low voltages.

A story on resettable fuses that an aerospace engineer once told me: GPS satelites have some of them. Now for ground testing, they use non-resetting fuses, which get swapped out for resettable ones prior to final assembly. After launch, the new satelites go through a series of tests to verify they are working correctly. One of these tests involved deliberately triggering the overcurrent protection. When they ran the test on one of two newly launched satelites, they suddenly lost contact with it. After a round of testing, debugging and analysis, they arrived at the conclusion that the fuses never had been swapped out, and the two satelites were launched with the test fuses still in place. Immagine the bone-chilling realization that there was another satelite in orbit with the same flaw, and ground control was about to begin the test sequence! A frantic phone call from the testing facility to ground control managed to get the test called off by mere seconds. So the second satelite had escaped doom by the skin of its metaphorical teeth. Bottom line is, one dead GPS satelite is orbiting earth, and another one has a damocles sword hanging over it, which is a very strange metaphor in microgravity. Oh and probably some GPS flight engineers and testers, when they have managed to entangle themselves in their bedsheets on a hot summer night, dream of that fuse getting hotter and hotter...

Congratulations on getting Mouser as a new sponsor. I have been buying from them since about 2007 and have always been very satisfied.

I've seen many PCB's with surface mount fuses. But I never thought that they were the resettable ones. So thank you for letting me know that and this video topic is awesome 👌.

Reminds me of when I did competitive robotics. We were limited to 12 rather underpowered motors that had these kind of fuses (we called them PTCs but I guess technically they were PPTCs). Between matches we would turn canned air upside down to spray the motors with the refrigerant or the PPTCs would trip in the next match. There were actually a few teams that got caught bypassing the PPTCs, which was a big no no.

This was a very well presented introduction to these fuses. I never knew they were that complicated, or available in so many different ratings. Thanks, as always ;-))

You should have mentioned that these components do degrade with each trip, and also degrade if held in a tripped state for long periods (degradation=untripped resistance increase). They are not suitable for applications that are likely to be regularly tripped.

My favorite technique is to use a resettable fuse followed by a transient-absorbing Zener such as a 1N6373 in parallel with the load. This not only protects from overvoltage but also protects against reverse voltage since the Zener would then be forward-biased instead of reverse-biased. I ran my own set of tests and melted the insulation on my power supply wires because the resettable fuse - transient Zener could handle more power than my power supply leads could. (The combo did get very hot though - space them away from your PWB!)

Hi scott! I just have to say that yours and Electroboom's videos are the videos that made me interested in electronics as a kid, and made me choose a Electrician major in HS. And videos like these make me love electronics even more. So, Thank you!

The problem with companies such as Mouser is that they tend to have very high delivery costs when only ordering a few parts. The advantage is that the components you receive are clearly marked and packaged in a proper way.

I just used this! So wonderful to have. Got a whole box for 250Vac. Thank you for the introduction and explanation.

I used PTCs years ago in industrial control circuits. They work a treat if you design a trip indicator into your circuit.

we use those resettable fuses at work, I never knew these existed so it was really cool to find out about these

one of the most informative videos I've witnessed in this channel, thank you for your service!

I watch your videos every Sunday you publish it on UKposts and I really like the fact that you in every video came up with a new idea to solve many problems and also explaining the basics

I've also have looked for resettable fuses. Ty for sharing!!!!

Excellent video, thanks :) I was incorporating resettable fuses into my projects but was never sure how exactly they behave.

Polyfuses are great, and I agree they are an underappreciated and underused component. They're quite useful, simple and easy to integrate into designs, and very affordable. You do have to watch out for their quirks as noted in this video ("soft" trip, temperature dependence, don't quite reset to the same point after they've been tripped once) but any time you need overcurrent protection, they're worth considering as an option. In most cases, I leave regular fuses for more "industrial" applications at higher currents especially where the chance of tripping them is very low unless somebody has done something seriously wrong. In the "electronics" space, if I have very tight thresholds for when to trip I'll use an e-fuse but otherwise the PPTC is my go-to for low current stuff. Another related useful technique is the "crowbar" circuit. Basically, you use some mechanism to detect a fault condition in your circuit and then you deliberately short across the power rails to purposefully trip the fusing element. This can really expand your options for exactly what trips your fuse and can give you more precise control over the trip point while using a soft/simple trip element like a polyfuse, while still retaining the easy "unplug it for a bit to reset it" behaviour.

I really love what ur doing since I followed u 4 years ago. Your brilliant Sir!

First time I ever saw one of these was in the battery holder for my SnapCircuits kit. Had a lot of fun with that kit as a kid, would recommend

I've seen these on circuit boards of equipment I've worked on or disassembled. I had no idea what the long tubular thing with what looks like heat sink blades was. Now I know. Thanks for the tip !

SUPER useful as always! I knew about PPTCs, but not their details, and didn’t know about e-fuses at all: gonna go watch that video of yours right now 😁

I love your content. I am a mechanical engineering student and I don't know much about electronics.Even so, your channel is has been an easy and great way to get close to this world. Thanks a lot 😁

I haven't watched your video yet, but your thumbnail gave me an idea that solves a problem I've been having all week! And I think it'll work and makes my solution 1000x easier, cheaper and more reliable!

Hey Scott! Just want to mention that 3D printers used PPTC's in the old ages of the RepRap project. If you take a look at the design of the RAMPS1.4 Shield you can see that they used PPTCs to protect against overcurrent/shortcurcuit, but sadly this method didn't work that well so it was scrapped and got replaced with blade fuses.

Mouser is awesome. I've been getting hard to find parts from them for years. They have the largest selection of parts that I've ever seen. And their prices are reasonable. The shipping costs are very high however.

A very effective way to protect a circuit is just a light bulb. When small intensity is consume it has a low internal resistance, in case of a short circuit it will limit the current to the rated lamp current. Of course a little more difficult to select but has the huge plus to emit light if "activated", 100% safe. Very useful in case of fugitive faults...

Glad you did this video and agree totally on Mouser. Have used them for many years.

The glass/ceramic fuses are similar to those used to protect your house installation as they will trigger at 10x their rated current within 10ms(FF Superflink) to 3s(TT Superträge) depending on the class/characteristic of the fuse. Die Schmelzsicherungen für Geräte sind ähnlich, zu denen, die in der Hausinstallation verwendet werden, da sie auch erst beim 10x ihres Nennstromes sofort 10ms bzw. innerhalb von 3s abhängig von ihrer Charakteristik auslösen.

I enjoy you videos and find the informative. I was disappointed to see this video was sponsored by Mouser. I have had unhappy times dealing with them last year. Mouser started canceling item from my orders saying "The following item(s) have been cancelled from your order due to either the manufacturers’ distributor sales restrictions or Mousers’ distributor sales restrictions", via a phone conversation with customer service they told me I must be a distributor because I buy to many parts to be a hobbyist. Their web sales policy states they can refuse to sell to anyone for any reason, so I just gave up and started using other sellers. I liked using Mouser because they have a wide variety of items in stuck at a good price and they do ship quickly. I now have to use four different sellers (DigiKey, Newark, TME and Arrow) to get what I used to be able to buy from Mouser. I hope you followers have better luck with Mouser then I did..

These capacitor shreds are an absolute horror to clean up, respect that you still did it, I once accidentally exploded a large capacitor, I had the whole wall full of the stuff😆

Great video as always and a big +1 for Mouser!!! Two things to be aware of with PTCs vs a normal fuse or breaker though. The max interrupt rating and how fast it interrupts. PTCs are fine for low power electronics, but if there is a device with a high current source feeding it the PTC can destroy itself or not stop the inrush of fault current. Since, as like in your example, they can be rated as low as a 60 Amp interrupt rating. Fine for devices with small power supplies. But if you are powering something with a large power supply that can deliver 100's of amps (batteries, mains powered power supplies) and the device has a solid short the PTC may not be able to absorb the current spike. Whereas fuses have interrupt ratings from 5k up to 200k amps. Why some fuse holders are reject style holders, they will only fit a certain interrupt rated fuse and you physically can't install a lower rated fuse in the holder. Then there is the speed. Sure, tripping a 1A fuse or PTC with 2A will take a while, but how fast will a 1A PTC interrupt a fault with 20A of fault current vs a fuse that will instantaneously blow. Sure most of the viewers projects would be fine with a PTC, but to avoid possible damage with higher powered devises a fuse or breaker is still needed. It can be in series with the PTC and at a higher trip level, yet will still provide protection in high current fault situations. PTC will take care of overloads and lower amperage faults and the fuse will take care of interrupting higher current faults that may have destroyed the PTC and NOT have interrupted the current flow.

Great walk-through of the different overcurrent protection Thanks for sharing your experiences with all of us 🙂

Thanks. I just realised I had to replace my PPTCs with the correct ratings. cheers mate.

Great as always! My best channel ❤❤

Interesting! I thought those are capacitors just from the thumbnail. Gave me the idea of making this fuse to trigger something like a relay to fully cut-off the current after the trip.

FWIW: In my designs I use a PTC & a TVS diode for overvoltage and reverse voltage protect. I put the TVS diode behind the PTC so if there is a overvoltage condition the PTC fuse will trip protecting the TVS diode. A unidirectional TVS diode can also protect against reverse polarity from the power source. TVS diodes (basically a Zener diode) will have a forward voltage drop of a bout 0.7V so it will limit reverse polarity to -0.7V. So with just two low cost components you get current protection, overvoltage protection, & reverse polarity protection.

This is one of the best starts to a video I've ever seen 😂😂

Thank you! 👍

Your videos are great! Scott🎉

thank you sensei !

Excellent video.. well explained... Thanks. Thom in Scotland.

Oh... Really interesting indeed, dude! Thanks!!! 😃 I'm going to try to use them in my next projects! Stay safe there with your family! 🖖😊

I took an electronics class in high school and remember having a Mouser catalog for ordering components by phone or by mail.

i often use fuses, but they usually don't blow until after damage has been done, that's why i always incorporate a crowbar circuit in my designs because they are faster, and can protect delicate IC's

Hey man love your work bro! keep the good deeds going on.. you video's are very knowable..!

Thanks for your sharing

One problem I have found with these as a result of the small power leakage is some devices like CVCC regulators can "crash" and when the fault clears are no longer regulating. Tried to do this with a battery charger and when there was an overload cleared it then would appear to work but the CVCC no longer limited and would have blown up the battery. The total cutoff of a fuse eliminates the "funky control failure" of chips due to the brownout the PTC causes in a fault state.

Good presentation. Thanks

May have been worth mentioning that a type of PTC can be used as heaters, too. These are common on crystals to keep them at a similar temperature.

The "Stay creative, I will see you next time" always does it for me!😅 Great content!

Nice video, GreatScott!

You have a very good knowledge.

We recently had a Fender amp with a PPTC inside. They reported it started play less loud over time and the unit eventually turned off. When we tried to troubleshoot it we found one of those PPTC inside which had tripped. Thanks for the great video!

I was studing pptc in this days.. the right video in the right time. thank you very much. i was asking me about theys slowness too..

never knew about resettable fuses before this! It's amazing how technology is evolving to make our gadgets safer and more durable. Can't wait to see this in action in more devices.

For example, if you have your normal current for your IC of about 500mA, in case of a short circuit you will have maybe 10A (if your power source can supply). So it means that typically, current consumption will increase not twice, but much-much more. And in this case, this kind of fuse will (must) react immediately.

Seen it in a homebuilt led lamp for plants. It was used to prevent thermal runaway in a 2s3p build. The goal was to achieve protection if one series broke and the other 2 got a higher current flow. When one was disconnected to simulate a brakeage it made the lamp dim because it limited the current. Interesting enough the other fuses actually restored themselves very slowly(almost simultaneously) until they tripped again. It will therefor slowly "blink" which can hint that something has happened. A perfect way to save the LEDs which can be pretty expensive in comparison to one of the PPTCs. Also the plants therefor never completely lost their lights.

Very nice! As always it comes down to the right tool for the job. Within micro-electronics, that's usually never the fuse. When working with mains, it very likely is a fuse.

Interesting stuff. Reminds me of the Frantone crowbar circuit with a PTC resistor and a Zener diode.

Thanks so much!!! I did not knew you ride simsons 💪 such a cool bike makes me wish I would live in germany

Wow man! These fuses are quite trippy. 👀✌

Amazing. I hear about this first time

Great(scott) video 2x👍 reverse current diodes are also very helpful keeping the components safe.

I tried using one of these to help limit the field current in a vintage car dynamo. It was originally 6v output but regulated for 12v & I needed to make sure the field coils weren’t getting too hot. It was absolutely hopeless, they just burned up (literally smoked). Eventually I settled on a self-resetting 1.6amp bimetallic fuse. That actually worked. From memory I was passing around 1 or 2 amps at low volts, according to the ratings it should’ve worked, but they didn’t like it 🔥 Thinking about it now, I think the load needed to be either on or off. Adding a resistance (as these do) was not the right thing to do.

thanks man

Great video! I occasionally restore old transistor radios which may or may not have shorts in any part of the circuit so connecting to a battery might be "terminal". I built 3 volt, 6 volt, 9 volt and 12 volt battery supplies with a tiny "pea" sized 100mA light bulb (for each voltage) in series. At 10-20mA (correct) current the light is off and the radio might work. If there is a short, the bulb lights up very quickly and limits the current, AND tells me that there is a fault. It uses less wires and needs less hands to work. In some ways it is like a PPTC but I have not done your accurate work in measuring the rate of heating and current limitation. Dave D. Australia

such a great video always love your videos!!

One day, when my mind grows up, I want to be just like you. Great video and thanks.

Darn fine write-up here. I will sometimes use a circuit breaker for small electronics, but this is a better idea.

Thanks ,Scott. It's helpful. 😊😊

I found out about resettable fuses as a kid when I accidentally covered my laptop PSU with a blanket. Thought it broke, only to find out it healed after a couple of hours. That blew my mind back then

Excellent 🎉

A VERY big plus on resetable fuses is many models also act as a heat protection device, disconnecting at a certain temperature.

Got to get me some of these fuses 👍🇮🇪💚🙏🏻

This video is definitely made for me. I keep blowing up almost everything I touch. And no, I am not a ghost yet

I think the previous intro was more fun to watch than the current now

Great video! See you next time!

Those little yellow claw connectors are really cool.

Very nice. Thank you for your informative video :)

Mouser is great! I have been ordering components from them for 20 years. Mouser my first preference when I order components 👍

Thats a cool video, thank you!!!

좋은 지식 영상 감사합니다.

I can confirm, amazing service from Mouser

THAT'S WHAT THOSE ARE!!!!!? I always though these were some kind of weird capacitor and never paid them any attention, and the SMD ones on my Arduino Due's USB ports really confused me - despite how pretty they look. But the timing of your video couldn't have been better, as I've been bringing myself up to speed on electrical engineering to design/simulate my first complete circuit for a prototype and I've been planning on adding a fuse to it for protecting itself and my Arduino... But now I might rethink that. PS: Just checked for these in the PC Power Supply I use for a bench power supply and found them, which explains why it cuts out when I accidently short it, but has never blown up or popped it's soldered-in-place fuse. So cool!

Wow what a good video about fuses. I learned very much and finally understood why the fuse in my selfmade motor driver circuit never tripped... To be honest, after you blew up the capacitor I had to zoom in to check if you started growing an unibrow ;)

New subscriber here, also a big fan of mouser, they legit have just about anything your looking for

Very good... I never used glass fuses in my projects, I think they take up too much space. I've always used resettable fuses mainly because of their size and the advantage of not having to change them all the time.

I Never Knew it Thanks!

I use automotive fuses. I take a U.S. outlet plug apart and align the contacts to the fuse blades then mount it all by the edge of the enclosure so the fuse sticks-out enough to pull if need be from the outside. Its not small though comparatively. But I trust it. Can handle 20a easily with the proper fuse. The hepa filter beside me pulls 1.9a on start then settles to 1.1, I put a 2a on it and its never popped.

There are also NTCs, that act as in rush current protection! It means that they have a decent resistance that decreases over time while it heats up.

I learned something new! :)

I popped one in my multimeter. Been going strong ever since.

awesome. every Sunday i wait your video and i like specially electronic basics like this. continue

This idea i am using since 2010 with a ptc, especially repairing smps of mirowave oven,air conditioner pcb or washing machine pcb but you share a new idea

Old fashioned fuses do trip faster than any of the alternatives in the cases of severe overloads, which can be a factor in some situations as well.

I’ve recovered a load of various sizes of these but never bothered to learn what they do. Now that I know I might reuse some of them.

I learned about thermistors a loooong time ago.

Well explained bro, such a clear Explanation about fuses,I enjoyed and learned from your video super bro👍👌

Excellent vid, really clear, much less of the annoying over-writing of the felt pens (a pet hate but I realise it is your thing so just ignore me)