Questions regarding physical fuses. Fuses are a safety device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level. PPTC, PTC, and Polyfuse questions should use the Polyfuse Tag. Please keep in mind that repair questions are typically closed if ...

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2
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1answer
85 views

AC Short-circuit Protection

I have a bunch of electro-mechanical relays on a board intended to switch 220VAC for CFLs. The maximum load on the relays will be 100W with inrush currents of upto 2A (lasting for less than a second). ...
5
votes
2answers
376 views

Short circuit protection for high current wearable: fuse, polyswitch, TBU, circuit breaker, something else?

I am thinking about design elements for a rather high current, battery powered, wearable application. Maximum current of 40A at 5V, but typically around a third to a half of that. Power would come ...
0
votes
2answers
137 views

Turn on an LED when power is lost with a relay

A friend of mine has just finished his race car but is having fan issues. What I want to help him do is setup an LED that turns on when the fans have lost power. Often the fuse blows. I would assume ...
1
vote
0answers
66 views

Can I determine a formula for fuse disconnection times?

This is the first time I have used this stack site so am not 100% sure this question is on topic (based on the tags I couldn't find) but thought someone may still be able to help me. For those not ...
0
votes
4answers
193 views

Why does a 10A fuse blow at 10A and 5V or 10A and 500V?

Something that's always puzzled me: Wire and fuses can handle a given max current, pretty much regardless of voltage. A 10A fuse will blow if you exceed 10A, if the voltage is 5V or 500V. Why is ...
13
votes
5answers
13k views

Fuses: What are the practical differences between Ceramic and Glass cartridge fuses

What are the practical differences between ceramic and glass tube cartridge fuses? I am trying to find new fuses for a piece of consumer electronics. The original fuses are going out of production. ...
1
vote
1answer
75 views

Battery power in the home: Fire Safety

I would like to use 12v LED tape powered by an 8 x AA battery holder and switched with a motion sensor. This will be connected in my home 24/7, so I would like to know what precautions (if any) I ...
15
votes
4answers
6k views

What not to do with a Multimeter

So I just bought and installed a new fuse for an analog multimeter I scored for free and now it works like a charm. The new fuse is the same rating as the blown one I found inside, which is 0.5A ...
1
vote
0answers
75 views

Atmega32 can't verify after setting correct fuses for external crystal. HELP

I am having trouble with some Atmega32A's purchased off from eBay. The MCU's does not seem to be fake as they are functioning properly. I am experiencig the following problem: I want to use external ...
3
votes
3answers
782 views

Transformer blows fuse at no load

I'm building a multi channel power amp and I am having trouble with the power supply. I'm in Europe, so I've got 230V mains and I'm running into a transformer which brings it down to 60V. The ...
0
votes
3answers
106 views

What are the big plugs for that you find on high demand devices in North America (120V-Areas)?

Talking about AMEA socket system and 120V. High power demand devices like A/Cs do have bigger plugs with some switches on them. What exactly is their purpose? Seems like a fuse but isn't the socket ...
0
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1answer
62 views

Does any thermal fuse with the same cut off temperature work?

Would any thermal fuse cutoff for 216°C work as a replacement for the fuse in the picture below?
0
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4answers
162 views

Is it reasonable to use a current limiting diode in place of a fuse?

I'm trying to source some fast-blow 5mA or 10mA fuses but Littelfuse has discontinued the only reasonably affordable ones I have found. My circuit when operating properly will not output more than ...
0
votes
1answer
73 views

1:1 isolation transformer fuse on secondary side - an option?

We sometimes use an old self build 1:1 isolation transformer (150VA) in our company to isolate devices under test. It is equipped with a primary 500mA fuse (slow) in series with a on/off switch. ...
0
votes
3answers
107 views

preventing blown fuses in simple circuit

I am trying to prevent blowing fuses in a simple circuit: that consists of a battery(12V), fuse, and 2 lights(50W). There are no switches; the lights are connected and disconnected from the live ...
0
votes
1answer
47 views

Downsides of using 5mm fuses in 6.3mm sockets

For my multimeter I need to replace a fuse. It is 6.3mm in diameter, 25mm long, rated 500mA/250V AC and 1500A interrupt rating. I have a couple of such fuses, but they are 5mm in diameter, and ...
1
vote
1answer
1k views

Are thermal fuses polarized?

I have a device with a thermal fuse in it. The fuse has failed, and I would like to replace it. Does thermal fuse have a polarity, similar to an electrolytic capacitor, or is it the same with normal ...
1
vote
1answer
88 views

Use a relay as a resettable fuse?

I was thinking; If a relay is used to power a circuit AND itself, if the circuit is shorted - the relay should lose its own power and turn off - almost like a resettable fuse. To power it up, I would ...
25
votes
3answers
3k views

Why did my fuse not blow?

I purchased a few fuses to get familiar with their workings, and I was surprised to see that the 100mA fast-blowing fuses I bought happily conducted up to 215mA (6V power supply, 10\$\Omega\$ ...
5
votes
3answers
152 views

Given metal dimensions and material, is it possible to determine the maximum current that the structure can handle? [semiconductor processing]

I have a linewidth structure that has very low resistance. I want to know the maximum current that this structure can handle. Since the resistance of the metal is so low, it's hard to measure the ...
6
votes
3answers
7k views

Should I use slow fuse or fast fuse?

When I design something or going to add a fuse to place where fuse isn't used now, should I prefer slow or fast fuse? I understand that this depends on situation, but I'd like to hear what do you ...
7
votes
5answers
34k views

Slow Blow vs Fast Acting Fuse

Is there any way to tell the difference between a slow blow and a fast acting Fuse? I had one blow in my amp and I know its 125v 5a, but i'm not sure if it is a slow blow or fast acting fuse. Is ...
1
vote
3answers
218 views

AVRDUDE with buring settings of AVR Studio

I make my own electronic boards often with an Atmel ATmega328P. I used AVR Studio for programming. Now I tried to make the same settings with avrdude and it looks, that they are not really ...
1
vote
3answers
125 views

What do the abbreviations “SPF” and “SPH” mean with respect to fuses? (Single line drawing for 480 V system.)

There are two lines connected between the transformer low voltage side and the 480 V bus, one with a fuse labeled "SPF" that connects to a GE power quality meter, another with a fuse labeled "SPH" ...
1
vote
1answer
85 views

How can I protect against shorts in low voltage AC ~16V

I'm looking for a method of protecting a circuit against shorting. I would rather not use a regular fuse as I expect I will short the circuit (unintentionally) fairly often (probably once or twice ...
0
votes
1answer
45 views

Rating for this circuit breaker at 120 voltsAC

Here is a circuit breaker rated 2 amps at 32 volts DC and 2 amps at 250 volts AC What is the amperage it will break at when I apply 120 volts AC
0
votes
1answer
100 views

Can I use a 600VAC PTC resettable fuse in a 700VDC application?

I've inherited an old design, and a part used has gone out of production. This part is a PTC resettable fuse, used in a bootstrap circuit, so it's one-shot. When the PTC opens, it has ~700VDC across ...
1
vote
1answer
262 views

What are the dangers of a DIY fuse in a multimeter?

For the past few years I have been running my Fluke 79III without a fuse in it's F44.100A 1kV fuse holder. This has meant that I've been unable to use the 40mA circuit. When I blew the old fuse, I ...
1
vote
1answer
1k views

Fuse configuration AVR dude for external 12MHZ crystal in Atmega 168

I have 2 microcontrollers (Atmega 168PA-PU). So far I have run the following program in one of them (say mc1). Now when I run the same code in the other one it gives erroneous results. Someone ...
6
votes
3answers
126 views

How do I size fuses to handle sudden changes in AC line voltage into a capacitive load?

Suppose I have a rectifier on the AC line, followed by some caps and a load. simulate this circuit – Schematic created using CircuitLab If the AC line is suddenly increased, there's a ...
0
votes
3answers
296 views

Why is this switched power inlet fused on both load and neutral sides?

I've purchased a Schurter 4304.6090 power inlet for a project and am a bit confused by the fuse configuration. The inlet requires two fuses: one on the load side and another on the neutral side of the ...
4
votes
4answers
4k views

what size of copper wire can act as a 150A fuse?

If I would like to use a piece of copper wire as a 150A fuse, what size of wire should I use? It doesn't have to be 150A very accurately, the parameters I need the wire to meet are: it needs to ...
3
votes
6answers
7k views

How does a fuse blow at its current rating, regardless of voltage?

I know from reading elsewhere that it's safe to use a fuse with a higher voltage rating when replacing one, so long as the current rating and reaction speed is the same. For example, if a fuse is ...
-1
votes
1answer
276 views

How to identify value of a surface mounted fuse

I have a PCB from a WIFI router and there is a lot of little surface mount components. I am looking for fuses, some of them might actually be them. My question is how do I identyfy them and find out ...
9
votes
4answers
6k views

How do I choose a fuse? Fusible Links vs Polyfuse?

I realise this is an extremely broad subject area but I need to know how to choose a fuse to protect a circuit. Recently, a cheap PSU of a friend's blew up quite spectacularly (the two primary ...
5
votes
3answers
477 views

Why isn't ammeter protected with a fuse

Why is it that the ammeter with low current (200mA) limit are fused and not the 20A one? I recently lost a multimeter because i connected the ammeter in parallel by mistake. Edit: All the ammeters i ...
4
votes
3answers
2k views

When should you use a fuse?

When is it actually practical to use a fuse? Like lets say your building a robot using an Arduino.....what area would you want to protect the most with a fuse? I mean do they even make fuses that ...
4
votes
1answer
258 views

How do I know whether a fuse is a DC fuse or an AC fuse?

For example, I want to buy a 10A 50V DC fuse and a 10A 220V AC fuse online. Which website(s) should I go ? I tried on Mcmaster, but I could not get clear enough information of whether the fuse is an ...
8
votes
3answers
851 views

Can a fuse be placed after a load?

Considering that the regular treatment of a fuse is to place it on the positive side, "before" a load, is this just common practice, or is it backed by an actual reason? Can a fuse be placed on the ...
6
votes
1answer
855 views

'Voltage Fuse' or better

I have a power supply with multiple outputs (5v, 12, 24v) According to the manufacture (and after testing) there must be a minimum load on the PSU for it to supply the stated voltages. Without a ...
6
votes
3answers
2k views

How do I measure startup/inrush current?

I have some small devices that draw 20mA. I'd like to add a resettable (PPTC) fuse to them but I am not sure what value to select. My thought is I need to find a value that will tolerate the startup ...
-2
votes
1answer
180 views

How do I calculate the voltage of a resistor after the fuse has been blown?

For example, theres a battery of 12v in a seris with R1 (resitor 1) of 49kilo ohms, then there's a blown fuse of 90uA, next is R2 of 11kilo ohms, then there's R3 of 60 kilo ohms. How do i calculate ...
0
votes
1answer
195 views

dual stage charger, is fuse needed?

I have a basic circuit: battery, fuse off (+)lead, 4 lights in parallel. My question is, when charging is a fuse needed? Also in the battery/charger circuit, which side is considered positive? ...
0
votes
4answers
625 views

Can I use a 500mA fuse instead of a 315mA fuse?

I have a guitar amp with a fuse on the power socket. It is a 250v 315mA slow blow fuse. My local electronic store only has a 500mA fuse. Can I use that or should I order a 315mA online?
0
votes
1answer
369 views

Choosing Fuses or MCB in 24VDC vehicle circuit

I am currently designing a 24VDC circuit for a small vehicle. I personally prefer using MCB's since they are simple to reset and easy to detect faults in the system, although i do find it rather hard ...
1
vote
3answers
219 views

DC Fuse Placement?

Imagine the following world's simplest diagram: 12V Battery -> 5V/3A Voltage Regulator -> Load My question is, would a 3A fuse best protect the circuit if ...
0
votes
0answers
49 views

Trying to replace a Sun 1/2 amp mini fuse

I am trying to replace a fuse on a board and I'm a novice. The fuse itself is labeled "Sun 1/2 amp" and looks similar to ceramic, although I am not certain of this. It is held to the board by 2 leads. ...
8
votes
3answers
343 views

Why might a multimeter ask for “wrong” fuse sizes?

Why might a multimeter ask for the "wrong" sizes of fuses? On the front of my Fluke 87 multimeter, the two probe ports for amperage are labeled as fused at 10A (max) and 400mA (max). When opening the ...
1
vote
1answer
480 views

Grounding in a DC circuit on a vehicle

I am working on a vehicle with batteries, but i am not quite sure if my grounding solution/design is correct. It is supplied with two 12VDC batteries in series, connected to a DC-DC (24VDC-24VDC) ...
-5
votes
1answer
127 views

Why Do Y Electrial DC Fuses Burn Out? [closed]

I am doing some re-search for my father that works with electricity. He say that his Y Dc Electrical Fuses start to burn out, a lot. Please Help. xx