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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6
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3answers
5k 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 ...
6
votes
5answers
21k 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
58 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
64 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
58 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
29 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
71 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
147 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
409 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
93 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
136 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 ...
3
votes
5answers
3k 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 ...
2
votes
6answers
4k 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
132 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 ...
8
votes
4answers
5k 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
375 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 ...
3
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
151 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
522 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
654 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
135 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 ...
3
votes
2answers
334 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
1answer
132 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
280 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
221 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
128 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
39 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
271 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
276 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
109 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
-2
votes
1answer
80 views

Cheap switch 125V 5A fuse blew [closed]

Cheap switch glass fuse blew, 125V 5A. Found a 125V 8A fuse in a string of Christmas lights. Can I use it to replace 125V 5A?
1
vote
1answer
123 views

Live-Neutral transformer fault

In this critique of an ELV PSU design, it is suggested that a "Live-Neutral" fault could result in a fault current of thousands of amps. I'm sceptical. Please could someone explain how this could be? ...
2
votes
5answers
469 views

Why do 0.02A fuses not protect a person? Why no protection from shocks?

I understand the user here so that fuses do not protect people from shocks. I am planning to put put fuses such as fast-blown fuses and PPTC fuses around all kind of positions such as ...
3
votes
3answers
273 views

Building a power supply, want to stay alive

I am building a power supply for a very old laptop. The circuit uses a transformer (220 V primary to 15 V secondary, 33 VA) and that worries me a little. (Please note that I an enthusiast and so far I ...
2
votes
1answer
107 views

Computing ampacity a of small fuse from change in temp on breakdown

I'm trying to design an experiment for an entry-level electronics course involving burning out fuses of an unknown rating and determining their rating by the temperature they were when they failed. Is ...
9
votes
1answer
277 views

Understanding fuse specs

Can somebody please help me in understanding the fuse specifications. Actually i went through many fuse parameters. I am getting cofused between the hold current and the cut-off current since there is ...
1
vote
1answer
369 views

Not sure how to replace a blown fuse in a building's fuse box

One of our fuses in our secondary fuse box just blew. Luckily, there there is a backup. I am not an electrical professional but I know a little 101. I just want to ask about the correct fuse / amps ...
2
votes
1answer
1k views

What does 3AG mean in “Fuse Block 3AG”?

I have read from a vendor website. It mentions 3AG fuse block. What does 3AG mean?
2
votes
3answers
739 views

How do glass tube fuses work?

This may be the an unspeakably stupid question for an electrical/computer engineering student to ask, but I ran across a few parts I didn't recognize (which, after some research, I found out were ...
2
votes
1answer
3k views

How to check if my multimeter's fuse is damaged?

I recently bought a cheap multimeter. I played around measuring stuff on simple circuits and I think I managed to damage it as I don't seem to be able to measure current anymore (always get zero ...
3
votes
1answer
114 views

Question regarding fuses

What is the difference between thermal fuse and MOV and polyfuse.Which is faster and also which companies produce polyfuse, especially in Asia. I have to search for a component that can save my ...
2
votes
2answers
379 views

Should a fuse with the correct amps, but is physically too small, still power my stereo unit?

I'm not sure if I'm asking the right kind of question for this site. But if someone could help me, I'd be grateful: I blew a 125V 2.5A fuse in my home stereo head unit. I couldn't find that fuse at ...
2
votes
1answer
168 views

Will an opening fuse cause an inductive kick, or not?

I'm looking at designing a high-current crowbar circuit. We need to blow a 1400A fuse on demand. One question that has arisen is, what about inductive kick? If you short a large capacitor through a ...
-3
votes
1answer
157 views

Which fuse and LED should be used for a no contact testing screwdriver? [closed]

I'd like to make my own testing screwdriver based on an existing one which has 2x LR41 batteries, a 2.2Mohms resistor, a KSP13 Darlington transistor, a 5x15mm fuse and a red LED. It works for ...
10
votes
2answers
243 views

How to ensure my device is safe for every day use?

I have put together a simple wake up light. It has an external powersupply, at the moment rated 7V and 600mA. Inside it has Arduino and bunch of LEDs controlled by a MOSFET. It works fine at the ...
1
vote
1answer
762 views

How do I choose the right replacement fuse for my multimeter?

I have a BK Precision 2709B Multimeter. I managed to blow the uA fuse (500mA/500V fast blow ceramic) on it. Is it an ok to replace this fuse with a 500mA/1kV fast blow ceramic fuse? What impact would ...
3
votes
1answer
260 views

Why use a double fuse for a relay-controlled heater?

After this question, another refrigerator "mistery" :-) This is the schematic of a no-frost refrigerator that I had to fix because the no-frost system failed and a huge quantity of ice clogged the ...
8
votes
3answers
421 views

Blowing a Fuse to Permanently Disable Functionality

Certain electrical designs require permanently disabling hardware functionality on the fly. Sending an overcurrent to a weak fuse may be a method for accomplishing this, breaking the circuit in a ...
2
votes
2answers
150 views

Negative Voltage Breakers?

I've been reading a bit on negative voltage, but I have a question that will probably reveal some ignorance, so I apologize ahead of time. If someone tells me that they want a (2) 5A breakers, (1) ...