Questions tagged [fuses]

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 not within the scope of the Site and FAQ.

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53 views

Melting fuses and not blowing up [closed]

I’m working on a small green house with temperature control over some Peltier modules. I’ve chosen 8 tec1-12706 modules to control the green house, since they came as a kit from aliexpress and after ...
2 votes
1 answer
43 views

Efuses, inrush and output drooping

Here's a simplified efuse diagram: Here is the efuse configurations in my circuit: The load is not present on this pcba. There is a 100mm long cable connecting this board to the load which is a ...
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How can I tell if a slow-blow fuse with a fiberglass center is blown? [closed]

I have a guitar amplifier fuse that I suspect is blown. It looks like a tightly wound spring. I assume the fiberglass center has somehow melted away. Am I correct in assuming this missing center is ...
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Kenwood Dnx891hd rca output fuse

I have a Kenwood dnx891HD and I've had problems with it for years I finally sent it in due to protect mode and they sent me a picture and told me it was this rca output fuse on the circuit board and I ...
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Using a 0 Ω resistor as a fuse

Can 0 Ω resistors be used as fuses? I can't find any fuses physically small enough to fit on my board that can also take the current we're expecting. In my application, 58 A is the expected continuous ...
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LiPo Battery (parallel cell) Protection - Fuse Selection to Support BMS

I'm designing a LiPo battery and I'm struggling with the protection, or more specifically, the fuse selection. Can I please have some help? This is a really convoluted problem with a lot of factors, ...
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2 votes
2 answers
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Powering long LED strip, injecting power. Correct way to fuse?

Recently I asked an opinion based question regarding LED strips. I have learned my lesson and now I have an actual question regarding "how power flows". I'll explain: I have a lighting ...
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4 answers
93 views

Why are fuses used for appliances that are plugged into the wall socket?

Fuses are there to ensure that the device being used doesn't short circuit and overheat. How likely is it that the current from a wall socket will actually exceed its given amount of current of, for ...
2 votes
1 answer
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Identifying and replacing fuse

Circa 1970s Hanimex model 101 record player with built-in pre- and power amplifier PCB stopped outputting audio signal. Found PCB glass-body fuse non-functional. Fuse has 'CONO GDL' and '0.5A250V' ...
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2 answers
58 views

Identifying a resettable fuse marked N⩙

I'm troubleshooting a control board that has a very long replacement lead time (about half a year) and I think I've identified the faulty component. It is – I believe – a surface mount resettable fuse....
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Fuse/PTC voltage derating

For safe operation of a PCB design, do I need to derate the voltage of a Fuse / PTC? Can I for example assume, that a femtoASMDC008F can be used in a circuit with a nominal voltage of 12V (but ...
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Use of MOVs without fuse?

I understand the MOVs become almost short-circuit when input voltage across them exceed a threshold. But how does this protect the circuit behind the MOVs? Suppose the input power supply voltage ...
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What is the correct size of fuse for a Igloo Iceless cooler? DC 12v 55w, Stock Fuse 250V 7.5A [closed]

I would like to know if the stock fuse is too big for the cooler, because the original cable to come with the cooler melted at the 12v plug. The plastic around the tip was melted to the point the tip ...
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Turning PNP fully off for fuse indicator

I'm having a little trouble with a PNP based blown fuse circuit. I'm using a similar circuit in other boards for blown fuse indications for 12VDC and 24VDC supplies without issue. I'm trying to ...
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Amp reading on multimeter significantly varies depending on port

I'm using a rapid 318dmm multimeter, and I am measuring the short current of a 5x5 inch solar cell which has a power rating of 2.7 W and a nominal voltage of 0.5 V. I'm measuring the current outside ...
3 votes
3 answers
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Interrupt rating of all fuses in branches of same circuit

I am redesigning my boat's DC electric circuit, and when looking at the main battery fuse to determine its correct interrupt rating (i.e. the current the fuse will be able to fully interrupt without ...
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finding replacement for resistor labeled as fuse in schematic

I am trying to find a replacement for what appears to be a burned resistor in a power supply unit. It appears to be labeled as "F3" on the PCB which is the designation for a fuse. As far as ...
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Using fuse during initial tests?

I've implemented the presented 80W PFC boost pre-regulator in the following application note without using the applied fuse at the input. Surely I will add the fuse to the finalized tested circuit. ...
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Electrical current fuse utilizing two PNP transistors not working

I have been trying for some time to get a modified current fuse design I found on the internet to work, with no luck. It should function as such: Current flows through the second transistor, that has ...
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1 answer
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What conditions can cause a PCB fuse to fail and act as a resistor?

Context: Tx circuit that shoots 24V pulses into a transformer to get 240V out of it. The purpose is to drive a piezoelectric transducer. The circuit itself has a fuse protecting it at the entrance (...
1 vote
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\$ I^{2}t \$ calculation issue

I tried to select the fuse based on this selection guide, but found my calculation for fuse I2t is not practical. Can someone point out the error in my calculation? The application scenario is a 240V ...
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3 votes
1 answer
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Reduce Resistance and Heat Dissipation in a fuse

I have a 240VAC, 200A switch. It has very tight space requirements, and has to be sealed - so no external air flow. I need to minimize heat as much as possible. I have redesigned bus bars, spacing, ...
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2 answers
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Power camping lantern with 12v AGM battery

I have a 3 AA battery powered LED camping light/lantern. It draws (measured with a multimeter in series) about 18 mA when ON and 0 mA when OFF (ON/OFF controlled by a switch button). It’s ON all night ...
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Need Help Identifying - Pentair pool automation motherboard

Hoping someone can help me identify the component in this picture. This is a Pentair pool automation motherboard - model number 520073. The top part of the photo shows what I believe is a capacitor ...
2 votes
1 answer
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How to safely protect input sensing AC Line Voltage

I'd like to detect the presence of AC line-level voltages in my PCB project, and I'd like to follow best-practice for doing this. I'm a controls engineer so I'm happy with dealing with mains with ...
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1 answer
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Can I replace a P labeled SMD fuse with a K labeled one?

I am fixing an "old" laptop and I needed to replace a broken screen. While disconecting and reconnecting the ribbon cable, I probably shorted something. Now the back light on both the ...
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Can this resistor be replaced by a wire or fuse?

My power supply got broken. Upon further inspection, I found out that the high power resistor (15 ohm, 10 W) was broken. Unfortunately, I can't purchase such a resistor (with the same specifications, ...
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Have I been poisoned by lead dust from my blown fuse

just wondering if I've poisoned myself. I was doing something silly and the 10A fuse exploded in my multimeter with the glass cylinder and alloy dust shattering and splattering making a mess on the ...
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OVP with crowbar + TVS?

I'm looking to design an over voltage protection (for > 13-14V situations) on the input of a power supply (the PS is taking input from a 12V vehicle). I was considering only using a crowbar circuit ...
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Safety check - Is this Amazon PV combiner box labeled wrong? 15A Vs 32A - 500V vs 1000V

I'm currently working on a solar circuit. I wanted to protect my internal systems from my panels in the event of a surge. I purchased a PV combiner box from Amazon - link to product. It claims to be a ...
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1 answer
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Trying to fix a possible non-removable permanent fuse

I'm having some issues with a PCB in an alarm unit. I think the unit shorted. I'm now trying to identify the broken component to replace it. The board is mains powered, but also has a battery - ...
4 votes
2 answers
252 views

DC power supply and fuses

I came across a DCDC converter JCK3012D15, that takes a 9-18VDC in and gives out +-15V @ 1A (pretty handy). I have some questions: What is the advantage of using a power MOSFET at the input over ...
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Can an extender with USB ports be wired direct to the mains?

I have an extension lead that has been wired directly into the mains (there is no space behind a cupboard to plug it into the wall socket that was there). I think this is the same situation as adding ...
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Why do Americans use fuses and not differentials and breakers like Europeans do?

I recently moved to North America, and I was wondering why the houses here seem to be protected by fuses rather than breakers and differential switches like we have in France for example. It would ...
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Can a lower gauge jumper be connected to a high amperage circuit as long as it is going to an appropriate sized breaker?

The 14 AWG wire is connected to an appropriate sized circuit breaker to prevent that run of wire from drawing too many amps; however, my concerns would be that the 2/0 cable being in such close ...
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1 answer
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Breaking capacity for fuses at mains inlet

Is there any official guidance as to what the breaking capacity should be for a mains inlet fuse? Assuming the appliance is intended to be fed from a normal domestic socket. I understand that in an ...
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I'm trying to replace a component on a circuit board. Is this a fuse?

This smd component has shorted. I'm assuming it is a fuse, but I don't understand what the 4 over the underscore means, if it is even a "4". Does somebody know what this component is and how ...
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1 vote
3 answers
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Why are Fuses on space heaters necessary?

Why does a space heater (electric fan heater for home use) have a fuse? Isn't the house itself connected via a circuit breaker? Wouldn't that stop potential safety issues? PS: First post on here :)
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Can I use a 315 mA slow blow fuse instead of a 375 mA slow blow?

This is my first post here and I am not an electronics engineer (just a simple guitar player) who would appreciate some advice. I have a relatively old (no longer produced) valve guitar amp which has ...
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How do you install a thermal fuse in a hairdryer?

Is it possible to manually wrap the thermal fuse's pins around the 'grommets' as shown in the picture? The arrows point to the two grommets, with the thermal fuse in the question across the top.
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Correct Fuse Sizing

How can I correctly select the size of the fuse on the primary side of a transformer based on a transformer? The regulators in this circuit are an LM317 and an LM337 which draw a maximum of 1.5 amps, ...
2 votes
2 answers
313 views

Resettable fuse hold current and trip current

When choosing a suitable current rating for a resettable fuse do we usually look at the hold current or trip current of the fuse? From what I understand, the fuse will not trip when current reaches ...
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Does an eFuse exist that latches off immediately (and does not reactivate) in case of a short-circuit?

I've just discovered eFuses (from Texas Instruments + Toshiba + STMicro). In case of a short-circuit on the output, MOS can be disabled in 150-500 ns by detecting a surge of current (called "fast-...
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What does "FB" for a fuse mean?

I have a blown GE 250v 20a FB WB27X27316 that I need to replace. Unfortunately, GE doesn't have them in stock for another 3 months. I want to replace it with another off-the-shelf fuse, but I don't ...
8 votes
9 answers
2k views

Do I misunderstand fuses?

A statement that I often read here goes: "Fuses protect the wire, not the load." However, in basically all cases I use fuses, I think they are there to protect the load - I.e. the device on ...
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2 votes
2 answers
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How should fuse selection be made in discrete-time alternating current?

My V(t) signal progresses for hours as 0.75 seconds on,5 seconds off.(Let assume V(t)=I_lamp(t),R_lamp=1 ohm) The general formula for fuse selection at room temperature is: In summary,what should I ...
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What kind of weird current protection "circuit" is this?

After seeing this schematic in this answer (from @VictorTito ... and others) in this post ... I was curious to try it ... Added one resistor and I simulated this (?) (DC Analysis) ... Meanwhile, by @...
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Are T4A and T4AL the same kind of fuse?

A power supply for some equipment I have blew its fuse. The fuse holding is labeled T4A 250v. When I look for replacements ...
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Need suggestions to replace fuse in broken coffee warmer [closed]

My coffee warmer suddenly stopped working after it did little sparky thing one day and I am trying to see if I can fix it. I opened the cover and tested all the capacitors and diodes and everything ...
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Selecting a fuse for a device that powers on at 48V @ 0.1 amps

I am passing current through an Ethernet cable in order to power on a device. Basically I am making use of the Blue and Brown cables: The device that I am powering uses 48 V DC and only uses 0.1 amps....
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