Questions tagged [polyfuse]
Questions regarding Polymeric Positive Temperature Coefficient devices, typically known as Polyfuses, PPTC, or Resettable Fuse. They are non-self-destructing versions of Fuses, similar to Circuit Breakers, in that they self reset when the high current draw is removed. Questions about regular fuses should use the Fuse tag.
84 questions
1 vote
1 answer
152 views
How do I know the voltage drop?
I recently made this circuit for a personal project of mine. I wanted to calculate the voltage drop prior to printing the PCB, but I wasn't sure how so I just went with it. And sadly, the voltage ...
- 51
1 vote
0 answers
76 views
What causes a PPTC fuse to permanently increase in resistance?
System Overview: We have a device installed in an industrial field environment, powered by a 24V SMPS. The power path and protection scheme are as follows: 24V Input Side: Protected by a 1A PPTC fuse. ...
- 47
1 vote
1 answer
104 views
Can a PTC Fuse be used in a PWM load?
I'm interested in adding a PTC fuse to the input side of my circuit, to protect the power supply from a short circuit. My circuit has a PWM load, with a duty cycle of 50% and a frequency ranging ...
- 559
0 votes
1 answer
68 views
Running a poly fuse between the holding and tripping current?
I'm running a circuit with some PolySwitch Resettable Fuses RXEF series 72 V 0.20 A. They have a holding current rating of 200 mA and trip current of 400 mA. The circuit is made of a constant current ...
- 109
1 vote
2 answers
152 views
Lifetime (number of switch off/on cycles) of a PTC resettable fuse, that does not trip
In most datasheets for PTC resettable fuses, the endurance is not well defined / discussed. A notable exception would be this one from Bourns It at least states, that the product is tested against a ...
- 2,042
2 votes
1 answer
82 views
1 Cell LFP Battery Pack Protection
I am starting a project that requires a single 3.2V LiFePO4 18650 cell to be in a housing with exposed contacts, suitable for easy swapping in and out of an unpowered device. The device will only be ...
- 21
3 votes
6 answers
1k views
Is there a better way to protect my power supply other than the efuse?
I use fairly cheap standard power supplies with no protection in my circuit experiments, usually with output of 5V, 12V, 18V, 30V and a current up to 1A. I use standard glass fuses to protect these ...
- 416
0 votes
0 answers
82 views
SMD PTC Fuse for 24 VDC
I am designing a new version of a PCB board with a microcontroller to drive two 24 V DC brushed motors, and I am looking for a self-resetting PTC SMD fuse for a 24 VDC supply line and max 2.5 A. The ...
- 1,950
5 votes
1 answer
528 views
Overcurrent protection (at 4A 100V)
On the PCB I'm designing, the total power consumption might be as high as 86W (including output power), with supply voltage between 18 and 75V DC (it is OK not to allow full output power bellow 22V). ...
- 9,675
0 votes
1 answer
1k views
How to use TVS diode for Overvoltage Protection while powering Arduino on Vin Pin?
I am trying to make a protection circuit for Arduino nano to protecting overvoltage. Normally if I powering "Clone" arduino NANO with 12 Volt, Arduino nano is starting to smoke. So I've ...
- 1,255
0 votes
2 answers
636 views
Why don't Arduinos have a fuse on the Vin pin?
I am designing a PCB for an Arduino Nano. I want to protect the Nano from over current and high voltage. In the schematic of the Nano, there is only one fuse at USB Vcc at Arduino Nano Rev3. No clone ...
- 1,255
1 vote
0 answers
867 views
\$ 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 ...
- 590
2 votes
3 answers
988 views
Polyfuse voltage significance
I would like to protect a circuit from overcurrent over 500 mA. The voltage in the circuit is only 5 V. Can I use higher voltage and lower current polyfuse, which results in same power flowing through ...
- 314
9 votes
2 answers
5k views
Self-resetting crowbar circuit for over-voltage protection
I'm trying to design an over-voltage protection circuit that doesn't rely on custom chips (the chip shortage has shown the danger of relying on this), so I put together a crowbar circuit like this: I ...
- 345
8 votes
9 answers
6k 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 ...
- 25.7k