Reset able fuses composition  - Page 1
Forum section: electronics / beginners

author: joniengr081
author_rank: Regular Contributor
timestamp: August 23, 2024, 09:47:40 am
content: I have read the article about reset able fuses. It describe reset able fuses in general, their purpose, function, application areas, advantages and disadvantages etc.https://community.element14.com/technologies/experts/b/comprehensive-guides/posts/a-comprehensive-guide-to-resettable-fusesIt also points to different types of reset able fuses, Ceramic PTC, Polymeric PTC, Radial Leaded PTC, and OXCG Series Surface-mount PPTC.Which type is more reliable is not mentioned. Also what they are made up of ? Is there any semi-conductor material in their composition ?

author: BILLPOD
author_rank: Frequent Contributor
timestamp: August 23, 2024, 01:00:49 pm
content: Good Morning Joniengr081, Personally I would prefer a 'circuit breaker', as theyperform more reliably. No basis for my opinion, just memory of past experience

author: Solder_Junkie
author_rank: Frequent Contributor
timestamp: August 24, 2024, 10:45:12 am
content: I use “poly” fuses in the Voltage distribution part of my home made radio equipment. They are widely used in cellular phones, and other lithium battery powered devices. By using LED indicators on the board, you can immediately see if there is a short circuit anywhere.Poly fuses work by “heating” under excessive current, which causes them to become high resistance.You can use sophisticated current sensing circuits and MOSFET switching transistors, which can protect against over Voltage, over current and reversed supply. An Analog Devices LTC4368 and a DMT6002 MOSFET are used in power supply protection boards for my ham radio power supplies, check the LTC4368 data sheet for the capabilities of these useful devices… the over current trip can operate in as little as 8uS and will not blow a 3A fuse placed directly across the terminals of a 35A power supply!Horses for courses, use whatever devices are appropriate.SJ

author: perdrix
author_rank: Frequent Contributor
timestamp: August 24, 2024, 03:34:41 pm
content: Aren't horses hooves a bit hard to solder?

author: Siwastaja
author_rank: Super Contributor
timestamp: August 24, 2024, 06:52:09 pm
content: It might not be the best idea to think PTC "polyfuses" as fuses (or circuit breakers) at all. They are variable resistors which limit but never completely cut current after certain current is exceeded. They also do not completely heal back so the next limiting event happens at a lower current than the initial one.

author: golden_labels
author_rank: Super Contributor
timestamp: August 24, 2024, 08:19:15 pm
content: Non-resettable fuses or circuit breaks serve different purpose than polyfuses. Sweeping statements in preference of either make little sense to me. The difference in their voltage and current rating should already be a strong hint.The first kind is meant to prevent a catastrophic failure inside device from escalating and leading to even more catastrophic outcome. Like burning down your home. While coincidentally they may, they generally don’t protect the circuit.(1)The currents needed to trigger that kind of protection will cause magic smoke to be released, even explosively. What they do protect against is things getting red hot. For larger values (≥10 A fuses) the home installation, for lower values the tiny plastic casing in which the circuit sits.Polyfuses work where temporary overcurrent situations are expected to happen during normal operation. They are unwanted events, but expected. That includes user errors. Good examples are USB ports or batteries.(1)Notable exceptions include overvoltage protection.