hybridfree/eevblog-posts huggingface dataset:
Funny light-bulb and question about life time/rating - Page 1
Forum section: electronics / beginners

author: edy
author_rank: Super Contributor
timestamp: November 07, 2017, 04:16:24 am
content: I have one of these incandescent light bulbs (see below) used for a night-light. It turns out that the filament is a little loose in the bulb and if you jiggle the bulb sometimes the filament "crosses over" at a point in the middle, thus creating a short-circuit and making the net length of the actual filament that is being "used" for conduction much shorter than the normal length. As a result, the bulb gets considerably brighter.I usually shake the bulb a bit and the filament is able to separate again where it is crossing over itself and the bulb goes back to being it's usual dim self, with the entire length of filament being lit.So a few questions that may seem obvious but may be educational to the beginner and meant to confuse the issue:1. As the filament shortens, the net voltage drop per length increases thereby causing more friction in the wire, leading to heat and light?2. As the filament shortens, the resistance reduces and therefore amperage increases given an equal voltage?3. As the filament shortens, there is less metal to dissipate the energy and therefore the shorter piece has more concentrated heat/light?Is the bulb going to burn out faster? Is it safe to keep the bulb in the brighter state? Will it heat up more? Could it cause damage to the night light housing or create a fire hazard?

author: IanB
author_rank: Super Contributor
timestamp: November 07, 2017, 04:37:07 am
content: Yes, shortening the filament is like turning up the voltage. The filament will glow brighter and will burn out sooner (maybe much sooner).It is unlikely to be harmful to the surroundings though. The filament is already white hot. A bit more white hot isn't going to make much difference.

author: Whales
author_rank: Super Contributor
timestamp: November 07, 2017, 04:42:55 am
content: 1. Yes2. Yes3. YesCan't comment of whether or not it will cause a fire. This depends on what it's mounted on/near. It will definitely generate more heat and last less time.The colour temperature of the bulb will also change (blue shift) due to the higher temp, but I'm not sure if it will be enough to notice.

author: amyk
author_rank: Super Contributor
timestamp: November 08, 2017, 03:16:55 am
content: https://en.wikipedia.org/wiki/Incandescent_light_bulb#Light_output_and_lifetimeLife is inversely proportional to thesixteenthpower of the voltage, so I would highly recommendnotleaving it in the partially shorted state.If you half the length of the filament, it will approximately mean twice the voltage density, and that means it will last only 1/65536as long. To put this into perspective, it means a lamp rated for 5 years will only last 40 minutes!
Funy! I can do it  - Page 1
Forum section: electronics / beginners

author: Dat Tran
author_rank: Contributor
timestamp: August 07, 2015, 01:04:21 pm
content: https://youtu.be/n6To7UU3krsAny ideas to develop

author: Mephitus
author_rank: Regular Contributor
timestamp: August 07, 2015, 03:08:18 pm
content: Looks like a pretty standard "flip flop" circuit using the caps as a delay. Simple, but a great way of understanding the basic functions of transistors.https://en.wikipedia.org/wiki/Flip-flop_(electronics)

author: Dat Tran
author_rank: Contributor
timestamp: August 07, 2015, 04:11:51 pm
content: Yesss. it's interested.

author: daybyter
author_rank: Frequent Contributor
timestamp: August 07, 2015, 08:11:16 pm
content: Develop? Hmmhh...if you could build this somewhat bigger...and synch it to some music...you could open a discotheque?

author: Dat Tran
author_rank: Contributor
timestamp: August 08, 2015, 10:25:11 am
content: Oh. I love discotheque. I like the loud
Fuse / Breaker size question - Page 1
Forum section: electronics / beginners

author: shanezampire
author_rank: Contributor
timestamp: July 10, 2019, 03:15:09 am
content: Hypothetically lets say you have a 24vdc 5a 120w power supply and you want to make a bench top variable power supply. You run it to the variable control module, potentiometers, binding posts, etc. Of course you want to put a fuse / breaker before the binding post (I assume that's the correct place) and I assume you want one after the 120v main line coming in.My question is what size do you use?Online calculators say Fuse rating = (watts/volts) x 1.25So you would need a 1.25a fuse or next size higher to main line coming inand you would need a 6.25a fuse right before the binding postIf this is correct ... wouldn't it be better to just stick with a 5a fuse OR one them Resettable Push Button Thermal Circuit Breaker Panel Mount to be on the safe side?

author: MosherIV
author_rank: Super Contributor
timestamp: July 10, 2019, 06:41:49 am
content: QuoteSounds about right. Try a Timed or antisurge type due to the inductance of the transformer.QuoteWhy? What are you trying to protect?It would be better to put the fuse on the output of the transformer to protect both the transformer output and the psu circuit.You would expect a bench psu to have current limiting and set that to some value to protect the circuit under test/development.Bench psu should be capable of withstanding a short circuit by limiting the output current to the current limit. They should also be able to deliver the rated current or current limit continuosly.
Fuse for battery protection - Page 1
Forum section: electronics / beginners

author: Moondeck
author_rank: Regular Contributor
timestamp: March 07, 2017, 07:22:33 pm
content: So, i am doing a project at school that requires battery protection, i am going to use this chiphttp://www.ti.com/lit/ds/symlink/bq2946.pdfThe schematic shows some sort of a fuse with resistors in it. I understand what it does, but i have been unable to find a fuse that would do this and have this 3 pinned setup. Could i use a normal fuse and the MOSFET would just short it? Could anyone give me link to one please (preferably at Farnell)?Thanks,moondeck

author: ConKbot
author_rank: Super Contributor
timestamp: March 07, 2017, 09:07:41 pm
content: It's a "chemical fuse" a fuse with a third terminal to trip it. It doesn't require as much current on the 3rd terminal, making it easier to trip. They are a big pain to find, like surprisingly so. You can use a chunky mosfet that can handle enough current to trip your fuse in the appropriate time frame, or you can use a thermal fuse (70-80c should be fine), and park a resistor next to it, so the resistor trips the thermal fuse.
fuse help - Page 1
Forum section: electronics / beginners

author: grifftech
author_rank: Frequent Contributor
timestamp: May 22, 2015, 10:45:55 pm
content: I need a .8 -.9 Amp fuse but only have .7 A and .4 A fuses I intend to draw 750 ma continuous can I just bodge 2 .4 A fuses in Parallel

author: jeroen79
author_rank: Frequent Contributor
timestamp: May 22, 2015, 11:26:10 pm
content: And what is your question?Can't you just buy fuses rated for a higher current?And besides .75A continuous (average?) current, what would be the peak currents?They could be much higher depending on what you are powering.

author: barry14
author_rank: Regular Contributor
timestamp: May 23, 2015, 01:40:21 am
content: Do not try wiring fuses in parallel. The inevitable slight differences in resistances of the wiring and the fuses will cause an uneven sharing of the current. This means the actual current for which one of the fuses blows is unpredictable.

author: Psi
author_rank: Super Contributor
timestamp: May 23, 2015, 03:23:30 am
content: A 0.7Amp fuse will last quite a long time with 0.75A flowing through it.You need double the rated current to blow it fast. 0.75 on a 0.7 fuse would probably last weeks/months of continuous operation.The thing that will kill it is inrush current (if your load draws more than 0.75A for a short time at startup)

author: Neilm
author_rank: Super Contributor
timestamp: May 23, 2015, 05:28:33 pm
content: Can you find a datasheet for your fuse? If it has the curves on it, you will see how long your fuse will take that current. Some fuses will happily take a 2 times overload for 30 minutes before blowing.

author: con-f-use
author_rank: Unknown
timestamp: May 23, 2015, 07:43:58 pm
content: Since you seem to be a beginner, be adviced that fuses generally don't prevent components or people from bing damaged. They merely (sometimes) prevent fires and overheating.
Fuse in small power supply needed? - Page 1
Forum section: electronics / beginners

author: Lee Leduc
author_rank: Regular Contributor
timestamp: March 03, 2018, 05:47:22 pm
content: Here is a typical 3 terminal regulator based dual power supply schematic that can be found on the net. It's used to power Op Amp breadboard circuits.Is a Fuse required in the low voltage winding of the wall transformer or is it optional?

author: Benta
author_rank: Super Contributor
timestamp: March 03, 2018, 09:16:51 pm
content: QuoteNo, it's optional (and not really needed, small wall-wart transformers are usually short-circuit proof).Primary side fusing is mandatory for fire protection, but I expect the wall-wart has this.

author: danadak
author_rank: Super Contributor
timestamp: March 03, 2018, 09:24:02 pm
content: I may have been around too long but nervous about quality of wall wartscoming out of far east. I would advise a fuse. I have had more than onemelt plastic due to faults not properly addressed.Regards Dana.

author: Lee Leduc
author_rank: Regular Contributor
timestamp: March 03, 2018, 11:47:26 pm
content: I found a site with an article entitled "Engineering with wall plug-in power supplies and AC adapters". It mentions internal fuses.https://www.powerstream.com/Wall-mount-FAQ.htm"Internal fusesThose wall plug-in power supplies certified by safety agencies are required to have an internal fuse to protect against fire if there is a short circuit. They are almost always soldered-in glass tube type fuses, and are almost never user replaceable. They are protecting the primary side of the transformer, so are typically rated at 240 volts. Don't get confused by this rating, even a 110 volt input wall mount transformer will use a fuse rated at 240 volts. The current rating is typically two to three times the rated input current."
Fuse inquiry about Pioneer CDJ-2000 (J marked SMD) - Page 1
Forum section: electronics / beginners

author: belzrebuth
author_rank: Frequent Contributor
timestamp: June 09, 2021, 02:49:56 pm
content: Hi all,I've found a blown fuse in a Pioneer CDJ-2000 SRVA board.The short was caused by another board that's now repaired (I know cause I have two units so I can compared).The SRVA board has a fuse marked as P 7302 PROTECTOR (1.250 A) DEK1123 which is an internal part number so I can't really know if this one is a fast or time-lag fuse.All I know is that's a 1206 1.25A ceramic fuse but I need to order a replacement and I'm torn between time lag or fast.Any ideas?
Fuse - is it necessary and which type for a USB-powered board? - Page 1
Forum section: electronics / beginners

author: Saimoun
author_rank: Frequent Contributor
timestamp: December 24, 2020, 05:14:57 pm
content: HiI have a product drawing about 70-80mA of current from a 5V USB plug. the board runs at 3.3V, the 5V circuit is only:plug -> diode -> (fuse?) -> 2 times (4.7uF MLCC cap -> 3.3V LDO)(I have two LDOs)Do you guys think a fuse is necessary (this is a professional project (hopefully) going to market), and if so which type? I was thinking PTC resettable.Thank you!

author: Siwastaja
author_rank: Super Contributor
timestamp: December 24, 2020, 05:30:19 pm
content: USB power supplies are (should be) always protected in such way fuse is not needed for fire protection. Computer ports turn off and report overcurrent to the operating system. USB chargers use hickup current limiting or similar and can't output much over 2A. I would likely not use any kind of fuse.PTC needs to be oversized in order not to cause problems. If the short is after the linear regulator, they have current limiting that would trig at the roughly the same time as the PTC. Of course you can add PTC and thermally couple it to the linear regulator so that excessive heating from the regulator lowers the PTCs trig current.Is there a reason why you are expecting a short circuit, such as something the user connects to your device? In that case, protect the user-facing port.The proposed diode is fine if you can afford the voltage drop.10uF of MLCC very likely creates a voltage overshoot issue during hot-plug, this is the biggest problem I see in what you propose. Dampen it with a 22..100uF electrolytic. Seehttps://www.analog.com/media/en/technical-documentation/application-notes/an88f.pdffor more information. Another potential issue is board flex causing MLCC cracking and shorting if the case size is big like 1210. Be careful with placement in regard of mounting holes.

author: Saimoun
author_rank: Frequent Contributor
timestamp: December 24, 2020, 05:41:56 pm
content: Thank you for the answer Siwastaja - good point about the overcurrent from the hosts - it seems it is in the USB spec as well.QuoteFrom the user's point of view, no error really possible, the outputs are behind ICs which will limit the current or die before the board burns or smth like that. And as you said anything happening on the 3.3V would be limited by the LDO's. So the only thing left are the two MLCC which could crack - they are 0603 though.So I'll guess that is enough reasons to drop the fuse?As for the diode, the plug cannot be put the "wrong way", so the only possible fault would be to use a wrong USB cable which inverts 5V and ground.So maybe the diode is not needed either?Just FYI - if someone wants more disccussion on the subject I found another post about it:https://www.eevblog.com/forum/chat/fuse-for-usb-powered-product/
Fuse Question - Page 1
Forum section: electronics / beginners

author: bostonman
author_rank: Super Contributor
timestamp: February 05, 2020, 03:18:11 am
content: I'm having a work related problem regarding fuses.It's regarding maximum A^2 * SI'm given two columns, the first has the titlePeak Current (A)and one of the values is 30. The second column hasMaximum [indefinate integral] I^2 * t , A^2 * sand has a value of 90.I understand the peak current being 30A, but don't understand the second column with regards to 90 being A^2 * s.I looked on LittelFuse, but didn't find anything directly explaining this. Basically I don't understand the connection between the indefinate integral, A^2 * s, and what it means with the value of 90.Can someone help end my confusion?

author: helius
author_rank: Super Contributor
timestamp: February 05, 2020, 04:57:31 am
content: The main parameters that are relevant to fuses are current capacity, arc breaking or interrupting current, speed, and energy absorption.The current capacity is the current that the fuse will pass without blowing over any amount of time. It's the intersection of the current diagram with t=∞ and is notated in amperes.\$ \int I^2 dt \$ is the area under the curve represented by the current squared on the Y axis, with time on the X axis. The idea is that this function looks like a hump rising up from (near) zero at a certain point, and then decreasing back to zero since the circuit is broken. Power is proportional to current squared: \$ P = I^2 R \$ , so the area under the curve is power times time, or the energy the fuse is rated to absorb. I would expect this parameter to be in kilojoules.

author: SG-1
author_rank: Regular Contributor
timestamp: February 05, 2020, 05:42:47 am
content: I2t (Amperes Squared Seconds) This is a value obtained by multiplying an effective current squared by the time of flow of the current in seconds. It is not a heat energy value, but represents heat energy for comparison purposes. Some common uses are to determine fuse selectivity and to select current limiting fuses that will limit this value to be compatible with the withstandability of semi-conductors that have an I2t rating.

author: bostonman
author_rank: Super Contributor
timestamp: February 05, 2020, 01:23:26 pm
content: QuoteSo to write it correctly, am I integrating I^2t dt or I^2 dt?Also, if I integrate, I get I^3/3 * t +C. What value do I use for C?

author: bostonman
author_rank: Super Contributor
timestamp: February 11, 2020, 09:22:43 pm
content: QuoteJust realized, I didn't get clarification about this.

author: rstofer
author_rank: Super Contributor
timestamp: February 11, 2020, 10:09:09 pm
content: Quote from: bostonman on February 05, 2020, 01:23:26 pmTo evaluate C, you need an initial condition. Just evaluate the expression for t = 0 and see what happens to C. Usually, you will have an expressions like f(t) = {the integral stuff} + C and C = f(0).
Fuse question - Page 1
Forum section: electronics / beginners

author: Electric flower
author_rank: Regular Contributor
timestamp: April 21, 2014, 09:05:13 pm
content: I bought used soldering station and label on it states that fuse used is T500mA.However i found that 3 fuses (2 +1 fuse in station) given to me were F6.3A 250V.I am going to replace fuses i got with ones that have rating T500mA 250V.But is it safe to do this? Replace fuse with one that has shorter blow time but higher current rating?And is there possibility that any sort of damange was done to the soldering station during 2 years of regular use?T stands for time and these are used on inductive loads such as primary coil of transformerF stands for fast and these are not ussualy used on inductive loads.Thanks for the help as usual.

author: Simon
author_rank: Unknown
timestamp: April 21, 2014, 09:13:29 pm
content: Well using the specified fuse is a good idea to start. What power is the iron ? 500mA gives you 120W @ 240V so if it's say a 60W iron that sounds about right.

author: Electric flower
author_rank: Regular Contributor
timestamp: April 21, 2014, 09:18:30 pm
content: Soldering iron is 80WStation is rated 95WSoldering station is Weller PU81Fuse is connected to primary of transformer

author: Simon
author_rank: Unknown
timestamp: April 21, 2014, 09:36:05 pm
content: 500mA 750mA tops

author: JOERGG
author_rank: Contributor
timestamp: April 21, 2014, 09:42:13 pm
content: I have the same soldering station and the original fuse insertet is T500 mA 250V as written on the label.

author: Holograph
author_rank: Regular Contributor
timestamp: April 21, 2014, 09:44:16 pm
content: Quote from: Electric flower on April 21, 2014, 09:05:13 pmOften you can do this, but you still have to size the fuse correctly. Overrating it if using a fast-blow in place of a normal/slow-blow or a normal in place of a slow-blow is correct, but going up from 0.5A to 6.3A is far too big a jump.1Since you need to buy fuses anyway, I'd stick with the rated fuse. If you go for a faster-blowing type, then perhaps 600-750mA.
Fuse symbol thinging? - Page 1
Forum section: electronics / beginners

author: rjardina
author_rank: Contributor
timestamp: April 18, 2016, 01:31:08 am
content: What the heck is this fuse symbol on the left, anything special about this fuse too? Fuse is from the secondary side of a transformer from a Milwaukee M12 charger.Thanks for your time and help.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 18, 2016, 01:37:28 am
content: Manufacturer logo. I don't recognize it. Probably Chinese.Tim

author: tautech
author_rank: Super Contributor
timestamp: April 18, 2016, 01:43:54 am
content: Quote from: T3sl4co1l on April 18, 2016, 01:37:28 am+1

author: elektroda
author_rank: Newbie
timestamp: April 18, 2016, 04:53:34 am
content: when you will be inserting new fuse , you must see what type (if this fuse is at primary side it's time-lag) .

author: tszaboo
author_rank: Super Contributor
timestamp: April 18, 2016, 11:33:44 am
content: It is a spaceship.
Fuse symbol - Page 1
Forum section: electronics / beginners

author: Gp!
author_rank: Contributor
timestamp: March 20, 2019, 06:47:01 pm
content: Hi,I am trying to decipher the symbol on the fuse in the attached picture but without much success. Any ideas anyone ? Is it possibly a company logo?Thanks for any help

author: coppercone2
author_rank: Super Contributor
timestamp: March 20, 2019, 06:48:30 pm
content: Littlefuse 1A?

author: chrisl
author_rank: Regular Contributor
timestamp: March 20, 2019, 06:58:17 pm
content: Looks like an 1A fuse.... What happened to the inductor behind the fuse? It seems it has cracked open in the picture.

author: Gp!
author_rank: Contributor
timestamp: March 20, 2019, 07:20:23 pm
content: Thanks to all. The board says it should be a T2A/250VAC.I've included an expanded picture.It's actually giving me a short on the fuse, but I still have to find the cause...very much a newbie here.. LOL

author: helius
author_rank: Super Contributor
timestamp: March 20, 2019, 07:47:38 pm
content: That isn't the Littelfuse logo.Quote from: Gp! on March 20, 2019, 07:20:23 pmDo you mean anopen, as opposed to ashort?The resistance across an intact fuse should normally be near zero, i.e. a short. When the fuse blows to protect the circuit, it becomes an open (infinite resistance).

author: Gp!
author_rank: Contributor
timestamp: March 20, 2019, 08:05:16 pm
content: sorry yes my bad, it's open as in blown. I was thinking of the short further down the circuit.The residue that you see around some of the components is because it was completely potted. It's a power supply to a Led Flood light.I am trying to fix it for fun and to learn.

author: helius
author_rank: Super Contributor
timestamp: March 20, 2019, 09:35:06 pm
content: Possibly the board is designed for worldwide supply voltages (120-240) and uses a 1 amp fuse for 240V countries, 2 amp for 120V countries.That isn't the Littelfuse logo, but you can use Littelfuse 0471001 as a replacement. Unfortunately these "pico-sized" fuses aren't cheap.

author: Gp!
author_rank: Contributor
timestamp: March 24, 2019, 08:51:08 am
content: Thanks !I really appreciate the code number for the part.I have placed an order, and yes you right not cheap at all (and long lead times ) !!!!
fuse value for small transformer - Page 1
Forum section: electronics / beginners

author: Chai
author_rank: Regular Contributor
timestamp: May 26, 2018, 12:18:54 am
content: I'm putting together a transformer in a box just for hobby stuff and I want to put a fuse on the primary.Did I understand the values correctly? Sorry for such a basic question!7.56 VAPrimary: 115VSecondary: 6.3VCT @ 1.2 AmpsPrimary fuse value: 7.56 / 115 = 0.066 -> ~80mA slow blowFull secondary max: 12.6V @ 0.6ACenter tap max: 6.3V @ 1.2A

author: james_s
author_rank: Super Contributor
timestamp: May 26, 2018, 12:32:29 am
content: That sounds reasonable. If you wanted to verify, you could measure the primary current while briefly shorting across the secondary and see how much it draws, then select a fuse value that is below that by a good margin.

author: Benta
author_rank: Super Contributor
timestamp: May 26, 2018, 10:08:05 am
content: You should rate the fuse higher, otherwise you'll probably be replacing it all the time. The primary fuse is not for overcurrent protection, but rather for fire protection should something go wrong. I'd suggest 250 mA slow.

author: Zero999
author_rank: Super Contributor
timestamp: May 26, 2018, 12:53:59 pm
content: Quote from: Chai on May 26, 2018, 12:18:54 amHow about the losses in the transformer?The primary current will be much higher than your calculations suggest.Small transformers are notoriously inefficient. Unfortunately I couldn't find the efficiency of the transformer you're using but it will be similar to any other transformer of a similar power rating. The data sheet linked below says 69% efficiency for a 6V transformer, so assume about 70% for your transformer., so the primary power will be around 14VA, giving a primary current of just over 120mA.http://www.farnell.com/datasheets/2603262.pdf?_ga=2.104444297.887224271.1527338544-47418993.1417808164As Benta said, the fuse isn't to stop the transformer from being damaged, but to protect against fire and making the fuse double the nominal current is a sensible suggestion, hence 250mA. I wouldn't recommend anything less than a 200mA fuse.Note that this transformer has a 6.3V secondary, not 12.6V!What load is the transformer powering? If it's a rectifier and smoothing capacitor, I hope you're aware that the maximum DC current will be around 70% of the secondary's rating.
fuse VS MOV for overvoltage protection - Page 1
Forum section: electronics / beginners

author: m4rtin
author_rank: Regular Contributor
timestamp: October 28, 2012, 08:14:55 pm
content: As I understand, ATX PSU's usually have both fuse and metal-oxide varistor(MOV) for overvoltage protection. Do they serve different purposes? Or are there just two layers of overvoltage protection?

author: M. András
author_rank: Super Contributor
timestamp: October 28, 2012, 08:19:35 pm
content: fuse is for overcurrent, what the mov will blow when the voltage reaches its treshold voltage

author: Kremmen
author_rank: Super Contributor
timestamp: October 28, 2012, 08:47:28 pm
content: A MOV will short overvoltages. It is effective against short spikes but sustained surges can cause it to absorb more energy than it is capable. For that reason there must always be a fuse on the supply side of a MOV, to break the current in such a case. The energy capacity of the MOV should match or exceed the rupture energy of the fuse to avoid the MOV exploding.So, as Andras stated the fuse breaks overcurrents and the MOV absorbs voltage spikes. The voltage margin should be sufficient to avoid MOV conducting under normal circumstances. For a say 230 VAC circuit, a 275 VAC MOV is usually specified.

author: jeroen74
author_rank: Frequent Contributor
timestamp: October 30, 2012, 03:39:06 pm
content: If possible, use a MOV that has a built-in thermal fuse. After every surge a MOV slightly degrades (the voltage at which it allows 1mA to flow lowers) and it's very possible that after a small surge it becomes low impedance, not low enough to blow the fuse, but low enough to act a nice little heater that dissipates a couple of watts. Can set your house on fire. A MOV can literally glow red hot. And explode very nicelycovering the whole innards of your widget with black stuff.IIRC in certain territories high mains is a frequent occurrence; that's a condition where the mains voltage is way too high for a couple of minutes.

author: ptricks
author_rank: Frequent Contributor
timestamp: October 30, 2012, 06:24:18 pm
content: Fuses will not work for over voltage they are over current devices when used by themselves. MOV are voltage sensitive and will basically short the power and ground together in an attempt to absorb the surge, that shorting causes current to increase , and if the current increases long enough the fuse will blow. Fuses also serve another function besides blowing when a MOV clamps, they limit current for the entire supply. If something blows in the supply like a FET , the MOV will do nothing but the increase in current from the shorted FET will blow the fuse.Years ago when I went to college they taught us to design power supplies that were current limited on the input using a resistor sized for the desired output, we also designed supplies so that individual circuits within the design had resistors limiting the power to those sub circuits, these supplies were very safe because regardless of what happened in the supply nothing could exceed the rated current. Now with everyone energy conscious they don't recommend these designs because of the power lost in the resistor.
Fuse with colored bands - Page 1
Forum section: electronics / beginners

author: Hex173t
author_rank: Contributor
timestamp: December 05, 2013, 01:56:31 pm
content: A friend has a tv with a blown fuse. I think it's 10 amp, with the wide blue band indicating a medium blow speed 50-90ms at 10x rated current per a website I found.Is this correct?

author: trackman44
author_rank: Regular Contributor
timestamp: December 05, 2013, 02:11:27 pm
content: Yep, that's about right. Also, the voltage rating is etched on the edge, rated at 250V.Will

author: Hex173t
author_rank: Contributor
timestamp: December 05, 2013, 02:52:13 pm
content: ThanksI know its a very basic question but I've never seen them marked like that and I sure wouldn't want to call it 10 amp if it wasn't. And the blue band threw me too.

author: VintageTekFan
author_rank: Regular Contributor
timestamp: December 05, 2013, 03:37:34 pm
content: Can you post the link for future reference?

author: Hex173t
author_rank: Contributor
timestamp: December 05, 2013, 03:49:37 pm
content: http://mw0gkx.co.uk/howto/fusecolours.htm

author: VintageTekFan
author_rank: Regular Contributor
timestamp: December 05, 2013, 06:48:22 pm
content: Thanks!
Fuse - Page 1
Forum section: electronics / beginners

author: lesr389
author_rank: Contributor
timestamp: November 08, 2015, 12:06:07 am
content: I am trying to repair a TV. The hdmi ports stopped working one at a time. There are 3 ports. What i think are fuses apear to be bad. Can anyone confirm this and maybe tell me where i can buy new ones? See attached pictureSent from my SCH-I545 using Tapatalk

author: tec5c
author_rank: Frequent Contributor
timestamp: November 08, 2015, 12:08:31 am
content: They are diodes, not fuses.Did you test these with a continuity test using a DMM? If so, they would show as open circuit...

author: helius
author_rank: Super Contributor
timestamp: November 08, 2015, 12:11:46 am
content: Those are MELF diodes. Why do you think they are bad?

author: lesr389
author_rank: Contributor
timestamp: November 08, 2015, 03:04:17 am
content: The hdmi ports stopped working one at a time. One of those diodes looked like it could be burnt. If it doesnt read continuity showing the circuit is open that would mean theyre bad right?Sent from my SCH-I545 using Tapatalk

author: lesr389
author_rank: Contributor
timestamp: November 08, 2015, 03:17:17 am
content: Diodes would read open...how can i find out if they are bad or the voltage to get a replacement if infact they are badSent from my SCH-I545 using Tapatalk

author: tec5c
author_rank: Frequent Contributor
timestamp: November 08, 2015, 03:26:01 am
content: Firstly, you made two threads of the same topic and are updating both of them. Thus, I will only follow the thread in the repair forum.Thread found here:https://www.eevblog.com/forum/repair/circuit-repair/
Fuses and inrush current - Page 1
Forum section: electronics / beginners

author: jolshefsky
author_rank: Regular Contributor
timestamp: July 13, 2018, 09:01:13 pm
content: The specific case I have is a device that draws about 20mA at 12V during operation. I'm using a Littelfuse 0437.500WR which is rated for nominal 500mA. However, the circuit has a 10µF input filter capacitor, and when it's powered from a lowly wall-wart supply, the peak surge current is over 9A for little 200nS bursts. The Littelfuse specs only say it's rated for 350% overcurrent up to 1 second, so only 1.75A, and their graph bottoms out at 1ms (maximum 4.5A). It seems to work fine, but I can't be sure it actually is okay. Is this just a normal thing that one must accept?I was fiddling with putting 10Ω in series (figuring it would limit inrush current to 1.2A at the full 12V but only drop 0.2V at normal operation) but that causes the internal DC-DC converter to power-cycle, so I can't afford a current-limiting resistor.

author: thm_w
author_rank: Super Contributor
timestamp: July 13, 2018, 09:26:16 pm
content: You could extend that graph or find the I2T value on their site:http://www.littelfuse.com/products/fuses/surface-mount-fuses/thin-film-chip-fuses/437.aspxNominal Melting I2T (A2sec): 0.018See page 13 here:https://www.schurter.com/content/download/676506/13549060/version/3/file/Guide_to_Fuse_Selection.pdfYou should be well under that calculated number from what I see. May also want to check for voltage spikes, and what the limit of the input circuitry is.

author: jolshefsky
author_rank: Regular Contributor
timestamp: July 16, 2018, 01:07:24 am
content: Quote from: thm_w on July 13, 2018, 09:26:16 pmExcellent—thanks. I knew there must be some way to characterize the way fuses accumulate the energy needed to melt. Even the "simplified" I2t where you just take the peak current over the whole time isn't enough in this particular case.

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 01:21:53 am
content: Fuses are not precision devices, don't over-think the matter. Consider what you are trying to protect with the fuse, generally it is futile to prevent damage to a semiconductor but then again often it's the semiconductor failing that blows the fuse in the first place, and what you normally want to protect is the wiring to and in the device and the traces on the PCB. The fuse should be there to prevent a fire or other collateral damage, it doesn't have to be on the ragged edge under normal conditions.Also if you have a high inrush current that can pose problems of its own, you might consider a thermistor or other means to soften that a bit.
Fuses HBC vs LBC - Page 1
Forum section: electronics / beginners

author: skcole
author_rank: Newbie
timestamp: January 12, 2018, 02:24:14 pm
content: I know what the difference is when it comes to low-power cartridge fuses -HBC = High Breakdown Current (the highest current the fuse will conduct without shattering, just before it severs. Generally KAmps)LBC = Low Breakdown Current (the highest current the fuse will conduct without shattering, just before it severs. Generally 10's of Amps)What I am confused about is why do LBC fuses still exist? Why doesn't everybody just buy HBC fuses and be done with it?Thanks.I'm trying to decide whether to spec a HBC fuse on a 19" rack unit, and a LBC fuse on an internal circuit board. As its a question, also, of fuse speeds, and I have heard that generally the speed difference between HBC and LBC is negligible, I don't really understand why LBC fuses still exist?!As a follow on question, has anyone got any good links to articles on spec'ing fuses so as to prevent a short-circuit tripping a fuse up-stream of the fuse which should blow locally? I get the feeling there should be techniques to checking fusing behaviour, and maybe even being able to choose fuse "families" based where in the chain of circuit-breaker/fuse-sequence the fuse is destined to live.Thanks for any help on this you can give.skcole

author: wraper
author_rank: Unknown
timestamp: January 12, 2018, 02:38:04 pm
content: QuotePrice, in case of small size fuses, it can also be a size constraint.QuoteIt's not about shattering but current that fuse is guaranteed to interrupt. Fuse may stay in one piece but be unable to interrupt the current flow.

author: Gyro
author_rank: Super Contributor
timestamp: January 12, 2018, 04:05:54 pm
content: Quote from: wraper on January 12, 2018, 02:38:04 pmThere are many places (inside equipment and non mains) where the prospective fault current is low and the interrupt rating of an LBC fuse is perfectly adequate. They also tend to be available in a wider range of (low) current ratings.EDIT: Fuse manufacturer sites and datasheets are a pretty good source of information on deciding fuse rating and most appropriate delay characteristics.

author: ConKbot
author_rank: Super Contributor
timestamp: January 12, 2018, 06:45:07 pm
content: As stated, cost and size. For example, take a 240v motor for something like a compressor, you feed it with say 30A rated 50KA interrupting HRC fuses in the disconnect, they are big and chunky. But the contactor inside needs a fuse for the coil and control circuit. Could you put a 1A rated HRC in there? Sure, but the fuse in the control panel only needs to handle a few hundred A before the upstream HRC is well on the way to blowing quickly. Perfectly safe, despite being significantly cheaper.
Fusing three transformers - Page 1
Forum section: electronics / beginners

author: liquibyte
author_rank: Frequent Contributor
timestamp: February 13, 2014, 12:48:39 pm
content: I've got a power supply project I'm working one and am wondering how to fuse the thing. It's going to have three transformers in it. The two main transformers are 28V @ 4.6A and the auxilliary tranformer is 12.6-0-12.6 @ 2A with everything running off of 60Hz. I'm still a little confused about the fuse sizes I'd need because I'm not quite grokking the different types and am not sure what the initial inrush would be at worst case. The two main transformers are going into two seperate supplies with smoothing caps of 15,000uF each but the auxilliary is just going to be powering bog standard linears to power fans, thermal circuitry and displays etc. I want to fuse everything before the transformers and am lost as to what size and type of fusing arrangement to use. I'm also not sure if I need to fuse per transformer or just the line before the split. I'm also wondering if circuit breakers might be a better idea but need some expert opinions on the matter. Could someone with more experience point me in the right direction?

author: AlfBaz
author_rank: Super Contributor
timestamp: February 13, 2014, 12:54:39 pm
content: I'd be inclined to protect each transformer separately for starters. If the device developed a fault that caused two transformers to draw no current and the third had a short the single fuse scenario could conceivably allow 15-20 amps to go where normally the max would be 4.6A or 2A

author: KDC
author_rank: Contributor
timestamp: February 13, 2014, 02:09:38 pm
content: I'd go with fusing them seperatly as well. Going with fuses no more than 25% greater than the rated current is pretty standard with larger transformers.It's possible that a time delay type fuse would also work to handle the inrush with no problems with the rated current.

author: liquibyte
author_rank: Frequent Contributor
timestamp: February 14, 2014, 02:48:31 am
content: I went with 6A x 2 and 2.5A slo-blo and a 3 circuit fuse holder arrangement. I was going to use circuit breakers but I think I'll hold off on that arrangement until I can do some load testing once everything is together. Thanks for your help.
Fusion 360 - layout tricks for repeating circuits - Page 1
Forum section: electronics / beginners

author: Belquay Neust
author_rank: Newbie
timestamp: June 16, 2022, 06:09:19 am
content: Hello dear EEVBlog fans,I'm working with Fusion 360 and I'm curious about tricks with layouting, because now I have schematics with several repeating items (H-bridges) and is it possible to do component placement a little faster or should I clench my teeth and work?Previously I've never worked on Fusion 360, then it might be a stupid question, but better to ask, right?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 16, 2022, 04:13:27 pm
content: I know KiCad has a "Replicate Layout" plugin, which works as follows:1. You do the layout of one sub circuit.2. You place one reference footprint for all the other sub circuits.3. You run the plugin.The plugin takes all the tracks of the first sub circuit, copies them to each other instance and also places all the other footprints relative to the reference footprint of each of the other sub circuits.In your program (Do they not call it "eagle" anymore?) you can probably do something similar:1. Do the layout of one sub-circuit.2. Use some copy operation to copy the tracks to other locations.3. Move and snap (does snap work in that program?) the other footprints to the right locations.
Futaba M402SD10FJ VFD(Display) drawing excessive current. - Page 1
Forum section: electronics / beginners

author: ALearningLad
author_rank: Contributor
timestamp: March 11, 2024, 11:14:30 pm
content: When I apply power to the input pins it will draw 2 amps at 3.3 volts, the datasheet says it should only be drawing 300MA at max. Anyone have any ideas? This is a brand new display that just arrived today, though it did also kill an esp32s flash while being properly hooked up. No dead shorts anywhere that I could find probing around.

author: ALearningLad
author_rank: Contributor
timestamp: March 12, 2024, 01:16:05 am
content: Hah, apparently 3 of the Parallel Input pins are configured to output 5v with how the jumpers are configured... whoops. That explains the esp32, but what about the excessive current draw?
Future proofing - Page 1
Forum section: electronics / beginners

author: Dfinney
author_rank: Newbie
timestamp: October 11, 2018, 12:59:43 am
content: I’m looking for advice on considerations when designing a project that will be maintainable for 10 years. Something with digital and analog I/O and built around a microcontroller and touchscreen HMI. How can one ensure that if a hardware component fails in a couple of years that the project will not have to be redesigned and built from scratch? I notice the some hardware from China could be “retired” after 2 years!

author: PartialDischarge
author_rank: Super Contributor
timestamp: October 11, 2018, 03:28:12 am
content: LT had a no obsolence policy, dont know if AD will keep it that waySlide 6,https://www.slideshare.net/mobile/MichaelSchreiner2/linear-technology-support

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: October 11, 2018, 04:02:52 am
content: Quote from: Dfinney on October 11, 2018, 12:59:43 amShort answer: you can't.When I worked in the Telecom industry, we (my colleagues and I) designed products meant to have a supported life of 30 years. Component choice was always an issue. We would avoid single-source components except in special cases.Even so, End-of-Life buys were common. When a component was about to go out of production, we'd buy enough to last the expected production and service usage. That would often prevent a redesign, but not always - redesigns would still happen due to part obsolescence.In some cases, redesigns would occur before obsolescence became an issue, because the redesign would provide a significant competitive edge (cost reduction + performance improvement).

author: MosherIV
author_rank: Super Contributor
timestamp: October 11, 2018, 06:36:00 am
content: Hi. Welcome to the forum.Pick components for certain industries can help because some industries demand lifetime support.Military or automotive sector demand 30 year lifetime, so the component manufacturers will often sign up to support this, at a price.Automotive is sufficiently high volumn that the component prices are not extortionate so try looking at automotive grade components.
FWH (Firmware Hub) Chip Vs other BIOS Chips - Page 1
Forum section: electronics / beginners

author: 2X
author_rank: Frequent Contributor
timestamp: June 10, 2025, 07:17:11 pm
content: Hi, could anoyone knows1. what is the difference between a FWH (Firmware Hub) chip Vs other BIOS chips?2. what are the advantages (instead of other categories of BIOS chips) and the funtion of it?I read the below links but I can say that I understanded it (especially the advantages in contrast to other categories of BIOS chips).FWHhttps://www.computerhope.com/jargon/f/fwh.htmIntel 810 Chipsethttps://www.anandtech.com/show/299/6LPC Firmware Flash/FirmwareHubhttps://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/DataSheets/01361A.pdf

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: June 11, 2025, 02:51:58 pm
content: Traditional BIOS Chips typically use Parallel EEPROM or SPI Flash. Those are plugged into dedicated BIOS sockets. Firmware Hub (FWH) Chips have features like read/write protection, firmware locking, and potentially encryption. Those are typically found on motherboards with Intel 810/820 chipsets.

author: amyk
author_rank: Super Contributor
timestamp: June 14, 2025, 04:43:09 am
content: FWH was an old attempt by Intel to reduce BOM cost over parallel flash. They eventually settled on SPI flash instead.

author: 2X
author_rank: Frequent Contributor
timestamp: June 14, 2025, 08:21:01 am
content: There is any link where I could read more about this differences/architecture?

author: 2X
author_rank: Frequent Contributor
timestamp: June 14, 2025, 08:29:35 am
content: Quote from: ahsrabrifat on June 11, 2025, 02:51:58 pmIf I understand right... the FWH are bios chips with embeded memory inside instead of traditional BIOS chips where need external Parallel EEPROM or SPI Flash (these memories as I know have features like read/write protection)? So, the result with the FWH chip with the embeded memory is the cost reduction?Also, if you please, what is the difference between read/write protection Vs firmware locking?

author: coromonadalix
author_rank: Super Contributor
timestamp: June 16, 2025, 09:53:05 am
content: what is your goal ?

author: 2X
author_rank: Frequent Contributor
timestamp: June 16, 2025, 10:33:40 am
content: Quote from: coromonadalix on June 16, 2025, 09:53:05 amI repaired a motherboard with a corrupt bios where have the FWH chip and I would like to learn more about them (if I know how they work it would be easier to check the faulty motherboards).

author: amyk
author_rank: Super Contributor
timestamp: June 19, 2025, 02:07:47 am
content: You can read the datasheet for that, but it's just another interface that's been used for EEPROM.It's like asking what's the difference between I2C and SPI flash.
FX-888D @230V 50Hz - Page 1
Forum section: electronics / beginners

author: Kantilo
author_rank: Contributor
timestamp: June 28, 2021, 01:37:06 pm
content: Hello, what are the risks of using the FX-888D at 50 Hz? Thank you

author: Zero999
author_rank: Super Contributor
timestamp: June 28, 2021, 04:26:51 pm
content: Presumably if it's run at the correct voltage, there are no risks at all. I have an American model running off a 120VAC transformer and it works perfectly at 50Hz. In theory, there might be a tiny bit of extra heating in the transfrmer, but I haven't noticed it.

author: RayRay
author_rank: Frequent Contributor
timestamp: June 28, 2021, 08:41:58 pm
content: According to the answer above, it should work fine, but it does boils down to the specifics of the situation really. Have you already purchased it, or asking to know in advance? FYI, Amazon UK sells the 230V version:https://www.amazon.co.uk/HAKKO-FX-888D-Soldering-Station-70W/dp/B08VBHY78F/ref=sr_1_1_sspa?dchild=1&keywords=888d&qid=1618010990And the "6 tip set" is in stock. You could easily replace the plug with your local one too. But if you've already purchased it, it's another story of course. The question is, do you already have a 120V>230V step up transformer with suffcient power to handle it, or not? If you do, you could prob use it, but if you don't, then I'd say opting to replace the 888D's internal transformer would be the better than purchasing a step up transformer. Also, keep in mind there are more affordable (T12) stations out there, so if you haven't purchased anything yet, that's another thing to consider.

author: Kantilo
author_rank: Contributor
timestamp: June 28, 2021, 10:03:23 pm
content: Thanks for your answers, I live in Europe so I bought this version :https://www.batterfly.com/shop/en/hakko_fx-888dBut in the description they did not indicate the frequency

author: RayRay
author_rank: Frequent Contributor
timestamp: June 28, 2021, 10:18:38 pm
content: Quote from: Kantilo on June 28, 2021, 10:03:23 pmWell, I've never heard of a 220-240V device that operates at 60hz, so I don't think you have anything to worry about.But if you've already gotten it, just check the sticker on the underside of the station (it should state the hz on it).

author: Zero999
author_rank: Super Contributor
timestamp: June 29, 2021, 07:36:27 am
content: Quote from: RayRay on June 28, 2021, 10:18:38 pmA few countries use 220V 60Hz according to Wikipedia, but it will be most likely designed for 50Hz.https://en.wikipedia.org/wiki/Mains_electricity_by_country#Table_of_mains_voltages,_frequencies,_and_plugsEven if it is designed for 60Hz, it will be the situation will be the same as my 120V 60Hz model working at 50Hz.