hybridfree/eevblog-posts huggingface dataset:
the so called "ac" in bjt's? - Page 1
Forum section: electronics / beginners

author: questron
author_rank: Regular Contributor
timestamp: November 01, 2016, 10:38:43 am
content: when bjt biasing, linear active region, the different bjt models, and what not about bjt's are talked about, the term "ac" is always used, such as "ac" signals, and "ac analysis". but, when i look close, there is nowhere in a bjt i could find "ac" currents, currents that actually reverse directions that is, thus a question: are bjt's a kind of devices that are only capable of "dc", and therefore not responsible for real ac currents in output signals at all?the terms "ac" and "dc" become fuzzy here. i like the terms evb149 used in his posts better, "varying unipolar dc current" and "bipolar ac current", (rehttps://www.eevblog.com/forum/beginners/video-by-request-bjt-amplifier-topologies/).evb149:thank you for the confirmation! that's what i need to be sure about it. it is also most interesting when you mentioned "... and you capacitively couple that voltage then you can end up with bipolar AC since the capacitor will not pass DC, only the AC component." now i realize that it is the capacitor that switches a varying unipolar dc current in a bjt into a bipolar ac current for the next stage, since if current does not reverse directions, voltage across the capacitor cannot change. it is the capacitor that gives rise to ac currents, not the bjt. this is great, thanks a lot for the help!T3sl4co1l:"The absolute, instantaneous current can be reverse, but this would be under somewhat unusual circumstances, involving fast signals and junction capacitances, or voltages very different from those indicated." thank you T3sl4co1l, this is most interesting as well! i can sort of relate to it when fast signals and junction capacitance are involved, and would like to find out more about it. is there a research topic as such? i searched for "bjt ac current", and only found "bjt ac ananlysis" which does not involve bipolar ac currents in bjt's at all. would this - "instantaneous current can be reverse" - phenomenon be an annoyance to circuit design, or does it actually have some useful applications?

author: Ratch
author_rank: Regular Contributor
timestamp: November 01, 2016, 10:32:31 pm
content: Quote from: questron on November 01, 2016, 10:38:43 amAC simply means "alternating cycle" and DC means "defined constant". Currents in a BJT don't reverse, but they can vary between cutoff and saturation, and can mimic any waveform within the frequency range of the BJT.Ratch
The sound of failing caps - Page 1
Forum section: electronics / beginners

author: cincin
author_rank: Regular Contributor
timestamp: October 23, 2021, 05:02:13 pm
content: Greetings!I *once* got rid of an oscillating hiss on an old amp, simply by recapping it.I just got a 2001 Novation K-Station synth, and it has a mild oscillating hiss to it. Not objectionable, yet, but very noticeable, borderline "could be normal" levels.Would I likely be on the right track to assume that this cyclical hiss is a pretty good sign of failing cap(s)? (In my experience I'd say yes, but I have almost no experience so I thought I'd reach out.)And if so, is the cyclical nature of the hiss literally the sound of a cap charging and discharging, or discharging unevenly?Cheers!

author: Jwillis
author_rank: Super Contributor
timestamp: October 23, 2021, 06:04:13 pm
content: Ticks , pops and hissing could be a result of failing caps but not always . Although electrolytics are more likely to fail than film or ceramics , arbitrarily changing capacitors isn't always the solution . Mechanical pots and switches that are getting worn out can also cause the same issues . Misplaced , loose or corroded grounds can also lead to all sorts of issues .
The ungrounded grounding strap? - Page 1
Forum section: electronics / beginners

author: ledtester
author_rank: Super Contributor
timestamp: August 24, 2021, 01:16:12 am
content: Is this use of a grounding strap offering any protection?At the 5 minute mark in this video for about 30 seconds:How To Adjust The Action on Your Chromebook Trackpad - Chrome Unboxedhttps://youtu.be/JVJLgsCsht8?t=5mand earlier at the 1:40 mark he suggests you can just connect the strap to "something metal".The laptop is unplugged.

author: John B
author_rank: Frequent Contributor
timestamp: August 24, 2021, 01:28:39 am
content: Doesn't seem too crazy. You want your body to be at the same potential as the ground potential of the laptop. Your body should then have some conductivity to mains earth ground and so the laptop should equalise to that as well.
The Vacuum Transistor  - Page 1
Forum section: electronics / beginners

author: W8LV
author_rank: Regular Contributor
timestamp: January 17, 2015, 02:44:41 am
content: Much like when the invention of the first transistor was initially underreported, here is (I think) the most missed story of (now) last year: The invention of the Vacuum Transistor, a new high speed device!http://spectrum.ieee.org/semiconductors/devices/introducing-the-vacuum-transistor-a-device-made-of-nothing

author: JoeN
author_rank: Frequent Contributor
timestamp: January 17, 2015, 04:04:06 am
content: Good, because I am getting sick and tired of the gigahertz bullshit. Terahertz or bust!

author: hamster_nz
author_rank: Super Contributor
timestamp: January 17, 2015, 05:27:09 am
content: Great article. The best thing I have read in a long while!

author: coppice
author_rank: Super Contributor
timestamp: January 17, 2015, 02:23:58 pm
content: They don't really explain what makes their work different from similar research in the 1980s, which never seem to go anywhere beyond cool demo devices.
The wired AND connection question - Page 1
Forum section: electronics / beginners

author: Lucky-Luka
author_rank: Unknown
timestamp: October 03, 2020, 06:08:57 pm
content: Hi allreading at the wikipedia description I haven't understood how it's possible it works out.Can anybody explain it to me?Cheers

author: Gyro
author_rank: Super Contributor
timestamp: October 03, 2020, 06:18:04 pm
content: You need the understand that both A and B need to be pulled low as a starting point. If either one or the other is taken high, the other input holds the output low via its diode. Only when both inputs are allowed to go high will the output also go high due to the pullup resistor.

author: Benta
author_rank: Super Contributor
timestamp: October 03, 2020, 06:26:20 pm
content: That Wikipedia article should be taken out and shot.Consider the AND boolean equations:A B C0 0 = 00 1 = 01 0 = 01 1 = 1The pull up resistor will make C=1 if A and B are unconnected.Connecting either A or B to 0 will make C=0.This works for open collector or open drain outputs as well.

author: IanB
author_rank: Super Contributor
timestamp: October 03, 2020, 06:35:28 pm
content: Quote from: Lucky-Luka on October 03, 2020, 06:08:57 pmIn a 5 V logic system let True be represented by ~5 V and False by ~0 V.Then if both A and B are at 5 V, C will be at 5 V. Therefore True AND True => True.If either of A or B are at 0 V, then C will be at ~0 V. Therefore True AND False => False, False AND False => False.This is the required truth table of the AND function, therefore the circuit does what is desired.

author: atmfjstc
author_rank: Regular Contributor
timestamp: October 03, 2020, 06:44:41 pm
content: Don't feel bad, the description on Wikipedia is indeed extremely strange, particularly the second paragraph. It sounds like it was poorly translated from some other language and nobody checked the article for accuracy.

author: Ian.M
author_rank: Super Contributor
timestamp: October 03, 2020, 06:47:36 pm
content: However to add to the confusion, that arrangement, when implemented as open collector/drain logic outputs wired in parallel, is most usually called a 'wired OR'. Technically its performing an AND function if logic '1' is a high level as is the usual convention for TTL and CMOS logic, but signals from ICs with open collector/drain outputs are usually active low, enabling any single output to assert the active level, i.e. an OR function for the active level.

author: Lucky-Luka
author_rank: Unknown
timestamp: October 03, 2020, 07:22:50 pm
content: What is the function of the diode in this circuit?

author: Gyro
author_rank: Super Contributor
timestamp: October 03, 2020, 07:24:57 pm
content: Quote from: Lucky-Luka on October 03, 2020, 07:22:50 pmTo isolate the inputs from each other, otherwise they wouldn't be able to pull the output low individually.

author: Lucky-Luka
author_rank: Unknown
timestamp: October 03, 2020, 08:11:08 pm
content: I've understood.Thank you all.
The worse condition calculation and How to read the datasheet - Page 1
Forum section: electronics / beginners

author: rxxbxyhxxb
author_rank: Contributor
timestamp: May 31, 2014, 08:41:32 am
content: Hi,I always confused something about the worse condition calculation and how to get the useful content from datasheet.The textbooks mentioned them scarcely.So, even with such a simple circuit, I always confuse how to select the values of component exactly.I try do it as following.Assuming VCC is 4.75 – 5.25, Ta is -15-85 degC, and don’t consider CTR attenuate with time.According to the spec. curve. ICEO(MAX) is 50uA4.75V – ICEO(MAX)*(R2*1.05) > 2.0V|VIH(MIN)=> R2 < 52kOhm5.25V –IC(MIN) *(R2*0.95) < 0.8V| VIL(MAX)Assuming IC(MIN) = 1mA=> R2 > 4.7kOhmHere selected the value of R2 is 5.1KAccording to the spec. curve.CTR(MIN)@VCE=5V = 50% * 0.8 = 40%According to the spec. curve.IF(MIN) >3.2mA (32% * 3.2mA ~=1mA)According to the spec. curve.VF range is 0.7-1.43VIF(MIN) < (24V – VF(MAX))/(R1*1.05)R1 < 6.7kOhm=>So selected R1 is 6.2kOhm.I have no idea about it is right whether or not.Would you mind helping me to review it?Further,I really want to know how can get the exactly design.I think I get the limit value from the datasheet has some problem.How to get the useful, exactly limit value from the datasheet which the company don’t provide.For some similar parts, the subtle differences of parameters always make me a headache.Two company always provide the parameters at a different test condition I can not compare them directly.Thanks.

author: rxxbxyhxxb
author_rank: Contributor
timestamp: June 01, 2014, 08:01:45 am
content: Who would like to talk about this topic?I usually see people shift the curve as this to obtain the limit value.But I don't know what the basis is.
Theory behind Bode and Nyquist stability criteria - Page 1
Forum section: electronics / beginners

author: mike buba
author_rank: Contributor
timestamp: November 17, 2013, 03:27:37 pm
content: Is there any theoretical or mathematical proof behind Bode and Nyquist stability criteria?Are there any reference materials on this topic?

author: Kremmen
author_rank: Super Contributor
timestamp: November 17, 2013, 03:55:09 pm
content: Oh indeed there is. There is also literally tons of reference material.I recently stumbled on a nice site of Nyquist. I'll try to find it again and post a link.
There are two oscillograms and two respective FFT plots of wide known IC... - Page 1
Forum section: electronics / beginners

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 16, 2019, 08:14:00 am
content: Hello everyone,There are two oscillograms and two respective FFT plots of wide known IC.https://datasheets.maximintegrated.com/en/ds/MAX1487-MAX491.pdfpage 11.Where,-Left, the signal shape looks good, however FFT plot is quite dirty.-Right, the signal shape looks worse, however FFT plot is clearer.To me that looks like they confused FFTs or so. Didn't they?What do you think about?thank you

author: palpurul
author_rank: Regular Contributor
timestamp: May 16, 2019, 08:23:02 am
content: That's what you'd expect.When the edges are shaper (faster rise/fall time), you got more freuqunecy content in your signal. As the edges slows down (slower rise/fall time), you expect frequency content to be less.That's why the one on the left looks more "dirtier" than the one on the right because it's got more frequency content (sharper edges).

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 16, 2019, 08:31:12 am
content: Quote from: palpurul on May 16, 2019, 08:23:02 amSo, why do they provide that? To show that ICs that belong to the left are better? Or?

author: palpurul
author_rank: Regular Contributor
timestamp: May 16, 2019, 08:48:53 am
content: Quote from: CiscERsang on May 16, 2019, 08:31:12 amDifferent models have different rise/fall time characteristics I think that's why they include two different FFT plots for different models of the trancievers.Faster rise time doesn't neccesarily mean better, it all depends on your requirements. If your application can tolerate slower rise time you should choose the ones with slower rise time because they radiate less and high frequency stuff is less relevant, making the design less complicated.

author: dzseki
author_rank: Frequent Contributor
timestamp: May 16, 2019, 08:49:18 am
content: the two ICs are for different purpose, as stated in the datasheet the MAX483 is slew rate limited, that is if you don’t need fast communication will not emitt much electronic noise (through the wires) as it has its spectra limited like the FFT diagram shows. MAX485 on the other hand will handle faster bitrate, but this is only possible with using faster edge transitions which may be emitted to the surrounding circuits. It is the designer’s duty to select which one suits the application more.

author: CiscERsang
author_rank: Regular Contributor
timestamp: May 16, 2019, 09:10:32 am
content: Ok, I've got that. Thanks to all.
Thermal Adhesive. lost in translation/terminology - Page 1
Forum section: electronics / beginners

author: manzini
author_rank: Regular Contributor
timestamp: March 14, 2014, 02:30:44 pm
content: HelloI am not english speaker, only google-translate-typing-expert and I am seeking any afordable "thermal adhesive" for some ic's and heatsinks on EU mouser/farnell.Artic thermal adhesive, it's a clear name but the rest..... Thermal pad also... but foundThermal compound ? thermal grease ? by example, it's "compound" an adhesive ? lost in translateAny product advise for gluing heatsinks in some IC's like xilink, infineon and possibly on some raspberry / BEAGLEBONE arm cpu?thanks in advance

author: Rigby
author_rank: Super Contributor
timestamp: March 14, 2014, 02:32:49 pm
content: http://www.adafruit.com/products/1468

author: Holograph
author_rank: Regular Contributor
timestamp: March 14, 2014, 02:52:08 pm
content: You can use a TIM (thermal interface material) / "thermal tape" as linked if you want and they are electrical insulators which is useful sometimes, but they also conduct less heat than thermal compound and thermal adhesive (AKA thermal epoxy). They can be good enough in many cases. They generally do not stick THAT well so I wouldn't suggest relying on it to keep your heatsinks stuck to your ICs, unless your heatsinks are very small and you won't be shipping it.Thermal "compound" is generally NOT considered the adhesive type. Compound would generally refer to something more basic like Arctic Silver 5, Arctic Cooling MX-2/3/4, IC Diamond, etc. It will be a little bit tacky but won't be useful as an adhesive whatsoever. It can't be trusted to insulate electrically because when you screw down your chip/heatsink, the layer will become very thin and will probably partially insulate, but not enough. If you need electrical isolation with thermal compound, there are some special insulators you can get (some of them are made from mylar, but not all mylar works for this) that will do that - but then they will lower the conductivity anyway.Thermal adhesive / thermal epoxy is basically epoxy with thermal compound in it so it both sticks and conducts heat (generally better than the TIMs). It takes some time to cure and you're unlikely to be able to remove the heatsink from the chip without damaging the chip. It also cannot be counted on to insulate electrically. Note that Arctic Silver also offers a thermal epoxy (as do many other manufacturers of regular thermal compound) - make sure not to confuse the two. I will also note that you shouldn't really rely on thermal epoxy to keep your heatsink on in some cases either. It will stick better than the TIMs but if it's not bolted down, it can rip your chip right off the board if subjected to mechanical shock (e.g. if you ship it). Depending on the size of your heatsink, the size of the chip and how well it's soldered to the board, and some other factors, it may or may not be acceptable.

author: manzini
author_rank: Regular Contributor
timestamp: March 20, 2014, 01:44:39 am
content: Rigby, Holograph. Thanks a lot !!
/\/\ thermal calculations problem (solved) - Page 1
Forum section: electronics / beginners

author: 3roomlab
author_rank: Frequent Contributor
timestamp: November 22, 2014, 01:06:52 am
content: hi folks, so i have been mucking around components/PCB thermal thingies ...say this situation :junction --> plastic case --> ambientif ambient is 30oCif R-ja = 50oC/wand the plastic case measures in at 50oCto get to actual T-junction, we find the watts going thru the plastic case( = 20/50 = 0.4watts)and the junction temp is = (0.4 x Rja) + Tcase ? = 70oCam i right? i have the feeling that i am missing something ...does R-ja actually means the resistance going thru the plastic package? or the entire item ?

author: kxenos
author_rank: Frequent Contributor
timestamp: November 22, 2014, 01:19:42 am
content: Rja is specified as the path of least resistance. If there is a tab in the chip then it's the resistance from junction to that tab. Else it's from junction to case

author: 3roomlab
author_rank: Frequent Contributor
timestamp: November 22, 2014, 01:32:05 am
content: yes it is, so the tab itself R-jc and the R-ja are infact parrallel "resistors" am i right? they both do dissipate simultaneously once there is a higher heat potential generated at junction?

author: kxenos
author_rank: Frequent Contributor
timestamp: November 22, 2014, 02:02:11 am
content: No, they're not parallel because you can either have the hole case area to dissipate heat to ambient so you use Rja or you have a heatsink so you use Rjc but not both at the same time.You could write that Pd = (Tj - Tc) / RjcAnd also that Tj = (Pd x Rja) + TaTherefore Tj = ((Ta x Rjc) - (Tc x Rja)) / (Rjc - Rja)But I don't know if this is valid or not because Rjc and Rja are used in different use cases aka with and without heatsink respectively.

author: IanB
author_rank: Super Contributor
timestamp: November 22, 2014, 02:15:35 am
content: Quote from: 3roomlab on November 22, 2014, 01:06:52 amYou don't really have enough information to say anything here.Rja is from junction to ambient (from junction to surrounding air). It says nothing about the case temperature, so any measurement of the case temperature must be thrown away. Now you are left with the air temperature alone. With only the air temperature you can say nothing at all about the junction temperature. It remains a complete unknown.On the other hand, suppose you also know the power dissipated by the silicon (= voltage drop x current), then you have two pieces of information, and now you can do a calculation. You have:Power = (Junction temperature - Ambient temperature) / RjaTherefore:Junction temperature = (Power x Rja) + Ambient temperatureAny time you have one equation in four unknowns you need to specify three of the unknowns in order to calculate the fourth.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: November 22, 2014, 04:30:12 am
content: ok i get it now thanks heaps
Thermal Calculations - Page 1
Forum section: electronics / beginners

author: ElectricGuy
author_rank: Regular Contributor
timestamp: October 12, 2014, 01:28:29 am
content: Hi all;I'm trying to calculate a thermal caracterisic of a regulator.Since i will not use dissipator, the formula is;Tj = Ta + (Rja x PD )orTj = Ta + (Rja x PD ) + (Rjc x PD )I look at google, but i allready see the 2 formulas, so i don't know each on should i use.

author: bobcat
author_rank: Regular Contributor
timestamp: October 12, 2014, 11:05:27 am
content: The first formula is for a free standing device like a TO-220 without a heatsink.The second formula is for a device that in addition to dissipation into free air, it also uses another heatsink, such as a pc board.

author: kxenos
author_rank: Frequent Contributor
timestamp: October 12, 2014, 11:43:33 am
content: I think the second formula is wrong.You either leave the device free standing in which case you need the R(junction-ambient) or you're fixing the device on a heatsink in which case you need the R(junction-case), the R(case-heatsink) and the R(heatsink-ambient).

author: KerryW
author_rank: Regular Contributor
timestamp: October 12, 2014, 12:28:35 pm
content: You are right, kxenos, the 2nd formula IS wrong.Rja = Rjc + Rcs + RsaThe spec sheet should give values for Rjc and Rja. The Rja value assumes no added heat sink, so the case IS the heat sink, and Rja = Rjc + Rcajc - junction to caseja - junction to ambientca - case to ambientcs - case to sinksa - sink to ambientSo for a TO220 regulator that specifies 3 d/w Rjc and 75 d/w Rja, without a heat sink, 1 Watt would generate a 75 degree rise above ambient. With a 5.5 d/w heat sink, you would have3 d/w Rjc.5 d/w Rcs (approximately)5.5 d/w Rca9 d/w Rja, for a 9 degree rise at 1 Watt.

author: ElectricGuy
author_rank: Regular Contributor
timestamp: October 12, 2014, 11:47:41 pm
content: Thank you all;Like i said before, i will not use heatsink, so Tj = Ta + (Rja x PD ).Thank you once again!
Thermal camera on Labview  - Page 1
Forum section: electronics / beginners

author: DanielPulg
author_rank: Newbie
timestamp: October 25, 2024, 11:46:20 am
content: I have a project to take video in labview of what the Infiray P2 PRO camera records and with the mouse pointer take out the temperature values,as well as the maximum temperature in a box. But the camera does not measure my temperature, it measures the light intensity.I would like you to measure the temperature. I have tried to find a mapping of light intensity to camera temperature but I have not found any solution.I leave the file here so you can help me.Thank you so much
Thermal camera - UTI260A or UTI260B - Page 1
Forum section: electronics / beginners

author: Denkarn
author_rank: Newbie
timestamp: December 29, 2022, 03:12:12 pm
content: Hello,I wanted to buy a thermal camera especially to detect short circuitsI spotted the UTI-260A and the UTI-260BI can't find the differences between the two, only the maximum temperature which is 400°C and 500°CWhich one do you recommend me? Is it useful to take the 260B which is more expensive for this use?Thank you

author: teddychn
author_rank: Regular Contributor
timestamp: January 02, 2023, 08:00:48 am
content: Just received my UTI260A and it works as expected. The only differences I know was UTI260A lack digital camera and has lower measuring range of 400°C. And the sensitivity of both seemed 50mK. But somewhere shows 60mK for the 260B.Obviously, having digital camera and larger measuring range are the pros of UTI260B. But I chose the 260A for saving money because I always prefer the thermal mode rather than the fusion mode, and maybe simpler could be better.The weird thing is that I can't find any information of UTI260A on UNI-T's official site. And UNI-T seems always has some similar models confusing customers. For now, I just can find a UTI720A which seems having the same specifications as the 260A. But the 720A hasn't been available on Taobao or AliExpress yet.BTW, the firmware version of the 260B was kind of 1.2.6 and my 260A shows 1.0.20.I have no confidence venturing too much money on it because we have a bad experience on Flir E4 which constantly having problems after it's use of 1~2 years. And UTI260B seem having some situations here as well. If the UTI260 can work as it in the future, it definitely worth the money.
Thermal Conductivity - Page 1
Forum section: electronics / beginners

author: ziggyfish
author_rank: Regular Contributor
timestamp: October 29, 2017, 12:41:41 am
content: Simple question, I can't seem to find the answer to.I know with heatsinks, the higher the thermal resistance, the less heat gets dissipated from the component.Am I right in thinking, that the higher the thermal conductivity, the more heat that gets transferred from the component to the heat sink Thermally conductive material?I.e With thermal conductivity, more is better. 0.8 W/(m.K) > 0.682 W/(m.K)ThanksBrendan

author: Brumby
author_rank: Unknown
timestamp: October 29, 2017, 06:41:51 am
content: Thermal resistance is the inverse of thermal conductivity ... and vice versa.Quote from: ziggyfish on October 29, 2017, 12:41:41 amDave has done a video that might be helpful....

author: IanB
author_rank: Super Contributor
timestamp: October 29, 2017, 06:58:36 am
content: Quote from: ziggyfish on October 29, 2017, 12:41:41 amThere are two separate concepts that are important to know. One is thermal conductivity, the other is the heat transfer coefficient.Thermal conductivity relates to heat transfer through the interior of a material. As such it is analogous to electrical conductivity.Heat transfer coefficients relate to heat transfer across the boundary between materials, for example between the surface of the component and the heat sink, or between the surface of the heat sink and the free air around it. An electrical analog might be an oxide layer on the surface of a contact.Often the heat transfer coefficient is the more limiting factor. Even if the heat sink material has a high thermal conductivity (like aluminium or copper), this is all for nothing if the heat cannot escape the surface of the heat sink into the surrounding air. Heat transfer is promoted by large surface area, fins, and forced air currents (fans).For basic design purposes all the resistances to heat flow tend to get combined into an effective system resistance, which is why you don't tend to see heat transfer coefficients mentioned in datasheets. But these details are known to the engineers who design heat sinks.

author: Ice-Tea
author_rank: Super Contributor
timestamp: October 29, 2017, 12:37:03 pm
content: Most important thing: the amount of heat stats the same, no matter the heatsink. In electricity terms, it's a constant current source (heatflow), not a constant voltage source (temperature).
Thermal Design Doubt - Page 1
Forum section: electronics / beginners

author: IuriC
author_rank: Contributor
timestamp: May 23, 2014, 02:04:53 pm
content: Hi everyone.I got stuck in a doubt about thermal design and I need a little help.My system will use a TRIAC, the BTA16-600BRG. Datasheet:http://www.st.com/web/en/resource/technical/document/datasheet/CD00002265.pdfThe current flowing is about 2A RMS, giving aproximately 2W of power dissipation in the device.The doubt is the following: Can I use a cooper board area as a heat sink for this device or I need a "real" heat sink? How would be the size of this area (mm²)?Thank you in advance.

author: KerryW
author_rank: Regular Contributor
timestamp: May 23, 2014, 03:51:29 pm
content: I looked in to this recently (for a motor driver), and got conflicting information. The data sheets sometimes give a suggested area, but that is usually for a top layer pad thermally connected to an infinite internal ground plane.The best data I could find for a top layer single sided heat sink was 1000/cm^2. Using that, and going for 75 C rise, you would need 26.67 square cm. About 2" x 2".I have not yet been able to test my board under full load, so I can't say how reliable this information is.

author: tszaboo
author_rank: Super Contributor
timestamp: May 23, 2014, 04:47:40 pm
content: Yes you can. Take a look at figure 11 in the datasheet. With about a 3x3cm PCB area, you have 30K/W thermal resistance, for 2W that is 60K. Even with 60 degrees ambient, you are still below the 125 degrees junction. So lower ambient and or bigger copper area should be fine.

author: IuriC
author_rank: Contributor
timestamp: May 23, 2014, 05:15:38 pm
content: The BTA16 is on TO-220 package, and this graph is for D²PAK

author: tszaboo
author_rank: Super Contributor
timestamp: May 23, 2014, 05:37:48 pm
content: Quote from: IuriC on May 23, 2014, 05:15:38 pmOk, that is true.If you want to use the PCB as heatsink, why arent you using the package which was designed to be used that way? The only reason to use the TO220 is to have a heatsink (or because you are stuck with it). If you have a TO220 than the only way to use it with the copper if you bend the leads and you surface mount it, in wich case it will act more-less than a D2PACK.

author: max_torque
author_rank: Super Contributor
timestamp: May 23, 2014, 06:25:52 pm
content: Assuming you are going to use the SMC Dpak, then if i had any doubt, i'd include the footprint for a suitable heatsink too!Even if you don't end up using it, it will help negate the need to re-spin the pcb.... ;-)I use these neat little ones:Because they stand over the package they hardly take up any extra real-estate, and need no mounting holes etc

author: IuriC
author_rank: Contributor
timestamp: May 23, 2014, 06:39:38 pm
content: As you guessed, I'm stuck with the TO-220 one.I was afraid of getting great difference bettwen D²PAK and the TO-220 bended and mounted in a copper area. I guess that the only way to figure it out is experimenting and taking some measurements.Thank you all.
Thermal fuse: what are the most commonly used? - Page 1
Forum section: electronics / beginners

author: lisafig
author_rank: Contributor
timestamp: December 30, 2018, 08:35:49 pm
content: This question goes with the "From no parts to decent stockpile, best approach?"{1}and "which electronics components should i always have on hand"{2}.Which thermal fuse do you use the most?Are some more commonly used than others? (In classic household appliance such as power supplies, chargers, battery packs, in electric fans, hair dryers…). (I'm aware that the best fuse is the one recommended...)Are there some "joker", that could fit in many situations, even temporary (the time to get the right one)?optional: in Europe is there a way to buy a 0.5€ component with fast shipping (7 days max), without paying 10-20 times the item in shipping fees?{1}https://www.eevblog.com/forum/beginners/from-no-parts-to-decent-stockpile-best-approach/175{2}https://electronics.stackexchange.com/questions/966/which-electronics-components-should-i-always-have-on-hand

author: soldar
author_rank: Super Contributor
timestamp: December 30, 2018, 08:53:33 pm
content: What are you using it for? Whay is it so urgent?https://www.ebay.com/itm/152871442415

author: floobydust
author_rank: Super Contributor
timestamp: December 30, 2018, 09:58:47 pm
content: I don't recommend "one fits all".The fuse trip-temperature is unique to each appliance. It depends when things will melt.A kettle, hairdryer, charger all have different temperatures for when things are dangerous.If you are going to do repairs, then spend $15 to have stock for a 100-piece kit on eBay.

author: Brumby
author_rank: Unknown
timestamp: December 31, 2018, 01:44:43 am
content: Quote from: floobydust on December 30, 2018, 09:58:47 pmThis: ^ ^ ^Don't go penny pinching when it comes to safety devices. A mismatched substitute can cause problems from nuisance failure if its underrated - and you'll be replacing the thing again ... and again - to allowing dangerous overload if its rated too high, where you could cook something more expensive ... like your house.
thermal fuse/protection IC with external thermistor? - Page 1
Forum section: electronics / beginners

author: Max2018
author_rank: Newbie
timestamp: July 26, 2022, 09:07:46 am
content: DELETED

author: Zero999
author_rank: Super Contributor
timestamp: July 26, 2022, 08:52:12 pm
content: Quote from: Max2018 on July 26, 2022, 09:07:46 amAn SCR can be used to blow a fuse.What's the IC?There might be a better way to do this. Is it possible it's being run too close to its absolute maximum rating?

author: langwadt
author_rank: Super Contributor
timestamp: July 27, 2022, 01:00:00 pm
content: Quote from: Max2018 on July 27, 2022, 12:08:49 pmwhich one?

author: Infraviolet
author_rank: Super Contributor
timestamp: July 30, 2022, 12:27:19 am
content: Are such IC fires a likely event? Could they be controleld by just putting the system overal in a well sealed airtight metal box to prevent any oxygen ingress which could fuel flames if they began? PCB materials (FR4) are supposed to be non-combustible anyway. The intention I assume, here, is not to save the chip, if it catches fire it is surely ruined already, but just to prevent fire spreading?
Thermal Pad for NVMe SSD - Page 1
Forum section: electronics / beginners

author: Hobby73
author_rank: Regular Contributor
timestamp: January 28, 2025, 07:47:49 pm
content: As you know, NVMe SSD's run hotter than other drives. The board contains the controller and the memory chips. I want to apply thermal protection to my SSD boards and have the following questions (as I tend to overthink everything):1) Should a pad be placed on both sides of the board, or only the outward facing side?2) Should a pad be placed along the entire length of the board, or only on the controller?3) Does a pad provide any thermal dissapation benefits when used alone, or is it only effective as a conduit between the board and a metal heat sink?

author: benj38
author_rank: Frequent Contributor
timestamp: January 30, 2025, 09:46:13 pm
content: Commercial heat-sinks for NVMe SSD's usually have pads on both sides of the board along the whole board. However, this may be because they are meant to be universal, i.e., fit many different SSD's.Basically, you just need the pad and heat-sink to cover the chips that get hot, which can be easily checked with a fingerThe thermal pad on its own does nothing to cool the chips. It is there to displace the air between the not-perfectly-flat surfaces of the chips and the metal heat-sink.

author: thm_w
author_rank: Super Contributor
timestamp: January 30, 2025, 11:12:46 pm
content: You can just get a kit on aliexpress:https://www.aliexpress.com/item/1005006585079345.htmlI don't know if this specific one will fit in all motherboards though.
Thermal Resistance - Page 1
Forum section: electronics / beginners

author: jose347
author_rank: Contributor
timestamp: October 11, 2018, 08:51:25 pm
content: thermal resistance (oC/W) how does it works?for the junction to case which will be better a higher value or a lower value?Thanks

author: RoGeorge
author_rank: Super Contributor
timestamp: October 11, 2018, 09:09:03 pm
content: Thermal resistance will tell how much the internal temperature of the transistor increases for each watt.Example: a transistor with R = 10*C/W, at 5W will raise the internal temperature with 50*C. If in the room are 30*C, the internal temperature of the transistor will be 30 + 50 = 80*C. For the same transistor but at 15W, the total temperature will be 30 + 150 = 180*C (=356*F). This will probably melt the transistor and destroy it.A lower value for the thermal resistance is better for the transistor.

author: Brumby
author_rank: Unknown
timestamp: October 12, 2018, 10:51:06 am
content: It's an older video of Dave's, but the principles have not changed...You basically take the ambient air temperature, work out ALL the thermal resistance components from the air to the working zone of the component (the silicon die for ICs, transistors and the like) and add them up. With this figure and the power your component is dissipating, you can work out the temperature that the die will get to when it is working at that power level. You then look this temperature up in the component's datasheet and see if it will survive.Understand that youmustkeep it under the maximum temperature, but getting that temperature down further will increase the reliability - and the life - of that component.

author: jose347
author_rank: Contributor
timestamp: October 15, 2018, 06:19:51 pm
content: Thanks All
Thermal testing of TO-220 package breadboard v pcb - Page 1
Forum section: electronics / beginners

author: bobbydazzler
author_rank: Regular Contributor
timestamp: March 03, 2021, 09:41:20 am
content: I did some thermal testing of a 7806cv voltage regulator earlier on a breadboard and soldered to a pcb and the results are as follows.Input = 12v DC7806cv breadboard = 0.24A 1.44w7806cv pcb + tinned copper "heatpipe" = 0.45A 2.7wThese readings were taken while thermal throttling the voltage regulators on purpose with a 10ohm dummy load. For the pcb test I heavily tinned the leads and the metal tab of the TO-220 package and also soldered 22awg tinned copper wire to the leads/metal tab to help heat transfer from the regulator. I was very impressed by how much extra headroom the 22awg wire added, and I didn't really go crazy with it I think more/heavier gauge wire would make a bigger difference.
Thermal transfer for a TO-92 - Page 1
Forum section: electronics / beginners

author: abit
author_rank: Contributor
timestamp: May 02, 2015, 01:04:25 am
content: If I solder it in-place with the leads bent so that the flat face of the IC is in contact with an exposed pad to the ground-plane - is this going to provide significant heat relief? How should I make this reliable or better, with some thermal compound, or this is not a good solution or not worth the effort? Lets assume the IC might going to run hot for a short while only, or switching, and in case it might not have thermal shutdown built-in as most transistors do not. Should I design a PCB with this option in mind?Update:Thanks, I suspected this, not worth the effort designing a PCB that way..

author: radioFlash
author_rank: Regular Contributor
timestamp: May 02, 2015, 01:19:33 am
content: To get good thermal transfer, you need to have some pressure applied, and bending the leads won't provide much force and won't be reliable, and TO-92s have a very large thermal resistance anywy, so you won't gain much. There are TO-92 heatsinks, but I don't think they're worth it. If you're concerned about heat, consider a TO-220 or other package.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 02, 2015, 01:33:09 am
content: As long as you have something filling the gap (you don't really need clamping pressure, but without it, the gap can creep open is the thing), you can get slightly better, but the plastic stinks for conduction, so it's not going to be much.If you can do SMT, SOT-89 or 223 will be much better, up to a watt or two.Tim

author: jay
author_rank: Regular Contributor
timestamp: May 02, 2015, 02:44:42 pm
content: Thermal adhesive might do the trick.

author: digsys
author_rank: Unknown
timestamp: May 02, 2015, 02:52:51 pm
content: Quote from: jayArctic cement / Arctic silver will give you the best thermal dissapation, but as others have said, the package isn't designed to get rid of heat.

author: abit
author_rank: Contributor
timestamp: May 09, 2015, 03:03:33 am
content: "Arctic cement / Arctic silver"Thanks, I never hear of these, thanks!

author: Gyro
author_rank: Super Contributor
timestamp: May 09, 2015, 10:23:57 am
content: I suspect that, given the high thermal resistance of the case, any minor difference in thermal resistance of exotic heat transfer compounds isn't going to make any significant difference.I'd stick with bog standard heatsink compound, maybe even superglue if the mating surfaces are in close flat contact (and secure them that way), Datron used to use it all the time to maintain matched components in close thermal contact in their instruments.The most effective thing you can do is maximise the area of copper attached to the center pin, that's the one the die is attached to.
Thermally isolating mini-gps from Raspberry Pi 3 without RFI? - Page 1
Forum section: electronics / beginners

author: cdev
author_rank: Super Contributor
timestamp: December 01, 2018, 04:27:27 pm
content: For a while I have been using Raspberry Pis with GPSs to provide a time server to my local LAN. But I have been using older models which generate a lot less heat. Even with them I have had problems with RFI so Ive had to keep the leads short.Now for various reasons I want to use an RPI3.But even when not enclosed it generates enough heat that I now would like to move the GPS farther away.But there also is some RFI produced by it- and the longer the distance is the more audible it is. Ive gotten rid of a lot of it.. some ferrite beads got rid of most of it but its still there. broadband hash, and a momentary blit every second.I am going to try a bunch more SMT caps, much smaller values, and maybe some more beads.Here is the way they are arranged now(top)Antenna (passive)pigtailGPS-Navspark miniheaders it plugs intoribbon cableflat ribbon cable ferrite (I cant find this in the old FairRite catalog I have but judging from its style its likely a Fair-Rite part, likely made of #43 material)cheap 'hat' ($2) board's floating contact areasadditional ferrite beads on wires to GPIO 18(1pps), Txd+Rxd UART, and +3.3 v positive power rail (not ground) and hat body which consists of the floating contact areas and the GPIO headers all marked to make them easy to connect the wires to.Bypass capacitors between positive rail and ground there. (If the additional bypassing doesnt cure it just for the knowledge's sake I am going to try slicing the trace for its 5v rail to remove that as a potential source of RFI for now since I currently have no use for it. I can always add it back in by bridging the trace with solder if I need to.) Experimenting now with different bypass caps values and types. Wondering if there is a suggested top limit?Some kapton tape on hats bottom to reduce (warm) airflow through hat's holes into GPS's area when/if it needs to be vertical. Pi is now being held in a sideways position. Heatsink on CPU fins orient vertically with this tilt. May end up mounting it on a wall.Pi body itself(bottom)No case currently until this gets sorted out.---Long somewhat useless musing deleted.---Are there any good online resources on reducing broadband noise radiation from 12c and SPI control lines, and also good one stop shop resources on the RPI hats and perhaps RFI in that context, in real life usage? (I am not using the hat for external power, although I likely will want to use a power backup in the future, but for now its just a time server, and that involves the Pi, and a GPS and soon one ambient temperature/humidity and barometric pressure sensor - at least one, possibly two of them. (one indoors, one outdoors) on a wire long enough to reach that distance..I am going to take a little break from working on this for now.If I cant eliminate the RFI better I may dump the hat for now and go back to attaching everything to a much smaller IDC header by itself.
Thermistor identification - Page 1
Forum section: electronics / beginners

author: chrisxbates
author_rank: Newbie
timestamp: December 20, 2023, 06:26:45 am
content: Hello,Can someone identify this thermistor please. Picture should be attached.It is connected to my boiler and senses the external ambient temperature.(If you are outside the uk, a boiler burns natural gas to heat water. This hot water keeps my house warm.)Thank you.Chris

author: MathWizard
author_rank: Super Contributor
timestamp: December 20, 2023, 06:35:28 pm
content: IDK if that's a color code on it, brown-blk-red could be 1000 ohms, what voltage gets applied to it ? It might be some high AC voltage too, and a lot more than 1Kohm.Did you check it with a multimeter ? The pins look corroded, I'd use a bit of sand paper on them 1st.

author: floobydust
author_rank: Super Contributor
timestamp: December 20, 2023, 07:55:50 pm
content: What make/model is the boiler?I would disconnect one leg and measure the resistance. The water damage and corrosion needs to get cleaned up- mainly on the terminal block and wiring connections.If an emergency then substitute a resistor to spoof a reasonable outdoor temp. or see if the control board is reading it properly.Vishay NTCLE1003thermistors use colour stripes but did not show red-blk-brn, wild guess it's a 2kΩ@25°C part and very likely the same used in other water temp sensors on the boiler.I have worked with Tekmar controllers and they use a vanilla 10kΩ@25°C B=3,892 sensor for both outdoor and water temp.

author: themadhippy
author_rank: Super Contributor
timestamp: December 20, 2023, 08:44:50 pm
content: thermistor colour codehttps://www.starlightsensors.com/deciphering-ntc-thermistor-color-code-for-electronics/according to that its a 200 ohm jobbie,which fits in with the vishays red red brown being 220 ohm

author: liaifat85
author_rank: Regular Contributor
timestamp: December 22, 2023, 08:04:47 am
content: You have already got an article about thermistor's color code. I am attaching a datasheet of a vishay thermistor:https://www.farnell.com/datasheets/3677059.pdf?_ga=2.154537848.136876557.1703231956-2016255744.1703231956I think it will also help you.By the way, if you become interested in doing thermistor- based projects later, here is a temperature logger that you can try:https://www.pcbway.com/project/shareproject/10_channel_NTC_thermistor_based_temperature_logger_b1c5cdfe.html

author: floobydust
author_rank: Super Contributor
timestamp: December 23, 2023, 10:51:53 pm
content: Quote from: liaifat85 on December 22, 2023, 08:04:47 amI don't appreciate the shill for your temperature logger, I don't see a schematic or BoM. Such a waste of time.

author: Andy Watson
author_rank: Super Contributor
timestamp: December 23, 2023, 11:50:41 pm
content: I think it is a 1k 2%. Thermistor colour codes are read from the bottom-up (who knew - apart from MathWizzard?) There's an outside chance that it's 68\$\Omega\$ 2%.
Thermistor - Zero-Power Resistance - Page 1
Forum section: electronics / beginners

author: 2X
author_rank: Frequent Contributor
timestamp: July 24, 2020, 06:32:32 pm
content: Hi,I am trying to understand what is the characteristic "Zero-Power Resistance" of a thermistor. I found the below explanation on the internet. If we take the thermistor in the picture (in red) will have 4ohm resistance at 25Celcious when the dissipated power on is 2.3Watt (for instance P=I^2*R = 0.76^2 A * 4 ohm ~= 2.3Watt)?General Information - Vishay Dale - NTC ThermistorsThis is the DC resistance value of a thermistor measured ata specified temperature with a power dissipation by thethermistor low enough that any further decrease in power willresult in not more than 1.0 percent (or 1/10 of the specifiedmeasurement tolerance, whichever is smaller) change inresistance.

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 24, 2020, 07:34:57 pm
content: If in short: zero power resistance is a resistance you may measure with DMM (Ohmmeter) if thermistor have a room temperature.

author: 2X
author_rank: Frequent Contributor
timestamp: July 24, 2020, 08:01:53 pm
content: Quote from: Vovk_Z on July 24, 2020, 07:34:57 pmCan a thermistor have 4ohm resistor in room temperature? If starts flows current throw it then the resistor (NTC) will drop in mohm scale?

author: anvoice
author_rank: Frequent Contributor
timestamp: July 24, 2020, 08:58:03 pm
content: I can't find any "4 Ohm at room temperature" from Vishay Dale on Digi-Key. In general, 4 Ohms seems a bit on the low side, typically the values are higher. E.g. 100 kOhms at room temperature is typical for 3D-printer thermistors.When measuring the resistance with a DMM, you indeed get a current flowing through the thermistor. However, it's typically below 1 mA, which means the thermistor will barely heat up (also depends on thermal mass of thermistor), so the change will likely be negligible compared to actual temperature perturbation.

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 24, 2020, 09:22:07 pm
content: There are two wide areas where NTC thermistors are used.The first one is temperature sensing, and its zero power resistance at ambient temp is in the several kilo-ohm range.The second is inrush current limiting, at power line voltages. These are available in tens of ohms or even single-digit ohms at zero power.An example from digikey:

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 25, 2020, 11:33:14 am
content: Quote from: 2X on July 24, 2020, 08:01:53 pmYes, it can. Resistance is backwards proportional to its temperature. Temperature is proportional to dissipated power (near linear law).Active power is P = I^2 × R.