hybridfree/eevblog-posts huggingface dataset:
What is the name of this component? - Page 1
Forum section: electronics / beginners

author: CyclicUK
author_rank: Contributor
timestamp: September 20, 2015, 08:44:21 pm
content: Hi all,I've just got a CB radio so I can get my head around RF, the one I ordered has buttons instead of a channel knob but a mic with channel up and down buttons. I can't have a CB radio without a proper channel dial - so I'm planning to build a little pre-mic circuit in a box with a proper channel knob. You know, it's like a potentiometer but it's also like a switch because it latches in at each channel. Does anyone know what that component is called?I've had a good search on ebay for various things like "channel dial", "channel tuner" and "latching potentiometer" but no luck.Can anyone help?Best,Cyclic

author: Chris C
author_rank: Frequent Contributor
timestamp: September 20, 2015, 08:47:34 pm
content: I think a "rotary encoder" is what you're looking for. Example:https://www.adafruit.com/products/377

author: CyclicUK
author_rank: Contributor
timestamp: September 20, 2015, 08:52:57 pm
content: Thank you so much!I've been googling around that sort of term for a couple of days - quick google makes that look like the culprit - an incremental one for my purposes by the looks of it.Kind regards and thanks again,Cyclic
What is the name of this connector ? (DIY power tool battery) - Page 1
Forum section: electronics / beginners

author: wwwill
author_rank: Newbie
timestamp: July 31, 2019, 02:42:57 am
content: Hello everyone.I am in the process of making my own battery for my Hitachi 18V drill. I almost finished modeling the case on Fusion 360.And I need to make a board to allow the electrical connections.So I need your help!Do you know how this type of connector is called?I tried with "double wipe", "prong contact" and many more but I can't find anything relevant.Thank you everyone!

author: Wendy_Preston
author_rank: Contributor
timestamp: August 02, 2019, 09:28:25 am
content: Hi, that really looks like a card guide, except for the fact I've not seen the double-height arms before. We used to supply them many years ago. I only know of one company that makes them, but I'm sure there must be others. Something like this:http://www.unitrack.com/pc-metal-card-guides/metri-guide/It's entirely possible Hitachi have had these custom made to their own requirements, maybe based on the concept of card guides. Sorry I can't be of any further help!

author: ledtester
author_rank: Super Contributor
timestamp: August 02, 2019, 11:02:39 am
content: Try googling "battery blade connector". Doesn't come up with that exact part, but you might find something you can use.
what is the name of this thing. - Page 1
Forum section: electronics / beginners

author: jismal
author_rank: Contributor
timestamp: November 30, 2018, 05:58:40 am
content: Hello can anyone say this clip name.

author: JackJones
author_rank: Regular Contributor
timestamp: November 30, 2018, 06:05:40 am
content: Test hook or hook clip I think are the most common names for them. Some people might call them grabbers too.

author: DTJ
author_rank: Super Contributor
timestamp: November 30, 2018, 06:10:39 am
content: Micrograbber?https://www.google.com/search?q=micrograbber&num=30&client=firefox-b-ab&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjU-o25uvveAhXRfd4KHU2hA3oQ_AUIDigB&biw=1920&bih=938

author: jismal
author_rank: Contributor
timestamp: November 30, 2018, 06:43:04 am
content: Thank u.I just spend 30 minutes in digikey to find that.

author: DTJ
author_rank: Super Contributor
timestamp: November 30, 2018, 11:56:49 am
content: Quote from: jismal on November 30, 2018, 06:43:04 amOne advantage of the big old printed RS and Newark catalogs was that you'd spend dozens of hours looking thought them while on the dunny and knew what all the neat little trinket parts were called.

author: Nerull
author_rank: Frequent Contributor
timestamp: December 01, 2018, 08:09:53 am
content: Those look like E-Z-Hook XKMs, to be specific.

author: W0MPM
author_rank: Contributor
timestamp: December 10, 2018, 01:02:54 am
content: Quote from: Nerull on December 01, 2018, 08:09:53 amIpad, Kindle, excellent replacement. Digikey has an App!
What is the name of this transistor package? - Page 1
Forum section: electronics / beginners

author: sonnytiger
author_rank: Frequent Contributor
timestamp: September 12, 2013, 10:31:04 pm
content: And/or what is the pin numbering?

author: xrunner
author_rank: Super Contributor
timestamp: September 12, 2013, 10:46:04 pm
content: Quote from: sonnytiger on September 12, 2013, 10:31:04 pmThese?Quotehttp://oddmix.com/semi/2n3646.html

author: oPossum
author_rank: Super Contributor
timestamp: September 12, 2013, 10:52:36 pm
content: TO-106 packageMay be a BC418, PNP, CBE

author: sonnytiger
author_rank: Frequent Contributor
timestamp: September 12, 2013, 10:56:35 pm
content: Quote from: oPossum on September 12, 2013, 10:52:36 pmThat is the package thanks!It's a 2n3645Thanks a lot!

author: sonnytiger
author_rank: Frequent Contributor
timestamp: September 12, 2013, 11:01:09 pm
content: I found this diagram though am not sure which one would be base, emitter etc. Can't find anything online with a 10 minute search.

author: Andy Watson
author_rank: Super Contributor
timestamp: September 12, 2013, 11:12:38 pm
content: QuoteUsually, (no guarantees though) the emitter is next to the flat and the base in the middle.

author: sonnytiger
author_rank: Frequent Contributor
timestamp: September 12, 2013, 11:37:28 pm
content: okay good enough for me thanks!

author: Unknown
author_rank: Unknown
timestamp: September 12, 2013, 11:58:15 pm
content: If you have a working sample then you can easily measure it: the BE and BC junction should act like a diode, with the BE having a slightly higher forward voltage drop than the BC junction.

author: sonnytiger
author_rank: Frequent Contributor
timestamp: September 13, 2013, 09:17:09 pm
content: Would that work in circuit?

author: vk6zgo
author_rank: Super Contributor
timestamp: September 14, 2013, 05:04:09 am
content: Quote from: sonnytiger on September 13, 2013, 09:17:09 pmIf the circuit is working it is easy!Just measure the voltages with respect to chassis.If it is an NPN,the highest positive voltage will be the collector,the lowest the emitter,& the base will be about 0.7 volts higher than the emitter.If it is PNP & the equipment has a negative supply,the above comments apply,with the polarity changed.Sometimes,transistors will be fitted "upside down"where the collector will be at,or close to, chassis potential,butthe relationships between elements still apply.

author: sonnytiger
author_rank: Frequent Contributor
timestamp: September 14, 2013, 08:03:37 pm
content: I meant measure with a multimeter in circuit, can't power it on :/

author: edavid
author_rank: Super Contributor
timestamp: September 14, 2013, 08:18:35 pm
content: Don't sweat it, a 2N part in TO106 will have EBC pinout.

author: sonnytiger
author_rank: Frequent Contributor
timestamp: September 16, 2013, 01:14:00 am
content: ok cool thanks!
What is the nature of such diod's behavior? - Page 1
Forum section: electronics / beginners

author: hohlov
author_rank: Newbie
timestamp: August 25, 2013, 12:47:09 pm
content: I want to look at the diod V-I diagram using an oscilloscope. But instead of solid curve I got a strange effect. My circuit is almost the same as on picture. The frequency is 50Hz. I tested bunch of diods and got the same result.What is nature of this?

author: Andy Watson
author_rank: Super Contributor
timestamp: August 25, 2013, 01:06:37 pm
content: Is the vertical channel set to A.C. coupling?

author: hohlov
author_rank: Newbie
timestamp: August 25, 2013, 01:49:26 pm
content: That picture was made with vertical channel set to A.C. coupling . When I set D.C. coupling the effect still persists but is four times smaller.

author: Andy Watson
author_rank: Super Contributor
timestamp: August 25, 2013, 02:01:54 pm
content: Quote from: hohlov on August 25, 2013, 01:49:26 pmYou need to set the input coupling to D.C. The A.C./D.C. coupling on a scope is usually set to have a roll-off somewhere around 20-30Hz , i.e. not too far from 50Hz. What you are seeing is the input capacitor integrating the signal.QuoteI don't know about that, was the horizontal set to A.C. too? If so, it may be taking slightly different paths as it retraces the negative half of the cycle.

author: WarSim
author_rank: Frequent Contributor
timestamp: August 25, 2013, 02:05:40 pm
content: Yes this a perfectly reasonable response for an ad hoc in circuit tester with the given circuit.One difference being you are not generating the test signal you are using the input from the inductor.Remember you are not testing the diode you are testing the diode in the circuit.
What is the part marked with a 205? - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: June 04, 2019, 02:44:22 am
content: What is the yellow part with the 205 on it?The whole circuit is the detector part of a laser alarm.The alarm goes off if the laser beam is interrupted.https://www.dropbox.com/s/esho9ia2oj3mbnz/Laser_Detector_Circuit.png?dl=0https://www.dropbox.com/s/i5g3qrd5s09mfqa/Laser_Detector_Circuit2.png?dl=0The photo detector is an awful small surface to have to aim the laser at.If possible, I would like a photo detector with a larger area.It works inside, but I have not tested it yet on my patio where the ambient light is much brighter.Thanks.

author: Nerull
author_rank: Frequent Contributor
timestamp: June 04, 2019, 02:55:35 am
content: A 2 meg trimpot.

author: james_s
author_rank: Super Contributor
timestamp: June 04, 2019, 04:56:33 am
content: If you need a larger area for the detector, use a lens, if you can find a small Fresnel magnifier that should work well. Keep in mind the larger your detection area, the more sensitive it will be to ambient light too.
What is the part number of UC3843 replacement in smaler than SOIC-8 package? - Page 1
Forum section: electronics / beginners

author: LinuxHata
author_rank: Frequent Contributor
timestamp: February 08, 2025, 06:18:12 am
content: Hello.In some cheapo power supplies, I've seen an IC, which, according to the circuit, seems to be a pin compatible replacement of UC3843, but in much smaller, MSOP or SOT package. These usually have no brand name/model name on them, so hard to find the exact P/N. Maybe someone can help?

author: benj38
author_rank: Frequent Contributor
timestamp: February 08, 2025, 02:43:03 pm
content: MIC38C43YMMhttps://ww1.microchip.com/downloads/aemDocuments/documents/APID/ProductDocuments/DataSheets/MIC38C42-43-44-45-BiCMOS-Current-Mode-PWM-Controllers-DS20006436B.pdf
What is the pitch of this heatsink? - Page 1
Forum section: electronics / beginners

author: Faringdon
author_rank: Super Contributor
timestamp: April 12, 2022, 06:01:37 pm
content: Hi,The heatsink called “SK 145 37,5 STS TO220” (Page A109)Heatsink…https://www.farnell.com/datasheets/1734934.pdf…does the “37,5” bit refer to the pin pitch?Also, do you think we can heatsink a GBJ5010 Diode bridge to its flat side?GBJ5010…https://www.mouser.co.uk/datasheet/2/258/GBJ50005_7eGBJ5010_GBJ_-2510579.pdf

author: tooki
author_rank: Super Contributor
timestamp: April 12, 2022, 10:34:33 pm
content: It’s the height.It’s a bit unclear because of the uncomfortable proximity of dimensions on the drawing. Here’s an annotated screenshot that hopefully makes it clearer.So no, that bridge rectifier won't fit: it's twice as wide as the channel in the heatsink. (Of course, you could always just mount it on the back of the heatsink.)

author: HwAoRrDk
author_rank: Super Contributor
timestamp: April 13, 2022, 02:38:51 am
content: I don't see how it's confusing - the pin pitch is explicitly labelled on the diagram as 25.4mm.

author: MarkF
author_rank: Super Contributor
timestamp: April 13, 2022, 03:35:00 pm
content: The only confusing part is that they use a symbol to indicate height where most specifications use a letter for a dimension.The hole is high enough to support the bridge rectifier and the width of the heatsink is slightly narrower than the bridge. So, you could bolt it onto the back side of the heatsink.
what is the point of LANGID in USB string descriptors ? - Page 1
Forum section: electronics / beginners

author: metebalci
author_rank: Frequent Contributor
timestamp: November 28, 2023, 08:30:35 am
content: So a device can indicate (in the string descriptor 0) that its strings support multiple languages. GetDescriptor for a string descriptor also sends a LANGID as a parameter. However, neither the string indices used in other descriptors (i.e. iProduct is just the string descriptor index, no mention of LANGID) nor the string descriptor entries use these LANGIDs. What is the connection here, how is LANGID actually used ?

author: ataradov
author_rank: Super Contributor
timestamp: November 28, 2023, 04:27:12 pm
content: wIndex of the Get Descriptor command specified the required language. It can be one of the values advertised in the string descriptor 0.You are supposed to have multiple strings in different languages for the same ID.So, if your iProduct string is at the index 3, then the host may request a string descriptor with index 3 and a language ID A and index 3 and a language ID B. You will have to return appropriate string.In practice, I don't think hosts care enough to do this.

author: metebalci
author_rank: Frequent Contributor
timestamp: November 28, 2023, 06:10:00 pm
content: Quote from: ataradov on November 28, 2023, 04:27:12 pmI thought the index has to be unique but it seems it does not have to be then. OK that makes sense. I guess for example if Windows is in German and device reports German lang support as well, Windows may request strings with German langid. Thanks.

author: ataradov
author_rank: Super Contributor
timestamp: November 28, 2023, 06:16:59 pm
content: The index is unique for a logical string. That logical string may be requested in multiple languages, but that does not change the meaning of the string. Product description is a product description in any language.I have never seen any device that would have multiple languages. It seems like a strange thing to do.I have seen devices using Chinese characters in the same US English langid (0x0409). And at least Linux terminal was able to show them correctly. I assume they are just interpreted as Unicode and shown directly.

author: metebalci
author_rank: Frequent Contributor
timestamp: November 28, 2023, 08:12:44 pm
content: Quote from: ataradov on November 28, 2023, 06:16:59 pmNot for languages like English and German using roughly the same alphabet but I think it makes sense for totally different alphabets.I also accidentally managed Linux to show Chinese/Japanese characters after a mistake in encoding.

author: ataradov
author_rank: Super Contributor
timestamp: November 28, 2023, 08:58:09 pm
content: Those strings are UTF-16 to begin with, there is no need to worry about the encodings. The language is there only to differentiate the strings in different languages. All those strings must be in UTF-16 in any case.The only reason to have language ID is to have different versions of the same string. But if you only have one, it can contain any characters.
What is the point of these squares - Page 1
Forum section: electronics / beginners

author: laejf
author_rank: Regular Contributor
timestamp: May 11, 2023, 07:22:45 am
content: I am wondering about the use of these squares on a PCB. Does anyone know?

author: moonz
author_rank: Contributor
timestamp: May 11, 2023, 08:22:07 am
content: It is for cooper balance of pcb.So that the amount of copper on all layers does not differ by more than ~20 percent from each other layer. Otherwise, the board may twist when released from the factory.It is also called Thieving.

author: RoGeorge
author_rank: Super Contributor
timestamp: May 11, 2023, 08:52:10 am
content: This guy says warping is not much of a problem nowadays, main reason being to assure uniform electroplating of holes or traces across all the PCB surface, otherwise the most copper dense areas won't get enough electroplating:http://ee-training.dk/pcb-manufacturing/copper-thieving-confusion.htmhttps://resources.altium.com/p/what-thieving-pcbs-and-why-it-done

author: Psi
author_rank: Super Contributor
timestamp: May 11, 2023, 09:02:03 am
content: Yeah, squares are not all that common today.We do put copper in the panel area of a panelized PCB sometimes though, to make the panel more rigid for pnp machines to hold. But that is a solid or hatched fill. A square pattern is not all that good for this purpose.

author: Berni
author_rank: Super Contributor
timestamp: May 11, 2023, 09:04:08 am
content: Warping is still a issue with unbalanced copper.While unbalanced copper boards might not have warping issues when they get manufactured these days, but the thermal expansion of copper is still pretty mismatched with FR4. So once the boards go trough the reflow oven the PCB can become a bimetal strip, making it bend during the soldering process, potentially causing issues.If you have the same amount of copper on both sides they will make both sides expand the same, so it won't bend in the oven.EDIT: Tho this is mostly a issue with very large boards since the amount of bend is not that huge.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: May 11, 2023, 09:53:01 am
content: Thermal balancing is very much an issue on thin PCBs - I did some 0.2mm ones and they curled up like tacos in the reflow oven!ISTR a while ago Eurocircuits complaining about unbalanced copper due to issues with their 4L plating process, not sure if this is still an issue

author: laejf
author_rank: Regular Contributor
timestamp: May 11, 2023, 12:45:28 pm
content: Thanks for all the answers!
what is the point of tiny ceramic caps on power rails  - Page 1
Forum section: electronics / beginners

author: nus
author_rank: Contributor
timestamp: May 01, 2019, 05:20:15 pm
content: so i just replaced the c15 100uf cap on 3j1-2 and there is 4v of ripple on the power rail. it was all over the place before this.probably going to replace the varistor and the ceramic cap on the line now, however i was wondering what is the point of these tiny caps, they always seem to be present on main power rails even after a larger cap

author: ataradov
author_rank: Super Contributor
timestamp: May 01, 2019, 05:33:38 pm
content: Here is a video on it

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 01, 2019, 05:35:56 pm
content: https://youtu.be/BcJ6UdDx1vghttps://youtu.be/P8MpZGjwgR0https://youtu.be/1xicZF9glH0

author: bson
author_rank: Unknown
timestamp: May 01, 2019, 05:58:28 pm
content: It's there to reduce high frequency ripple because the electrolytic cap's impedance climbs quickly with frequency so it can't do it alone.It's not technically a decoupling cap - those go across loads to reduce high frequency loop currents.
What is the power rating of Darth Sidious ? A sci-fi guess  - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 29, 2018, 05:26:40 am
content: IDk, 1.21 jigawatts ? He was able to move so fast Anakin didn't even know what was attacking Mace Window at the beginning of the end for MW.Electrons in massive gravitational fields get relativistic boosting. Also in ultra dense/compact plasma's, electrons can get R.B'ing.The Emperor seems to just do spark gap discharging, of slow electrons. I wonder what the x-ray and gamma-ray spectrum of this would look like.And now watching movie LS battles looks just like acting/play-fighting compared to real-life LS battles or in video-games on top of the line rig's

author: Brumby
author_rank: Unknown
timestamp: April 29, 2018, 06:35:28 am
content: Quote from: lordvader88 on April 29, 2018, 05:26:40 amCross-franchise heretic!Let Star Wars get its own parameters, not that it even tries to - unlike BTTF which has made more of an engineering effort.
What is the purpose of a bus transceiver? - Page 1
Forum section: electronics / beginners

author: MarkS
author_rank: Unknown
timestamp: January 13, 2016, 03:20:21 am
content: I'm curious what a bus transceiver, like the 74LS245, does? It transmits a signal in either direction based on the direction pin. I get that part, but why would this be necessary? What benefit is there to using these? What would be a good example of a system that would fail or malfunction without them and why?

author: retrolefty
author_rank: Super Contributor
timestamp: January 13, 2016, 03:38:34 am
content: Quote from: MarkS on January 13, 2016, 03:20:21 amMany use is because it has much higher current output of the transceiver Vs standard logic level outputs. As Bus structure tends or can have many devices wired to the bus, the standard fan-out of normal rated output pins is not strong enough.

author: ade
author_rank: Unknown
timestamp: January 13, 2016, 03:44:16 am
content: They are typically used to interface (connect) two different busses which may operate at two different signal/voltage levels. They provide signal translation, isolation, buffering, etc., between the two busses.E.g., you might have an internal bus at 3.3V and an external peripheral bus at 5V. The bus transceiver helps to create a bridge between the two busses, allowing bi-directional communications between them.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: January 13, 2016, 03:47:26 am
content: Another application would be to connect devices of different bus widths. Clock in one byte at a time. Alternatively the latching bus transceiver 74373 is useful for this.

author: MarkS
author_rank: Unknown
timestamp: January 13, 2016, 01:26:03 pm
content: Thanks everyone! That makes more sense. They seemed like very bulky and cumbersome PCB traces and that just didn't make sense.

author: XFDDesign
author_rank: Frequent Contributor
timestamp: January 13, 2016, 03:35:15 pm
content: Some time ago, parallel busses were the rage.If you were designing your own digital blocks, however, you needed to disconnect your device from the microprocessor's databus until told to do otherwise. The 74xx245s were not only bi-directional, but tri-statable. You can effectively "disconnect" 8 databits from the data bus. If you're given a write operation, you can set the direction "from" the databus "to" your device, and then enable the part to drive your inputs. Reverse it, and you can drive the databus from your device, based on changing 1 bit for direction.Logic level translation is only a relatively "new" use for them, and likely then only works so far as1. It's an HCT type technology, or2. It's a pin-for-pin part with the level translation built in.The '245 was made in the days when a digital device was built up of SSI, and MSI logic. No FPGAs, and only a rare PLA on high end systems.
What is the purpose of the small dimples at the bottom of RK097 pots? - Page 1
Forum section: electronics / beginners

author: dusan
author_rank: Regular Contributor
timestamp: August 07, 2024, 05:34:36 pm
content: At the bottom of every RK097 are these tiny plastic dimples. They are 0.6mm tall. What is their purpose?

author: Kurets
author_rank: Regular Contributor
timestamp: August 07, 2024, 05:37:06 pm
content: To lift it slightly above tha board. This allows a solder fillet to form on the top of the board without the solder flowing onto the plastic body of the pot. Also, if the board goes through washing, having some stand-off avoids cleaning fluid getting stuck underneath the component.
what is the purpose of the transformer/inductor in this tone circuit - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: October 20, 2019, 01:31:16 pm
content: I found this circuit while searching for 4P24T rotary switches on eBay.and found this circuit that intrigued me cause it uses 2 coils of some sort and is meant for a strat, it's some kind of tone circuit, doesn't use any batteries (passive) and I have no clue what they use the transformer looking things for. maybe you have a better clue to what it's for:
What is the purpose of the VIA stitching in PCB design - Page 1
Forum section: electronics / beginners

author: Eevbs
author_rank: Newbie
timestamp: March 06, 2015, 07:51:18 am
content: hello,can anyone please explain me what is the purpose of the VIA stitching inPCB designorPCB prototype? what it does? does it only important in multi-layer PCB's?i design 195W DC/DC power supply, do i need to add that to the power tracks ( i have one or maybe two layers PCB)?thanks

author: Ice-Tea
author_rank: Super Contributor
timestamp: March 06, 2015, 08:00:32 am
content: Mostly done on ground planes. You'd want that if you have a ground plane on top and bottom that for all intents and purposes they can be seen as a single continuous ground plane. So you need to make sure the connections between top and bottom are not far apart but pretty close to each other so that return current does not have to travel far to "jump" layers.

author: Rerouter
author_rank: Super Contributor
timestamp: March 06, 2015, 08:08:26 am
content: It is all about return path impedance, you likely know about the path of least resistance, but as your frequency (transition speed) increases, a greater share of the return current will try and follow as close as possible to the signal above, via stitching is a way to ensure that there is a smaller gap between them, as any deviation is both a noise source and seen as impedance,If your edge rates are getting close to a 10Mhz sine wave, you follow the path of least impedance, and plan around that, above a 1Ghz sine, you ignore the path of lease resistance and focus only on impedance,It can all so be used to increase power heatsinking on the board, if you have a lot of via's into a big ground plane right next to a high current power trace the increased surface area will soak up the heat better and let it run cooler,

author: Torrentula
author_rank: Regular Contributor
timestamp: March 06, 2015, 09:16:27 am
content: Also done near or under surface mount power components to spread the heat to another (maybe bigger) ground plane on the other side of the PCB, also called thermal vias.
what is the purpose of these components? - Page 1
Forum section: electronics / beginners

author: oldguyjohn
author_rank: Contributor
timestamp: December 02, 2016, 08:03:49 am
content: Hi all,I'm studying other peoples circuits in an attempt to understand more and have a problem with this power supply circuit. I do not understand the purpose of D10 or R16. The diode I assume may be some protection for the transistor, but I cannot get my head around the benefit of R16. The resistor is specified as a 1K. Breadboard experiments seem to show that the circuit works pretty much the same either with or without these components. In fact the output voltage, with respect to varying current, appears more stable without R16, which appears to supply a small proportion of the output by bypassing the main transistor? Very confusing, but I assume there must be a reason for the inclusion of these components. Can anyone please explain the designers intention here.

author: strawberry
author_rank: Super Contributor
timestamp: December 02, 2016, 08:22:27 am
content: R10 prevent it from oscilating and D10 blocks negative voltage

author: CJay
author_rank: Super Contributor
timestamp: December 02, 2016, 08:34:36 am
content: Damnit, beat me to it.Emitter stabilisation resistor, it helps reduce overshoot and oscillation.Try simulating it with a rapidly changing load.

author: David Hess
author_rank: Super Contributor
timestamp: December 02, 2016, 04:37:43 pm
content: D10 prevents potentially damaging base-emitter breakdown of Q2 and Q4 if the output voltage was somehow greater than the input voltage like if a battery was connected to the output while AC power was removed. D10 also allows the output to be pulled down and C7 to be discharged via R15 and Q1 when AC power is removed.R16 counteracts collector-base leakage and removes storage charge from Q4. This has the effect of allowing Q4 to turn off more quickly and prevents amplification of Q4's leakage current which might be a problem at high temperatures. Q2 and Q4 are configured as a Darlington pair and Darlington transistors always include base-emitter shunt resistors. U2 can pull Q2's base to ground so no base-emitter shunt resistor is required although I might have included one anyway.Be warned that this power supply design is known to have overshoot problems on startup.

author: oldguyjohn
author_rank: Contributor
timestamp: December 02, 2016, 07:13:25 pm
content: Thanks for the detailed reply David, an explanation of how things work always helps when your just starting out. This will give me a good starting point for more research.All replies are appreciated as a beginner, but detailed answers in SIMPLE language help most.Thanks again for all replies.
What is the purpose of these holes on PCB? - Page 1
Forum section: electronics / beginners

author: miketan3904
author_rank: Contributor
timestamp: October 22, 2020, 03:54:29 pm
content: I have seen this kind of holes on the PCB of some modules (below shows some examples). Does anyone know the purpose of having these holes on the PCB?

author: Alaezae
author_rank: Contributor
timestamp: October 22, 2020, 03:58:05 pm
content: Probably mounting holes? I don’t know what else they would be.I’m also a beginner, take my opinion with a grain of salt.

author: atmfjstc
author_rank: Regular Contributor
timestamp: October 22, 2020, 05:21:26 pm
content: Definitely mounting holes.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 22, 2020, 05:37:33 pm
content: The latter one specifically, not having room for screw heads, you are likely supposed to run a cable tie through the holes.

author: jfiresto
author_rank: Frequent Contributor
timestamp: October 22, 2020, 05:40:14 pm
content: Or use nylon mounting hardware?

author: SerieZ
author_rank: Regular Contributor
timestamp: October 23, 2020, 09:55:44 am
content: Some newbie PCB Designers like to forget these Holes and then you have big trouble in putting it in a caseMaybe also interesting for Beginners are the small golden dots top left and bottom right of the Mounting holes on the adafruit board. Those are fiducials and used by machines to know the Orientation of the Board for automated assembly etc.

author: RoadRunner
author_rank: Frequent Contributor
timestamp: October 23, 2020, 11:02:36 am
content: These are just mounting holes, As pointed out by other, Because of low clearance either nylon screws or cable ties can be used.

author: JacobPilsen
author_rank: Regular Contributor
timestamp: October 23, 2020, 07:19:05 pm
content: Maybe these are holes for better gluing with glue from a hot melt gun.

author: Carl E
author_rank: Regular Contributor
timestamp: October 23, 2020, 07:59:11 pm
content: If they have traces going to them, they could be test points used by gen rad or other auto test equipment.
What is the purpose of these transistors in power indicator circuit? - Page 1
Forum section: electronics / beginners

author: canadaboy25
author_rank: Regular Contributor
timestamp: July 18, 2024, 08:52:26 pm
content: I have a USB-C power supply that is capable of supplying 5V, 9V, 12V, 18V, and 20V depending on what device it is connected to. The USB-C connector on the end was torn from the cable.The USB connector is mounted on a little PCB at the end of the cable and there are also two little LEDs that light up whenever the supply is plugged in. I have some replacement USB connectors with little breakout PCBs that are similar to the original to replace the damaged connector. The supply has 4 wires, red, white, black, and blue.I wanted to be sure that I got the sensing connections on the new connector correct to avoid sending incorrect voltage to a connected device, so I worked out the schematic of the original board.Clearly, I just need to connect the black, white, and blue wires to the new connector and the supply will function normally. The red wire is obviously just supplying voltage for the LEDs.However, I am curious as to the purpose of the two PNP transistors in the circuit for the LEDs. As far as I can tell, Q2 will conduct, lighting the LEDs. But I do not see the purpose of Q1. Also, since this is just a constant supply for two LEDs, why have the transistors as all? A current limiting resistor and two LEDs would be all that is needed for a simple power on indicator.I don't plan on adding LEDs to the replacement connector, I am just curious about the function of the original circuit.

author: Andy Chee
author_rank: Super Contributor
timestamp: July 18, 2024, 09:03:15 pm
content: Quote from: canadaboy25 on July 18, 2024, 08:52:26 pmIf the voltage at RED is wide ranging 5V-20V, a simple current limiting resistor may give dim to bright, hence the constant current circuit.A dim/bright power indicator may be ambiguous.

author: canadaboy25
author_rank: Regular Contributor
timestamp: July 18, 2024, 09:04:57 pm
content: Quote from: Andy Chee on July 18, 2024, 09:03:15 pmI am pretty sure the red wire provides a constant voltage, regardless of the output voltage on the white wire.I will double check this once I have the new connector in place.

author: magic
author_rank: Super Contributor
timestamp: July 18, 2024, 09:09:45 pm
content: I can't explain why they included it, but it's a well known constant current regulator. When Q2 and LED current becomes ~0.7mA, voltage drop across R2 turns on Q1 and Q1 collector steals R1 current away from Q2 base, preventing further increase in Q2 current.

author: canadaboy25
author_rank: Regular Contributor
timestamp: July 18, 2024, 09:55:43 pm
content: Quote from: canadaboy25 on July 18, 2024, 09:04:57 pmMy mistake. I just completed the repair and the voltage on the red wire does in fact change with the voltage on the white wire.This makes a lot more sense and obviously some active regulation is required for constant brightness.Quote from: magic on July 18, 2024, 09:09:45 pmThanks for the explanation. It all makes a lot more sense now.
What is the purpose of this AC trace in this SMPS (schematic) - Page 1
Forum section: electronics / beginners

author: Beamin
author_rank: Super Contributor
timestamp: June 11, 2018, 03:55:45 pm
content: I watched the video but he doesn't explain two things the purpose of the cap I circled in red or why they have AC going through the switched part of the circuit (red line also goes trough mystery cap). Does this go through that first coil on the bottom right and provide power to the chip that is the oscillator seen on left side?How does the 60 Hz AC stay in step with the FETs feeding those other coils? I would think you would want that line isolated and its strange tat it terminates at the neg of the box shaped rectifier not the other AC line is tis because of that cap?Full video:fhttps://www.youtube.com/watch?v=eq5YpKHXJDM

author: Dukov Ahzrukhal
author_rank: Regular Contributor
timestamp: June 11, 2018, 05:31:07 pm
content: The red trace is not actually AC, notice its connected to the big capacitors. The reason it has the AC in connected to it is because that rectifier can operate as a voltage doubler depending on the voltage selection switch. You should look online for voltage doubler circuits if you are not already familiar with them. The capacitor you circled appears to be a DC blocking capacitor but to be honest im not really sure of what its doing there. I will attach the schematics of an AT computer power supply, its somewhat similar to what you have there so you may find it helpful to look at it.

author: free_electron
author_rank: Super Contributor
timestamp: June 11, 2018, 06:12:28 pm
content: look up 'resonant converter'.this has all the smell of that type of converter

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 12, 2018, 12:02:34 am
content: Nah, that's bog standard half bridge, capacitor coupled, forward converter.Capacitor coupling is used to prevent "flux walking", a silly term when the culprit is DC bias in the core. Cap blocks DC, all is well.Tim
What is the purpose of this AND gate on the USB input? - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: June 13, 2017, 09:43:17 am
content: HiI'm designing a USB to audio as part of a bigger circuit. I choose the PCM2901 form tihttp://www.ti.com/lit/ds/symlink/pcm2901.pdf. In the datasheet it shows an AND gate connected to the USB power and the 3.3V for the chip. So at first I thought it might be to power the ship on when both supplies where on. But then I saw that the output connected to the data+ of the USB. What is the purpose of this gate? is it to do with the USB specification? can I use 2 2N2222 instead of a complete logic chip?Also I don't get the SSPND pin. Any clue to what that does?Thanks in advance.

author: newbrain
author_rank: Super Contributor
timestamp: June 13, 2017, 10:44:43 am
content: A pull-up on D+ (or D- for low speed) is needed to signal the host that an USB device is connected, using an AND gate will make sure that will happen only when both Vbus and Vdd are there (but it is not shown where the AND should get its power...Vcc?).For further details seehere, in the "Speed Identification" section.There should be no problem in driving the pull-up with a suitable BJT circuit.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: June 13, 2017, 10:53:46 am
content: Quote from: newbrain on June 13, 2017, 10:44:43 amProbably wont matter in my case as both come on at the same time from two regulators.

author: newbrain
author_rank: Super Contributor
timestamp: June 13, 2017, 11:19:20 am
content: If the device is bus powered (i.e. Vcc/Vdd derived from Vusb), you can just connect the 1.5KOhm pull up to Vcc/Vdd (when Vusb goes away, the pull up goes away).If, instead it's self powered, you need to sense the Vusb, a transistor and some resistors will nicely do.

author: Zero999
author_rank: Super Contributor
timestamp: June 13, 2017, 09:24:22 pm
content: Quote from: abdullahseba on June 13, 2017, 09:43:17 amYou could use transistors but why would you want to? If you need to save space, then there are single and dual NAND/AND gate packages available.http://www.ti.com/lit/ds/symlink/sn74lvc2g00.pdfhttps://assets.nexperia.com/documents/data-sheet/74HC_HCT2G00.pdfhttps://assets.nexperia.com/documents/data-sheet/74LVC1G08.pdf

author: abdullahseba
author_rank: Frequent Contributor
timestamp: June 14, 2017, 06:52:47 pm
content: Quote from: Hero999 on June 13, 2017, 09:24:22 pmThanks! Will do.
What is the purpose of this voltage monitoring relay? - Page 1
Forum section: electronics / beginners

author: fubar.gr
author_rank: Unknown
timestamp: November 27, 2024, 08:31:11 pm
content: https://www.se.com/ae/en/product/RM17UAS15/voltage-control-relay-rm17u-range-65-260-v-ac/Datasheet:https://download.schneider-electric.com/files?p_enDocType=Instruction+sheet&p_File_Name=S1A1959100_02.pdf&p_Doc_Ref=S1A19591The datasheet describes two products, the one I'm interested in is the RM17UAS15, the first one.It can be configured to detect overvoltage and undervoltage, but not both at the same time. It also has an adjustable hysteresis up to 20%. What is the reason for such a high hysteresis value? That means that if it is set for detecting an overvoltage of 260V, and the hysteresis set to 20%, if it is triggered it won't reset until voltage drops below 260-20% = 208 Volts, which is well below the nominal 230V.In contrast, the other model in the datasheet, RM17UBE15 has a fixed hysteresis at a more reasonable value of 3%

author: SteveThackery
author_rank: Super Contributor
timestamp: November 27, 2024, 08:53:09 pm
content: Isn't the hysteresis adjustable down to 5% though? Mind you, I can't think why you would need a hysteresis bigger than the normal mains operating range, either.Interesting how it insists it must not be used in safety critical applications.

author: indeterminate
author_rank: Regular Contributor
timestamp: November 27, 2024, 09:23:01 pm
content: Not everything runs on nice stable city mains electrical suppliesin rural settings and sites that run off local diesel generator supplies you can get huge voltage fluctuations as large loads turn on/offOr you might just want a tel tail indicator at a site to show that there has been a over voltage event.
What is the purpose of those resistors? - Page 1
Forum section: electronics / beginners

author: uliano
author_rank: Regular Contributor
timestamp: May 30, 2025, 08:46:44 am
content: This seems to correspond to an ADS1256 board easily found on aliexpress et al.I'm wondering what may possibly be the function of the R5,R7,...R22 Resistors. They are actually not mounted on the board but if this guy actually bothered to account for them there should be some kind of purpose... that I have no clue about.

author: kjr18
author_rank: Regular Contributor
timestamp: May 30, 2025, 09:00:50 am
content: My guess would be a voltage divider for each input, for sampling higher voltages than ic normally allows.

author: Zero999
author_rank: Super Contributor
timestamp: May 30, 2025, 09:56:30 am
content: The resistors on the right hand side have NC are marked on the schematic, which implies they're not fitted. If this is true, then the ones on the left limit the current into the the protection diodes on the chip, should the input voltage exceed the supply. In a different design, for higher input voltages, the values will be different and the empty spaces will be filled with resistors, forming potential dividers to scale the voltages, as mentioned above.

author: uliano
author_rank: Regular Contributor
timestamp: May 30, 2025, 09:58:39 am
content: Quote from: Zero999 on May 30, 2025, 09:56:30 amindeed, they are not fitted in my board.for the other resistor (the one fitted) in conjunction with the capacitor (also fitted) I would assume that's a low pass filter

author: uliano
author_rank: Regular Contributor
timestamp: May 30, 2025, 10:01:36 am
content: Quote from: kjr18 on May 30, 2025, 09:00:50 amIf it is so then I would modify my question to:How would the second resistor for the voltage divider influence the RC filter cutoff frequency?

author: Andy Watson
author_rank: Super Contributor
timestamp: May 30, 2025, 10:26:18 am
content: Quote from: uliano on May 30, 2025, 10:01:36 amIt would lower the impedance and therefore increase the cutoff frequency.

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: May 30, 2025, 11:06:09 am
content: Quote from: uliano on May 30, 2025, 08:46:44 amR4, R6, R8, ... R21 are series input resistors between the external header (P1) and the ADC analog input (AINx). These serve primarily for filtering (with the C12–C19 caps) and current limiting.

author: Zero999
author_rank: Super Contributor
timestamp: May 30, 2025, 11:12:26 am
content: I didn't notice the capacitors. I hate schematics like this, with parts drawn all over the place and connected by net names.The RC filter is most likely there to prevent RF interference, as the cut-off frequency will well above the 6.106Hz -3dB bandwidth of the ADS1256, at the maximum data rate, given on the data sheet.https://www.ti.com/lit/ds/symlink/ads1255.pdfR = 100RC = 100nF = 100*10-9FC= ⅟(2π+RC) = ⅟(2π*100*100*10-9) = ⅟(2π*10-5) = ⅟(2*3.1416*10-5)= ⅟(6.2832*10-5) = 15.915*103= 15.915kHz.
What is the relation of Load capacitance and Drive strength? - Page 1
Forum section: electronics / beginners

author: kakiitek
author_rank: Newbie
timestamp: August 24, 2022, 08:06:41 am
content: Hi all,Is the maximum load capacitance in any way related to the configurable drive strength on output pin?This is what I understand -1. As long as the total output capacitance of input pins are below the max capacitance of the output pin, the AC specification of the chip will be valid.2. When the total output capacitance exceeded the max capacitance of the output pin, we need to check on the delay due to this additional capacitance. For slower speed communication, this should be fine assuming we are operating within the timing specification.3. Setting a higher drive strength would decrease the rise/fall time.Question -Does setting higher drive strength helps to reduce the delay caused by high total load capacitance?How are these two related or are they related at all?Thanks.kakiitek

author: MrAl
author_rank: Super Contributor
timestamp: August 24, 2022, 09:42:41 am
content: Quote from: kakiitek on August 24, 2022, 08:06:41 amHi,That may be true in the general case but i believe it is best to decide this on a case by case basis. That is, for each part you intend to use check that out for that particular part. If you use a different part, check that out separately.

author: Terry Bites
author_rank: Super Contributor
timestamp: August 24, 2022, 10:41:38 am
content: The rise time will be determined by the available current from the drive and the load capacitance. The load capacitance is the sum of wiring, the input capacitance of the driven pin and the output capcacitance of the driver pin.Driving multiple inputs from one driver will add capcitance. Increased line capacitance draws more power from the driver. Power wasted as heat.V= 1/c ∫i dtor i=C dv/dt
What is the ripple current rating of this film capacitor? - Page 1
Forum section: electronics / beginners

author: Faringdon
author_rank: Super Contributor
timestamp: January 16, 2022, 04:45:37 pm
content: Hi,What is the ripple current rating of this film capacitor? (at 50/60 Hz and 20kHz)MAB MKP 12/400 12UF +-5% 400V AC 30000h.....https://www.ebay.com/itm/DVE-EN60252-MAB-MKP-12-400-12UF-5-400V-AC-30000h-Capacitor-New-Quantity-1-/372816438683Here is its "datasheet"https://www.rgbautomatyka.pl/media/docs/en/96/12UF%20MAB%20MKP%2012-400%20SIEMENS%20-%20product%20information.pdf(it doesnt weigh 1Kg)Attached also is datasheet...none tell the ripple current

author: Gyro
author_rank: Super Contributor
timestamp: January 16, 2022, 07:00:20 pm
content: Whatever the current they will pass at 50/60Hz AC (sine) at full rated voltage. They are intended for induction motor use and nothing more. If you push them harder, they will start to self-heal and lose capacitance.Specifically, they arenotrated for 20kHz.

author: Faringdon
author_rank: Super Contributor
timestamp: January 16, 2022, 07:58:30 pm
content: So their current rating is VAC(rated)/Xc ?WhereXc = Xc at 50Hz and 12uF?...that comes to 1.5A in this cap.Also, Do you know anything about Film caps not having a ripple current rating, but just a dv/dt rating?

author: Gyro
author_rank: Super Contributor
timestamp: January 16, 2022, 08:06:55 pm
content: Try Epcos-TDK if you want fully rated high value, high dV/dt film caps. Be prepared to pay for them though! They're a lot more expensive than bog standard / ebay motor run types.

author: Faringdon
author_rank: Super Contributor
timestamp: January 16, 2022, 09:50:16 pm
content: Thanks, woudl you agree that the above cap is rated to 1.5A at 50Hz?

author: Gyro
author_rank: Super Contributor
timestamp: January 16, 2022, 10:28:28 pm
content: That seems a reasonable assumption.