hybridfree/eevblog-posts huggingface dataset:
SMPS zener value identification  - Page 1
Forum section: electronics / projects

author: meisstupid
author_rank: Newbie
timestamp: July 12, 2023, 06:12:35 am
content: I am planning to make 24v 30A (720w) smps to power 2 units of my flyback speaker driver (build cost of the smsp is one-fourths of a ready-made one, and my budget is low).I found a nice one with SC and OC protection by a youtuber 'Long Technical', here's the link to the video -.In the diagrams he attached, few values are missing, and i am still a rookie in electronics. Since the output is 24v, i am guessing the zeners are 24v too, but i may be wrong; I have sent an email to the youtuber but he isn't replying.The zeners and the ntc are my main concern, zeners encircled in green and red colour and ntc toward the extreme left (photo of bare and assembled pcb attached blw), there are 2 poly caps too but i think i will find them out myself.Any help or suggestion is much appreciated.Thank you

author: wasedadoc
author_rank: Super Contributor
timestamp: July 12, 2023, 08:07:29 am
content: You already postedhttps://www.eevblog.com/forum/projects/any-warningssuggestions-before-i-invole-myself-into-making-this-smps-at-home/msg4953481/#msg4953481where the gist of the replies was to buy a ready made unit.

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 12, 2023, 08:18:24 am
content: Red cuircuited four suspiciously look like a diode bridge but not Zeners.(It's easier to guess when you have a PCB in your hands).And two in green near two powerful MOSFETS look like they are gate protection Zeners, so they could be 15-16-18 VDC rated.

author: meisstupid
author_rank: Newbie
timestamp: July 12, 2023, 08:30:15 am
content: sadly, the budget is constraining me(around 20usd short)

author: ArdWar
author_rank: Frequent Contributor
timestamp: July 12, 2023, 11:48:53 am
content: All diodes are actual rectifying diode. The one near FETs are gate turn off control, the one near 358 are rectifying signal from the current transformer (yes, I'm just as confused). Left cap is part of HV snubber circuit. NTC should be quite beefy low resistance one since it going to bear the entire input current without relay bypass.This is at the core a fairly basic SG3525-based half bridge SMPS, albeit with some questionable design and routing decision. For example you should treat the auxiliary 15v supply and the whole 555/358 circuitry as primary side.I mean, what kind of PSU design need completely separate external power supply to work...

author: MathWizard
author_rank: Super Contributor
timestamp: July 20, 2023, 04:42:39 pm
content: Would the diodes near the 555 and 358 be for making some PWM drive with those chips ? So just some 1N4148's ?
SMPS - Page 1
Forum section: electronics / projects

author: Tenzin
author_rank: Newbie
timestamp: February 20, 2018, 09:12:12 am
content: what SMD component sizes are used while designing SMPS?

author: Siwastaja
author_rank: Super Contributor
timestamp: February 20, 2018, 11:17:04 am
content: Often based on availability. You want a specific part, you often don't have much packaging choices.Also, you'd typically want to miniatyrize as much as you can. I.e., prefer small parts over big parts, unless a big part is really necessary.SMPS is often constrained by parasitic inductance, which can be minimized using smaller parts. This is important in power semiconductor and gate driver packaging.

author: fourtytwo42
author_rank: Super Contributor
timestamp: February 20, 2018, 02:37:17 pm
content: Quote from: Siwastaja on February 20, 2018, 11:17:04 amAssuming we are talking direct ofline at 110/240Vrms components often need to be large enough to cope with the voltages imposed AND provide suficient creepage distance to meet regulatory requirements. You may find it simpler to go for through hole in some situations. Let's hope you fully understand creepage and clearance before considering such a beast
SMS from GSM modem works only once after bootup? - Page 1
Forum section: electronics / projects

author: awallin
author_rank: Frequent Contributor
timestamp: July 12, 2016, 11:48:58 am
content: I have a Sony/Ericsson GSM modem for sending SMS messages, connected via RS232.For some strange reason sending an SMS works exactly ONCE after booting the device, after that I get:(using gsmterm.py fromhttps://pypi.python.org/pypi/python-gsmmodem)Code:GSM> atzOKGSM> at+cmgf=1at+cmgf=1OKGSM> at+cpin?at+cpin?+CPIN: READYOKGSM> at+cmgs="+358<my-number>"Type your SMS message, and press CTRL+Z to send it or press ESC to cancel.test+CMS ERROR: 255GSM>In the guides CMS error 255 is "undefined" so it doesn't help much.at+csca? reports an OK number for sending sms:s.Strange because either by hand using the terminal, or with sendsms.py from the pypi package itdoes work, but ONCE - and then I have to power-cycle or else I get ERROR 255 again...ati: GM47ati1: CXC1122112at+gmi: Sony Ericsson+GCAP: +FCLASS, +CGSMany ideas? thanks!

author: Desert Leo
author_rank: Newbie
timestamp: July 12, 2016, 11:54:31 am
content: Before sending SMS check network registration. Check also GSM supply. If it is weak, possibly modem hangs.

author: StillTrying
author_rank: Super Contributor
timestamp: July 12, 2016, 12:02:55 pm
content: Random thought.Have you tried sending a different message the 2nd time, add a number after "Test" or something, it might not like sending the same message to the same number in quick succession.Another even more random thought.Have you started by clearing any/all on board SMS memories.

author: bingo600
author_rank: Super Contributor
timestamp: July 12, 2016, 07:45:24 pm
content: +1 for checkking the supply - and place a large CAP 220 or more uF directly at the gsm board.I had this occur , and the module was silently resetting , i found out ny checkking CPIN after the first sms , it was NOT ready.A large cap on the module supply pins cured it./Bingo
SMT bad for copper fills - Page 1
Forum section: electronics / projects

author: rea5245
author_rank: Frequent Contributor
timestamp: January 07, 2015, 11:38:02 pm
content: Hi,I've started using SMT devices - especially microcontrollers - in my projects. I've noticed they make it really hard to get a good copper fill.Since everything is on the top, with no through-holes, the autorouter tries to put all the traces on the top, and only resorts to vias and traces on the bottom when absolutely necessary. After the autorouting, I create a copper fill on the top connected to Ground. But with all those traces on the top, some of the ground pins on my chips get "landlocked", i.e. there's no way for a copper fill to reach them.Have other people seen this? Are there any tricks for solving the problem?Thanks,Bob

author: c4757p
author_rank: Super Contributor
timestamp: January 07, 2015, 11:41:41 pm
content: Don't autoroute? I've never had this issue without letting the autoruiner make a god-awful mess of the layout.(Also, do the fill on the bottom...)

author: langwadt
author_rank: Super Contributor
timestamp: January 07, 2015, 11:51:16 pm
content: just "stitch" the top fills to the ground on the bottom with vias
SMT package installer/assister idea - Page 1
Forum section: electronics / projects

author: Skimask
author_rank: Super Contributor
timestamp: January 12, 2015, 10:10:34 pm
content: Got a project coming up for a guy, 10 boards (maybe more). Each board has 96 TSSOP16's on it (ADG5408's and 74595's). Basically a big signal switcher/router type deal.Was trying to think of decently faster way to get all those TSSOP16's put in place for soldering, short of getting it all done at an assembler.Since I've got a 3D printer, I'm thinking I'm going to add 2 holes to each TSSOP16 package on the PCB, both centered on the package, one slightly off chip on top and one on the bottom.I'll design and printer out a holder of some sort which will hold and center the chip in the holder between the two pins which match the holes made on the PCB for that particular package. Obviously have to make another component in the library...TSSOP16 and TSSOP16-Holder, maybe go ahead and do that with a bunch of SMT types and see what happens.Put the chip in the holder (friction fit? some sort of clamping arms that grab what little of the chip there is on the sides? gum? vacuum?).Put the holder's pin in the holes, the chip magically gets centered. Press down on a center rod to hold it there a bit. Tack solder the corners, take off the holder, solder the rest.Seen anything similar?
SMT SMA - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: August 26, 2014, 05:39:43 pm
content: The recent post about rf connectors got me thinking about my board with SMAs on it.I've decided to go withwww.samtec.com/documents/webfiles/.../SMA-J-P-X-ST-EM3-MKT.pdfsince I don't know for sure the thickness of the board I didn't go with the stronger-looking edge mount ones with the four legs.Anyone ever use these? Are they meant for semi-permanent use or can they put up with daily connections, let's say?

author: eurofox
author_rank: Unknown
timestamp: August 26, 2014, 05:56:39 pm
content: Quote from: Alex Eisenhut on August 26, 2014, 05:39:43 pmLink is not working

author: Marco
author_rank: Super Contributor
timestamp: August 26, 2014, 06:10:26 pm
content: http://www.samtec.com/documents/webfiles/cpdf/SMA-J-P-X-ST-EM3-MKT.pdfhttp://www.samtec.com/documents/webfiles/pdf/SMA.PDFhttp://www.samtec.com/documents/webfiles/prodspec/sma_specs.pdfThey're brass, Samtec doesn't seem to have a mating cycle rating but others go from 100-250 for brass (~500 for stainless steel). So even ignoring the mechanical stability daily use seems like a bad idea, without plug savers.
SMT Spacers / Standoffs sturdy? - Page 1
Forum section: electronics / projects

author: satyamfifa
author_rank: Regular Contributor
timestamp: March 09, 2023, 06:09:53 am
content: Hey All,I wonder how study and robust SMT Spacers / Stadoff such as these:offered by Würth are? Are the susceptible to vibrations if the PCB is mounted on a moving platform?-Sparsh

author: jc101
author_rank: Frequent Contributor
timestamp: March 09, 2023, 01:09:54 pm
content: I hope pretty well, as I use them in devices fitted to light aircraft and for holding a display on in a handheld device.Probably close to 10,000 out there now, and I've never had an issue.I use the M3 threaded SMT posts in 5mm, 6mm, and 7mm lengths.

author: coppercone2
author_rank: Super Contributor
timestamp: March 09, 2023, 06:37:51 pm
content: I don't know, I think you should drill a hole use the swage ones, or threaded.I think the solder joint is very sturdy, it just depends on how much you trust the laminations and circuit board quality. That's not something easy to inspect IMO. At least like the right angle ones, the others are still sandwiched with a bolt so it does not matter too much.
SN74HCxx vs CD74HCxx - Page 1
Forum section: electronics / projects

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 21, 2015, 09:29:58 am
content: At Texas Inst., you can find IC both in the form ofSN74HCxx or CD74HCxxas for example the CD74HC245http://www.ti.com/lit/ds/symlink/cd54hct245.pdfandSN74HC245http://www.ti.com.cn/cn/lit/ds/symlink/sn74hc245.pdfI was not able to find the difference between these IC. Why do these two series coexist ?

author: krivx
author_rank: Frequent Contributor
timestamp: December 21, 2015, 11:55:11 am
content: Looks like the operating temperature ranges are quite different.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: December 21, 2015, 01:50:00 pm
content: It maybe on this one, but there are others where the temperature range is the sameas for the cd74hc244http://www.mouser.com/ds/2/405/cd74hc244-441110.pdfand sn74hc244ww.mouser.com/ds/2/405/sn74hc244-ep-445994.pdfSo this is probably not the proper answer to this question. Normally, SN should be the manufacturer mark for Ti, but what is CD ?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 21, 2015, 01:58:04 pm
content: CD was RCA's Digital (the original metal-gate CD4000 CMOS), likewise CA was their analog line (now Intersil, of the few parts that remain).I forget, did TI buy everything CD-?Ed: ah yeah, "Datasheet Acquired From Harris" -- who had CDxx after RCA (or maybe there were more acquisitions inbetween).Not knowing any better, I think I'd be surprised if they weren't identical dies inside...Looking further, it seems like it fills in some holes in their line; there's SN74HC32 but not 30; there is CD74HC30, however.Tim

author: free_electron
author_rank: Super Contributor
timestamp: December 21, 2015, 03:17:23 pm
content: Quote from: T3sl4co1l on December 21, 2015, 01:58:04 pmRCA -> HARRIS -> part of it ->TIHARRIS -> part of it ->intersil (old intersil)-> part of it National-Semi -> TI

author: free_electron
author_rank: Super Contributor
timestamp: December 21, 2015, 03:24:11 pm
content: http://www.computerhistory.org/semiconductor/companies.html
SN74LVC1G19 1 bit inverter? - Page 1
Forum section: electronics / projects

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 19, 2020, 04:14:09 pm
content: For a circuit I am looking at I need a nCS and I have a signal which is CS... so basically I need a 1 bit inverter and I need it small and cheap and efficient etc...I came across SN74LVC1G19 which seems a bit weird but might work... for me nE would always be LOWould that be a sensible choice?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 19, 2020, 04:21:59 pm
content: A mux..?Recommend avoiding LVC unless you need the speed or some special features. HC is abundant, and you're looking for the '04 or '14. So, *74HC1G14.If you don't need speed, and a little current consumption is acceptable, also consider a pull-up resistor and a switching transistor, MMBT3904 (also with base resistor) or 2N7002 for example.Tim

author: NivagSwerdna
author_rank: Super Contributor
timestamp: June 19, 2020, 06:55:27 pm
content: 74HC1G14GW looks perfect!

author: Benta
author_rank: Super Contributor
timestamp: June 19, 2020, 07:14:43 pm
content: There are a plethora of single-gate logic (aka kludge logic) families available from several suppliers. CMOS 4K, HC, AC, LVC etc. Just find the one that matches the rest of your circuit.

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 19, 2020, 07:50:43 pm
content: One-gate logic is the greatest invention since sliced cheese.It has saved more than one engineer, myself included, to kludge a gate with diodes, resistors and transistors. What is euphemistically known as Mickey Mouse Logic.http://musicfromouterspace.com/analogsynth_new/ELECTRONICS/mickeymouselogic.htmlAnd with packages sizes ranging from SOT23 and smaller, total board real state is similar to a single discrete transistor.
SN76489A frustration - Page 1
Forum section: electronics / projects

author: netdudeuk
author_rank: Frequent Contributor
timestamp: July 17, 2016, 05:14:17 pm
content: HiI bought some of these to give me sound output from a retro computer that I'm building.I made a test setup connected to an Arduino but got no sound.So, I got another chip out and took it down to the basics, with just a 4MHz clock and /CS low.I've read that the chip should make an initial tone (as in the first of the BBC Micro power on bleeps) until told to be quiet.However, the scope shows a sine wave at 431 kHz on the output. At that frequency, I'm not expecting to hear anything.When I was running the Arduino code, the frequency was about the same.I disconnected the oscillator and fed in a square wave, going all the way down to 100kHz. However, the output frequency remained pretty much the same.Any ideas please ?Thanks

author: bitslice
author_rank: Frequent Contributor
timestamp: July 17, 2016, 06:29:10 pm
content: Quote from: netdudeuk on July 17, 2016, 05:14:17 pmThe SN76489AN has a maximum clock of 500KHzThe SN76489A has a maximum clock of 4MHzNoted that you later changed the osc frequency, so dunnoEdit: you appeared to have changed your title from SN76489AN to SN76489Awould have been nice to acknowledge the edit in case people think I can't read :|
Snake! on my TTL breadboard CPU (Hackaday article) - Page 1
Forum section: electronics / projects

author: visrealm
author_rank: Contributor
timestamp: July 12, 2020, 03:45:11 am
content: Pretty chuffed - it seems someone wrote a Hackaday article about Snake running on my breadboard CPU build... in April. Seems I was a bit late to realise.https://hackaday.com/2020/04/26/breadboard-computer-plays-snake-on-character-display-also-in-a-browser/CheersTroy

author: Kashif
author_rank: Contributor
timestamp: July 12, 2020, 03:56:16 am
content: Wow looks very cool! just curious what is your CPU clock speed?

author: visrealm
author_rank: Contributor
timestamp: July 12, 2020, 04:10:33 am
content: Quote from: Kashif on July 12, 2020, 03:56:16 amThanks.It's variable (using a 555), so I can get below 1Hz. I can also single-step it.It currently goes up to around 20-25KHz at full tilt. It *might* be capable of faster, but I haven't tried ...and being on breadboards, probably wouldn't go much faster than that.
Snap dome buttons - Page 1
Forum section: electronics / projects

author: james_s
author_rank: Super Contributor
timestamp: December 13, 2022, 10:13:53 pm
content: I need some of those metal snap dome buttons for a repair project, those cheap things that are typically just taped over a PCB and then have an overlay sticker laid over them. What is the proper name for those and can I get a small quantity of them from someplace like Digikey?

author: floobydust
author_rank: Super Contributor
timestamp: December 13, 2022, 10:25:59 pm
content: I see them fromKeystone Electronics

author: thm_w
author_rank: Super Contributor
timestamp: December 13, 2022, 10:49:20 pm
content: You can literally type "snap dome" into digikey search and get what you wanted. That is the correct name.https://www.digikey.com/en/products/detail/keystone-electronics/5135/6834371

author: james_s
author_rank: Super Contributor
timestamp: December 14, 2022, 02:54:31 am
content: Quote from: thm_w on December 13, 2022, 10:49:20 pmThat's weird, I could swear that's exactly what I tried searching for and found nothing.

author: tooki
author_rank: Super Contributor
timestamp: December 14, 2022, 10:45:38 am
content: Digi-Key is sensitive to typos (in that they don’t have a fuzzy search, which I largely appreciate). It’s certainly happened to me that I got no results and then realized I’d mistyped.
Snap together board-to-board hinge connector - Page 1
Forum section: electronics / projects

author: davidb_
author_rank: Newbie
timestamp: September 29, 2015, 11:19:52 am
content: I've got an idea to make a snap together electrical connector inspired by the lego hinges shown in the images below. The fingers of the hinge would be the electrical contacts and would be spaced/sized so that the connector is only connectable one-way. Before I embark on modelling this and attempting to fabricate it using a 3d printer, I'm wondering if something similar is commercially available. I've thumbed through a couple connector catalogs and tried searching online but haven't found anything yet.The goal is to allow two PCBs to snap together with a hinged connection so the boards can be unsnapped and re-arranged (and hinged to allow 3D structures). For prototyping, I can just use ribbon cables but I would like to find/make something like the lego hinge shown in the image that is prettier and easier to dis/re-connect.If something similar or that would work already exists, that's great. If not, if anyone has advice for me if I decide to go down the 3D-printed housing/connector route, I'd be glad to hear it.Thanks!
Sniffing digital wireless protocols at 2.4Ghz with RTL-SDR - Page 1
Forum section: electronics / projects

author: MrOI
author_rank: Newbie
timestamp: January 22, 2014, 01:43:25 am
content: I just documented my journey to sniff and decode popular digital wireless protocols off the air for very cheap. So cheap practicality anyone can obtain the equipment quickly.I was able to decode NRF24L01+ and Bluetooth Low Energy protocols using RTL-SDR. with some very cheap analog trickery.This opens a world of possibilities at the ISM 2.4Ghz band.Detailed walk-through of the journey from idea to a working solution.http://blog.cyberexplorer.me/2014/01/sniffing-and-decoding-nrf24l01-and.htmlThought it would be interesting for the folks here.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 22, 2014, 01:56:54 am
content: Another option is to get one of those old 802.11g or 802.11b WiFi cards or APs (those that had the baseband and RF separate) and tap into the receive IF. Or hack one of those 2.4GHz video receivers.

author: lgbeno
author_rank: Frequent Contributor
timestamp: April 30, 2014, 03:21:27 pm
content: I just stumbled on this post now, awesome writeup and work, I especially like the clever repurposing of cheap components to make it work!

author: tonyarkles
author_rank: Regular Contributor
timestamp: April 30, 2014, 05:07:26 pm
content: I haven't done a writeup yet, but I've successfully decoded data from a TI CC2500 with the exact setup described in the original post (which was inspired by the original post). Thanks a bunch!
Snubber cap on primary side of 75W PSU working at ~100ºC - Page 1
Forum section: electronics / projects

author: nuno
author_rank: Frequent Contributor
timestamp: February 26, 2018, 01:21:58 pm
content: The primary side of a 230V -> 12V switching PSU has a transformer primary RC snubber with a 1W 51R resistor and a 1nF 1KV ceramic capacitor, and both run at 90ºC - 100ºC. Do you think this is normal design? As far as I can see (capacitance and DC resistance) the cap looks good. If I load the output (tested with 50W) it keeps the output voltage regulation.

author: fourtytwo42
author_rank: Super Contributor
timestamp: February 26, 2018, 08:13:17 pm
content: How are you measuring temperature ? If your using an IR gun you could be picking up heat from adgacent components.

author: nuno
author_rank: Frequent Contributor
timestamp: February 26, 2018, 09:54:06 pm
content: I'm using a thermal camera.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 27, 2018, 01:55:08 am
content: Can you tell what type the capacitor is (C0G, Y5P, X7R..)?I suppose it can't be too bad, even if it's a type 2 dielectric; it'll just self-limit as it approaches Tc (which is still a long ways off at 100C, so it shouldn't even be very different already).100C for a power resistor is very pedestrian. Depends on type, but most are rated upwards of 200C.Tim

author: abraxa
author_rank: Frequent Contributor
timestamp: February 27, 2018, 10:40:19 am
content: Quote from: T3sl4co1l on February 27, 2018, 01:55:08 amWhile that is true, I share the OP's concerns because I would be worried about both components heating up other components in the vicinity for which 100°C may be near the maximum operating temperature. Without a picture of the board it's difficult to tell of course, just sharing my thoughts.

author: CopperCone
author_rank: Super Contributor
timestamp: February 27, 2018, 03:00:46 pm
content: How do you harden the gate driver against emi?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 27, 2018, 03:57:55 pm
content: Quote from: CopperCone on February 27, 2018, 03:00:46 pmTim

author: nuno
author_rank: Frequent Contributor
timestamp: February 27, 2018, 04:06:26 pm
content: It's in a consumer product, nothing I'm developing.I have no idea what's the dielectric type. The number and letters on the cap's front are very similar to some other 30yo caps I have around.I re-measured. It's colder here today, so the cap is at 89ºC and the resistor at 78ºC.
Snubber Component Type - Page 1
Forum section: electronics / projects

author: chris243
author_rank: Newbie
timestamp: February 20, 2013, 10:31:16 am
content: Hi AllPlease forgive me if this is a silly question but I am currently looking to design a snubber circuit for a design i am working on but wanted to ask a question about component selection. Its an RC snubber for a 240V mains circuit driven by a triac (1A 600V) and opto isolated triac driver and i currently plan to use the following partsCapacitor: Digikey # 495-1325-NDResistor: Digikey # RPC2512JT39R0CT-NDCan anyone see an issue with using these parts for this purpose? and by this i mean the type of resistor and capacitor, not the value etc as I believe that is correct. It may seem like a slightly strange question but with mains would rather be safe than sorry. I am also aware that if i need to ask maybe i should be staying away from mains but rest assured despite the question I do know what i am doing, its just not a strength of mine and thought i would take advantage of the wisdom of others encase i have missed something. Any insight would be greatly appreciated and thanks for taking the time to check this out.

author: Niklas
author_rank: Frequent Contributor
timestamp: February 20, 2013, 12:13:34 pm
content: We have used that kind of resistor, maybe not the same brand but with similar specs, in a commercial product for a couple of years. Good with 500 Volts rating to handle transients that passes through the capacitor.The capacitor looks ok generally, MKP, voltage etc, but I would recommend you to have a look at an X2- or X1-rated one. If a third party test house would test your product, then it is nice to have components with good documentation to minimize the hassle. X2-rated caps are meant to be used this kind of applications with live voltage. We have used the R46-series from Arcotronics/Kemet and the MKP339-series from Vishay. Epcos are also good but they were a bit more expensive back when we did the circuit design.Panasonic has a range of capacitors ECQ-** that we where interested in first with a good price and availability. However, they claimed "non cumbustible plastic" but did not back it up with test reports or references to UL94-V*. We could have used them but then we would have had to pay our test house for the extra glow wire testing to pass CE certification for household equipment.

author: CarlG
author_rank: Regular Contributor
timestamp: February 21, 2013, 12:19:24 pm
content: No expert in this field, but isn't it carbon composition resistors that traditionally has been the choice for these kind of applications? The suggested type Endurance specification is only 1000h/5%. Is that good enough? What happens after 1000h?

author: chris243
author_rank: Newbie
timestamp: February 24, 2013, 02:59:03 pm
content: Thank you Niklas and CarlG for your input. After looking over the data sheets i am considering changing the capacitor toDigikey # BC1600-NDThis way it comes with the X2 safety approvals, although it does come at the cost of decreased pulse handling and AC voltage rating.Does this seem like a better choice?
Snubber for 250V ac/dc  - Page 1
Forum section: electronics / projects

author: Jester
author_rank: Frequent Contributor
timestamp: January 14, 2019, 04:23:34 pm
content: I'm looking for an affordable way to switch a 20A, 250V ac/dc resistive load .Obviously relays exist for this, however they are big and expensive.When switching high currents the voltage will be low, less than 50VWhen switching 250V, the current will be low, 5A maxOne thought was to use an inexpensive relay like this:https://www.mouser.com/ProductDetail/TE-Connectivity-PB/T9AP1D52-12?qs=sGAEpiMZZMtSzCF3XBhmW%2fHkUL8cHIexYxdlOkSBp0I%3dthat is not rated for DC and help it with an active snubber, for example:https://www.mouser.com/ProductDetail/IXYS-Integrated-Circuits/CPC1968J?qs=%2fha2pyFaduggqnz%252bdP%252bTMHGhYnLgauQSBn6kv3xcIxY%3dThis SSR has a 10ms, 25A peak rating, so if I turn it on for say 10ms, 5ms after disabling the relay, in theory the SSR will be doing all the work with respect to breaking the DC arc.I should also have a RC snubber to help out.Thoughts on this, do you think it will work? Is there a better approach?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 14, 2019, 05:15:50 pm
content: What drive is available?What budget?Size?Transient ratings?Yes, double-switching would seem likely to work.Snubber value is unclear, presumably you want it smaller than would be irritating for AC operation. So, not, like, >10uF and 1 ohm or something, roughly.The low voltage operation doesn't buy you much, the switch still needs to be rated for full V and I. Or more, if transients are expected (the 250V is mains-connected). A normal "250VAC" relay includes that in its UL rating, AFAIK (the '250V' is a type rating and the actual breakdown is some kV?). Or hmm, maybe not, that would be something a disconnect would need to be rated by, but not necessarily a relay? Or contactor? Look up the standards to be sure.If you need absolute least cost, and safety is not a concern, then just use whatever relay and be done. If you need UL approval, buy the 250V AC/DC relay and be done.If this is one-offs, what are you even worrying about, you've already spent the $10 difference thinking about it!Tim

author: Jester
author_rank: Frequent Contributor
timestamp: January 14, 2019, 05:35:04 pm
content: Quote from: T3sl4co1l on January 14, 2019, 05:15:50 pmThis relay is close,https://www.mouser.com/ProductDetail/Phoenix-Contact/2908044?qs=%2fha2pyFaduhG2tsweHCXD2XrOo%2fLGBsP%2fANbF9f62x8%3d
Snubber for relay - Page 1
Forum section: electronics / projects

author: iXod
author_rank: Frequent Contributor
timestamp: September 13, 2019, 05:44:02 am
content: I want to use a simple RC snubber on a relay that provides 230vac to a small controller board (low voltage inputs and outputs).The relay NO contacts switch one leg of the 230v. The input of the controller PCB consists of a 10w TDK-Lambda PS brick.The snubber will be a simple series 0.01uF cap and 220 ohm resistor—unless anyone has other values to suggest.But my question is really this: do I place the snubber across the relay contacts or across the AC input terminals of the PCB?Thanks.

author: Zero999
author_rank: Super Contributor
timestamp: September 13, 2019, 08:42:33 am
content: What are you trying to achieve?A relay snubber can help by reducing arcing when switching inductive loads, but a switched mode power supply is not an inductive load. It's capacitive, so a snubber will do nothing. If you want to increase the contact life of the relay, then limiting the inrush current to the switched mode power supply will do a lot more than a snubber.

author: Le_Bassiste
author_rank: Frequent Contributor
timestamp: September 13, 2019, 01:46:47 pm
content: as for the question where to put the snubber, you would put it across the load's contacts, not across the relay contacts, because you want to avoid any leakage currents into the load while the relay contacts are open.and, as zero999 already stated, such a snubber protects the contacts from inductive loads, it won't help on capacitive loads.however,ifyour power brick contains a (either active or passive style) PFC front-end, having a snubber is not a bad idea at all (in addition to an inrush limiter).

author: iXod
author_rank: Frequent Contributor
timestamp: September 13, 2019, 03:40:42 pm
content: Can’t tell if this PS has PFC front end:https://www.us.tdk-lambda.com/ftp/Specs/kw.pdfDatasheet says inrush is limited to 30A for this model (10w) with nominal 200v input.I’d like to further limit inrush when the relay contacts switch on.Thanks.
SO-DIM mounting - Page 1
Forum section: electronics / projects

author: richcj10
author_rank: Unknown
timestamp: December 30, 2015, 10:28:42 pm
content: I am working on a project that has SO-DIM cards that control different functions of the device.The device will be in a car. So to keep the card in. I was adding a screw on the top to keep it fastened down. I do however wanted to add a soldered down or pressed fit nut to keep in the board in. But i need the height of the card off the PCB. I can't find any info on this. Does anyone have experience on this?

author: ajb
author_rank: Super Contributor
timestamp: December 30, 2015, 11:01:42 pm
content: You'll have to consult the drawing for the socket you plan to use. Some sockets will hold the DIMM closer to the board to reduce overall height, others will hold it higher to allow components to be placed underneath the DIMM.

author: stmdude
author_rank: Frequent Contributor
timestamp: January 02, 2016, 06:19:49 pm
content: Quote from: ajb on December 30, 2015, 11:01:42 pmAgree.The socket I'm using is a TE Connectivity 1473150-4 ( Cheapest one at Mouser ), and it has a clearance of 3.4mm according to the datasheet, however, as the "flip down" isn't latched or locked in a precise way, it will vary a little (even between components from the same reel). They can always be pushed down/up to 3.4mm though (with this socket).Please note though. As far as I know, there are no automotive-grade SO-DIMM connectors, meaning that they're not great at dealing with vibration, nor are they designed with sub-zero temperatures or humidity in mind.
So, I am trying to breadboard this amp - Page 1
Forum section: electronics / projects

author: Hextejas
author_rank: Frequent Contributor
timestamp: March 16, 2018, 12:18:15 am
content: And other than a bit of heat, thatscall the output. I don't know how to debug it. Plus I have a question.I have a small scope and I can see the 1k Hz test wave until it hits the BC550C. Where else should I look and for what ?I did not design this but others have built it successfully and liked it so I thought that I would give it a try.What is the reason to put the sine wave onto the gate of the BC550C ?

author: LeoTech
author_rank: Regular Contributor
timestamp: March 16, 2018, 07:41:51 am
content: Well, are you sure this schematic is correct?Because for this to be an amplifier it needs an input, output and a power supply, and as far as this particular schematic goes, there is no output.Although I would presume that the output is the 8 ohm resistor (R11), pretending to be something like a speaker or so? Please clarify this and I(we) will be able to assist you further.Leo

author: Audioguru
author_rank: Super Contributor
timestamp: March 16, 2018, 03:00:53 pm
content: Quote from: Hextejas on March 16, 2018, 12:18:15 amYou need to learn about transistors to understand how the circuit works.The BC550 has a base for its input, not a gate. A BC550 is a bipolar transistor, but a Mosfet has a gate for its input. This circuit does not have a Mosfet.The output power of this amplifier is very low but it produces a lot of heat because it operates in class-A. Its current is probably too high for the contacts on a solderless breadboard, solder the connections together on a pcb instead.

author: Hextejas
author_rank: Frequent Contributor
timestamp: March 16, 2018, 03:58:40 pm
content: Quote from: LeoTech on March 16, 2018, 07:41:51 amThank you Leo, and that 8 ohm resistor is supposed to represent the speaker. That was my reading. I tried asking the author but got no response

author: Zero999
author_rank: Super Contributor
timestamp: March 16, 2018, 11:22:49 pm
content: The trouble is with the way it's biased, the collector voltage will be heavily dependant on the Hfe. My guess is a couple of volts, at most, so far too low.Reduce the resistor values and add a capacitor to keep the base bias constant, irrespective of the signal. See attached. For convenience, I just used a constant current source, rather than the LM350 circuit.The circuit is fine for very low output levels, but will distort horribly, at higher amplitudes. Being class A it's also very inefficient and is a poor choice for driving a speaker. I've used a similar design, in a mic. pre-amp and it was fine, but wouldn't consider using it as a power amplifier!Removing C2 will make it more linear, at the expense of gain. Another option is to AC couple a resistor from Q2's collector, to Q1's base, which will reduce the gain and the distortion, but not as much as removing C2.
so I built a an internet weather station... kinda - Page 1
Forum section: electronics / projects

author: exe
author_rank: Unknown
timestamp: October 23, 2024, 08:58:52 am
content: Hello everyone!For a long time I've been running Home Assistant with a few sensors around the house. I didn't have much use for it, part because I'm too lazy to go the website or check the app. I wanted to have a standalone gadget that would just show me outdoor temperature. So, here it is!I'm pleasant with the result, though designing enclosure and buying parts took much more time than I anticipated.Some details. The battery is 2.5Ah, though, I don't think the MCU board (xiao esp32c6) can charge it above some 4.13V or below 3.4V (presumeably due to buck regulator set for 3.3V output). So, I estimate useful capacity somewehere 70-80% of full capacity.Charging current is only 120mA, so it takes forever to charge the battery.Current consumption is like 200uA for display plus mcu board, and 300uA for backlight which is permanently on. That's in sleep mode. In active mode I didn't profile much except noticing that it consumes some 36mA when MCU is active, and over 100mA when talking to WIFI.I don't have any question or anything, I just wanted to show my latest creation. Though, if you, guys, have suggestion for good small and efficient LCD screens, please post them here. I'm using nokia 5110 screens, they are a bit too small in size and resolution.Sources are here:https://github.com/kopchik/weathermoon

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 23, 2024, 09:21:17 am
content: Since your update rate is 10 minutes (correct?) I think this would be a nice candidate for an E Ink display.

author: exe
author_rank: Unknown
timestamp: October 23, 2024, 10:45:35 am
content: Quote from: PA0PBZ on October 23, 2024, 09:21:17 amHa-ha, yesQuote from: PA0PBZ on October 23, 2024, 09:21:17 amThey don't come with backlight(. I figured I like if the screen glows just a little bit so it's readable in the night. I also use it as a clock.
So I made a $5 Theremin with an OTA and a few other things... - Page 1
Forum section: electronics / projects

author: DrGonzoDK
author_rank: Regular Contributor
timestamp: January 11, 2018, 02:26:19 pm
content: EDIT: The schematic is availableherefor the interested!Actually, I was going to build a fancy ring modulator (and probably still am). But I was playing around with the prototype (three "panes" of strip board), and decided I could a more interesting form of pitch control than simple pot turning. So having ruminated over this over dinner, I ran in and speed-soldered an "optical theremin controller" - a low-angle power THT LED and an LDR in an adjustable divider (to adjust for background light and general sensitivity, etc. - and got thishttp://ee.david.promo/theremin-open.jpg...and when closedhttp://ee.david.promo/theremin-closed.jpgOf course - there's a video of my /fantastic/ skills at making 1950s ghost movie noises-http://ee.david.promo/Theremin.mp4Apologise for the whining in the background - it's some sort of modulation with the heater radiator in the background (it's not audible "in person").The tinkling sound in the background is my cat trying to figure out what is making that noise (cat tag on collar)And, for the interested, here's the schematic -http://ee.david.promo/optotheremin/opto-schematic.pdf. If you buy cheap IC's - the NJM13600 instead of the LM13700, and the TL062 instead of the TLV2372, you can definitely make this for $5! The reason the oscillator uses an op amp in its feedback loop, is the improved stability against DC offsets, rather than using the integrated Darlington buffer of the LM13700.And nope, the LED/LDR combo isn't an ideal control. This probably will get turned into that ring modulator prototype. But it's a fun project, doesn't take too long, and is genuinely fun to play with! The nice thing, also, is that it's basically a VCO. So many types of control can be rigged in.The actual output waveform (the triangle - the square is just a comparator-derived waveform from the triangle) is very nice and symmetrical, with very limited distortion,An improvement on this would be to use the second OTA - and a second LDR/LED pair - to create the amplitude modulation function of the Theremin. That way, it wouldn't be at a constant volume, but instead be controllable with the other hand. That's why i love OTAs. They are so damn flexible :-P
So i made this, is this safe? - Page 1
Forum section: electronics / projects

author: jacobdel
author_rank: Newbie
timestamp: March 07, 2019, 02:20:36 pm
content: Greetings,So i made this device to detect a jackphone voltage. But the question is,can i trust this device 24/7 plugged in?The battery used is aNiCd NIKKO battery. Minimum current is 0.5mA and maximum current is 100mA +-Possible future shorts are not really my concern, but you never know.(i did not add that fuse)But i've never heard/seen NiCd batteries catch fire :/I've attached 2 imagesKind regards,Jacob

author: Zero999
author_rank: Super Contributor
timestamp: March 07, 2019, 02:25:56 pm
content: I don't know. The image isn't very clear. It appears to be have converter to a very low colour depth, 4-bit, then saved in jpeg, normally a 24-bit format.

author: jacobdel
author_rank: Newbie
timestamp: March 07, 2019, 02:31:06 pm
content: Quote from: Zero999 on March 07, 2019, 02:25:56 pmwoops sorry about that, thought the limit was 100kb

author: Zero999
author_rank: Super Contributor
timestamp: March 07, 2019, 04:15:19 pm
content: The second image with the higher colour depth is has a smaller file size then the other one with the lower colour depth, which is odd.The big thing which stands out to me as dangerous is the lack of over-current protection. There should be a fuse or PTC resistor to protect against short circuits. You were wrong that it's not a concern. Whilst the likelihood of a short circuit may be low, the impact is big, since NiCd cells have a very low impedance and high short circuit current, which can cause wires to glow red hot and set fire to nearby flammable materials.What's the case made out of? Ideally it should be flame retardant. In other words if you expose it to a flame, it shouldn't continue to burn, once the flame has been removed.

author: daniel444
author_rank: Regular Contributor
timestamp: March 08, 2019, 06:53:28 am
content: just house it in an old ceramic pot
So it's soft - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 11, 2017, 04:54:23 am
content: http://www.ebay.ca/itm/161805560034?_trksid=p2055119.m1438.l2649&var=460778692563&ssPageName=STRK%3AMEBIDX%3AITbut is it flexible? Every once in a while I look at my half-century (!) old Tektronix probes with stiff cables. If I strip off the old plastic covering, can I get the cable flexible again with this tubing?

author: gamalot
author_rank: Super Contributor
timestamp: March 11, 2017, 05:21:40 am
content: Those Chinese words are:Soft and flexibleHigh temperature, corrosion resistanceAnti-aging, long life-60 to +200 degrees Celsius

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 11, 2017, 05:35:24 am
content: Thanks, I don't mind buying and trying things but the mail seems real slow these days, 2-3 months from China. That's like an entire season, at that rate by winter I'll be on my second experiment...
so my phase inverter seems to be doing the completly impossible - Page 1
Forum section: electronics / projects

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: April 23, 2020, 11:55:42 pm
content: I have signal only out ofoneside of the PI, but what's weird. is that it's the other side, not the one that the signal gets sent into the grid.I've disconnected the rest of the circuit with no change, still no signal out of that one side. I've checked the resistors that could cause this and they all seem fine.I've checked the voltage on that side and it's good,if I have signal out the other side, then both sides have to be conducting right? right.so only thing that would explain this is if the 90k resistor is shorting when current is drawn, I'm gonna change is but I am pretty sure it wont help so I'll still post this,also I've tried a few diffrent 6N2P's and they all did the same[ Attachment Invalid Or Does Not Exist ]

author: H713
author_rank: Regular Contributor
timestamp: April 25, 2020, 08:05:30 am
content: A few comments.First, a 6N2P (12AX7) is pretty wimpy to drive the output tubes. IIRC, the grid leak resistor for a 6L6GC should not be less than 100K. There is also some miller capacitance to consider.A better solution would be to use something like a 6SN7, 6N1P or 12AT7 in an long-tail pair. Use equal value plate resistors (27K works well for a 6SN7 at 400V) with a CCS on the tail. If you can tolerate the idea of using a little silicon, the IXCP10M45S is anexcellentlittle device for this purpose.The 12AU7 will work in a LTP here as well, but it isn't as linear as the 6SN7.
So you want to do digital signal processing - Page 1
Forum section: electronics / projects

author: rhb
author_rank: Super Contributor
timestamp: January 18, 2024, 03:41:45 am
content: I get PMs fairly often asking me about DSP. Most of the people expect me to provide a canned answer at no charge. And then ignore it and do whatever they were going to do no matter how stupid their scheme is. I've reached the point that I have a minimum requirement to obtain my assistance.Buy these 3 books and read them in the following order:An Introduction to Digital Signal ProcessingJohn H. KarlAcademic Press 1989The Fourier Transform and Its ApplicationsRonald Bracewell2nd edRandom DataBendat & Piersol4th edMy apologies for lack of publisher and date for the 2nd and 3rd books but my copies are MIA at the moment. I have about 40 ft of shelving full of seismic/DSP books. These three are my mainstays. I'll update the information when I find them.Bendat & Piersol is the ne plus ultra of DSP. It's pure math end to end, but it will explain how to recover arbitrary amplitude data using just the "sign bit" (aka "hard clipping") 0 or 1 input values only. However many bits you want out if you acquire enough data. Sam Allen was recpording seismic with 1024 channel systems in the late '60s when everyone else was doing 16 or 24 channels. Bendat & Piersol do not cover the exotica of seismic noise removal, but for general DSP it is the best.What they don't cover is pretty much restricted to seismic processing techniques peculiar to that domain. Those would fill many books the same size and mathematical rigor. You don't want to go there if you are not looking for oil. You don't have to read all of Bendat & Piersol as that is serious work, but I am likely to simply reply with a page number from Bendat & Piersol if you ask a question worth answering.This is not intended as a discussion, but rather something I can refer people to if they send a PM asking for help. After a while answering very basic DSP questions gets tedious. If you're not willing to buy and read Karl, please don't bother me. Get to Bendat & Piersol and I'll be happy to discuss anything.Have Fun!Reg