hybridfree/eevblog-posts huggingface dataset:
Ceramic, Polystyrene & tantalum caps replacement - Page 1
Forum section: electronics / beginners

author: gkmaia
author_rank: Frequent Contributor
timestamp: March 25, 2019, 01:02:06 am
content: I would like to replace a few capacitors and do not have all the right type as per boom but would like to check if they will perform as intended.Note that some of the original caps are rated 100, 500 or 600v but the voltage on the block where these caps sit won’t exceed 50v.Replace680p 630v Polystyrene (sty)for680p 100v Polyester mylar plastic film (green cap)Replace100nf 63v single-layer ceramic (NPO CDS)For100nf 1kv single layer ceramic high voltageReplace3300p 50v single-layer ceramic (NPO CDS)For3300p 100v Polyester mylar plastic film (green cap)Replace470nf 35v tantalumFor0.47uf 50v electrolytic cap

author: Jwillis
author_rank: Super Contributor
timestamp: March 25, 2019, 10:16:25 pm
content: Depends. Different types of caps of similar rating respond differently with frequency and application.

author: dmills
author_rank: Super Contributor
timestamp: March 27, 2019, 12:29:27 pm
content: I am suspicious of a 100nF C0G, nice part, but it is a little specialist.In general C0G are (above tiny values) only used for a reason, and something as out there as a 100nF of C0G would be the sort of thing anyone would try hard to design out if they could (It exists, but is physically quite large (1206, never happymaking in ceramic caps, and relatively expensive), it is probably there for a reason (If you have identified that part correctly).WHY are you replacing these, apart possibly from that tant there is noting there where your replacement is likely to be an improvement in ANY parameter that matters, and even the tant may be the appropriate choice depending on the circuit, and most of these parts would be the last places I would look for a problem.Regards, Dan.
ceramic vs film capacitors for  < 1 uF  450V-630V - Page 1
Forum section: electronics / beginners

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: June 03, 2015, 02:07:45 pm
content: Repairing some vintage electronic equipment, I am often faced with the necessity to replace capacitors,electrolytic or not, with high voltage ( 450, 630 V).For caps under 1uF, I am thinking of using ceramics or film capacitors, rather than electrolytics,but I do not want to stock too many kinds.What would you recommend ? ceramics (X7R) or film ?Please do not discuss outside from the focussed range : cap < 1 uF , voltage from 450 V to 630 VThanks

author: SeanB
author_rank: Super Contributor
timestamp: June 03, 2015, 06:00:43 pm
content: I would go for film units from around 10n to 1uF, and under that 1kV ceramic capacitors. that way you have good stability with the low value ceramic units, and reasonable size for the film ones. Standardise on 630V film, as then you have a lot of room for derating with temperature. same for the ceramics, as 1kV are going to be lower change with voltage, though they will be bigger. You can use ceramic up to 47n 1kV as the size is not too bad, but for most applications in old equipment the film device is fine. will in any case be smaller than the one you are replacing.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 03, 2015, 06:28:29 pm
content: Meh, I'd go down to 1n in film. Ceramics in MLCC format are okay up to 10n, but discs are expensive. Anything in Type 2 dielectric is nonlinear. C0Gs (disc or otherwise) are affordable in the <200pF range (and are usually good to *well* over rated voltage, if you feel like risking it!).As I recall, CDE's DME series were possibly the best value as far as capacity per size and dollar. Are they still around? Ah, yea:http://www.mouser.com/Cornell-Dubilier/Passive-Components/Capacitors/Film-Capacitors/_/N-9x371?P=1z0x4lnZ1z0x6fvZ1yx4awuZ1z0x6exZ1yyirz7Z1yx4awvZ1yx4awxZ1z0zlgf&Keyword=dme&FS=TrueBut you're welcome to find whatever you need. Polypropylene may be desirable for precision filters, but shouldn't be necessary for most anything in vintage electronics. Most common application was bypass and AC coupling, both of which are low current uses; capacitor type simply does not matter, go for the smallest/cheapest.Do make a point of replacing anything that touches the AC line, with proper X1 (line-to-line) or Y1 (line-to-ground ... if they even used a safety ground wire!) rated caps.Tim

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: June 04, 2015, 09:32:13 am
content: Thanks Sean and Tim. These advices are helpful.I was concerned about the film capacitors, as many of them have very short legs, not usable for random replacement in old equipment.But the ones you mention seem to be OK (I usually shop at Mouser).Quote from: T3sl4co1l on June 03, 2015, 06:28:29 pm
cfd lamp - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: June 07, 2020, 04:47:22 pm
content: hi all,i have a cfd lamp in my kitchen,when its turned off it flashes once about every 20 seconds,any idea why this is happening?

author: Zero999
author_rank: Super Contributor
timestamp: June 07, 2020, 05:15:38 pm
content: What sort of switch is it? Leakage would explain this, especially if you have a switch with active circuitry, such as a touch switch.

author: m3vuv
author_rank: Super Contributor
timestamp: June 07, 2020, 06:14:32 pm
content: its just a standard uk light switch.

author: Monkeh
author_rank: Super Contributor
timestamp: June 07, 2020, 06:23:08 pm
content: Is it by any chance a two-way switch?

author: m3vuv
author_rank: Super Contributor
timestamp: June 07, 2020, 06:26:15 pm
content: yes on and off

author: Monkeh
author_rank: Super Contributor
timestamp: June 07, 2020, 06:28:50 pm
content: Well then, that's unusual. I would suggest an electrician.

author: m3vuv
author_rank: Super Contributor
timestamp: June 07, 2020, 06:31:18 pm
content: sorry about the sarcasme,but its a 3gang switch,and the lamp in question is double switched from the halway light thats also a 3 gang switch.

author: Monkeh
author_rank: Super Contributor
timestamp: June 07, 2020, 06:33:15 pm
content: Quote from: m3vuv on June 07, 2020, 06:31:18 pmOh, well, in that case I was on the money.. and I'd still suggest an electrician. Hopefully one who knows how to deal with this stuff.What you've got is capacitive coupling between the two switched lines, or one switched and permanent. There's a few ways to fix it, alternatively you could just try a different lamp.

author: m3vuv
author_rank: Super Contributor
timestamp: June 08, 2020, 11:15:43 am
content: thanks for the repllies,i think i will just leave it.
CFL + Leyden Jar + Flyback transformer = Fun - Page 1
Forum section: electronics / beginners

author: zeal422
author_rank: Contributor
timestamp: June 19, 2023, 07:18:00 pm
content: I hope you enjoy it since I'm still a noob at electronics but I've made this... I made something...And I don't need likes and all that... I thought yt would be the most optimal platform for people to access.Cheers!

author: Infraviolet
author_rank: Super Contributor
timestamp: June 21, 2023, 03:44:59 am
content: Maybe there should be a separate forum section for "high voltage" type projects. They tend to give fairly interesting results, but they're just so different to the sorts of circuits which process signals or data at low voltage, and different even to mains circuits providing power, that most people aren't thinking about them. I guess that's why there aren't that many responses to this sort of thread when in the general electronics section.

author: zeal422
author_rank: Contributor
timestamp: June 21, 2023, 06:29:41 am
content: I have purchased a 1000W ZVS, I'm just waiting for it. This is only powered with a pewny CFL and directly to the primary of the transformer.
CH224K Schematic - Page 1
Forum section: electronics / beginners

author: Sebastian1771
author_rank: Newbie
timestamp: May 09, 2023, 08:12:08 pm
content: Hi together,i need your help for the USB PD Chip CH224K. I found the datasheet / this website:https://components101.com/ics/ch224k-usb-power-delivery-controller-icNow... it looks like the C1 / C2 connections are actually switched. Does anyone have experience with this chip and can confirm that the datasheet has an error before i print / assembly my board and be devastated :-)Thanks a lot for your help!Sebastian
CH340 & AVR - proper external + internal power supply - Page 1
Forum section: electronics / beginners

author: nemail2
author_rank: Regular Contributor
timestamp: November 20, 2021, 08:43:16 pm
content: Hiif I have a device which is powered by an internal voltage source and that has an AVR (1284p in that case)@5V + a CH340@5V for USB/UART conversion, how do I properly connect the 5V lines?If I connect the AVR to the 5V of the USB port and the CH340, the AVR will get voltage through USB, which I don't want. The device has a mains switch and should stay turned off, even with a USB cable connected to it.If I connect the AVR to the internal voltage source and the CH340 to the USB 5V+ and the device is powered off, the CH340 will receive power from USB while the AVR is turned off and probably drive the RX/TX UART lines high which could light up the AVR through the RX/TX lines.If I connect the AVR and the CH340 to the internal voltage source, and if the device is powered off, the CH340 may see voltage coming in from the PC through the D+/D- lines of the USB port, although VCC being 0V.I'd like to be able to leave the USB cable connected to the device all the time without powering anything parasitically through data lines.Is there an easy, proper way to do this or would I just do the last option and ignore the D+/D- lines?Thanks!

author: magic
author_rank: Super Contributor
timestamp: November 22, 2021, 04:09:06 pm
content: Not sure about CH340 but some USB devices like FT232 can tolerate USB signals while being unpowered (as may occur in a self-powered application).Interestingly, FT232 datasheet also recommends keeping the chip in reset while USB is disconnected because otherwise the chip would apply 3.3V pullup to the data lines which reportedly causes incorrect operation of some USB hubs when the device is finally connected.One option which sidesteps all problems at the cost of two components:- add a diode so that CH340 TX can only pull down- pull up MCU RX to the external supply with a resistor
CH340G does not report as serial port ( and crystal isn't working ) - Page 1
Forum section: electronics / beginners

author: soFPG
author_rank: Frequent Contributor
timestamp: August 22, 2021, 02:09:23 pm
content: Hello EEVBloggers,I finished populating my first PCB witht a USB <-> UART bridge IC (in my case: CH340G with external 12MHz crystal).Unfortunately, the CH340G doesn't report itself as a serial port in windows device manager.I probed the crystal's pins and I only got a stable 3.3V instead of some kind of waveform. I checked the capacitors, they are 16pF.Schematic is in attachments.Any ideas why this wouldn't work?

author: wraper
author_rank: Unknown
timestamp: August 22, 2021, 02:18:35 pm
content: So you have 3V3 connected to VCC and V3 but where does it come from?

author: soFPG
author_rank: Frequent Contributor
timestamp: August 22, 2021, 02:28:31 pm
content: From ME6209A33M3G

author: mon2
author_rank: Frequent Contributor
timestamp: August 22, 2021, 03:46:49 pm
content: Check the soldering of your crystal.What are details of this applied crystal? Is it a fundamental 12 Mhz crystal ? If possible, test with another crystal.

author: soFPG
author_rank: Frequent Contributor
timestamp: August 22, 2021, 04:30:14 pm
content: I tried with a 16MHz crystal and same result (3.3V and no serial port)What do you mean "fundamental 12MHz crystal"? It is one of those:https://en.wikipedia.org/wiki/Crystal_oscillator#/media/File:16MHZ_Crystal.jpg

author: magic
author_rank: Super Contributor
timestamp: August 22, 2021, 06:09:28 pm
content: If both pins are 3.3V then something is wrong with the chip / configuration / pinout / supplies / etc. There should be an inverter between these pins.

author: soFPG
author_rank: Frequent Contributor
timestamp: August 22, 2021, 06:19:47 pm
content: Is the CH340G supposed to work in this configuration with 3.3V?

author: mon2
author_rank: Frequent Contributor
timestamp: August 22, 2021, 11:10:21 pm
content: 16mhz will not work for the usb framing (has to be 12mhz) but it should be oscillating. How are you confirming that the crystal is not working? Are you checking with an oscilloscope? May be a good idea to post your pcb layout to review for possible issues.

author: soFPG
author_rank: Frequent Contributor
timestamp: August 23, 2021, 09:49:15 am
content: You are correct, 16MHz wouldn't work. I just switched crystals to see if my 12MHz crystal somehow is defect or a fake.I checked with an oscilloscope. You can see the PCB layout in the attachments.This is kind of frustrating because I already redesigned the PCB once due to a routing mistake of mine
CH341A Programmer software - Page 1
Forum section: electronics / beginners

author: Prog
author_rank: Newbie
timestamp: August 06, 2016, 05:33:31 pm
content: Short Q:Could be a problem if I've used CH341A v1.17 Programmer software that have in list onlyW25Q128BVinstead ofW25Q128FVthe last one being my original Chip too?According to the manuals (BV version page 71 Ordering information section and FV version page 97), 128B or 128F the same density 128M-bit, V=2.7..3.6V in both cases.I don't see any difference, more than that, I have successfully writen / verified the Bios chip and get into the windows again but just want to be sure.Any thoughts? thanks
Chaining Optical Endstops - Page 1
Forum section: electronics / beginners

author: King_bob
author_rank: Newbie
timestamp: February 24, 2019, 10:43:53 pm
content: So I looted a bunch of optical endstops from a printer, and wanted to use them as limiter switches, but to do this I need to connect two of them to one output pin, as seen below. Unfortunately I can't figure out what I am doing incorrectly. When I measure signal to VCC I get a full 5V but when I chan them as seen in the diagram, I only get 2.5V. I don't understand why this is happening, nor how to fix this issue.Any help would be appreciated.
Challenge with arbitrary function generator - Page 1
Forum section: electronics / beginners

author: mossygreen
author_rank: Contributor
timestamp: July 04, 2021, 01:46:21 pm
content: In trying to get an understanding of RC filters I used a function generator to create an adjustable sweep. I have two questions:When I set it to sweep from X to Y spending M milliseconds to do it and use the trigger output to watch the signal on a scope, that's what it does - except that the starting point (where in amplitude the trigger starts) drifts. Depending on X, Y, and M it drifts either fairly slowly or fast at human time scales. I can use the scope's controls to freeze a particular event so that I can measure things using scope cursors, but it seems like the generator should be able to always start the sweep at a fixed phase offset (like, 0) aligned with the trigger. However, I can't see any way to do this. I did give 0ms for the "return" time which it let me set, It won't let me set 0Hz as the start point, changing that to 1 micro-Hertz so presumably an immediate return is okay .The generator is a 2-channel unit and I'd like to have the second channel be a ramp that starts with the start of the sweep and ends when the sweep completes. This would mimic how an analog generator could drive and XY display. However, I can't see how to do this within the unit itself. I haven't yet tried splitting the trigger output between the scope and back into the generator itself and making the second channel "go" on the external trigger. However, that seems pretty silly since this seems like something you'd generally want to do. Maybe that implies that I'm thinking about one or more things wrong.

author: David Hess
author_rank: Super Contributor
timestamp: July 05, 2021, 01:27:37 am
content: You did not say which digital function generator you are using, but I have done exactly as you have described with my ancient analog swept function generator without issues. It may actually be preferred for the trigger to not be phase aligned with the frequency output so that the display fills in properly at low frequencies.It also helps to have a logarithmic sweep to produce a more useful display but this is not strictly necessary.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: July 05, 2021, 02:22:33 am
content: Can you trigger both of them from a third device like a simple pulse generator.

author: mossygreen
author_rank: Contributor
timestamp: July 06, 2021, 03:02:38 am
content: Thanks for the input. It is a Tek AFG31022 unit.Given that nobody has said "hey, you totally missed setting X" I'm going to route the event output to the input and make channel 2 reference the trigger input as its start condition. I suspect that will work for #2.I hadn't thought of using a logarithmic sweep, but it does make sense. I've spent a few hours playing around with a linear sweep and the very next opportunity I have I'll look at the logarithmic output.
change AA to 1s Li-ion - Page 1
Forum section: electronics / beginners

author: reaper38
author_rank: Newbie
timestamp: April 09, 2017, 11:17:17 am
content: Hello, I want to change 2 AA batteries in series to one li-ion cell. Problem is that I want to use power indicator from device, so voltage must drop as cell discharing from 2,4 to 1,8 volts. Any suggestion how to do it?

author: mariush
author_rank: Super Contributor
timestamp: April 09, 2017, 12:10:43 pm
content: estimate the average power consumption of that device and the peak current (both at 1.8v, the minimum voltagE0, then maybe pick a buck switching regulator with small enough quiescent current and enough current output for your needs, and configure it to track the discharge rate of the battery ( 4.2v full to 3.6v discharged ... so 2.4v to 1.8v ... basically half the input voltage)High frequency dc-dc regulators would use very little space, it would be just an issue of balancing the maximum frequency (for tiny inductor and capacitors) vs efficiency at some output current range.For example seeTPS63030which uses only a 1.5uH and a bunch of tiny ceramic capacitors and can output up to 800mA of current.Or see NCP1406 / NCV1406 for lower frequency.Or seeTPS62240for 300mA maximum current.Since you want exactly half the voltage (1.8v .. 2.4v for a battery that would have 3.6v to 4.2v) ... for low currents (like 50-100mA), you could look into voltage doubler chips which can also be configured to output half the input voltage.For example,For maximum 40mA of current , seeLM2665M6For maximum 60mA of current, you could tryTPS60403For max. 100mA, you haveLM2660MXfor max 200mA you haveLM2662MXSee the datasheets included on the pages linked above.

author: reaper38
author_rank: Newbie
timestamp: April 09, 2017, 10:05:12 pm
content: Thanks for your reply. How to make it track voltage? Not connect feedback pin?

author: ebclr
author_rank: Super Contributor
timestamp: April 11, 2017, 04:34:01 am
content: Li-ion have a very different discharge curve than AAA cellIf you let the cell discharge more than 3.1 V , cell live will be reduced or even kill the cellThis paper have some useful informationhttp://www.ti.com/lit/an/snva533/snva533.pdf
Change switch on Velleman decision maker - Page 1
Forum section: electronics / beginners

author: Rye
author_rank: Newbie
timestamp: February 22, 2024, 12:12:05 am
content: Hi all I'm hoping you can help I really want to change the switch on the velleman decision maker to a momentary switch. Is there anyway this would be possibleHere is the kitAnd I want to change it to this 2 prong switch as I want to put this into a 3d printed boxAny help would be hugely appreciated

author: Ian.M
author_rank: Super Contributor
timestamp: February 22, 2024, 12:47:55 am
content: That's easy enough to do when you first build the kit. If you check the supplied switch with a multimeter, you'll find that its four pins are permanently connected in two pairs then when you press it all four pins connect together. You'll need to look at the PCB layout to see which two pins to connect the external switch wires to. Worst case you may have to add fixed wire links to join the pads the switch normally permanently connects. If you've already built it its not so easy. I'd leave the switch and connect your external one in parallel. Reading theassembly guide, It looks like the best places top-side to hook up to are the red wire from the battery, and the anode (no stripe) end of D1.

author: Rye
author_rank: Newbie
timestamp: February 22, 2024, 01:23:25 am
content: Thanks so much for getting back to me. I've attached images of the PCB. Am I right in thinking how I've highlighted it would be the correct way? Sorry for such a silly question

author: Ian.M
author_rank: Super Contributor
timestamp: February 22, 2024, 01:27:34 am
content: Looks OK.
Change Triac in soldering station ? - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: June 06, 2019, 06:18:26 pm
content: My main soldering station is a cheap $40 ebay model with a Triac. I think it's a 40-60W iron, I find that out, I don't remember anymore. There's only the triac, and 2-3 resistors, switch light, basically. I'll map it out soon. I have tons of resistors, and pots too.So I want to boost it's power by 10-20W and see if everything's fine and works better. Until I get a real Hakko FX-888d, why not?? I bought some BT136-600 TRIAC's 600V 4A, just at random so I'd have TRIAC'shttps://www.promelec.ru/pdf/BT136-600-NXP.pdfI'll map out the circuit in my station maybe today, does anyone know what I should change if I put that more powerful BT136 in ? Assuming the tip can handle a few more watts.I have a variac, so I can slowely turn up the voltage to see if it works. But how is a lower rated triac biased with the resistors? For all I know they can be left the same.What about a 125V dimmer switch for a 60 or 100W lightblub, can that be used to upgrade my cheapo station a few watts ?Yes I could power the SS off the variac at 135V, but I'm assuming that thing gets hot just plugged in, I don't want to use it for that.

author: Zero999
author_rank: Super Contributor
timestamp: June 07, 2019, 09:40:14 am
content: Changing the TRIAC won't make any difference to the power output of the heating element.If the supply voltage is 120V and the rated power is 60R, the element will have a resistance of 60Ohms and changing the TRIAC will not alter that. The maximum power will still be determined by the heating elelment's resistance and supply voltage.By the sounds of it, the cheap temperature controller is just a lamp dimmer, with no feedback. I'd recommend investing in a real temperature controlled iron, with feedback, to keep the temperature constant.The TRIAC is just a switch. Changing it will have the same effect on power, as changing a light switch.
Changes in LM317 data-sheet example circuits - Page 1
Forum section: electronics / beginners

author: beatle
author_rank: Contributor
timestamp: August 03, 2013, 09:44:39 pm
content: Hello!I was reading my Art of Electronics (love it!) and noticed that some differences in example schematics from the current LM317 data-sheet (http://www.ti.com/lit/ds/symlink/lm117.pdf) and an old version from the book's appendix.What confuses me is Figure 50. from page 24 in the new IT's data-sheet as I see no purpose for the R4 resistor. As I understand it, the R3 is the one that turns on the transistor when the current limit has been reached and R4 just wastes power by dropping more voltage unnecessarily. What is it that I am not seeing?Furthermore, Figure 56. from page 26 that shows almost identical circuit (and is also present in the old version of the data-sheet) has no equivalent for R4.Thank you for any hints!(And sorry if this is a stupid question!)

author: fcb
author_rank: Super Contributor
timestamp: August 03, 2013, 10:04:37 pm
content: Fig 50.If R4 wasn't there, the ADJ pin would only go as low ~Vbe on the transistor. The 317 output is 1.25v above Vadj. R4 allows the Vadj pin to go at least 1.25V below 'ground', thus giving you 0v output (imagine shorting the 317 output to ground).Fig 56.Effectively this is a standard fixed voltage 317 circuit, with a transistor to pull the adjust pin down to limit the current. I certainly wouldn't suggest anyone charge batteries like this, but in principle it would work. It doesn't need to be able to shut the output down to 0v as the battery is unlikely to be <0.9v per cell.

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: August 03, 2013, 10:31:46 pm
content: Is it just me or do others agree that its easier to just bypass all of that and use some diodes to get it down to 0v because of their voltage drop?

author: Bored@Work
author_rank: Super Contributor
timestamp: August 03, 2013, 10:51:17 pm
content: Diodes are a good choice - if you really want to get rid of whatever little precision and accuracy an LM317 has.

author: EpicIntelGamer
author_rank: Regular Contributor
timestamp: August 03, 2013, 11:01:53 pm
content: Quote from: Bored@Work on August 03, 2013, 10:51:17 pmLol I didn't even think of that.

author: beatle
author_rank: Contributor
timestamp: August 03, 2013, 11:46:19 pm
content: Quote from: fcb on August 03, 2013, 10:04:37 pmThank you very much, this is an great explanation!I had already made myself content with the idea that one can't make LM317's output go lower than 1,25V. Somehow the possibility of pulling the ADJ pin negative so easily didn't dawn to me.Thanks again, now I am at peace!

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: August 05, 2013, 05:49:19 pm
content: Just wanted to note that, old as it is, the 317 is still a remarkably good voltage regulator. Properly implemented and bypassed the noise is very low. If you don't get near textbook performance, the layout or component choice is probably not quite optimum.
Changing a 120v 60Hz adapter to 240v 50hz - Page 1
Forum section: electronics / beginners

author: spacey
author_rank: Newbie
timestamp: March 15, 2021, 09:47:55 am
content: I recently bought a power tool from the USA, which works great but the battery charger adapter they included in not dual voltage. I have looked at changing it but it becomes problematic, as they seem to change the batteries slightly between them all. I didn't really fancy buying a Chinese knock off (well not yet).I did see a few videos on youtube eluding the to the fact you can alter the input voltage by changing the capacitors on the board. I wanted to ask if it really that simple, and one video I saw only had one capacitor on it. Opened this one up and as you can see I was slightly thrown.What do I need to change (apart from the blown orange item)?Is it possible and easy to do?

author: tunk
author_rank: Super Contributor
timestamp: March 15, 2021, 11:19:03 am
content: Look at the capacitors to the left, they should be rated at 400-450V.I wouldn't know "if it really (is) that simple".

author: Zero999
author_rank: Super Contributor
timestamp: March 15, 2021, 01:28:10 pm
content: I wouldn't bother. Use a small auto-transformer to step 240V down to 120V. Presumably it doesn't use much power, say <50VA? If so, there are cheap mains adaptors which provide 120V, from 240V.https://www.amazon.co.uk/Skytronic-240-120-Stepdown-Voltage-Converter/dp/B002KRJ7ZA/ref=sr_1_4?dchild=1&keywords=240v+to+120v+adapter&qid=1615814818&sr=8-4https://www.amazon.co.uk/BiuZi-Voltage-Converter-Transformer-Step-Up/dp/B07VMF3R46/ref=sr_1_5?dchild=1&keywords=240v+to+120v+adapter&qid=1615814818&sr=8-5https://www.connevans.co.uk/product/3079097/MX651004/UK-Step-Down-Voltage-Converter-240V-120V--100VA--

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: March 15, 2021, 01:28:15 pm
content: I'd expect you'd have to change the transformer.

author: spacey
author_rank: Newbie
timestamp: March 15, 2021, 03:08:18 pm
content: Wish I had seen the step down before someone tried it. They blew the fuse and that resistor.No the two capacitors are lower spec. I know they make the black and decker charger here for us and the Stanley, two subtle differences between them but they can be adjusted if one of them would work

author: Zero999
author_rank: Super Contributor
timestamp: March 15, 2021, 03:23:15 pm
content: Quote from: spacey on March 15, 2021, 03:08:18 pmThe brownish-yellow disc shaped device is a metal oxide varistor. It protects against high voltage spikes by drastically reducing its resistance, to short circuit them. It should be fairly easy to replace it and the fuse, but other parts might have also been damaged.

author: spacey
author_rank: Newbie
timestamp: March 15, 2021, 03:25:39 pm
content: I can take a punt abs replace those the dues is harder to find with RS I found the varistor easily
Changing a Buck Converters Input Voltage Instantly (From 5V to 20V) - Page 1
Forum section: electronics / beginners

author: rents
author_rank: Newbie
timestamp: November 25, 2022, 11:24:19 pm
content: Hi all! It's my first post, be gentle.I'm currently designing a carrier board with usb power delivery for a FPGA system on module. i'm using buck converters that are working between 1000kHz-1500kHz switching speeds for different voltage levels i need. As far as i can understand when you first plug in your type c cable you get 5V from VBUS and then source and sink establish a communication and then you get your desired voltage. Let's say i have programmed my PD controller(i'm usng FUSB302) to give me the maximum voltage and current source can provide. And let's say that is 20V. My VBUS voltage is going to increase from 5V to 20V almost instantly. My question is would i get a voltage spikes at the output of the regulators that can damage components? How fast does buck converters react to feedback?I made a circuit with a buck controller that can output 5V 5A and a power switch (basically a comparator shuts down a PMOS that is connected to VBUS and enables the buck controller when VBUS voltage is higher than 5.5V).And i was going to connect all of the other buck converters to that but it's messy, takes too much space and expensive. Is there any other solution that can look in to?

author: thm_w
author_rank: Super Contributor
timestamp: November 26, 2022, 12:20:37 am
content: Post the part number of the buck converter you are using.In the datasheet there will be a specification called "Line regulation", that will provide some of your answer.https://www.tek.com/en/documents/application-note/simplifying-dc-dc-converter-characterization-0You say the Vbus will almost instantaneously switch from 5 to 20V, but in terms of time scale a regulator can deal with, it is probably relatively slow. As there is a regulator inside the USBC supply that is having to change from 5 to 20V.The actual time might be in the USB spec somewhere.

author: jwet
author_rank: Frequent Contributor
timestamp: November 26, 2022, 04:21:13 am
content: In the USB PD Spec, the basic slew rate max is .03v/ms, so a 10v change takes somethings like .3 ms, not super fast. Settling is about 300 mS, which is leisurely. Like most USB stuff, I don't know how compliant commodity USB PD sources are but a decent power supply could easily handle that kind of a step. There is a similar negative slew which can also create issues if your supply can't sink.

author: David Hess
author_rank: Super Contributor
timestamp: November 26, 2022, 01:35:46 pm
content: The regulator's "line regulation" specifications cover what happens to the output when the input changes.Current mode regulators have better, actually excellent, line regulation and as jwet points out, the USB specification is not particularly fast. There should not be any problem.
changing diode and capacitors - Page 1
Forum section: electronics / beginners

author: Mepakos
author_rank: Contributor
timestamp: August 01, 2019, 08:22:48 am
content: I need help guys. If you reverse the two diodes and capacitors what would happen?

author: ogden
author_rank: Super Contributor
timestamp: August 01, 2019, 08:28:06 am
content: Quote from: Mepakos on August 01, 2019, 08:22:48 amDraw schematic, compare to original. What you see?

author: Mepakos
author_rank: Contributor
timestamp: August 01, 2019, 09:20:15 am
content: I think no current flows through D2?

author: ogden
author_rank: Super Contributor
timestamp: August 01, 2019, 09:34:59 am
content: Quote from: Mepakos on August 01, 2019, 09:20:15 amWhy you think so? Hint: Tr1 is transformer, it means AC voltage source. Look at both circuits assuming that all capacitors are non-polar, think again what happens.  Do you really think that reversing diodes can introduce such a fundamental change as removing current from one of diodes? Why?

author: Mepakos
author_rank: Contributor
timestamp: August 01, 2019, 09:58:08 am
content: Because of the direction. I read that current flows only from anode to kathode of a diode and cant flow from kathode to anode. If thats not the case maybe nothing would change if i reverse them.

author: Zero999
author_rank: Super Contributor
timestamp: August 01, 2019, 10:14:49 am
content: Quote from: Mepakos on August 01, 2019, 09:58:08 amThe transformer outputs AC.In the original schematic, assuming node B is 0V, D1 conducts when the AC cycle is positive and D2 conducts when it's negative. If their polarities were reversed, then this would be the opposite.
Changing number of horizontal divisions on a Rigol DS1052e - Page 1
Forum section: electronics / beginners

author: dog80
author_rank: Regular Contributor
timestamp: December 12, 2012, 07:49:13 pm
content: I am trying to do the Bode diagram on a filter using a scope and a generator as per the recent video Dave uploaded.But my Rigol has 12 horizontal divisions so it is kinda hard to see where each frequency corresponds on the resulting graph.Is there any way to change the horizontal divisions to 10?

author: c4757p
author_rank: Super Contributor
timestamp: December 12, 2012, 07:53:35 pm
content: Ignore the extra two? Just line up the graph with the middle or leftmost ten.

author: dog80
author_rank: Regular Contributor
timestamp: December 12, 2012, 09:51:22 pm
content: Thanks! It was so obvious...

author: c4757p
author_rank: Super Contributor
timestamp: December 12, 2012, 10:09:58 pm
content: Yep!We all miss little things like that sometimes. The extra two divisions are a bonus - you can show more stuff on the screen.

author: ikrel
author_rank: Contributor
timestamp: December 15, 2012, 09:03:24 pm
content: if you click/pushing the horizontal control it will switch to a finer resolution so you can adjust to a more sensitive point just like for vertical controls.
Changing parts in Eagle - Page 1
Forum section: electronics / beginners

author: electrolust
author_rank: Unknown
timestamp: October 25, 2015, 07:14:42 am
content: I've been using schemeit, but it doesn't have integrated PCB design so I am trying Eagle.In schemeit, you just blithely draw your schematic with little concern for what the part is going to be. Then you can go and use the BOM integration (really nice) to choose parts.In Eagle, you have to know what part you are going to use, while you're still drawing the schematic. eg, 0603 vs 0805 SMD resistor. This seems very painful, especially so if you want to go through and change parts.Am I missing something?

author: FreddyVictor
author_rank: Regular Contributor
timestamp: October 25, 2015, 08:40:18 am
content: Quote from: electrolust on October 25, 2015, 07:14:42 amyou can change the package (physical part) by clicking the Change icon (Wrench) and then select Package and click the part you want to change (but this only works if the part has multiple packages!)if you want to learn eagle, there is apdf tutorialwhich is worth reading as it is not super-intuitive

author: Kleinstein
author_rank: Super Contributor
timestamp: October 25, 2015, 09:38:56 am
content: In a limited range one can use the change package function. This does not work well with older part definitions, where different sizes are separate parts, but at least for resistors and capacitors there are new definitions that allow this.

author: electrolust
author_rank: Unknown
timestamp: October 25, 2015, 10:26:03 pm
content: Ok cool.Is there an easy way for me to know which parts (at least passives) have multiple footprints?I noticed for example that there is a *1458 part which has "technology" "LM" and footprint variants "N" and "D". These show up in the parts list as 2 distinct parts LM1458N and LM1458D. I see now that I can change that part between the 2 variants. But from the part selector GUI I can't see how I would know this.EDIT: I figured it out, I think. Looks like a library contains only devices (duh?). Therefore if you drill into a library, that top level has only devices. Anything that looks like a folder represents a device that has multiple variants, which I suppose means different footprints (although I guess technically it could be the same footprint with different connections).
changing smt electrolytic caps for tantalum chip caps - Page 1
Forum section: electronics / beginners

author: ME
author_rank: Frequent Contributor
timestamp: May 10, 2025, 04:31:50 am
content: Is it ok to swap smt electrolytic caps for tantalum chip caps of the same values?.

author: bdunham7
author_rank: Super Contributor
timestamp: May 10, 2025, 04:34:08 am
content: It depends on the circuit. Sometimes tantalum caps have been used where electros would work, other times there is a need for low ESR or high frequency capability (low inductance).

author: Siwastaja
author_rank: Super Contributor
timestamp: May 11, 2025, 06:30:05 pm
content: By default, no. Capacitor types have different characteristics and different reasons to be used.Electrolytic to tantalum:Tantalums specifically are special snowflakes which just go boom if you don't understand their limits on inrush current, and voltage derating required. They are usually completely unsuitable for hot-pluggable power input bulk filtering, for which aluminum electrolytics are pretty muchoptimum, so chances are high that blind replacements leads to a fireball.Tantalum to electrolytic:Chances are high tantalum is used for specifically stable value of ESR, capacitance, or both. Replacing with aluminum electrolytic only works if the original design used tantalum "for no good reason".

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: May 11, 2025, 07:53:00 pm
content: Besides the stability performances already mentioned by Siwastsja, tantalum caps have a higher volumetric efficiency as compared to aluminum electrolytic.But they have some caveats that the user must take into account. Most important the voltage derating and the fact that they simply cannot withstand any reverse voltage.There are also papers which mention that when exposed to the solder reflow temperatures, there is some tantalum oxide degradation, which requires reforming at an even lower voltage.

author: benj38
author_rank: Frequent Contributor
timestamp: May 12, 2025, 09:03:29 pm
content: This was discussed in the past:https://www.eevblog.com/forum/beginners/any-reason-to-not-replace-surface-mount-electrolytic-caps-with-tantalum/Sometimes the search bar is your best friend.
Changing TCR with time - Page 1
Forum section: electronics / beginners

author: analityk
author_rank: Regular Contributor
timestamp: September 18, 2022, 12:00:45 am
content: Hello.Resistors have TCR. Ordinary carbon resistor have +-200ppm and more. But now i have looking for resistor, where i do not care about absolute value even in changing temperature, but i have to know how big change of TCR is in time. I want use it in thermostate, for polarisation of NTC. Nomen-oment for NTC resistor drift of TCR are specified.Did i should use low TCR resistors (metal film) or ordinary carbon film resistor can fit in my ideas?Sincerely.Simon

author: Teledog
author_rank: Regular Contributor
timestamp: September 18, 2022, 04:44:04 am
content: Check the spec sheets for the resistor(s) you intend to use?Vishay & similar are available online, with derating factors, etc.

author: Gyro
author_rank: Super Contributor
timestamp: September 18, 2022, 08:59:35 am
content: Just use a metal film resistor. The change in TCR with time should be insignificant.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 18, 2022, 09:58:08 am
content: Are you needing to linearise a thermistor. Is the TC of the linearising resistor that interests you?The TC of the thermistor is very large compared with any fixed resistor. So the TC of the the fixed resistor has almost no effect.

author: strawberry
author_rank: Super Contributor
timestamp: September 18, 2022, 11:36:01 am
content: carbon film ~200ppm minimummetal film =~ thick/thin filmthin film is relatively better stabilitybulk metal 0..10ppm maxresistor dimensions/construction affect long term stabilityeven some carbon film resistor go bad after ~40y

author: Terry Bites
author_rank: Super Contributor
timestamp: September 19, 2022, 06:18:14 pm
content: Its worth mentioning that TC for ordinary resistors is sometimes specified as postive or negative or both. TC is a poor predictor of resistance change with T. There's no guarantee that the TC does change with T.TC is not a parameter you want to use in a design- usually just the oposite.Resistor ageing is unpredictable. But generally you get what you pay for.

author: strawberry
author_rank: Super Contributor
timestamp: September 19, 2022, 07:08:15 pm
content: carbon film vs wirewoundheat them in oven to 100C deg.what chemical compound or solid metal will change its properties
Changing the Duty cycle of a given signal - Page 1
Forum section: electronics / beginners

author: Spemo
author_rank: Regular Contributor
timestamp: April 14, 2021, 07:36:41 pm
content: Hello everyone,I'm trying to find a solid state solution for a small problem.The situation is as follows:A Timing circuit with a CD4060BE and a 4027BE, the output is a 1Hz signal with a 50% Duty cycle.This 1Hz 50% signal goes into a "signal shortener" which is made up out of two DPDT relays, a transistor, capacitor and resistor, to shorten the signal to a short pulse, my guess is around 15% on, 85% off.Now, I have two problems with this: first, relays. It works, but the noise it creates is not wanted. Second, there is reliability to think about.I'm looking for a really simple solution that changes the duty cycle of the given signal from 50% to let's say 15%, or adjustable at best.I've tried googling and the forum search, but I couldn't find the answer I was looking for.Maybe there is an obvious solution for this... If you happen to know one, please share it with me, it would be apreciated a lot!Thank you for your time,Daniel

author: Renate
author_rank: Super Contributor
timestamp: April 14, 2021, 07:40:53 pm
content: If you AND the last two bits of the counter you will get a 25% duty cycle.If you AND the last three bits of the counter you will get a 12.5% duty cycle.etc...Or you can NOR them.

author: Ian.M
author_rank: Super Contributor
timestamp: April 14, 2021, 07:54:28 pm
content: .... and if for any reason you cant tap into the counter, so have to work with the 1Hz 50% signal, you could use a monostable.Are there any other constraints on the required output signal?

author: Spemo
author_rank: Regular Contributor
timestamp: April 15, 2021, 04:48:25 pm
content: Hi!The monostable, that's the solution I'm looking for!Silly me, since it's already in a different part of the complete circuit, with a 555... Thanks a lot!
Channel Coding - Probability of Error? - Page 1
Forum section: electronics / beginners

author: tec5c
author_rank: Frequent Contributor
timestamp: October 24, 2015, 03:54:20 am
content: I'm a little confused in calculating the probability of error when using error correction coding.I am fine with finding the probability of error when there is no error correction code involved though I don't quite understand the difference between the probability of error between the demodulator output and the pr. of error at the decoder output.Anyone have experience in this field that could offer me some insight?
Characteristics of a ceramic disc capacitor  - Page 1
Forum section: electronics / beginners

author: claudiux
author_rank: Newbie
timestamp: August 22, 2017, 10:59:01 am
content: Hello,I am looking for the same capacitor as in the attached pictures.Can someone tell me its characteristics and explain me how to understand the label ?Thanks in advanceClaude

author: Cliff Matthews
author_rank: Unknown
timestamp: August 22, 2017, 02:57:53 pm
content: Not the nicest printing.. 3300pf, use as an X1 cap 400v or as a Y2 cap 250v.More info on these safety caps here:http://www.justradios.com/safetytips.html

author: mikerj
author_rank: Super Contributor
timestamp: August 22, 2017, 05:00:55 pm
content: Quote from: Cliff Matthews on August 22, 2017, 02:57:53 pmThat's an understatement, they must be pushing 10 DPI or so

author: Benta
author_rank: Super Contributor
timestamp: August 22, 2017, 06:03:32 pm
content: Safety cap, like already said.3300 pF, 400 V as X1, 250 V as Y2Safety markings:CSA, VDE, NEMKO, DEMKO, SEMKO plus a couple more I can't recognise.Doubt that it's ceramic, though. For this kind of application I'd say Mica. Looks like that as well.

author: Cliff Matthews
author_rank: Unknown
timestamp: August 22, 2017, 07:15:00 pm
content: Benta, I thought Mica was those brown epoxy "lumpy" ones? **editThese ones are stated to be ceramic.

author: claudiux
author_rank: Newbie
timestamp: August 22, 2017, 07:25:07 pm
content: Thanks, I didn't even know there was X1 or Y2 typesWhat are the first characters on the top left (332M ? ) giving you 3300 pFThanks for the links too

author: Cliff Matthews
author_rank: Unknown
timestamp: August 22, 2017, 07:30:05 pm
content: Yes, correct. 330 would be 33pf, so just add the 2 zero's

author: Cliff Matthews
author_rank: Unknown
timestamp: August 22, 2017, 07:34:08 pm
content: Oh, forgot, welcome to the forum! PS: It may be off the right side of your screen, but it's much easier to say thanks with a single click. (and believe me, I give thanks a lot on this forum, because everyone is so helpfulit's the best!)

author: Benta
author_rank: Super Contributor
timestamp: August 22, 2017, 08:00:07 pm
content: Quote from: Cliff Matthews on August 22, 2017, 07:15:00 pmYeah, my knowledge might be a bit out of date here. Earlier, ceramics were not approved for safety caps, but technology advances...