hybridfree/eevblog-posts huggingface dataset:
Possible to change voltage on cheap Chinese buck converter - Page 1
Forum section: electronics / beginners

author: gmc
author_rank: Regular Contributor
timestamp: September 21, 2019, 02:10:03 pm
content: I bought one of these cheap ass Chinese buck converters. Supposed to take 9V and convert to 5V. The problem is I received the 3V3 version.Is anyone familiar with these. Is it just a case of changing some of the resistor values to change the output voltage, or is it setup in the chip?I've looked on the net and can't find any details on the chip used. All it has on 1HRE. (6 pin)https://www.alibaba.com/product-detail/DD4012SB-3V-1A-DC-DC-Step_60752474667.html?spm=a2700.7724857.normalList.64.34e11c7eFw4nT1

author: nuclearcat
author_rank: Unknown
timestamp: September 21, 2019, 02:18:49 pm
content: Just trace output over PCB and check if resistor divider is there(of yes, most likely you are lucky), check values, check voltage on divider while running it, and try to solder different, appropriate resistor in divider.

author: soldar
author_rank: Super Contributor
timestamp: September 21, 2019, 04:01:26 pm
content: Why don't you just ask the seller to send you the right part? And that way you have an extra 3volt part.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 21, 2019, 04:51:44 pm
content: yes its highly likely to be adjustable by changing voltage divider there. and ask partial refund if its seller mistake. and next time dont buy that, if thats the price (link) you pay for it, because with adjustable buck with built-in trimpot ready, you can get cheaper, and more current too...10PCS Super mini 3A DC-DC Converter Step Down Power Supply Moduleif you really want that to be fixed, you can remove the trimpot for part and put appropriate resistor in place. ymmv.

author: gmc
author_rank: Regular Contributor
timestamp: September 21, 2019, 05:09:53 pm
content: The seller is sending me the correct part but I thought I'd see if I can get it to put our 5V.I'll play around with the resistor values and see what happens.

author: JustMeHere
author_rank: Frequent Contributor
timestamp: September 22, 2019, 01:07:11 am
content: Look up the chip on the back. The two high value resistors on the top are your voltage set.The answer should be on the right module when you get it.

author: amyk
author_rank: Super Contributor
timestamp: September 22, 2019, 02:10:04 am
content: Quote from: gmc on September 21, 2019, 02:10:03 pmQuoteAnyway, 1Hxx appears to be the marking for an ME3116, which you'll see if you search pictures from sellers of the part... as well as for the DD4012 model number:https://easyeda.com/Alterac/buck-to-220-replacement
Possible to charge a lifepo4 leisure battery with starter battery jump starter? - Page 1
Forum section: electronics / beginners

author: electroniclearner820327
author_rank: Regular Contributor
timestamp: November 12, 2024, 04:33:55 pm
content: The lifepo4 battery is a fogstar drift 105ah:https://www.fogstar-drift.co.uk/products/fogstar-drift-105-12v-1ooahSpecification sheet is on that page.The starter battery jump starter is like a powerpack that you charge at the mains, or apparently from cigarette lighter. I am not sure the exact model as did not find it online when I had a first look but it says it is 11000mah and gives a starting charge of 200ah and peak of 500ah.Solar is really poor at the moment in the uk meaning I am running a deficit when there are long runs of bad days. I am still yet to ascertain if I am running an overall deficit even including 'good' days in these short daylight periods and thus whether it justifies making more aggressive attempts to increase my overall power.As I was given this jump starter I wondered if it would work to give the leisure battery a boost. To charge it I thought I could recharge it when driving via the cigarette lighter.The 200ah and 500ah look daunting though. Could that damage the leisure battery being dumped to it all at once or would that not happen since the leisure battery, not being a starter battery, would not 'ask' for that power? It was rather expensive so don't want to take unnecessary risks with it. On the other hand it would be very handy if it could top it up and no one has given me a rational reason why it would/would not work, only blanket 'don't be silly' statements (on none electronics specific forums) with no explanation given for why it would not work.I read some forum reply somewhere on some closely related question which one reply stated that the leisure battery would not risk damage because it would not draw more amps than it could handle. Is that right?I would like to get an explanation of if it would work and why it would be ok and not harm my battery or conversely why it would be a bad idea and could harm it. Not just ignorant 'you stupid' that I got elsewhere when clearly they didn't even have a clue about it and just because it was not 'normal' then = bad/stupid.

author: ebastler
author_rank: Super Contributor
timestamp: November 12, 2024, 04:37:25 pm
content: No!A jump starter is designed to provide very high currents to your car's starter. It is not suitable in any way to charge a battery with a controlled current.Pleasedon't even think about trying this, it it very dangerous.Edit: I posted the above after coming here right from the OP's other thread, on the challenges of charging his notebook. Maybe the "no" here is not as absolute and big-letter-red. But without knowledge of the details of both, the battery and its BMS as well as the jump starter, I would not touch this. And I certainly would not recommend that someone with very limited knowledge about electricity touches this.
Possible to configure xbee's like this? - Page 1
Forum section: electronics / beginners

author: eevfan007
author_rank: Contributor
timestamp: May 20, 2014, 08:02:37 am
content: 1. Is it possible in AT mode to configure an end device to send data to all other devices on the network?2. Is it possible in AT mode to configure a coordinator to send data to all other devices on the network?I found this statement on a website: "In order to send a Broadcast message set the DH=0x0 and the DL=0xFFFF. With these settings all XBee modules on a given PAN will get the message.", but when I try to configure it i does not work. This was attempted with one end device and one coordinator device.Any input here?Thanks

author: tld
author_rank: Regular Contributor
timestamp: June 15, 2014, 10:31:28 pm
content: Hi,Post is a bit old, but no takers, so I'll ramble a bit.I think this is more of a "how" than an "if". I don't really recall broadcast-specific to AT-mode, as I'm looking more at API-mode.What fits best also depends on application, and which other messages you'll need to send.That said, you should be able to do this. Worst-case, you could cycle through destinations on the writing node. Set one receiver, send, set next, send, and so on.One thing not everyone seems to be aware of, is that you can mix AT and API-modes, and this is perhaps the route I'd look at here. You can set most nodes to AT-mode, and send AT-compatible frames using a coordinator in API-mode, and thus target individual nodes with messages. I think it should work with broadcast as well, but don't know for sure, and haven't tried.Personally, I usually prefer API-mode when you have multiple modules talking to each other, for the added flexibility, knowing which node sent a message, etc.tld
Possible to extract this firmware? Or find its datasheet? - Page 1
Forum section: electronics / beginners

author: Coldblackice
author_rank: Contributor
timestamp: February 25, 2022, 12:41:54 pm
content: I'm trying to extract firmware from aGoXLR-MiniI know it's not ideal, but I'm trying to extract the 64MB firmware without removing the chip. I've done this before, but I also realize it's a case-by-case thing whether that can work. Unfortunately, it seems this board's layout results in it getting powered by my SPI tool (Buspirate), failing to extract.I believe the issue is due to the flash chip's HOLD pin unable to get pulled high, as the current meant for that pin from my Buspirate instead dissipates throughout the circuit. I left 3.3v unconnected and tried reading the chip's ID: when I try to pull the HOLD pin high, a small micro-LED next to the processor dimly lights.In researching this, I found an old thread where someone mentioned the possibility of keeping a CPU in reset possibly working? So I started looking for this processor's datasheet, but I've only been able to find a basicsummary datasheet, no pinouts or schematics.For reference, the chip is aTCD3020-CGDo you think it'd theoretically be possible to dump the firmware without removing the chip if I'm able to find a way to keep the CPU pulled in reset? TIA

author: Swake
author_rank: Frequent Contributor
timestamp: February 25, 2022, 05:06:19 pm
content: The 8 via's named X6 in the middel of the board makes me think it is some programming interface. Could you trace them?besides that I have no idea if the firmware would be protected or not.Does the manufacturer offer firmware updates?

author: amyk
author_rank: Super Contributor
timestamp: February 26, 2022, 03:01:14 am
content: These might be what you're looking for:https://www.datasheetarchive.com/companies/tctechnologies_tc.htmlIn particular:https://www.datasheetarchive.com/whats_new/14f8986215aedcb96bdd971fd4278987.htmlApparently the company suddenly disappeared a few years ago... and so the above seems to be the only remaining traces of information on their products

author: Swake
author_rank: Frequent Contributor
timestamp: February 26, 2022, 06:04:19 pm
content: good find!This one details the pins and jtag information:https://www.datasheetarchive.com/whats_new/910ffb7bfbf8e22046fbc930e5665a0d.html

author: DavidAlfa
author_rank: Super Contributor
timestamp: February 26, 2022, 11:00:45 pm
content: How can you be struggling with a single soic-8 spi flash?Takes 5 minutes to remove, insert in a CH341A, read and solder back.
Possible to make an non-antistatic floor mat antistatic? - Page 1
Forum section: electronics / beginners

author: Croy9000
author_rank: Contributor
timestamp: February 24, 2018, 12:33:31 am
content: I just received a very large vinyl floor mat online (to cover my carpeted floor) and totally underestimated how much static these things build up. Just walking 3 steps from one side of my home lab to the other gives you a heck of a jolt when grounding yourself.Short of dumping the mat, any tips on mitigating the effects? I wonder if those solutions like Staticide really work? Any better ideas?

author: nanofrog
author_rank: Super Contributor
timestamp: February 24, 2018, 12:52:21 am
content: The Staticide works, so I'd give it a go (acrylic runs ~$50 per gallon, ultra ~$65 per gallon).I'd also go with an ESD heel strap to dissipate any charge that builds up.

author: Stray Electron
author_rank: Super Contributor
timestamp: February 24, 2018, 01:51:41 am
content: Mix some Dawn dish washing soap with water and wet down the mat with that and let it dry on the mat. It actually helps. Our HP-41 calcs were very sensitive to static so we treated the plastic carrying cases with Dawn and it did prevent some static crashes. Also the fabric softener sheets used in clothes dryers help prevent static so run your mat through a dryer with one of those if you can or else try to rub some of the wax off of the dryer sheet onto your mat.

author: floobydust
author_rank: Super Contributor
timestamp: February 24, 2018, 05:28:29 am
content: It gets very dry here in Canada, spraying carpet or a mat with Downy fabric softener stops static. You can add some water and dilute it.I'm not sure how it works at stopping "static cling" for laundry, but I have um cheap customers that use it.

author: Croy9000
author_rank: Contributor
timestamp: February 24, 2018, 01:03:36 pm
content: Thanks for the tips. Ordered some Staticide 2003 to try.
possible to reverse engineer/dissect Gerbers? - Page 1
Forum section: electronics / beginners

author: src1989
author_rank: Contributor
timestamp: March 19, 2021, 10:32:04 pm
content: i've put together a PCB design in sprint layout (it's based on one of BigClive's designs that he made available), had boards manufactured and made a video about it. someone is asking if i'm making my gerbers available....now, my question is, if i made them available as a gerber .zip archive (not the sprint .lay file); can someone download, strip my name/website out of the copper layer and repackage the design as their own?

author: mhuber1
author_rank: Newbie
timestamp: March 19, 2021, 10:37:54 pm
content: Yes you can edit gerber files and there is no (easy) way of preventing this

author: src1989
author_rank: Contributor
timestamp: March 19, 2021, 10:49:33 pm
content: cool, thanks. i assume the easy way of preventing it is not releasing the gerbers?

author: amyk
author_rank: Super Contributor
timestamp: March 20, 2021, 12:00:06 am
content: Quote from: src1989 on March 19, 2021, 10:49:33 pmYes. Then someone will have to trace it, and can then create their own. Ironic that you mention BigClive, because he does that all the time...
Possible to use 48v telecom rectifier as a solar controller?  - Page 1
Forum section: electronics / beginners

author: Yakapo7
author_rank: Newbie
timestamp: December 11, 2021, 09:27:20 pm
content: I have two strings of solar panels -around 280v each. The pv inverter I have doesn’t support batteries, so I need a different way to charge my 11kwh 48v lifepo4 battery during an outage. Yes, I could buy an off grid inverter, but that would cost me another $1,000. I was told elsewhere that it is possible to use a telecom rectifier as a controller / regulator. I have more time than money, so if this is a feasible solution, I’d like to explore it. Please help me get started. Thanks!

author: bob91343
author_rank: Super Contributor
timestamp: December 12, 2021, 05:47:10 am
content: What is a telecom rectifier? If you would describe it perhaps we could help.

author: SeanB
author_rank: Super Contributor
timestamp: December 12, 2021, 05:59:14 am
content: Telecom rectifier is a power supply and charge controller generally used to maintain a 48V battery bank, made up of individual 200Ah lead acid cells. Typically 56V output and a pretty high power supply ability. Yes they can be used to charge the 48V lithium iron battery, though you would need to change the output voltage slightly to match the lithium iron battery, but they will do the job.

author: fordem
author_rank: Regular Contributor
timestamp: December 12, 2021, 12:36:10 pm
content: Telecom rectifiers generally take a utility feed - where do you plan on getting that fromduring an outage? I'm assuming that this point that your "pv inverter" is grid intertie unit, so it'll shut down when it has no grid to sync with, and it seems to me that leaves you at square one.
Possible uses for Power Divider (Narda 2-8Ghz 2ports) - Page 1
Forum section: electronics / beginners

author: FPSychotic
author_rank: Regular Contributor
timestamp: March 14, 2021, 11:57:05 pm
content: Hi, I'm trying to learn some basic things of RF. Mainly I want to do things related with hobbies like mesure antennas VSWR and S11, EMi measurenents..Just I got a Power divider because I think it was at very good price and it is a good one for hobby, thinking in maybe I can build something with it or use it in some testing maybe.I have an Adalm Pluto, LNA, x2 UWB directional antennas, direc.couplers, decent cables and atennuators all rated ar 6Ghz. Also I have many Arduinos, flight controlers ardupilots etc.Can give me anyone ideas of what I can do with it, from tests for RC, EMI to make an antenna tracker, I don't know, for what useful thing I could use this?Thanks! i just want learn a little with experimentation or make something useful.But without some advice I dont know even what look for...

author: jkro
author_rank: Newbie
timestamp: March 18, 2021, 09:04:03 pm
content: Power dividers can be good for dividing 1 signal into two output signals (same frequency) with pretty low losses. You can also use them to combine 2 signals, to create some harmonics, which may be useful to generate different frequencies. Good luck!
Possibly a silly question.  - Page 1
Forum section: electronics / beginners

author: Anson
author_rank: Regular Contributor
timestamp: April 06, 2013, 09:11:25 pm
content: Is there a method for looking up datasheets on transformers from power supplies? I seem to keep getting custom numbered ones or ones that simply do not have datasheets available. Well I say not available but what I mean is I cannot find them. For example I have two low voltage supplies from a couple of dead web tv consoles. One has the Matsushita logo and the numbers BD1B4A and 842350 on the transformer and on the board the logo and number EXTPH084A1B and on the bottom two more number 8429Q4 and NPX084A1-2. I have tried googling all these numbers and get no where. Is there a secret site for these? I have tried datasheetarchive and alldatasheet.Is there a way to test these to see what they are? I tried one of these in the past hooking up direct ac current but that didn't go so well.

author: c4757p
author_rank: Super Contributor
timestamp: April 06, 2013, 09:34:31 pm
content: They are custom transformers, you're not going to find any datasheets.Quote from: Anson on April 06, 2013, 09:11:25 pmIf they're meant for an SMPS, then they're designed for such a high frequency that 50/60Hz AC might as well be DC - and we all know what happens when you stick DC up a transformer!Quote from: Anson on April 06, 2013, 09:11:25 pmLCR meter. I've got an old LCR-740 manually-operated impedance bridge and I can do a pretty good job of characterizing a transformer with it (well, except that it only goes to 40 kHz). Stick ohmmeter probes everywhere possible to figure out what's connected to what. Measure the inductance of each winding - calculate the inductance ratios, then take the square root to get the turns ratios. Leakage inductance can be calculated by measuring one winding while shorting the others. The magnetizing current will beroughlyV/(2*pi*L*f) for V = applied RMS voltage, L = inductance of primary, f = frequency.

author: Anson
author_rank: Regular Contributor
timestamp: April 06, 2013, 11:09:30 pm
content: Thanks. Lots of good info there. Will have to wait till I get my hands on an LCR.
posting delay or failure - Page 1
Forum section: electronics / beginners

author: rowlandcrew
author_rank: Newbie
timestamp: June 12, 2022, 08:43:55 pm
content: I attempted to post in the repair section, but it appears to not post. is there a delay, or a secret button I need to push?thank you

author: Gyro
author_rank: Super Contributor
timestamp: June 12, 2022, 09:27:21 pm
content: Welcome,It appears to have worked.

author: tunk
author_rank: Super Contributor
timestamp: June 12, 2022, 09:30:51 pm
content: I saw it recently when trying to post in an existing thread.Looks like someone was posting at exactly the same time. Posting again worked.
posting on here - Page 1
Forum section: electronics / beginners

author: m3vuv
author_rank: Super Contributor
timestamp: April 28, 2022, 10:04:52 pm
content: is there a way to get notified to your own posts on here without having to tick the box,ie make that the default so if you dont want that you can turn it off ?,most times i forget to do it then have to go and modifie the post and tick the notify me of replys box,i am sure i am not the only one?.
posting - Page 1
Forum section: electronics / beginners

author: Bogden777
author_rank: Newbie
timestamp: March 15, 2021, 04:28:42 pm
content: why can i post in test equipment but will not post in the repair section

author: StillTrying
author_rank: Super Contributor
timestamp: March 15, 2021, 04:39:47 pm
content: I can, what's happening? Have you got the repair section in anot logged intab, refreshing the page will make the posting buttons appear.

author: Bogden777
author_rank: Newbie
timestamp: March 15, 2021, 05:23:51 pm
content: strange i can post here and test equipment but not in repair section

author: Bogden777
author_rank: Newbie
timestamp: March 15, 2021, 05:43:17 pm
content: i got it my attachment was to large
Pot adjustment tools  - Page 1
Forum section: electronics / beginners

author: Ranger14
author_rank: Regular Contributor
timestamp: January 31, 2016, 10:45:50 pm
content: Is it necessary to have pot adjustment tools??The reason I ask cause I have work on a new scope that might need some basic calibration andmost time I used a screwdriver for this .. Also is it better to buy a kit of different tools or will the basic one do the job??? I would like to pick one up for the bourns 10turn pots..

author: Supercharged
author_rank: Regular Contributor
timestamp: January 31, 2016, 10:56:14 pm
content: The biggest problem with using a normal screwdriver is, that it might short out some part of the circuit if you slip off. But there probably is a non metal screwdriver included with the probes of the scope, unless its some higher end scope, but in that case you probably shouldn't calibrate it yourself.

author: uncle_bob
author_rank: Unknown
timestamp: January 31, 2016, 10:56:31 pm
content: HiAs with all questions the real answer is going to be "that depends".For something like a 10 turn pot, it's rare to need anything other than a normal screwdriver.For things like a half turn "open frame" pot where the adjustment slot is directly connected to the pot wiper ... yes a plastic or ceramic tool will save some grief.You mention scopes, so there is another category. Stuff that has high voltages on it can be tricky. A pot that has 2.3KV on all it's terminals is going to be hazardous regardless of it's construction. Unless it has a grounded shaft (like a chassis mount part), use a ceramic tool on it. The same caution (watch out for high voltage) is a generally good one to remember if you have grown up with low voltage stuff. Back years ago (in the days of tubes), getting killed working on circuits was not at all uncommon.....Bob

author: Gyro
author_rank: Super Contributor
timestamp: February 01, 2016, 01:39:54 pm
content: Pot adjustment tools are particularly useful for multi-turn trimmer pots. One end usually has the blade recessed into the plastic skirt so that it actually sits over the screw head. Very useful if your applying several turns because it doesn't keep slipping off!

author: w2aew
author_rank: Super Contributor
timestamp: February 01, 2016, 03:27:29 pm
content: It should be pointed out that if any of your adjustments are on variable capacitors or tunable inductors (often found in radio and high frequency circuits), then you'll need non-conductive adjustment tools (diddle sticks), because a metal screwdriver blade will alter the capacitance/inductance.

author: macboy
author_rank: Super Contributor
timestamp: February 01, 2016, 04:17:31 pm
content: Quote from: w2aew on February 01, 2016, 03:27:29 pmI recently received a set of ceramic screwdrivers that I ordered from China. They definitely took the slow boat (~6 weeks) but I was in no particular rush. They are reasonably well made for a ~$1 tool. Non-conductive and non-inductive, and the slightly rough surface of the ceramic also helps grip to prevent "cam out". I think I'll shrink some clear heatshrink tube onto each tip to help prevent damageifwhen I drop them.
Pot marking Q - Page 1
Forum section: electronics / beginners

author: Sivand12
author_rank: Contributor
timestamp: November 20, 2014, 11:08:43 am
content: I found some nice Piher pots at a garage sale. They are marked "1M - 812M PIHER"They seem to be linear taper as they read about .5m at the halfway position and about 1m at full position.My question:I know the "1M" refers to its rating of 1 megohm but what does the "812M" marking mean? Or, is that just some sort of stock number?

author: tinytim
author_rank: Contributor
timestamp: November 20, 2014, 11:12:26 am
content: http://sound.westhost.com/pots.htmsomething for you to check out on your way roundi wouldnt worry too much about the rest of what is printed as there does seem to be a lot of debate elsewhere on forums about what it is used for.Maybe contact Piher or search for a datasheet ?http://www.piher.net/sensors/index.php?option=com_content&view=article&id=2&Itemid=2#tim

author: w2aew
author_rank: Super Contributor
timestamp: November 20, 2014, 02:18:03 pm
content: It could simply be a date code...

author: olsenn
author_rank: Frequent Contributor
timestamp: November 20, 2014, 02:46:07 pm
content: If your pot is marked "White Widow", it is good stuff!
Pot marking Q - Page 1
Forum section: electronics / beginners

author: simpson
author_rank: Contributor
timestamp: July 28, 2014, 04:02:45 pm
content: I found some nice Piher pots at a garage sale. They are marked "1M - 812M PIHER"They seem to be linear taper as they read about .5m at the halfway position and about 1m at full position.My question:I know the "1M" refers to its rating of 1 megohm but what does the "812M" marking mean? Or, is that just some sort of stock number?
Potential damage via ground looping? - Page 1
Forum section: electronics / beginners

author: cvriv
author_rank: Frequent Contributor
timestamp: February 17, 2017, 10:59:37 pm
content: I bought a Saleae Logic Pro 16 and was reading on their site about issues that I could run into when there is a ground loop... I'm kind of nervous now. What's deal with this?I'm going to be using the analyzer mostly for school right now. I had to built this converter in class for my projects. It basically provides a stable +5v volts for anything my professor has us doing. The converter is powered by a 9v, 0.5A wall brick I bought off amazon. The gates we'll be messing with will be powered by this converter I built in class.Can someone explain to me, simply, what ground looping is? From what I read I think it's when two or more devices share a common ground and if I touch a ground pin from the analyzer to a source terminal, the analyzer and laptop short the mains?

author: Vtile
author_rank: Super Contributor
timestamp: February 17, 2017, 11:06:58 pm
content: Have you watched the "How not to blow up your DSO" or similar video from Dave?

author: cvriv
author_rank: Frequent Contributor
timestamp: February 17, 2017, 11:16:18 pm
content: Nope. I guess I should watch that video?

author: Vtile
author_rank: Super Contributor
timestamp: February 17, 2017, 11:18:49 pm
content: It is a good starter and might give you enough information to solve the rest with some logic thinking.IIRC Dave goes pretty detailed explanation in it.

author: Brumby
author_rank: Unknown
timestamp: February 17, 2017, 11:43:05 pm
content: Quote from: cvriv on February 17, 2017, 11:16:18 pmYep:
Potential difference development - Page 1
Forum section: electronics / beginners

author: Freshman
author_rank: Regular Contributor
timestamp: February 27, 2025, 10:54:10 am
content: Is there a way to create a voltage difference between the neutral and the ground (earth) terminal of a system?

author: PGPG
author_rank: Frequent Contributor
timestamp: February 27, 2025, 11:11:13 am
content: Quote from: Freshman on February 27, 2025, 10:54:10 amTake enough 'strong' voltage source and connect between them.

author: Grandchuck
author_rank: Super Contributor
timestamp: February 27, 2025, 11:52:04 am
content: With high current flow there can be some potential difference between neutral and ground.

author: jpanhalt
author_rank: Super Contributor
timestamp: February 27, 2025, 11:57:59 am
content: Of course, resistance between ground and neutral should be quite low. Google says 5 to 6 Ω in household wiring. Putting a larger resistance there might be a less dramatic way to create a voltage difference between the two.

author: tggzzz
author_rank: Super Contributor
timestamp: February 27, 2025, 01:22:15 pm
content: Quote from: Freshman on February 27, 2025, 10:54:10 amYes. Pass a current between the two, and (unless they are superconducting) there will be a voltage between them.How to do that and/or how that occurs is left as an exercise for the student.

author: Freshman
author_rank: Regular Contributor
timestamp: February 27, 2025, 01:24:48 pm
content: How do we do that?

author: CaptDon
author_rank: Super Contributor
timestamp: February 27, 2025, 01:44:49 pm
content: Think about it for a minute and the answer will be obvious? The neutral and earth ground are often tied together at the breaker panel. All wire will have some measurable resistance. Let's say from your wall socket to the breaker panel your neutral has one ohm of resistance. Now plug in a 10 amp load to the wall socket. That 10 amps flowing through your neutral having a resistance of one ohm will make the neutral AT THE WALL SOCKET appear to be 10 volts when reference to the earth ground AT THE SOCKET. Questions?

author: PGPG
author_rank: Frequent Contributor
timestamp: February 27, 2025, 03:57:33 pm
content: Quote from: Freshman on February 27, 2025, 01:24:48 pmI have already told.If you want to make a voltage difference between two points you use enough 'strong' voltage/current supply and connect it between these two points.

author: SteveThackery
author_rank: Super Contributor
timestamp: February 27, 2025, 10:34:46 pm
content: Quote from: Freshman on February 27, 2025, 10:54:10 amCould you tell us exactly why you want to do that? It might help the discussion.
Potential divider wattage calculations - Page 1
Forum section: electronics / beginners

author: netdudeuk
author_rank: Frequent Contributor
timestamp: July 02, 2018, 09:51:43 am
content: HiI'm looking at using a split rail supply (+-12V or +-9V) with a potential divider using a 1kΩ trimmer resistor (https://uk.rs-online.com/web/p/products/5220883/) to produce a voltage output within that range. This would be to create a variable offset bias for an op amp.Here are my calculations to work out the wattages -+-12V supplyI=V/RI=24/1000I=0.024AP=VIP=24*0.024P=0.576W+-9V supplyI=V/RI=18/1000I=0.018AP=VIP=18*0.018P=0.324WThis makes me think that a 1/2W trimmer would be ok for the +-9V supply but not for the +-12V supply. Do I have this right ?I guess that going for a 10kΩ trimmer instead of the 1kΩ would allow me to use this trimmer resistor with either voltage setup ...

author: LateLesley
author_rank: Frequent Contributor
timestamp: July 02, 2018, 10:37:01 am
content: yes, your calculations look right. Is there any particular reason to go with such a low resistance trimmer though? if it's feeding the bias if an op-amp, a 10K trimmer would be good enough, and you may even get away with 100K. The benefit of this is it reduces power consumption, and the power dissipated in the trimmer. I'd try and pick as high as a value that you can get away with. Op-amp inputs tend to be in the megΩ range, so you shouldn't need too low a value trimmer. I'd try 100K, if it's just for a voltage divider to an input.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: July 02, 2018, 10:48:20 am
content: Quote from: LateLesley on July 02, 2018, 10:37:01 amThanks for the prompt reply. I've ordered a couple of 100k and a couple of 10k to experiment with.

author: rs20
author_rank: Super Contributor
timestamp: July 02, 2018, 10:52:53 am
content: It can also be a good idea to have a capacitor between the wiper of the trimmer and ground. If the value of the capacitor is appropriately chosen (there's a wide range of valid values, just apply T=RC with the value of the trimmer as R as a rough approximation), this will have virtually no effect on the responsiveness of the adjustment (at least as far as a slow human observer can tell), but can calm down any scratchiness coming from the trimmer, and also kills any RF noise on that highish impedance node.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: July 02, 2018, 10:54:41 am
content: Quote from: rs20 on July 02, 2018, 10:52:53 amThanks for the tip. I'll do that.
Potential Ground Loop Problem - Page 1
Forum section: electronics / beginners

author: james2k2
author_rank: Contributor
timestamp: January 25, 2016, 03:09:26 pm
content: Hi All,Got (hopefully) a simple problem, and trying to find a good solution before I buy parts. I've got one of those pre-made amplifier PCB's from ebay (this one:http://www.ebay.co.uk/itm/231179156525), and also one of those 1A Car USB chargers, which I've dismantled to get just the PCB to convert the 12V to a 5V USB so that I can either charge a phone, or power in this case my Chromecast Audio.With the Chromecast Audio in place, it has an annoying inconsistent buzz. With the Chromecast on it's own PSU, it works fine. Now my feelings are there's an Audio Ground Loop. The attached diagram is not very good (accuracy with symbols, or correct use), but demonstrates what I mean. I've shown it with the physical connections as I have it wired.As I've ruled out the amp on its own, as well as the Chromecast, it's either a poor DC-DC converter (quite likely for £1), or there's the loop I mentioned. Any thoughts? I haven't a lot of room in the box I've used, so those tiny USB Car charger PCB's are kind of my maximum, and I'm not sure, but I think a 7805 might generate too much heat in such a small space with a 1A load.Thanks for any insight anybody has.

author: samnmax
author_rank: Regular Contributor
timestamp: January 26, 2016, 02:23:53 pm
content: I would place my bet on a noisy DC-DC, as £1 car chargers must be quite shitty.You could try to power the amp and the charger with different isolated 12V supplies to rule out a ground loop. If the buzz is still there it means the problem is the DC-DC.If that's the case, you may be able to get away with a 7805 as the Chromecast audio seems to use 1.5W max:http://forums.slimdevices.com/showthread.php?104383-Chromecast-Audio-ideal-for-Squeezebox-replacement-hardware&s=546a0aa7b8ed9a308765fb6be6099432&p=832361&viewfull=1#post832361https://productforums.google.com/d/msg/chromecast/61Hpnta5yC8/2xJN-vpxBwAJhttps://productforums.google.com/forum/#!topic/chromecast/NTC-VRU9IeUSo that's 0.3A at 5V: 12V-5V=7V, 7V*0.3A=2.1W to be dissipated at the 7805.

author: james2k2
author_rank: Contributor
timestamp: January 26, 2016, 06:59:10 pm
content: Thanks for the info. That's a great help. I didn't realize how little power the CC Audio used!I have ordered a better DC-DC block (very similar in appearance, but features a LOT more protection and features):http://www.ebay.co.uk/itm/252110025993But if that still fails, then I'll do what you suggested of testing the DC-DC unit on a separate supply. The current unit is actually still in place, but just doesn't power anything. However, I have now noticed that there is a slight hiss coming from the amp where there wasn't before, so my gut is telling me the converter is junk.As another test I used my phone connected up in place of the CC Audio and found the noise didn't change - so the CC Audio obviously has something to do with it slightly too.
Potential Relay Replacement - Page 1
Forum section: electronics / beginners

author: RyanG
author_rank: Regular Contributor
timestamp: February 19, 2017, 09:17:42 am
content: I am trying to change out some of the motor starting potential relays we use at work. I was wondering if it is doable in solid state form. The relay contacts burn out fairly quickly with the number of times the motors turn on and off, probably a few hundred to a thousand times in a day. The relays run on 120vac across the contacts and coil, and they are normally closed. I attached a random schematic from google search, but it is basically the same as what I am dealing with. I thought about using triacs, but I don't really know if I can make one act as normally closed without some significant modifications to the current circuitry. Everything does have to be done with 120vac.Here is a link to a relay that is almost exactly the same as the ones we use.Relay

author: Ian.M
author_rank: Super Contributor
timestamp: February 19, 2017, 10:58:00 am
content: If the motor's under 5HP,http://www.supco.com/supr&apr5.htm

author: Jeroen3
author_rank: Super Contributor
timestamp: February 19, 2017, 01:29:56 pm
content: If you're really turning the motor on and off a lot I would use an VFD. It will also reduce the stress on the motor and shaft itself.

author: RyanG
author_rank: Regular Contributor
timestamp: February 22, 2017, 08:25:30 am
content: How does this look?Blue goes to my start capacitor and red goes to the start winding.
Potentially daft Supercapacitor related question, this is rated at 25V! - Page 1
Forum section: electronics / beginners

author: bsodmike
author_rank: Regular Contributor
timestamp: November 28, 2021, 12:11:12 pm
content: Hi all,I've got a 82mF Supercapacitor rated at 25Vhttps://export.farnell.com/kemet/als70a823df025/cap-82000-f-25v-alu-elec-screw/dp/2729143Every article/video I can find on the subject, usually refers to an operational voltage of 2.5V; even the "Balance" chargers / Voltage safety PCBs on eBay are listed to work at 2.5Vdc.My obvious assumptions aboutthissupercapacitor:Charge voltage should be ~90% of the max, so around 22.5VDC. Can we charge at 25VDC?Charging at around 0.5A to 1A should be safe? Normally, the rule is not to exceed "1C" of a single cell, well at least for LiPos; a 1000mAh Lipo can be charged at 1A safely. Does this apply here as well?Minimum voltage: Unclear, thoughts?Rough back of the paper calculations say 25V at 82mF can provide a max energy of 7.1mWh. Given that a 9VDC battery has ~5.5Wh capacity, means this Supercapacitor can hold ~770 less energy? (Anyone able to double check these numbers?).Thanks!Cheers M.

author: wraper
author_rank: Unknown
timestamp: November 28, 2021, 12:16:01 pm
content: It's not a supercapacitor. Just a large aluminum electrolytic capacitor.

author: Gyro
author_rank: Super Contributor
timestamp: November 28, 2021, 12:39:09 pm
content: The PDF datasheet is on that page too.

author: rsjsouza
author_rank: Super Contributor
timestamp: November 28, 2021, 12:39:26 pm
content: Indeed. The ones below are super capacitors, which usually start at many Farads, not micro or milli Farads.https://www.newark.com/c/passive-components/capacitors/supercapacitors/prl/results

author: bsodmike
author_rank: Regular Contributor
timestamp: November 28, 2021, 12:56:14 pm
content: Oh nuts, sorry that was a normal cap for different projectRight here’s a Supercal 5F but rated at 12V. Does this mean it’s minimum voltage should not drop below 12V?The data sheet does not mention minimum voltage limits.https://export.farnell.com/kemet/fs1b505zf/cap-5f-12v-super-cap-radial/dp/2777893Thanks!Cheers M

author: Gyro
author_rank: Super Contributor
timestamp: November 28, 2021, 01:05:50 pm
content: Looking at the datasheet, that is a memory / low current standby capacitor. It has a 4 ohm internal resistance and charge / discharge currents in the mAs range - 18mA discharge is mentioned.12V is themaximumvoltage you can put across it. You treat it like a capacitor, not a battery, ie. it discharges to zero volts.

author: bsodmike
author_rank: Regular Contributor
timestamp: November 29, 2021, 06:48:00 am
content: Aha that makes sense!! Thanks
Potentiometer DC motor and current draw question - Page 1
Forum section: electronics / beginners

author: Stephen Durr
author_rank: Contributor
timestamp: May 31, 2014, 08:52:30 pm
content: Hello Everyone,This is my first post on the forum so I hope it won't be too ridiculous. I'm not an engineer, just an old fart that likes to play with old cars so I don't know much electronics. Even though I am old Dave would call me a "young playa" in electronics.Most of the stuff I work on is very simple DC electrical circuits on old cars, but I am interested in learning more about electronics. I have probably watched over a hundred of Dave's videos so far and I really enjoy them! Perhaps electronics will become my second hobbyFor my very first question on the beginner forum I hope someone can teach me a little something about the current draw of a DC motor controlled by a potentiometer. Unfortunately I do not have a schematic of the circuit but maybe the answer is so simple that one is not needed. Anyway, I have this old car (1970 Dodge Challenger) that is equipped with variable speed windshield wipers. Long story short, I no longer have the OEM/factory dashboard or any of the original switches so I ordered a new switch and I wanted to bench test it with the wiper motor before installing it. I wanted to test the current draw so I would know what size fuse to use to protect the circuit. So I hooked up a DMM and tested it. This is where my confusion comes in. On the lowest speed setting (potentiometer turned to lowest setting) the current draw was about 2.5 amps. As I turn the potentiometer clockwise the motor speeds up as expected, but the current draw decreases down to about 2.0 amps on the fastest speed. Why does it draw less current to run the motor faster?Here is a short video of my bench test... about as long as a bee's dickEdit 1: can someone please tell me how to properly embed a youtube video in a post? I just pasted the URL directly into the body of the post since I did not see any buttons for "embed video". But it just shows up as a hyperlink. How do you get it to display as a youtube video?Edit 2: Ok, I guess the forum doesn't like the "embed url" that has youtu.be in it. So I deleted that and pasted in the full "video url" that hasin it and then changed the https to http. I'm not sure if that's the official technique, but anyway it seems to have worked.

author: SeanB
author_rank: Super Contributor
timestamp: June 01, 2014, 06:30:08 am
content: 2-3A unloaded is fairly typical for these motors. You will need a 10 or 15A fuse to handle the full load current and yet still blow when the motor is jammed or tries to move heavy snow or ice.The reduced current is because as the motor turns faster the back EMF generated by the rotor increases, and this reduces the current draw. The control either works by dropping power in a resistor, or by PWM of the voltage to the motor, likely in your case it simply adds a variable resistance to the circuit as it is fairly old.
Potentiometer prefix - A, B, C? - Page 1
Forum section: electronics / beginners

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: December 04, 2021, 01:36:11 am
content: I'm looking for some potentiometers and I noticed that the various values are prefixed by A, B or C. Is there any significance to these letters or do I only concern myself with the resistor's value?

author: ledtester
author_rank: Super Contributor
timestamp: December 04, 2021, 01:48:17 am
content: It signifies the "taper" -- the relationship between how much the pot is rotated and the resistance at the wiper.More information here:https://eepower.com/resistor-guide/resistor-types/potentiometer-taper/#In particular, see this chart at the end of the article:

author: YurkshireLad
author_rank: Frequent Contributor
timestamp: December 04, 2021, 01:49:57 am
content: Thanks! Taper was the keyword I needed to search for.

author: retiredfeline
author_rank: Frequent Contributor
timestamp: December 04, 2021, 01:52:31 am
content: Log, linear, and antilog taper.
Potentiometer signal smoothing - Page 1
Forum section: electronics / beginners

author: opamp
author_rank: Newbie
timestamp: December 19, 2014, 01:26:21 pm
content: Hello!I need to smooth voltage signal from potentiometer with op amp. Can i do it with op amp active low pass filter? But my circuit have some limitations. Single supply op amp and maybe rail to rail. Supply voltage is 5V. Signal from potentiometer swings from 0.5V to 4.5V What op amp could i use? Please provide some guidence or some sample circuit.

author: Simon
author_rank: Unknown
timestamp: December 19, 2014, 01:38:58 pm
content: I think you need to explain more clearly what you are doing and the cut off frequency and where the noise comes from. If your talking the noise made by the wiper when moved you could put a capacitor across the output. How much filtering is required ?

author: opamp
author_rank: Newbie
timestamp: December 19, 2014, 02:44:47 pm
content: i think potentiometer tracks are little damaged under a lot of usage. voltage change from 0.4v to 1v are not smooth. i want to smooth it out with some active filter where i could control smoothnes. i think to use lm324 op amp or mc33204like on picture.

author: Jeroen3
author_rank: Super Contributor
timestamp: December 19, 2014, 03:05:39 pm
content: What is the purpose of the potentiometer, and why isn't it being replaced?

author: Zero999
author_rank: Super Contributor
timestamp: December 19, 2014, 03:10:18 pm
content: That filter is AC coupled so is no good if you have a DC signal.Some noise when adjusting a potentiometer is normal. If the potentiometer is worn out then the correct solution is to replace it, rather than masking the problem with a filter.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 19, 2014, 03:12:47 pm
content: Your questions only raise more questions. You have jumped directly into "solution space" without fully explaining the situation. Or why you arrived at the conclusion that you could "filter" the signal.Your amplifier circuit will not work. It is designed as a low-pass filter for AC signals. Presumably (because you have provided no context) you need a DC signal out of your potentiometer. The circuit you showed has an input capacitor AND an output capacitor. Those will COMPLETELY KILL DEAD any DC signal that you need from your potentiometer.Suggestion: Start over again back at the beginning and describe what the gadget is, what the potentiometer does, what is the effect of noise, etc. etc.It is possible that the solution could be as simple as a capacitor between the pot wiper and ground to "smooth out" the noise when the pot is turned.

author: opamp
author_rank: Newbie
timestamp: December 20, 2014, 03:24:45 pm
content: Thanks for reply!
Potentiometer tool name? - Page 1
Forum section: electronics / beginners

author: Lycaon
author_rank: Contributor
timestamp: December 23, 2015, 03:17:19 am
content: What's the tool that I see youtubers using to turn the little brass knob on the small blue multiturn potrntiometers? I can't seem to find any with classic words like "tool" or "turner"

author: Kappes Buur
author_rank: Regular Contributor
timestamp: December 23, 2015, 03:24:48 am
content: trimpot adjustment tool

author: tautech
author_rank: Super Contributor
timestamp: December 23, 2015, 03:26:12 am
content: Quote from: Lycaon on December 23, 2015, 03:17:19 amTrimmer tool.http://www.newark.com/vishay-spectrol/008t000/trimmer-adjustment-tool-w-clip/dp/67F5795http://www.newark.com/bourns/h-90/adjustment-tool-trimming-pot/dp/12F9866?MER=ALT_N_L5_Resistors_Nonehttp://www.vishay.com/docs/57015/8.pdf

author: xygor
author_rank: Regular Contributor
timestamp: December 23, 2015, 03:37:51 am
content: Alignment Tool.Diddle Stick.

author: Lycaon
author_rank: Contributor
timestamp: December 23, 2015, 04:33:28 am
content: Ah, thank you guys very much.

author: Stonent
author_rank: Super Contributor
timestamp: December 23, 2015, 06:39:27 am
content: Screwdriver?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: December 23, 2015, 11:30:18 am
content: Quote from: Stonent on December 23, 2015, 06:39:27 amWorks for me.The nice thing about the adjustment tools vs. a plain screwdriver is that the tool has a recessed blade inside a sleeve so that the thing doesn't slip off the head of the adjustment screw. The second nice thing is that the tool is insulated, so when you do slip it doesn't short out nearby components. I achieve the same effects by using a bit of heatshrink tubing around the shaft of an ordinary small screwdriver.

author: KJDS
author_rank: Super Contributor
timestamp: December 23, 2015, 12:14:12 pm
content: The last set I bought were thermoplastic, rather than thermosetting plastic. When I tried twiddling something hot the plastic melted and the metal insert fell out.Need to buy some decent replacements.

author: dom0
author_rank: Super Contributor
timestamp: December 23, 2015, 02:06:46 pm
content: For adjusting capacitors (and the mechanical zeroes on analog meters) you want to use a plastic or ceramic screw driver. Scope probes usually include a small plastic screw driver.

author: Lycaon
author_rank: Contributor
timestamp: December 26, 2015, 06:40:25 pm
content: Yeah, the one with a recessed blade and a sleeve around it is what I am looking for. I am currently using a precision screwdriver but it slips very easily and I've cultured some very impressive sparks already. Luckily the circuit appears undamaged so far :p