hybridfree/eevblog-posts huggingface dataset:
Dual power requirement on board - Page 1
Forum section: electronics / beginners

author: JohnStein
author_rank: Newbie
timestamp: May 10, 2021, 03:58:45 am
content: Hi All,I have been lurking around for quite a while and finally decided to take the step and start interacting. I am new to electronics and have been learning for a while. I studied basic electronics but that was 20 years ago. I am fascinated with how things have changed.I am designing a board that has a two different power requirements. Some components on the board require 12v and some (MCU) 3.3v. My input voltage would always be between 12v and 24v.I have been designing a buck converter circuit for the board and currently my thinking is to use two step down converters (TP5430 (https://datasheet.lcsc.com/lcsc/1811081920_Texas-Instruments-TPS5430DDAR_C9864.pdf)). The first converter will convert to 12V. The output from the first converter can then be used on the board for the 12V components and the output also fed into the second TP5430 to convert down to 3.3v.Is this an efficient design or is there another standard way of achieving this requirement maybe?Would appreciate any help.

author: bob91343
author_rank: Super Contributor
timestamp: May 10, 2021, 04:23:55 am
content: If you could run the lower voltage from the source it would probably be more efficient, since the load current wouldn't pass through both converters.

author: tooki
author_rank: Super Contributor
timestamp: May 10, 2021, 10:48:24 pm
content: I wanna say that I read somewhere that in fact, going through multiple steps is actually more efficient, not less. (I remember because it totally surprised me, as my gut feeling would have been that it’s less efficient.) It might have had to do with the fact that most converters aren’t super efficient at very low load. Doing it in steps keeps each converter loaded a bit more, and I think there were less losses when the voltage drop is smaller.

author: tooki
author_rank: Super Contributor
timestamp: May 10, 2021, 10:50:40 pm
content: Quote from: JohnStein on May 10, 2021, 03:58:45 amUse TI’s Webench power designer tool, on their website, to get reference designs. You put in your parameters (input V, output V, current, minimum component size, etc) and it spits out a list of designs, complete with simulations, schematics, PCB layouts, all of which you can modify and re-simulate. Very useful for working out this kind of thing.

author: bdunham7
author_rank: Super Contributor
timestamp: May 10, 2021, 11:14:02 pm
content: How much current will you need on each leg? That regulator may not work if your Vindrops to anything near your 12 volt output.

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2021, 12:41:12 am
content: Quote from: JohnStein on May 10, 2021, 03:58:45 amThere is nothing wrong with that method. It is what I would do unless I wanted to deal with custom magnetics or had special requirements.
Dual Rail Power Supply Design Center Tap Connection - Page 1
Forum section: electronics / beginners

author: D3K
author_rank: Newbie
timestamp: August 26, 2012, 02:23:33 pm
content: Hi All,I am attempting to design my first linear dual rail power supply, and I came up with the following problem:I have seen a lot of circuits on the internet and most of them connect the center tap connection of the transformer to the ground connection between the two filter capacitors at the input of the power supply ( figure attached). My question is that if the other two terminals (NOT centre tap) are being fed to the full bridge rectifier, what is the purpose of this connection?The typical capacitances used as filters are very large, I have found one circuit with 10,000 uF capacitaces. Are these capacitances not large enough to guarantee a stable virtual ground for the power supply?Thank you.

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 26, 2012, 02:35:24 pm
content: And how is the charge of the capacitors going to be divided between the 2 if your positive and negative load isn't exactly the same?Or, why would you want a virtual earth if you can have a real one?

author: madires
author_rank: Super Contributor
timestamp: August 26, 2012, 03:11:05 pm
content: Quote from: D3K on August 26, 2012, 02:23:33 pmThe center tab is your ground connection. Imagine V1 and V3 are alternating around V2.QuoteThe capacitance is based on the current the prower supply has to provide and the ripple which would be acceptable for your application. Higher current and lower ripple equals to larger caps. Rule of thumb: about 2200 µF for 1 Ampere.

author: T4P
author_rank: Super Contributor
timestamp: August 26, 2012, 03:12:20 pm
content: Center tap-grounding is a method used in full wave bridge rectifiers to attain positive and negative voltages

author: D3K
author_rank: Newbie
timestamp: August 26, 2012, 03:24:40 pm
content: Thank you for your replies.As regards to:QuoteMy initial query was that ifV1 and V3are fed to the full bridge rectifier, what is the purpose of having the power supply ground to the common connection?

author: madires
author_rank: Super Contributor
timestamp: August 26, 2012, 04:19:48 pm
content: Quote from: D3K on August 26, 2012, 03:24:40 pmI thought I answered that question :-) Ok , let's try another way. Since you want to have a dual rail power supply you need at least 3 terminals, one for +V, one for -V and a common ground which is related to +V and -V. The filtering caps are put between +/-V and the common ground. Actually that third terminal is missing at the right side in your picture. If you leave the common ground (V2) away you got a single rail power supply. But then you would only use a single filter cap or put both caps in parallel.

author: shebu18
author_rank: Frequent Contributor
timestamp: August 26, 2012, 05:17:56 pm
content: I may be rude but if you don't know why they do that with the transformer than it would be better to read theory before starting to design. Gather more knowledge.Sent from my GT-I5800 using Tapatalk
Dual-rail power supply with parallel DC-DC converters? - Page 1
Forum section: electronics / beginners

author: inventhouse
author_rank: Newbie
timestamp: March 08, 2018, 02:42:56 am
content: I'd like to branch out into audio / synth circuits, many of which call for a dual-rail power supply. I was wondering if I could build a simple one by connecting two little DC-DC buck converters with their inputs in parallel and one output set to half of the other.In theory 0/9v/18v looks a lot like -9v/0/+9v, but with how cheap and plentiful these little converters are these days I have to wonder why Instructables and the like aren't full of "plans" along these lines... Of course, with how cheap they are, I might just pick up a six-pack and try it.

author: Ian.M
author_rank: Super Contributor
timestamp: March 08, 2018, 03:18:45 am
content: That wont work because the 9V output rail cant sink current from the 18V rail.You can use *SOME* boost converters to generate a negative rail e.g. LM2596 based modules, however they need a stiff high current supply as input to start up successfully. See:LM2596 buck module hacked for negative outputAn other option would be to use arail splitterwith a floating 18V supply. However that's a linear solution so if you need the derived ground rail to source or sink much current the rail splitter dissipation will be significant. Search the forum from its main page for several topics about using them

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 08, 2018, 12:09:03 pm
content: It works if you preload the one rail so its load current is always positive, or use a synchronous buck module that allows negative output current.If you're making the converter yourself, you can also make a negative supply using a dual winding inductor. The regulation won't be as good as two independent converters, but that's fine for most purposes. (Same constraint applies, it must be synchronous or the positive output needs preload.)Tim

author: MasterT
author_rank: Frequent Contributor
timestamp: March 08, 2018, 01:17:01 pm
content: Buy isolated DC-DC converter, +5V -> +-15Vhttps://ca.mouser.com/ProductDetail/709-DPU01L-15
Dual Rail Supply Options - Page 1
Forum section: electronics / beginners

author: Factotum
author_rank: Contributor
timestamp: June 18, 2023, 07:06:18 am
content: Goal - to build a -24/0/24 power supply for a small audio amplifier module (approx 2A per rail) from relatively off the shelf hardware to replace the unsalvageable factory PSU.I could use linear voltage regulators.I'm well aware that just taking a pair of 24v plug pack type units won't work connecting them A+ / A- joined to B+ / B- where the supplies are not isolated.I know virtual ground is also an option.Finally I suspect that I could use a couple of isolated DC-DC converters being mindful that they need n volts above / below their output voltage depending on what's required.Curious to know your thoughts on what works best in the real world for this kind of thing where there will be unbalanced audio interconnects etc...

author: Terry Bites
author_rank: Super Contributor
timestamp: June 18, 2023, 04:27:51 pm
content: Some mains bricks have grond connected to output 0V and some do notThey might not be suitable from noise point of view.You'll find many AC and DC-DC dual supply regulator modules on Aliexpress PotatovisionLD or Ebay etc eg Seach for "24V Dual Output Switching Power Supply" on ebay.auNo doubt you'll need some filtering- still at 15 bucks well worth a punt.Build a dual rail linear supply, 150VA or greater Torroid (probably>$30!), a "!!Full Bridge Rectifier!!" and a pair of reservoir caps. [I would, but then I'm old school and only think smps for car battery chargers and radio jamming purposes.]Do you really need tight regulation?Above 1A simple regulators get more complex, outboard pass transistors and such.Rail spitting is fine for mA, not so easy for higher currents.Many components needed Seewww.tubecad.com/2018/02/blog0412.ht

author: TimFox
author_rank: Super Contributor
timestamp: June 18, 2023, 04:33:09 pm
content: An old rule of thumb about solid-state linear power amplifiers is that, if the power supply uses linear regulators, they must be as good as the amplifier itself to avoid problems.For most analog audio amplifiers, an unregulated supply, with sufficient filter capacitance, suffices.A good analog amplifier will have a respectably high power-supply rejection ratio.

author: David Hess
author_rank: Super Contributor
timestamp: June 19, 2023, 12:14:10 am
content: Quote from: TimFox on June 18, 2023, 04:33:09 pmI will second this. Audio power amplifiers should have enough common mode and power supply rejection to not require regulated supplies.
Dual SCR vs single TRIAC to switch on Inductive load - Page 1
Forum section: electronics / beginners

author: anishkgt
author_rank: Frequent Contributor
timestamp: August 10, 2017, 09:12:25 pm
content: What would be an ideal switch to control an Inductive load, Dual SCR or a single TRIAC ?I was using TRIAC to switch a MOT at the peak of a sine wave. Then i read that some use Dual SCR's to control inductive load as that is how its done in an industrial environment. Can it be said Dual SCR design is the old way of controlling an ac load and TRIAC being bi-directional was the newer version to SCR's.From a design perspective, a TRAIC uses less space and fewer components compared to a dual SCR design. Would that be all ?

author: schmitt trigger
author_rank: Super Contributor
timestamp: August 10, 2017, 09:30:31 pm
content: SCRs would have fewer loses.But most importantly, as they conduct in a single direction, they would not be re-triggered by high dI/dt

author: Circlotron
author_rank: Super Contributor
timestamp: August 10, 2017, 10:06:36 pm
content: Triac should be good enough for a MOT provided you have good enough snubbing. SCRs have the advantage of greater tolerance to dv/dt as well as much greater surge current capability.

author: anishkgt
author_rank: Frequent Contributor
timestamp: August 10, 2017, 11:09:10 pm
content: Thanks guys the dv/dt is a sure thing to bear in mind when the load is highly inductive. I guess then my design with the dual SCR would be correct.Sent from my iPhone using Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: August 11, 2017, 07:44:30 am
content: The only disadvantage of SCRs is they don't trigger on all quadrants. The gate needs to be positive whilst the anode is positive.

author: oldway
author_rank: Super Contributor
timestamp: August 11, 2017, 07:47:42 am
content: Quote from: anishkgt on August 10, 2017, 11:09:10 pmThis was true a few years ago, but with new developement and improvement of 3 quadrants (snubberless) triacs, it has changed.The new technology snubberless triacs has high dv/dt, as high as scr's.There is no reason to use dual scr, a single snubberless triac can do the same job with the same reliability and is easier to trigger than dual scr's.

author: anishkgt
author_rank: Frequent Contributor
timestamp: August 11, 2017, 08:03:39 am
content: Yea snuberless was something that I had in mind as well but wasn't sure if I should stick with the old way or snuberless.Sent from my iPhone using Tapatalk

author: oldway
author_rank: Super Contributor
timestamp: August 11, 2017, 08:57:16 am
content: For high power, the dual scr's solution is still preferred because limited range of 3 quadrants triacs.https://www.google.be/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&ved=0ahUKEwj4it_g5s7VAhVEblAKHZEtB9kQFgg-MAM&url=http%3A%2F%2Fwww.aeg-ups.cz%2Fcz%2Fdownload%2F1404042748%2F%3Fat%3D1&usg=AFQjCNHyv24f9MEFgaNQnrhfY-9ZpGdVUw
Dual source for opamp ? - Page 1
Forum section: electronics / beginners

author: Nhan95
author_rank: Contributor
timestamp: April 07, 2015, 12:48:47 pm
content: When we use opamp LM741 or others, we need to supply a dual source. Could you tell me how to create a dual source from single one. Ex. from 9V we create dual source (+9V)_(-9V) . thanks

author: electr_peter
author_rank: Unknown
timestamp: April 07, 2015, 02:33:50 pm
content: Quote from: Nhan95 on April 07, 2015, 12:48:47 pmNo, you don't need dual voltage supply. Single supply is enough if signals can be shifted to ~half rail.Quote9V DC can be split into 4.5V and -4.5V with resistor divider and op-amp in follower configuration. To get +/-9V you need to either increase voltage 2 times or create negative 9V voltage with DC/DC converter.

author: Richard Crowley
author_rank: Super Contributor
timestamp: April 07, 2015, 02:41:38 pm
content: As electr_peter said, it is not necessary to use dual/split power voltages for an op-amp. There are many circuits that operate on a single supply and use methods such as creating a "virtual ground" of VCC/2, etc.There are also circuits (and commercial modules) that take some positive voltage and generate an equivalent negative voltage. Some of these are quite inexpensive and available on ebay, etc.Since you did not disclose anything about your proposed application/circuit, we are unable to recommend any particular solution.

author: jlmoon
author_rank: Unknown
timestamp: April 07, 2015, 03:00:39 pm
content: If this is a new design, I hope you're forward looking in selection of your op-amp part. I believe the 741 is severely outdated and would suggest something much better / newer such as the TL0xx series. They will perform much better with single supply as well. I have never tried using a 741 at +- 4.5 Volts either, not sure that is within the minimum supply rail specifications.

author: Obin
author_rank: Contributor
timestamp: April 07, 2015, 04:13:39 pm
content: fromhttp://tangentsoft.net/elec/vgrounds.htmli love the tle2426If you're going to put a lot of 'load' on the ground, it's best if you put a simple buffer behind the TLE to soften the blow
Dual supply amplifier ratings - Page 1
Forum section: electronics / beginners

author: init
author_rank: Contributor
timestamp: March 09, 2016, 11:33:13 am
content: Hi guys, I am looking for the maximum ratings for a dual supply mode of operation using an INA332http://www.ti.com/lit/ds/sbos216b/sbos216b.pdf. No on page 2, it says that Supply voltage, V+ to V- = 7.5 V, fair enough, the difference between them can't be above this voltage. On page three, under power supply it says that specified voltage range is min:+2.7V and max: +5.5V. Does this mean that the V+ pin must be within this range? What about the negative rail V-, where are its ratings? AM I correct in thinking that a -5V to +5V dual rail is above specs but a -3.3V to +3.3V is within specs?Sorry for all the questions, just trying to wrap my head around dual supplies.

author: ElektronikLabor
author_rank: Regular Contributor
timestamp: March 09, 2016, 02:35:52 pm
content: If you supply the amp with voltage range of 2.5V and 5.5V between V+ & V-, the amp will operate according to the specifications.If you exceed the 7.5V, the amp could be destroyed (absolute maximum rating). If you apply more than 5.5V and less than 7.5V the amp would work fine; but it's possible that it doesn't meet some of the specifications anymore.The power supply voltage is always measured between V+ and V-

author: suicidaleggroll
author_rank: Super Contributor
timestamp: March 09, 2016, 08:13:59 pm
content: Quote from: init on March 09, 2016, 11:33:13 amIt means V+ minus V- must be within that range. Circuits have no concept of absolute voltage, voltages in a circuit are all relative. V+ needs to be 2.7-5.5V higher than V-. How either of these voltages relate to the point in your circuit that you arbitrarily choose to call "ground" is irrelevant.Quote from: init on March 09, 2016, 11:33:13 amNo. You need an amp that's designed to operate correctly at +/- 3.3v (dual supply) or 6.6v (single supply). There's really no difference between a single supply and a dual supply op-amp, which is why most of them list both ratings.

author: uncle_bob
author_rank: Unknown
timestamp: March 10, 2016, 01:21:05 am
content: HiOne spec missing so far is "common mode input range". That is the range of voltage (relative to V-) that the inputs must stay in. If you go outside this range, odd things happen. Some op amps have "rail to rail inputs". In that case the inputs are OK as long as they are inside the V+ and V- rails. It is never save to *guess* that an amp is rail to rail. You need to check the specs.Just for the sake of getting it all said: The same thing applies to the output of the amp. Here you also need to check the output current they will handle as they get to whatever limit is mentioned. If you load is not 1uA then the sated spec (at 1uA load) may not apply to you.Bob
Dual Tracking Power Supply from Single Output Isolated Power Supply - Page 1
Forum section: electronics / beginners

author: hteo
author_rank: Newbie
timestamp: September 27, 2012, 12:46:50 pm
content: Hi. I have an Agilent E3615A single output isolated power supply rated for 35V at 1.7A. It has the +ve and -ve terminals together with a mains earth terminal. Instead of getting a dual output tracking power supply for dual polarity use such as with opamps, would it be possible to connect the +ve terminal of the E3615A to the positive power rail, the -ve terminal to the negative power rail and connect the mains earth to the ground?Would this configuration even work? Of course, the circuit will not be isolated anymore and one would have to be careful where one connects the ground leads when probing with a scope to avoid shorts. If it does work, are there any drawbacks?Thanks.

author: madires
author_rank: Super Contributor
timestamp: September 27, 2012, 01:40:46 pm
content: Since the output is isolated you won't close a circuit loop by connecting your OPamp to -ve and earth or +ve and earth. You may test that by measuring the voltage between the earth terminal and the -ve/+ve terminals.

author: DaveW
author_rank: Frequent Contributor
timestamp: September 28, 2012, 07:45:13 am
content: Quote from: hteo on September 27, 2012, 12:46:50 pmFor low current use like simple op-amp circuits, have a look at rail splitting circuits (or virtual grounds), like thesehttp://vsagar.com/2011/12/02/what-is-a-virtual-ground-discussion-on-virtual-ground-circuits/.You use a potential divider to find the half way voltage and then use an op-amp to buffer this. If you set your power supply to say 30V, this gives you +-15V, with the ground being generated by the rail splitter

author: Stephen Hill
author_rank: Regular Contributor
timestamp: September 28, 2012, 10:35:36 pm
content: DaveW,The article you linked to is a copy of one written by Warren Young:http://tangentsoft.net/elec/vgrounds.html

author: Stephen Hill
author_rank: Regular Contributor
timestamp: September 28, 2012, 10:53:14 pm
content: Infact, that whole site smells of copied content. I checked a random sample of articles and the contents were all copies from other websites. Shame on the website owner!
Dual transistor gate driver question. - Page 1
Forum section: electronics / beginners

author: Oneminde
author_rank: Regular Contributor
timestamp: November 19, 2021, 07:15:56 pm
content: HiWas looking at a schematic and ran into this configuration as a MOSFET gate driver. I asked a friend who proposed the theory presented in the image.My question to you fellas are: Does this configuration have a name and theory attached to it that I am not aware of ?

author: fourtytwo42
author_rank: Super Contributor
timestamp: November 19, 2021, 07:40:05 pm
content: Not enough of the schematic presented to evaluate it, try the rest of it

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 19, 2021, 08:04:38 pm
content: Emitter follower with bootstrapped collector.Doesn't seem to actually do anything, unless they're running out of voltage ratings. Which doesn't seem the case as the zener has a fairly low voltage, it's not like it's half or mid supply (I didn't check the transistor type but it must be rated >120V as shown). And the gates will have fairly high capacitance, much more than the measly few pF the collector adds to it.Audio amps are good for study / analysis exercises, but mind they do not, in general, make good reference material. Audiophiles have an attraction to the unusual, and because audio applications are extremely tolerant of bandwidth, stability and reliability factors (e.g., 20-20k Hz is a small fraction of the low ~MHz available from most BJTs and power MOS), they can entertain some outright dubious ideas for sake of novelty.Tim

author: Oneminde
author_rank: Regular Contributor
timestamp: November 19, 2021, 08:08:17 pm
content: Quote from: fourtytwo42 on November 19, 2021, 07:40:05 pmThis comes from an Accuphase differential input and single ended push-pull output, the A-65 - here is the output brd for that amplifier-

author: Oneminde
author_rank: Regular Contributor
timestamp: November 19, 2021, 08:12:45 pm
content: Quote from: T3sl4co1l on November 19, 2021, 08:04:38 pmThanks for your input. The reason why I found it interesting was that it allowed for a simpler driver stage than what is usually the method of using 1 bjt per FET output when multiple FETs are paralleled.But I guess one can do that as long as the bjt has enough Ic handling, then using several is not needed. That way, each FET tracks or drift the same (thermal drift).
Dual USB Cigarette lighter adapter problem - Page 1
Forum section: electronics / beginners

author: jbs
author_rank: Contributor
timestamp: February 23, 2024, 04:13:44 pm
content: Hi,I have bought this dual USB adapter and I want to connect a Gopro Hero 11 on USB type A and a 12V micro fan on USB type C.https://www.amazon.co.uk/UGREEN-Charger-Charge-Adapter-Compatible/dp/B09DSV9G78I have connected the fan to a 12V USB C PD trigger modul, to force it to pull 12V.My results:-) When I only plug in the fan, the voltage reads 9,14 V-) When I plug in both, the Gopro and the fan, the voltage reads 5,14 V on the fan.Do I have the wrong adapter? I basically want the fan to run with at least 9 V...how can I achieve that?Thanks in advance,Joël

author: sparkydog
author_rank: Regular Contributor
timestamp: February 23, 2024, 06:29:23 pm
content: Have you checked what simultaneous outputs are supported? A.co.uk hates me, so I'm not sure what exact charger you're using, but if it's a 30W, well...As you may already know, USB PD doesn't have a 12V out; your options are 5V, 9V, 15V, ... So your "12V USB C PD trigger module" is most likely only requesting 9V, and your voltage reading with only the fan plugged in is expected. Also, 9V only delivers up to 27W, which is basically the limit of a 30W charger. The moment you plug something else in, it's probably limiting both ports to 5V/15W, which would explain why the fan drops to 5V.I suspect you need a charger that can deliver 15W on USB-Aandat least 27W on USB-Csimultaneously. For example,https://www.ugreen.com/products/ugreen-69w-usb-c-car-charger."But I don'tneed27W for the fan!" I hear you complaining. True, but I'm not sure USB PD works that way; I'm not sure you can negotiate for low wattage at high voltage. (Mind, I'm fairly confident nothing will gowrongif you draw less wattage, but the charger has toassumethat, if you're asking for 9V, you might draw no less than 15W, and so won't give you the requested voltage if it can't guarantee at least 15W and possibly 27W.)Your other option is to either use a 5V fan, or use a DC-DC converter to run the fan off 5V. If you just need "a fan", Noctua makes fans from 40mm to 200mm in 5V.

author: jbs
author_rank: Contributor
timestamp: February 25, 2024, 08:44:39 am
content: Thanks for your help with the USB adapter issue! 🤗 Upgraded as you suggested, and everything's working great now. Really appreciate it. You saved my project 👍

author: sparkydog
author_rank: Regular Contributor
timestamp: February 26, 2024, 06:33:28 pm
content: Cool; glad that worked! Thanks for sharing the update!
Doubts about SPICE analysis - Page 1
Forum section: electronics / beginners

author: RawCode
author_rank: Regular Contributor
timestamp: March 09, 2019, 09:59:08 am
content: Hello there!I'm an electronic enginering student, and at the moment I'm attending the ECAD subject. I use Micro-Cap 12.0.2.1 Evaluation Version as a ECAD software, and at the moment I can't switch to something simpler like LTSPICE, since i have to take an exam with Micro-Cap.First thing: what is, what is the purpose and when i should use the PSS(Periodic Steady State) analysis in the transient analysis?I was messing around with a guitar effect, but I found something strange in the simulation.Let's start.First thing strange: i was studying this buffer stage, which has this spectral response:Is that normal that i get a transient response (a sinusoidal wave @60k) of this kind? I mean, i know that there is a resonance at more or less 11kHz, but i didn't expected this behavior at the beginning, because i'm "far" from the resonance.(Blu=input, Red= output)Here it is another strange thing. I was analyzing the input and output impedance of this stage with the ac analysis - i'm using a what micro-cap calls "generic model" for the opamp.(blu=input, red=output)But in the plot of the analysis, it shows something strange, like a "resonance of impedance" at more or less 12kHz of almost 1Meg, and everywhere else an impedance of 10k. For me at least this is very strange, because i expected something near zero impedance.but if i remove the toggle to the option "operating point" i get this kind of impedance, which is more "reasonable".What am i doing wrong? Can you help me?

author: exe
author_rank: Unknown
timestamp: March 10, 2019, 10:15:04 pm
content: The oscillation could compensation/stability issue of the opamp. Which opamp is that? Anyway, I'd first increase the compensation cap to see if behavior changes.

author: RawCode
author_rank: Regular Contributor
timestamp: March 12, 2019, 07:56:20 pm
content: Quote from: exe on March 10, 2019, 10:15:04 pmI'm using the ne5532.I solved the issue with the impedance though, doing the analysis of the input impedance grounding the output and vice versa. I thought that I could do the complessive impedance analysis in one shotInviato dal mio LG-H930 utilizzando Tapatalk

author: exe
author_rank: Unknown
timestamp: March 13, 2019, 08:35:08 am
content: Did you ground the output of opamp?

author: RawCode
author_rank: Regular Contributor
timestamp: March 22, 2019, 08:46:45 am
content: Yes I did.Anyway I solved this simulation issues and all my doubts.ThanksInviato dal mio LG-H930 utilizzando Tapatalk

author: exe
author_rank: Unknown
timestamp: March 22, 2019, 11:57:28 am
content: Could you please explain why grounding is needed? I thought input impedance of opamps is generally high and not related to output anyhow (unlike a bjt amplifier). Also datasheets mention input bias current, this should sort of tell the input impedance immediatelly. Or you mean impedance of opamp input and surround circuits?
Dumb Altium Question  - Page 1
Forum section: electronics / beginners

author: FotatoPotato
author_rank: Regular Contributor
timestamp: October 03, 2018, 01:56:18 am
content: Hey all,So I just switched from 6 years of Eagle to Altium designer and it has been quite the experience so far... While I do like altium there are some things that just piss me off royallyAnyway, I'm working on a power supply layout and I was wondering if anyone knows how to assign relief connections to specific polygons and specific parts but not others. If you look at the attached picture, I don't want any reliefs on the GND pad of the IC but I do want them on all of the MISC components around it. I also don't want reliefs on the big connection coming in from the right corner. Lastly I did set my clearance to 50mil on all polygons the Design Rules but it seems to have changed nothing and as you can see the distance between the two planes is really small.Thanks for the help
Dumb question on power supply - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: February 20, 2018, 12:43:41 pm
content: Hi,If I put a 1 ohm motor across the voltage wire of a regulated power supply1- If I set the voltage to 3 volts and the amps at 4 amps the motor will overcome one or the other2- If I put the amps at 3 amps and the voltage at 4: the motor will overcome one or the otherWhat is the use of a preset amperage?I can control the voltage OR the amperage, not both.Dumb guy

author: Nerull
author_rank: Frequent Contributor
timestamp: February 20, 2018, 12:47:53 pm
content: What happens when you spend a few hours breadboarding a new circuit and you accidentally miswire something, creating a short, and then you connect this circuit to a unregulated supply with no current limit?What happens when you want to charge a lithium ion battery, which needs an inital charge at some given constant current and then needs a final slow charge at a given constant voltage?And of course you can't control voltage and amperage at the same time. That's physics. Think ohms law - for a given resistance and voltage, current is fixed. There's no way you can force a circuit to pass more or less current than ohms law allows, and the same with voltage at a given current.

author: andtfoot
author_rank: Unknown
timestamp: February 20, 2018, 12:53:20 pm
content: In terms of a lab power supply when setting the voltage and current:- The supply will keep a constant voltage as long as the current is below the setting- When the current hits the set limit, the supply will keep that current constant. It will do this by dropping the voltage to suit.So for your examples (assuming a purely resistive load):1 - voltage will be kept at 3V, current then is 3A (below the limit, so supply is in constant voltage mode)2 - voltage will be dropped down to 3V, to keep the current at 3A (supply is in constant current mode)Just think Ohm's law and it might make more sense.
Dummy Lab PSU questions - Page 1
Forum section: electronics / beginners

author: aluck
author_rank: Regular Contributor
timestamp: April 05, 2012, 04:57:12 am
content: I have a single-output lab PSU with three terminals on the output - plus, minus and ground. The ground is wired internally to ground pin on the wall outlet. Plus and minus are floating.1. What's the point of having ground terminal? Can you think of some reasonable usage?2. If I would get another one single-output lab PSU (also floating output), could I just wire (+) of one PSU to (-) of the other, call it the "ground" for my project, and use them for supplying both positive andnegativevoltage?

author: IanB
author_rank: Super Contributor
timestamp: April 05, 2012, 05:11:59 am
content: This other thread probably answers your questions:https://www.eevblog.com/forum/beginners/what's-the-'ground'-terminal-for-on-all-these-dc-power-supplies/

author: aluck
author_rank: Regular Contributor
timestamp: April 05, 2012, 07:15:33 am
content: Quote from: IanB on April 05, 2012, 05:11:59 amThanks.But the second question still remains.

author: Unknown
author_rank: Unknown
timestamp: April 05, 2012, 07:54:05 am
content: Yes, that's the whole point of floating power supplies. Either connect the center terminal to the ground terminal on one of the supplies, or call it something like 'circuit ground' to distinguish it from physical earth. You can just connect them like batteries in series or parallel (within limits, don't go crazy and connect them to high voltage supplies).

author: aluck
author_rank: Regular Contributor
timestamp: April 05, 2012, 10:35:35 am
content: Quote from: alm on April 05, 2012, 07:54:05 amThanks a lot.

author: saturation
author_rank: Super Contributor
timestamp: April 07, 2012, 02:32:52 pm
content: When connecting 2 or more floating PSU in parallel, say for more current, be careful to match the output voltage as near exact for all paralleled supplies. All paralleled supplies sense and will adjust to regulate the voltage output. If they have unequal output voltage or even regulation specs, the better supply will compensate for the lesser supply. In high current usage, it could overheat the better supply. You could say all specs of the better supply will be reduced somewhere between its specs and the lesser supply's specs: regulation and recovery time, ripple etc.,
Dummy load and return loss bridge? - Page 1
Forum section: electronics / beginners

author: elroy
author_rank: Regular Contributor
timestamp: November 17, 2017, 02:55:45 am
content: I've been seeing return loss bridges of this type:http://transverters-store.com/rf_bridge/rf_bridge.htmlon eBay and elsewhere, and have been trying to get more educated on how they are used to characterize antennas.In the writeups and videos I've seen, a signal/noise source is connected to the input, an instrument like a spectrum analyzer is connected to the output, and the antenna being evaluated is connected to the DUT port.I noticed, however, that some of the bridges being sold (such as the one linked above) have an additional port marked REF. I asked one eBay seller about it, and he said it was for a dummy load; for additional information, he said "google it."So I'm just a little unclear on how/why you would use a dummy load while testing an antenna connected to the DUT port. Can anyone help me out here, or point me to anything that covers this specific point?

author: hendorog
author_rank: Super Contributor
timestamp: November 17, 2017, 06:29:44 am
content: The way these bridges work is by measuring the in-balance of the bridge - which in real terms is how close the device attached to the test port is to 50 ohms. The bridge is balanced when the both the DUT and the reference have the same impedance - nominally 50 ohms.So to do the comparison you need something which is known to be 50 ohms to act as a reference.Some bridges are built with a 50 ohm resistor built in as the reference. Others just have a port where you attach your own reference - in this case you use a 50 ohm dummy load to provide the 50 ohm reference.

author: elroy
author_rank: Regular Contributor
timestamp: November 17, 2017, 07:08:02 am
content: Thanks, very clear!

author: IconicPCB
author_rank: Super Contributor
timestamp: November 17, 2017, 07:38:25 am
content: You could make it yourself with a bit of care and attention to detailYo could expect better than 30dB directivity that is to say You could measure return loss up to 30dB and more than 500MHz with the unit depending on the detector You use.

author: Tony_G
author_rank: Super Contributor
timestamp: November 17, 2017, 03:24:34 pm
content: While not the same design, this article has some background info on the broad idea and usage of a SWR bridge:http://www.w1ghz.org/QEX/A_UHF+_VSWR_Bridge.pdfTonyG

author: elroy
author_rank: Regular Contributor
timestamp: November 18, 2017, 12:12:16 am
content: Quote from: Tony_G on November 17, 2017, 03:24:34 pmThanks!
Dummy Load Experiments - Page 1
Forum section: electronics / beginners

author: PsychoMaster
author_rank: Regular Contributor
timestamp: April 18, 2015, 10:16:17 am
content: HiI have ordered lots of different op amps and I am trying them out on Daves dummy load circuit as they arrive. I am using a 10k pot, a irfz44n mosfet and a single 100 watt 1 ohm resister as current source for a meter and checking this against a inline multimeter . A lm358 works either fully on or fully off no matter what voltages .A single lm741 will not take negative feedback from the mosfet source pin but works beautifully when sourced at the gate and is very accurate. Putting a car headlight bulb before the mosfet takes heat away from it and still I get very acurate meter readings.Two mosfets in direct parrallel do not share the load equally and require a ballast resister on the source.Some say this works without ballast but I have found it not so.One was cold and the other burnt my fingers but warmed up when I removed the hot one.

author: PSR B1257
author_rank: Frequent Contributor
timestamp: April 18, 2015, 10:28:17 am
content: QuoteFairly high value unless you stay under 1A load current.QuoteIt shouldn't. Have you connectet it correct?QuoteRight. You can connect MOSFETs in parallel only in switching applications. But if they operate in linear mode they do not spread the load current even (do to different gate-source theshold voltage and thermal effects).

author: PsychoMaster
author_rank: Regular Contributor
timestamp: April 26, 2015, 06:02:19 pm
content: HiWith the lm358 I have tried using just one internal opamp as well as using one as a buffer but still I get the same affect.My lm324s have just arrived which I will now try.I now have my first oscilloscope (475A Tektronix) so I can see what is happening better. I did not expect the LM741 to give such good results on 5 volts and a 50% attenuation ratio.Remember Daves psu circuit when he first used a op amp to drive the current LED and the output would swing straight from low to high?, I think this is behaving in a simular manner.
Dump Intel MA2155 Firmware - Page 1
Forum section: electronics / beginners

author: DrLov
author_rank: Newbie
timestamp: August 03, 2024, 04:18:22 am
content: Hello, everyone, is everything okay with you?I need to copy the Firmware of an Intel MA211 and I can't find any information on the internet. I've already looked for the complete datasheet and I can't find anything either. I was trying to see the pins for the JTAG connection, but I couldn't find anything. I have some defective boards for this Processor, I would like to copy the Firmware to flash new chips and solder them again to recover the boards.Can anyone help me? If possible, I can pay for this help!
Dump MX29LV flash memory? - Page 1
Forum section: electronics / beginners

author: Agentfoot
author_rank: Regular Contributor
timestamp: November 16, 2024, 03:31:27 am
content: I would like to pull the firmware from a MX29LV flash memory chip. Anyone know how this could be done? Attached is a picture of the device PCB. Arrow points to the MX29LV. Chip data sheet https://www.mouser.com/datasheet/2/819/MX29LV640E_T_B_2c_3V_2c_64Mb_2c_v1_7-3370947.pdf/url].Would love to know what the connections in the yellow circle could be if anyone knows.

author: u666sa
author_rank: Frequent Contributor
timestamp: November 16, 2024, 11:36:14 am
content: With Xgecu T48 or T56 and BGA48 adapter, no problem. You remove it. You stick it into adapter. Get the dump. Then you reball it, no stencil needed, just microscope and individual balls will do. Reflow back into its home.Adapter is ADP-BGA48-0.8 for T48 & T56Here is wiring schematicThere are no instructions on how to connect it via ISP cable.

author: Agentfoot
author_rank: Regular Contributor
timestamp: November 16, 2024, 01:17:40 pm
content: Quote from: u666sa on November 16, 2024, 11:36:14 amThanks for this information. Unfortunately if removing the chip is the only option I will not be attempting this. I don't have the skills or tools needed and this is not the project to learn on. I thought just maybe the pads around the chip or the pads in the circle were for some sort of communication with the chip.
Dumpster diving: NEC SpectraView 2690 Monitor - worth a go? - Page 1
Forum section: electronics / beginners

author: jewelie
author_rank: Regular Contributor
timestamp: December 29, 2018, 03:48:59 pm
content: So, I've just noticed that there's one of these been dumped in our domestic communal bin area-NEC SpectraView® Reference 2690 High-end 26 inch professional widescreen LCD monitor for colour critical applications with outstanding features and benefits for best picture quality and colour accuracy, outstanding ergonomics and economics.• Consistent Wide Colour Gamut (107% AdobeRGB) from any angle with H-IPS display Truer colours with a wider colour gamut as soon as you switch on due to X-light® Pro and hardware calibration with 12-bit LUT (look up table) for 36-bit colour control and gamma correction, independent per colour and input•Ergonomically mastered for comfortable viewing with ErgoDesign® and TORO™: Heightadjustable stand (150 mm) with 90° portrait capability•Extraordinary features such as Digital Uniformity Control (ColorComp), Power On timer,ambix3™triple input, OSD KeyGuide, self diagnostics and X-light® Pro•SpectraView® Profiler software, SpectraView® • Certifier document includedhttps://www.nec-display-solutions.com/p/uk/en/support/productsupport/rp/Reference2690.xhtmlIt doesn't look like it's been rained on since it's been put out. Externally it looks in *exceptionally* good condition.Is it worth a look do you think?2009. Is this near to the bad caps plague?Jx

author: LapTop006
author_rank: Unknown
timestamp: December 30, 2018, 04:41:29 am
content: I'd certainly give it a try.I'd guess given the line it was assembled in Japan, so likely Japanese caps which are unlikely to be bad.

author: james_s
author_rank: Super Contributor
timestamp: December 30, 2018, 05:26:09 am
content: I'd certainly grab it and take a look. Even if it had been rained on that's not necessarily the end of the world. I recently grabbed a monitor that was laying in the grass by the side of the road getting rained on for a week. Turned out it works just fine after drying out, no idea why it was left there.

author: spec
author_rank: Frequent Contributor
timestamp: December 30, 2018, 09:54:44 am
content: Quote from: jewelie on December 29, 2018, 03:48:59 pmHi jewelieThat is a nice monitor- go for it. The normal problem with LCD monitors is the back-light if it isELCCFL. Either theELCCFL tube goes or the connections corrode. The fix is not that difficult but fiddley. You can get replacementELCCFL tubes and they are not that expensive, even from the US. But even if you can't get the monitor working, it would be a good source of parts.

author: james_s
author_rank: Super Contributor
timestamp: December 30, 2018, 05:47:51 pm
content: I think you mean CCFL. I've never seen an EL backlight in a consumer monitor.

author: spec
author_rank: Frequent Contributor
timestamp: December 31, 2018, 06:01:50 am
content: Quote from: james_s on December 30, 2018, 05:47:51 pmQuite right- will correct post.
Duplicating an audio signal with a buffer splitter - Page 1
Forum section: electronics / beginners

author: Jungle-Jim
author_rank: Newbie
timestamp: November 20, 2022, 08:40:00 pm
content: Hi allI am wanting to duplicate a stereo pair audio signal from a car stereo head pre-amp so it can go into two amps. It's a standard car stereo, and it outputs into several amps individually as it should.If I use a passive y-splitter and just run the signals into each amp, will these signals be lower-output or lower quality given they are sharing the juice? The signal cables won't be long - 50-70cm each. Or is it a good idea to use something like a JFET buffer circuit to give each new output a boost. I don't want these new duplicated output signals to be louder than the original - ideally they would be basically the same as the original, and as transparent as possible.Making a simple circuit such as one with some JFETs is easy and doable for me, I just need pointing in the right direction here.Knowing about signal impedance would no doubt be helpful - hopefully I can learn about this with this project.Thanks

author: Benta
author_rank: Super Contributor
timestamp: November 20, 2022, 08:45:24 pm
content: Just use a passive y-splitter. Output impedance is low enough, and input impedance is high enough that it makes no difference.Exception could be very old pro equipment using 600-ohm transformer coupling, but those are rare as hens' teeth. On modern kit it's no issue at all.
Dupont housing, breadboard friendly, open barrel connectors: which series? - Page 1
Forum section: electronics / beginners

author: Watth
author_rank: Frequent Contributor
timestamp: May 23, 2016, 12:42:04 pm
content: Ohai!I'm trying to find the right kind of connector contact that meets these requirements.I know it exists; I already had them but I forgot from which vendor it wasFits Dupont housingIs breadboard friendlyFastens to wire by open barrel crimpingExists in male and female versionsI can't seem to find the right series from the vendors I usually buy from (RS, Farnell).Thanks a lot!
Duratech el cheapo - Page 1
Forum section: electronics / beginners

author: sm0kew0n
author_rank: Newbie
timestamp: May 13, 2016, 07:03:55 pm
content: Hi,I've been tinkering with some old computers recently and after having watched far too many of Dave's videos I decided it was time to ditch my crappy plug in the wall solder iron and get something that won't burn holes in every pcb I touch. I'm a beginner and don't have much money so I ended buying this un-used Duratech TS-1570 for half a sheckle, I've attached some pictures for everyone to have a laugh at and because I've watched too many eevblog videos I didn't turn it on, I took it apart! (well, the cover off) Give me a heads up if you see something highly dangerous, I've no idea how old it is.Looking forward to getting my raspberry pi zero wired into my old psion!Cheers!

author: Raj
author_rank: Frequent Contributor
timestamp: May 14, 2016, 11:57:22 am
content: looks good to me ( Note: this type of crappy product is common in india thus making me blind towards itself plus, I am someone who had to repaired burnt out computer pow supplies for training until they go up in flames or work for a day perfectly with good voltage. i've seen those blue sparks a lot many times)BTW. it's iron gets rusted extremely quickly so you better paint it from inside

author: tautech
author_rank: Super Contributor
timestamp: May 14, 2016, 12:56:01 pm
content: Quote from: sm0kew0n on May 13, 2016, 07:03:55 pmWelcome to the forum.You'll be pleased with it and oohh is that what they look like inside.Grabbed mine on special as our and Aussies Jaycar were clearing them for flashier digital versions.It's been 100% reliable for the at least 5 yrs I've had it. (touch wood)Elements that fit the 900M, L, 907, 908, 913 and 914 irons will work with these stations.Got a spare soldering iron for it from eBay, IIRC for less than $10.Get yourself a few extra tips and you'll be good to go.

author: amyk
author_rank: Super Contributor
timestamp: May 14, 2016, 02:55:09 pm
content: Looks like a typical 936 clone judging from the iron, it'll work just as well as the others.

author: sm0kew0n
author_rank: Newbie
timestamp: May 14, 2016, 03:43:02 pm
content: Quote from: tautech on May 14, 2016, 12:56:01 pmThanks for that info, the only thing it didn't come with was spare tips so I need to get some, knowing what fits makes it easier.