hybridfree/eevblog-posts huggingface dataset:
Accuracy Specifications for Instruments - Page 1
Forum section: electronics / beginners

author: Rainer Dynszis
author_rank: Newbie
timestamp: September 05, 2019, 06:36:40 pm
content: Hello all,my first and probably dumb problem is:I have trouble understanding the accuracy specifications for instruments, such as multimeters and the like.For instance, the manual for the Fluke 28 II says that DC current readings in Ampere are accurate to +-(0.2% + 4 digits), and I'm not sure what to make of that. My understanding is that you always have a certain probability of error, but the concept of probability is nowhere to be seen in these specifications.Is +-(0.2% + 4 digits) the standard deviation of measurements around the true value, or does the readingneverdeviate more than +-(0.2% + 4 digits) from the true value, or what does it mean, really?

author: bob91343
author_rank: Super Contributor
timestamp: September 05, 2019, 07:05:09 pm
content: The confidence level of that specification is very high. In fact, the manufacturer assumes you will take the specification as a maximum, not a standard deviation. All units that fall outside this range will be rejected.So your last sentence with bold face font for the word 'never' is true. The error will never exceed that amount.

author: magic
author_rank: Super Contributor
timestamp: September 05, 2019, 07:21:02 pm
content: Well, there is one exception to the "never": those specifications are usually only guaranteed for some time after last calibration.Which means that the device can slowly drift and needs to be periodically checked for accuracy and adjusted.

author: Rainer Dynszis
author_rank: Newbie
timestamp: September 05, 2019, 08:08:44 pm
content: Thanks. From the word "guaranteed" I understand the error is "never" bigger in the sense that otherwise a new unit would be eligible for replacement or repair.I forgot that there are two error sources, (1) nonperfect repeatability, and (2) systematic deviations due to nonlinearities or miscalibration.I conjecture that (1) is smaller than (2) by orders of magnitude, so that probabilities don't really come into play here, yes?

author: ArthurDent
author_rank: Super Contributor
timestamp: September 05, 2019, 08:46:06 pm
content: Some instruments I've had are more specific and will give those accuracy specs you showed but will say that they only hold for something like 50% to full scale and the error may be greater on the lower part of the range.

author: barry14
author_rank: Regular Contributor
timestamp: September 05, 2019, 09:08:58 pm
content: One should also note that most accuracy specifications only hold for a limited range of environmental conditions: mostly temperature but humidity, vibration and altitude may also be specified.
AC/DC adapter - any thoughts about safety - Page 1
Forum section: electronics / beginners

author: Lagittaja
author_rank: Newbie
timestamp: November 01, 2016, 02:40:11 pm
content: Hey everyone, I figured EEVblog forum would probably be one of the best places to ask.I need to replace a 12V1.5A power adapter of a "massage pillow" and I'm on a relatively low budgetSo I purchased this, quite cheap, AC/DC power adapter.http://www.ebay.co.uk/itm/311691321651?_trksid=p2060353.m2749.l2649&var=610598135566I decided to take a look inside and took a bunch of pictures from the inside.I'm wondering if you professional EE's think it's innards look "safe enough" to actually use it?No clue what the snipped off V+ V- and L N on the left side of the PCB are/were.https://goo.gl/photos/13CwrRjHzUma2BhT8?Sorry if the pictures are a little bit grainy, if they are not good enough I can go and take new ones in better lighting.(Edit: Took half a dozen better images, they're in the same album now)Looks like the IC is a THX203Hhttp://monitor.espec.ws/files/thx203h_________115.pdfEdit2: I'm sorry if this isn't the correct subforum for a thread like this, as I'm a beginner I thought the "Beginners" subforum would be OK for something like this.Though now I noticed there's a subforum (Other equipment & Products) which specifically mentions teardowns. If that was a better place to post this, sorry again and moderator, can you move this if you think it's a more appropriate subforum)

author: Monkeh
author_rank: Super Contributor
timestamp: November 01, 2016, 02:50:00 pm
content: That's a salvaged board of seemingly reasonable quality, shoved in a new case, with wires attached wherever was convenient.

author: Lagittaja
author_rank: Newbie
timestamp: November 01, 2016, 02:59:05 pm
content: Thank you for your reply Monkeh, reasonable quality sounds good enough to meI won't of course be leaving it plugged in unless it's being used.

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: November 01, 2016, 03:00:55 pm
content: Judging just from the photos looking at the creepage distance it looks quite ok. But keep in mind that nobody can say anything about the quality of the used transformer and other components. The cut off wires are, as monkeh already mentioned, signs of the pcb being salvaged from something and repurposed in this wall wart power supply. They were just the connections for the mains input and the original DC voltage output.

author: Lagittaja
author_rank: Newbie
timestamp: November 01, 2016, 03:13:32 pm
content: Thank you to you as well Ysjoelfir, I understand that nobody can say anything about the quality of the components. I guess I was just mainly concerned/curious about the overall "quality" (how it looks) or safety of the design itself. Who knows how bad or good the output of it is without actually testing it but considering it's just powering two motors and an infrared heater I'm not that hugely concerned about it. And the product it's going to power is already in the neighbourhood of 7 or 8 years old, if I get a little teeny bit more life out of it with this power supply I'm happy
AC/DC PCB Module Testing - Page 1
Forum section: electronics / beginners

author: kkessler
author_rank: Regular Contributor
timestamp: April 27, 2017, 04:45:38 pm
content: I’m working on a project where I will be putting a microcontroller inside a wall switch, and I’m investigating 3.3V power options. I have a Mean Well AC/DC module from Mouser, a Hilink from Aliexpress, and I’ll possibly be testing a capacitive transformerless power supply. I started looking at efficiency, to get an idea of how much power loss and heat I’m going to get from these devices, so I setup a kind of naive test with a DC load on the output and multimeters measuring voltage and current on the input. I realize, though, that to get a measure of input power, I need to take the power factor into account.The way I can think of to measure PF is simply to use an Oscilloscope to measure the voltage across the input, and for current, maybe just measure the drop across the ammeter. I have my test setup connected through an isolation transformer (how does that affect the PF calculations?), although I’ll still probably pull out my old Rigol scope instead of risking my new one.I have a relatively inexpensive device that plugs into an outlet to monitor power usage, and it gives the PF, but I don’t know how accurate they are. How do they work? I suppose they could just be using a microcontroller’s ADC to poll drops across shunt resistors, but maybe they are using a better way to measure PF.I guess I am just asking for any input on characterizing my power supply options, especially where it pertains to power loss and heat.

author: kkessler
author_rank: Regular Contributor
timestamp: April 28, 2017, 03:37:43 am
content: I plugged in my scope, and what I saw was not was what I expected. Googling around I learn a great deal on how these switch mode power supplies work.

author: ebclr
author_rank: Super Contributor
timestamp: April 28, 2017, 03:42:30 am
content: Do you know this tool?https://webench.ti.com/webench5/power/webench5.cgi?origin=ti_panel&lang_chosen=en_US&VinMin=14.0&VinMax=22.0&O1V=3.3&O1I=2.0&op_TA=30

author: kkessler
author_rank: Regular Contributor
timestamp: April 28, 2017, 11:10:52 pm
content: That link certainly sent me down some very interesting rabbit holes that I'm still exploring. It's obvious to me that the question I should have ask was:I have an application to put a microcontroller inside a wall switch. I need a 3.3V power supply that only needs to supply about 20mA. What options exist that 1) won't burn my house down, 2) won't require me to rip open my wall to install it, and 3) won't break the bank?
Achi IR 6500 - Page 1
Forum section: electronics / beginners

author: GAM3x0V3R
author_rank: Newbie
timestamp: December 31, 2019, 03:27:22 pm
content: Hi all i recently bought a achi, im trying to setup the lower PID controller i ran auto tune and i can get it to go to the desired temp and stay they but it takes ages to get there.There is a setting in the PID, PI if i lower that temp rises quicker but i get huge overshoot. Any ideas im completely lost.
Acronym PWR In Electric Scheme - Page 1
Forum section: electronics / beginners

author: Kaio Macedo
author_rank: Contributor
timestamp: November 01, 2016, 06:52:45 am
content: Hello guys, I have a question about the acronym PWR.Think mean power, but want to find out the reason of having onths numbers 250, 1000, what they mean ...

author: Ammar
author_rank: Regular Contributor
timestamp: November 01, 2016, 09:53:32 am
content: Some context would be helpful. What is the document about?

author: Aeternam
author_rank: Unknown
timestamp: November 01, 2016, 01:46:21 pm
content: Trace widths on the PCB?

author: Kaio Macedo
author_rank: Contributor
timestamp: November 01, 2016, 02:30:22 pm
content: Quote from: Ammar on November 01, 2016, 09:53:32 amYou're right, this is the scheme>https://drive.google.com/file/d/0BwigVntf89cRZlBuUXlERXloZm8/view?usp=sharingQuote from: Aeternam on November 01, 2016, 01:46:21 pmI'm not sure when it's width usually have the relationship in mm ...But I'm open to suggestions ...

author: AndyC_772
author_rank: Super Contributor
timestamp: November 01, 2016, 02:34:49 pm
content: I'd guess it's the name of a set of design rules which apply to that net on the PCB.PWR1000 could easily mean 'power trace, min width 1.000 mm'.
Acrylic LED strip sign - Page 1
Forum section: electronics / beginners

author: lewc
author_rank: Newbie
timestamp: January 26, 2020, 12:04:37 pm
content: Hi All. I'll start of by saying hello. First post here. I have the tiniest idea about what I'm doing with electronics. I can cut wire and solder it to a battery but that's about it. I thought I'd do a bit of a search online to see If I can work out a few things and here I am. I'm hoping that this is the right place to ask.I work as a teacher (Design&Tech) and am trying to develop a new project for my year 8 students. I tend to focus on timber and metal but I'm trying to broaden my knowledge a bit. The idea I came across was a LED and acrylic sign.https://i.ytimg.com/vi/omPt6U_8ws8/maxresdefault.jpg.There are 100 students to take through this project so I'm trying to find a balance between cost effective, a certain degree of challenge and having a final product that looks good and they're proud to take home.My first prototype was to get a AA battery case with switch and use that as the power source. It lights up the strip well and I've had it going for about 15hours so far. The problems I've found with this method are a chunky battery case and it would be difficult to secure the case and change the batteries when needed.My next idea was to use a AAA case with another switch. It's smaller and lights up the lights. A few more parts to solder but I think this is a winner in terms of the size of the battery pack.I suppose my questions would be along the lines of: Does this seem on the right track? How would you go about creating this simple circuit? Any comments would be welcome.Sorry about the long post. I've got a lot to learn.

author: lewc
author_rank: Newbie
timestamp: January 26, 2020, 12:08:36 pm
content: I've used this switchhttps://www.jaycar.com.au/spst-round-rocker-switch/p/SK0960with one of thesehttps://www.jaycar.com.au/2-x-aaa-cell-battery-holder/p/PH9226

author: Zero999
author_rank: Super Contributor
timestamp: January 26, 2020, 09:17:11 pm
content: It looks fine to me. Another option is 12V LED strip and a mains power supply.https://www.jaycar.com.au/12vdc-400ma-ultra-slim-switchmode-power-adaptors/p/MP3147
ACS709 fault reset - Page 1
Forum section: electronics / beginners

author: stoyanoff
author_rank: Contributor
timestamp: August 09, 2021, 03:12:30 pm
content: Greetings! I need to substitute my current sensor and ACS709 is available. Has anybody ever used this sensor? I need to know if the fault pin resets if the fault condition is not present? Do I have to use the FAULT_EN pin? Because I don`t have extra pin for this.Thanks!

author: Jwillis
author_rank: Super Contributor
timestamp: August 10, 2021, 03:23:04 am
content: I think it works in conjunction with pin 22 .19 FAULT Over current Fault pin. When current flowing between IP+ pins and IP– pins exceeds the overcurrent fault threshold, this pin transitions to a logic low state.22 FAULT_EN Enables overcurrent faulting when high. Resets FAULT when lowPage 16 ofACS709 Datasheet
ACSII Code - Page 1
Forum section: electronics / beginners

author: cvriv
author_rank: Frequent Contributor
timestamp: February 28, 2017, 12:18:16 am
content: Im reading my digital book and it says that ACSII is a 7 bit code and therefore has 2^7 = 128 possible codes. I don't get that because 2^7 is a 8 bits. ASCII only uses 7 bits, so wouldn't that be 2^6 = 64 possible codes? I'm aware of the parity bit, but I was under the impression that it was only for error checking? Is the party bit a part of the unique string of 7 bits making up the ASCII code?I just don't understand how it has 128 possibilities if it only uses 7 bits.

author: cvriv
author_rank: Frequent Contributor
timestamp: February 28, 2017, 12:35:09 am
content: Oh nevermind. I got it. I always find myself getting confused with that.... argh.

author: Terrius
author_rank: Contributor
timestamp: February 28, 2017, 01:40:26 am
content: Just have to remember that the Exponent is the number of bits. So 2^7 is 7 bits not 8 bits.The thing that always gets me, is that bits start at 0, so 7 bits is actually 0-127 not 1-128. Am I correct in assuming that the bit formula is 2^X-1?

author: cvriv
author_rank: Frequent Contributor
timestamp: February 28, 2017, 02:48:58 am
content: Yes you are right. The largest number that can be represented by 2^n is (2^n) - 1, because the first number is zero. That part never really screwed me up. It's the total number of numbers that screws me up. I was thinking that 2^(n-1) was the total number of numbers. It's not. I have a midterm this week. I better remember this! HA HA HA.

author: Brumby
author_rank: Unknown
timestamp: February 28, 2017, 02:54:13 am
content: If you get confused, just write out the whole series for 3 bits.0000010100111001011101118 combinations which count from 0 to 7 ... then take it from there.
Activate 12v DC relay from 240v AX - Page 1
Forum section: electronics / beginners

author: scarr999
author_rank: Contributor
timestamp: February 02, 2022, 09:26:26 am
content: Hi All,What is the best / safest way to activate a 12V DC relay from 240v AC mains?RegardsStepen Carr

author: perdrix
author_rank: Frequent Contributor
timestamp: February 02, 2022, 09:38:19 am
content: You don't - you replace it with a relay that uses a 240V AC coil.David

author: 4kruby
author_rank: Contributor
timestamp: February 02, 2022, 09:42:54 am
content: Using a SMPS circuit may be?something like this,https://robu.in/product/hlk-20m12-12v-20w-switch-power-supply-module/or a 12v step down transformer + rectifier and filter?

author: SmallCog
author_rank: Frequent Contributor
timestamp: February 02, 2022, 09:44:31 am
content: We have a lot of legacy sites where mains presence was monitored by a 240VAC relay wired across the mainsRather than have screw terminals at mains potential in an enclosure that’s otherwise all 12 and 24VDC we’ve progressively been swapping out these relays for 12V models that plug into the same DIN rail base and just energising them with a wall wart / plug pack
Active balancer.... anyone want to speculate how this work? - Page 1
Forum section: electronics / beginners

author: mikerj
author_rank: Super Contributor
timestamp: August 19, 2019, 04:12:17 pm
content: Looks like a buck/boost balancer. AFAIK these simple non-coupled inductor designs can only transfer charge between adjacent cells, so on anything with more than two cells you can't transfer charge between the end two cells.

author: SparkyFX
author_rank: Frequent Contributor
timestamp: August 19, 2019, 04:26:29 pm
content: Underside of the PCB would be interesting, should there be anything.I suspect it just makes use of an inverting boost converter, which could enable charging the lower cell and might be able to switch to non-inverting for reverse operation.

author: paulca
author_rank: Super Contributor
timestamp: August 19, 2019, 06:28:43 pm
content: Quote from: mikerj on August 19, 2019, 04:12:17 pmThat's the thing. It "seems" to be working on a 3 series and... bidirectionally too.

author: mikerj
author_rank: Super Contributor
timestamp: August 19, 2019, 11:03:02 pm
content: Quote from: paulca on August 19, 2019, 06:28:43 pmYes it still works on a 3S, but the limitation on transferring energy between adjacent cells means it may have to transfer the energy multiple times across cells which drops efficiency but still a lot better than the simple resistor load style balancers.Lots of info on this and other topologies if you google "buck boost cell balancer"
active balancing li-ion cells - Page 1
Forum section: electronics / beginners

author: chota.sanjiv
author_rank: Contributor
timestamp: June 07, 2017, 06:53:23 pm
content: Hi Guys,I am designing a li-ion (3.7 v) active balance based upon LTC3300-1 Chip for my 24v pack, the concept is that extra charger can be stored in a transformer and then can be provided to the battery stack or vice versa, the design uses multiple transformers for each cell and suggests 1:1 turn ratio, I want to know how this extra charge will be used when I will have multiple transformer providing charge @ 3.7 v in parallel to the 24v stack voltage, and if I increase the turn ratio and make it close to 24v will it increase the efficiency of charge transfer to the stack. ?thanks,Sanjeev
Active inductor Design - Page 1
Forum section: electronics / beginners

author: nq93
author_rank: Newbie
timestamp: February 08, 2023, 06:35:50 am
content: I am interested in designing a CMOS-based active inductor (few uH) with an operating frequency of 50 MHz. Could anyone guide me on which topology should i use for active inductor design?

author: Bud
author_rank: Super Contributor
timestamp: February 08, 2023, 07:52:13 am
content: You may get more replies if you do not use fancy fonts, which are useless and make your posts hard to read.

author: Benta
author_rank: Super Contributor
timestamp: February 08, 2023, 12:04:50 pm
content: Try searching for "gyrator".

author: nq93
author_rank: Newbie
timestamp: February 09, 2023, 01:41:30 am
content: I have searched for it however the maximum value I can get from the gyrator as an active inductive is in a few nH. but in my case, i am looking for microHenry.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: February 09, 2023, 04:16:12 am
content: While it is not CMOS, Analog Devices claimed multiple Henries using the BUF-03. AFAICR there is a TI appnote heavy on Gyrators, but I seem not to have made the keyword entry.And what exactly do you mean by 'CMOS'? Using CMOS buffers as linear elements or using proper CMOS OPAs?

author: nq93
author_rank: Newbie
timestamp: February 09, 2023, 04:30:55 am
content: by CMOS I mean that I am using 180nm TSMC technology using ads software to design an "active inductor" for uH (microhenry).
Active-Low enable input driven by high voltage signal - Page 1
Forum section: electronics / beginners

author: mspider65
author_rank: Contributor
timestamp: September 20, 2021, 08:51:21 am
content: Due to the chip shortage I am trying to adapt a circuit to use what is available.In particular, I have to replace a Step-Down which, starting from the voltage of an e-bike battery, should generate 5V.The doubt concerns the Enable signal of the new DC-DC which is now active low.What I have is an output (PSU_ON) which in case of ON is at battery voltage while in case of OFF it is at GND or floating.The EN input must be less than 0,8V to enable the chip and must be above 1,8V to disable the chip.Max Voltage at enable pin is 7V.I thought of using the circuit you see below but I ask those who have more experience than me for an opinion if it can be good or if there is a better way to go.In particular i have a very small footprint to accommodate everything and any suggestion to lower the number of needed component is welcome.

author: iMo
author_rank: Super Contributor
timestamp: September 20, 2021, 09:42:44 am
content: Doublecheck the max Vgs of your mosfet. With Vin=60V the Vgs will be 15V.Otherwise zeners (for example 5.1V one) instead of the R3 and R4 would be a more rugged solution, imho.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 20, 2021, 01:16:11 pm
content: Yeah, replacing R4 with a zener is a good idea, and one in parallel with R3. Note that you should leave R3 in circuit, not replace it -- a floating EN might take a long time indeed to turn off, if it ever does. (Maybe this situation never occurs so it's justified to leave out; but it's a good idea otherwise.) Its value can then be somewhat larger, so the zener takes most of the EN current and the R3 just serves to discharge the capacitance of the zener and gate.Dual zeners in SOT-23 are common, and offer TVS ratings as well; Comchip CPDT-5V0U-HF comes to mind.Tim

author: iMo
author_rank: Super Contributor
timestamp: September 20, 2021, 02:04:05 pm
content: A potential issue with zeners could be they would need a bit larger current, imho.I do not know what is the lowest current to see their knees nicelyHere is a sim with it.With 60V the loss in the resistors will be 90/110mW.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 20, 2021, 02:54:09 pm
content: Leakage is not bad for 5V zeners. I wouldn't go any lower in voltage rating, or I'd look for another method (shunt regulator, clamp into LV supply?) if needed. But with the 7V+ ratings here this is a fine combination.Note that current consumption can be saved by using a depletion mode MOSFET as a current source. This draws the same current for any Vin > 5V say, rather than having to choose a resistor for Vin(min) which then passes excess current at higher Vin. (Probably doesn't matter from a battery, where Vin won't vary much.)Tim
Active low pins and circles - Page 1
Forum section: electronics / beginners

author: ingamedeo
author_rank: Newbie
timestamp: June 30, 2018, 02:56:12 pm
content: I know that circles, when normally used in logic circuits, mean "not", therefore they invert the signal. (e.g. on the output of an AND port).However, what is their meaning when they are present on the edge of a Flip-Flop, for example, with the CLEAR signal?In order to CLEAR the FF, do I need to send a low ("0") value on the wire before the circle or a high ("1") value?My understanding is that the circle simply means that the CLEAR signal is active-low, so I would send a "0" signal which would get inverted into a "1" and fed into the FF, activating the CLEAR function. Is that right? Or shall I send a "1" signal, which then would be flipped into a "0" and fed to the FF?Thank you

author: rstofer
author_rank: Super Contributor
timestamp: June 30, 2018, 03:04:32 pm
content: The signal is active low. When you want to clear the flop, set the pin to logic 0.

author: ingamedeo
author_rank: Newbie
timestamp: June 30, 2018, 03:05:19 pm
content: Quote from: rstofer on June 30, 2018, 03:04:32 pmThank you! Grand!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 30, 2018, 07:41:00 pm
content: The circle means "active low". It's sometimes used to show active-low signals, like if you see inverted inputs connected to inverted outputs. Example, sometimes you'll see a chain of inverters (usually for buffering or delaying signals) with inverted outputs connected to inverted inputs.Of course, an inverter with active-low input and active-high output is just the same thing as the other way around. Or an active-low-input OR is identical to an active-low-output AND (de Morgan's theorem).Tim

author: glarsson
author_rank: Frequent Contributor
timestamp: June 30, 2018, 08:27:39 pm
content: Quote from: T3sl4co1l on June 30, 2018, 07:41:00 pmThis is important to know when looking at older schematics. The way I, and many more, drew schematics was to use rings on all "active low" inputs and outputs. A line would always connect a ringed output with a ringed input, or non-ringed output to a non-ringed input. If the intention was to express "OR function between two active low input signals" the symbol would be drawn as an OR/NOR gate with ringed inputs, not as an AND/NAND gate as shown in the data sheet for the part used. E.g. a 7400 NAND gate could be drawn as an AND gate with ringed output or as and OR gate with ringed inputs.
Active Op-Amp Feedback Configurations - Page 1
Forum section: electronics / beginners

author: sddavis14
author_rank: Newbie
timestamp: July 25, 2016, 07:20:03 pm
content: Hi everyone,I have a general question about Op-Amp feedback loops. I've encountered design situations where it seems like it would be useful to put a secondary amplifier in a feedback loop. For example, take this circuit:This is designed to force a 1A current through the load no matter the load resistance (within limitations). I know there are better ways to implement a circuit that performs the same function. However, I am curious if there are any fundamental issues with using the secondary differential amplifier in the feedback loop. I know stability will probably be an issue - but is that something that can be fixed with some simple compensation caps/filters? It seems like this configuration could be useful in a lot of different situations. I've done a lot of googling, but I just can't find any good app notes or documentation concerning placing op-amps in feedback loops.Thanks.

author: rstofer
author_rank: Super Contributor
timestamp: July 25, 2016, 08:31:25 pm
content: I sure doesn't seem like it will work. The upper op amp will be at one rail or the other, all of the time. Except for when it is oscillating. Then again, I don't know a lot about op amps.http://www.ti.com/lit/an/slyt103/slyt103.pdf

author: sddavis14
author_rank: Newbie
timestamp: July 25, 2016, 08:46:14 pm
content: Hi rstofer,The circuit definitely works conceptually. I've simulated it and it does produce 1A of current through the loop with the load resistor. Of course I know simulations are not always indicative of real world behavior, which is why I'm curious. I've looked at that app note and It doesn't really answer my questions. I'm curious about the rules of thumb and general guidelines for designing op-amp circuits like this.

author: danadak
author_rank: Super Contributor
timestamp: July 25, 2016, 09:03:51 pm
content: This circuit looks to be noting more than M1/OA1 acting as a constant I source,and OA2/R1 acting as a high side current sense. Seems legit, but redundant inthat OA2 is really not needed. But it is clever in that this is a current source, notsink, so simplified version (one OPAmp) has error term related to supply stability.This eliminates that as long as diff amp is well balanced for R ratios that controlCM rejection.Regarding using OAs in a fdbk loop, you have to look at phase margin of the loop.You can calc that or use time domain techniques (disturb loop with impulse and usescope to look at ringing/phase margin) to get an idea of what loop is doing. There isa ton of phase margin/loop compensation ap notes online discussing these issues.http://search.edaboard.com/measure-phase-margin-and.htmlRegards, Dana.

author: MosherIV
author_rank: Super Contributor
timestamp: July 25, 2016, 09:20:54 pm
content: Do not forget another real world op-amp problem : input offset voltage.This will cause a output on op2 voltage even when there no current flowing.Can be corrected by adjusting R2 or R4.
Active PFC and true sinewave UPS? - Page 1
Forum section: electronics / beginners

author: fubar.gr
author_rank: Unknown
timestamp: August 17, 2015, 10:34:52 am
content: People say that computers with Active PFC PSUs require true sinewave UPS, else bad things can happen.Is this true and why? I can't find anything conclusive on the subject

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 17, 2015, 10:57:01 am
content: Power Factor Correction (PFC)I suspect they are looking for a sine wave to compare current to, and get stuck with a modified square wave which makes them go nuts.

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 17, 2015, 11:05:34 am
content: eeeeeh, what a complicated subject, or at least they want it so....

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 17, 2015, 11:13:10 am
content: relatedhttps://www.eevblog.com/forum/projects/what%27s-this-dc-buss-circuit-add-on-doing/

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 17, 2015, 11:23:06 am
content: Depends on the controller IC. Some are just fine with any waveform, given the response time of the control loop (don't expect 400Hz or harmonic-rich waveforms to have high PFC). Including DC. Others are rather special purpose and require that the input always dip to zero (internal offset compensation?) or oscillate smoothly at a mains-esque frequency (low voltage harmonics).As a generality, true sinewave is the only thing you can be assured will work with any load (given that it can deliver startup current as needed), anything else is either-or.Tim

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 17, 2015, 11:34:28 am
content: Theoretically, a true power factor correction circuit won't care what the input voltage waveform looks like; it will shape the current drawn by the downstream load to match it.That said, some PFC controller ICs seem to choke if presented with anything but a sinusoidal voltage waveform (e.g. - UCC28070, which, let's just say, has not been one of the more glorious ICs to come out of Unitrode/TI).If you want to go to the trouble of figuring out whether a particular PFC device can deal with a MSW inverter, check the datasheet for the PFC IC to see if it can handle a DC input (e.g. - UC3854, which *is* one of the more glorious ICs from Unitrode/TI).All that said, an MSW inverter may damage any kind of load that isn't mostly/purely resistive and you don't have to pay too much of a premium anymore for a pure sine wave output so why take the chance?NB - Seems T3sl4co1l beat me to it.
active poe splitter / variable or modify it to other voltage outputs - Page 1
Forum section: electronics / beginners

author: Cdgold3
author_rank: Newbie
timestamp: June 02, 2024, 11:20:36 am
content: Hi,Not sure if you can help me but I'm trying to see if I can make a cheap active PoE splitter variable or modify it to other voltage outputs.The main aim for this was to power a 9v tp-link c310 cctv camara over PoE but my mistake I bought a 12v off eBay. 9v ones are about that are the same style but only really on AliExpress. I have seen TP-link do a Poe10r that can be switched from 12v, 9v and 5v and are not really that expensive.I was hoping that maybe changing a resistor my adjust the voltage but when using a multi-meter, it fells like the transformer is dropping the 48/52v to 12v unless I'm wrong?Thanks

author: aliarifat794
author_rank: Regular Contributor
timestamp: June 04, 2024, 01:51:56 pm
content: It's safer to purchase a PoE splitter that already supports multiple output voltages like the TP-Link PoE10R. These devices are designed to switch between different output voltages safely and reliably.

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 04, 2024, 02:43:36 pm
content: Quote from: aliarifat794 on June 04, 2024, 01:51:56 pmI agree. The input voltage range is actually much wider, because some voltage will be lost in the cabling, and that varies (depending on cable length).That particular unit uses external magnetics (GTR2201H), dual full bridge rectifiers above it, and I'd guess the middle part is the switchmode DC-DC controller logic. I can't tell the controller chip markings (it's also upside down in the image), but even knowing what it was, trying to adjust the output voltage would mean reverse-engineering all that mess first...In comparison, TP-Link PoE10R costs about 15€-20€ here in Finland, and is known good (802.3af compliant) implementation. It's switchmode supply is designed to support the three different output voltages (5V, 9V, 12V) based on an external switch setting, too.

author: perieanuo
author_rank: Frequent Contributor
timestamp: June 05, 2024, 04:55:57 pm
content: old school says reducing voltage is done using series with recttifier diodes, not resistors, with resistors you push full voltage on end of the circuit, then voltage drops according to divider. with diode method, you loose approx 0.6V on each rectifier, do the math

author: Cdgold3
author_rank: Newbie
timestamp: June 12, 2024, 08:59:31 pm
content: Thanks for the info, I ended up buying a few TP-Link PoE10R to power my tp-link c310 in the end.
Active twin t notch becomes an oscillator - Page 1
Forum section: electronics / beginners

author: Ayax
author_rank: Newbie
timestamp: May 09, 2018, 02:36:22 pm
content: Hello everyoneFirst of all i need to say: sorry for my bad English.My circuit is based on thishttp://www.radio-electronics.com/info/circuits/opamp_notch_filter_2/opamp_twin_t_varq.gifI used the active twin t notch filter with some modifications and got great results,BUT sometimes the entire circuit becomes an oscillator.The input recived the signal from a pasive instrument like a bass, guitar, even a dinamic microphone oran active like keyboard, goes to a preamp and then to the notch.Sometimes the oscillation happens when the signal input is too big like a beat, and it stops if you repeat the beat.Sometimes it starts when connecting the power supply (a 9v battery).I need to avoid this.. "parasitic oscillation"? "oscillation problem"?I leave you images so you can see how i made the entire circuit and my modifications.Thank you all in advanced

author: Benta
author_rank: Super Contributor
timestamp: May 09, 2018, 02:56:29 pm
content: What frequency is the oscillation? Which opamps are you using?

author: Ayax
author_rank: Newbie
timestamp: May 09, 2018, 03:01:31 pm
content: The frequency is the same of the center of the filter, so in case of the "filter 1" it´s 120hz. I´m using the TL072.

author: Audioguru
author_rank: Super Contributor
timestamp: May 09, 2018, 11:20:40 pm
content: I have used many TL072 dual opamps powered with a 9V battery many times without problems. But its minimum supply is 7V which happens soon to a 9V battery.Like most old Fet-input opamps, The TL07x and TL08x opamps have the "Phase Inversion" problem where the output goes as high as it can if an input becomes within a few volts from the negative supply that is 0V in this circuit.Applying the battery and a high input level will cause the (-) input of the opamp to go near 0v and cause this problem that might cause oscillation.

author: mikerj
author_rank: Super Contributor
timestamp: May 10, 2018, 12:24:38 pm
content: Add some decoupling to your 4.5V rail splitter.

author: SuzyC
author_rank: Frequent Contributor
timestamp: May 10, 2018, 01:11:11 pm
content: Your problem is in feedback to the unsymmetrical twin-t you've created. It is no longer even close to a twin-t, just another malformed phase shift oscillator just waiting for a kick for it to ring into oscillation.You can stop the oscillation by replacing R5 with a 100K pot to make the feedback adjustable (just like it is shown in the basic design example)and then you can set the level of feedback until your circuit is stable again.In a twin-t symmetry is everything, you've distorted that principle.Unless you have very low max Vdd opamps, that resistor in series with the battery is just wasting power.
Active Volume Regulator - Page 1
Forum section: electronics / beginners

author: Greate
author_rank: Contributor
timestamp: April 06, 2012, 08:22:21 am
content: I need to regulate the volume of my TV so that my neighbor wont complaint.My wife and I attend online meeting regularly at nighy using yahoo messenger and ustream.tv on my computer plugged on my sony 46 tv. Most of the time the volume from my co legues are not in the same level so if the first one to speak has low volume I have to turn up my volume up so I could hear but if the next one has high volume then it really gets loaud and disturbs the neighbor.Is the any pre-amp kit I could assemble or buy a premade one that would automatically regulate the volume?Or is there such software yhat I could just install on my computer?Sent from my A100 using Tapatalk

author: amyk
author_rank: Super Contributor
timestamp: April 06, 2012, 09:14:49 am
content: I think the term you're looking for is "Automatic Gain Control".

author: Rerouter
author_rank: Super Contributor
timestamp: April 06, 2012, 09:35:54 am
content: if your on windows 7, there is an enhancement for speakers called "loadness equation" it in essense flattens to sound out a little, but as a bit of a warning, it generally starts by making the volume a bit higher, so turn down your volume a bit before you apply it

author: AndreasF
author_rank: Frequent Contributor
timestamp: April 14, 2012, 08:50:33 pm
content: What you want it called "dynamic range compression" or just "compression" in professional audio. It's used heavily in music production etc.http://en.wikipedia.org/wiki/Dynamic_range_compressionThe wikipedia article has links to several software options, which may help you.

author: G7PSK
author_rank: Super Contributor
timestamp: April 15, 2012, 03:30:39 pm
content: What you need is SRS Labs true volume, The video on the link explains.

author: sonicj
author_rank: Frequent Contributor
timestamp: April 18, 2012, 01:57:31 am
content: are you sure your 46" Sony doesn't have compressor/limiter built-in? my 40" xbr had a "steady sound" option buried in the audio menu.-sj
Activity LED on RJ-45 port - Page 1
Forum section: electronics / beginners

author: brendan-petrol
author_rank: Contributor
timestamp: August 11, 2012, 08:10:36 am
content: Hello people!I want to put an activity LED on my RJ-45 port, whilst also putting RX and TX Leds on the PCB. What is the easiest way of doing that (keeping in mind that I'm running out of space as it is! haha.I was thinking run the RX and TX LEDs through power, LED, resistor, then through each channel on a 2 channel Opto. The on the output side, run these through 10k resistors, then into an OR gate like this one:http://www.ti.com/lit/ds/symlink/sn74lvc1g32.pdf,then hang the activity LED off the end of that (through a suitable resistor, of course).Does this work? Is that the most efficient way of doing it? Lastly, will that OR gate be able to handle running the LED directly, or can they only handle very small amounts of current (this will all be running at 3.3v).Thanks people!

author: brendan-petrol
author_rank: Contributor
timestamp: August 11, 2012, 08:23:51 am
content: A schematic might help.TX_LED and RX_LED are pulled low when on.

author: notsob
author_rank: Frequent Contributor
timestamp: August 11, 2012, 08:37:43 am
content: there are Magjacks on the market that have built in Tx Rx LEDs examplehttps://www.sparkfun.com/products/8534

author: brendan-petrol
author_rank: Contributor
timestamp: August 11, 2012, 08:39:22 am
content: The one I have has two LEDs, one I want to use as a Link light, and one as an Activity LED... But inside I would like to be able to see if it's sending or receiving data.Does that make sense?

author: amyk
author_rank: Super Contributor
timestamp: August 11, 2012, 08:40:46 am
content: From page 4 of the datasheet, this device can source 16 or 24mA at 3V with a minimum of 2.4 or 2.3V at its output, or sink 16 or 24mA with a maximum of 0.4/0.55V at its output.A small LED that only needs 5-10mA to light should be OK, but keep in mind the forward voltage.

author: brendan-petrol
author_rank: Contributor
timestamp: August 11, 2012, 08:58:27 am
content: Does that schematic check out?

author: David_AVD
author_rank: Super Contributor
timestamp: August 11, 2012, 10:14:39 am
content: I doubt you'll have enough headroom to run 2 LEDs in series off a 3v3 rail.You should be able to do what you need with a couple of diodes (for the OR function) and a transistor, etc.

author: brendan-petrol
author_rank: Contributor
timestamp: August 11, 2012, 11:04:47 am
content: Won't the opto provide enough power to light the second LED (so they strictly aren't in series are they?)...Just trying to make sure I understand how you mean, that's all!

author: David_AVD
author_rank: Super Contributor
timestamp: August 11, 2012, 11:05:18 pm
content: In your circuit above, you have the visible LED (in the RJ45) in series with the LED in the opto. Once you add their Vf figures, it may be more than the 3v3 available.

author: brendan-petrol
author_rank: Contributor
timestamp: August 12, 2012, 01:03:19 am
content: It's just as well I posted in the beginner forum. I read your response and went 'awh crap *facepalm*'Do you have any examples on how I could run it?
Actually good datasheet section on planes - Page 1
Forum section: electronics / beginners

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 02, 2018, 01:28:52 pm
content: http://www.ti.com/lit/ds/symlink/ads1246.pdf10.3 (page 86) and beyond.The underlying lesson is: learn what's actually going on so you can determine for yourself what's best, but failing that -- at least take these documents with ahugegrain of salt.Oftentimes you'll see "separate analog and digital grounds", and FYI, that advice is almost always incorrect.Fig.123 in particular is the key that a lot of appnotes are lacking.Tim

author: iMo
author_rank: Super Contributor
timestamp: December 02, 2018, 01:59:04 pm
content: Similar from Maxim:https://www.maximintegrated.com/en/app-notes/index.mvp/id/5450
AD581 voltage ref - Page 1
Forum section: electronics / beginners

author: ivo3510
author_rank: Contributor
timestamp: June 16, 2024, 07:24:27 pm
content: Hello, everyone!Just created voltage reference with two AD581. I measured two of a bunch of 5, that are equally away from exactly 10 V, and combined their outputs.It seems it works well, I would like to ask for an opinions for a buffer, or any reccomendations for the schematic.I think I need to power the two from two separate sources, probably with two 7815, and then combine their outputs to the inverting, and non-inverting inputs of an opamp, I have OP177 at hand.Please, see my measurements with Agilent 34401, is ther eanything suspicious?Thank you!

author: Kleinstein
author_rank: Super Contributor
timestamp: June 16, 2024, 08:55:22 pm
content: There is no need to have separate power sources for the 2 references. It can even cause more complications during start up.A would avoid a trimmer and use 2 fixed resistors (may be selected values) instead.One would likely want a slight load to both reference, expecially the one with the lower voltage. It is not clear if the AD581 can sink current well.

author: magic
author_rank: Super Contributor
timestamp: June 16, 2024, 09:11:50 pm
content: Quote from: ivo3510 on June 16, 2024, 07:24:27 pmNot sure what you mean by that? To get the average of two outputs, use the resistor circuit you currently use and then buffer its output with an opamp voltage follower.Quote from: Kleinstein on June 16, 2024, 08:55:22 pmIt's clear it can't sink very well, because it sinks by reducing class A bias on the output emitter follower. But stealing a few μA may be within the usual production tolerance and still OK. One could calculate the available bias current by dividing 10V by the resistance between Vout and GND.editWait, there is Q15 for sinking. But it only comes to play under heavy loading. Under light sinking the mechanism above works. There is an intermediate point where both Q7 and Q15 are off. Not sure what happens there, maybe nothing good and that's the reason why sinking load regulation is not specified.

author: ivo3510
author_rank: Contributor
timestamp: June 16, 2024, 10:34:59 pm
content: Thank you, magic!Ok, will sum and buffer the output with opamp.Maybe I should put another potentiometer, with viper to GND, to create sort of a resistor bridge?So the chip will have to sink less current?

author: David Hess
author_rank: Super Contributor
timestamp: June 17, 2024, 01:03:38 am
content: Quote from: ivo3510 on June 16, 2024, 07:24:27 pmThe OP177 will work fine as a buffer, but I would add transistor follower to its output within the feedback loop. Buffering the output of the operational amplifier will improve its performance.QuoteThe averaged outputs should go to the non-inverting input, with the operational amplifier used as a follower.
AD5940 - Wemos D1 R1 (Arduino IDE) - Page 1
Forum section: electronics / beginners

author: hiepss12
author_rank: Newbie
timestamp: March 20, 2025, 06:22:22 am
content: Hi everyone, I'm now in trouble. Specifically, I connected my Wemos D1 R1 to 'eval-cn0565-ardz' to measure 4-wire Impedance by controlling AD5940 microcontroller (SPI). But when I used my oscilloscope, no waveform was displayed at CE0 (in the picture below). I even configured "Waveform Generator", "High Speed DAC -> Gain -> Excitation Buffer", "Switch Matrices" and enabled all of them.Note: I did 'write to' and 'read from' registers successfully.Someone may give me a piece of advice. Thank you so much.

author: jwet
author_rank: Frequent Contributor
timestamp: March 20, 2025, 04:35:22 pm
content: Bringing up new hardware/software can be difficult. You don't if you have a software, hardware, configuration or bad part, etc.Let's assume that the eval board is good. Check Vcc and ground at the device. Watch the SPI signals with your oscilloscope and make sure that what you think you're sending is really correct. If you can find some example code or library, study it. Are you doing all things that you need to do to enable the output.Looking for CE0 is a good first step. You might post your code since there is no way you can no if its good and you can stare at it for days.Good luck.

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: March 27, 2025, 01:30:49 pm
content: There maybe some issues in your code also.

author: Terry Bites
author_rank: Super Contributor
timestamp: March 28, 2025, 11:36:55 am
content: Did you compare your register set-up settings with those used in this example code?https://github.com/analogdevicesinc/ad5940-examples