hybridfree/eevblog-posts huggingface dataset:
About USB signal analyzers - Page 1
Forum section: electronics / beginners

author: MrZwing
author_rank: Regular Contributor
timestamp: March 25, 2017, 03:29:27 pm
content: I just wondering how good a USB signal analyzer is?i need to measure as low Hz about 20Hz to 30kHz and looking at a Chinesium USB "all in one unit" that claims to measure 20hz - 300kHz with a resolution of 1Hz increments.Or should i get a decent bench dynamic signal analyzer instead, noticed that its hard to fins one without breaking the bank and shipping from the US is a nighmare often higher then the equipments value?
about Wander-Azimuth Mechanization ! - Page 1
Forum section: electronics / beginners

author: ammjy
author_rank: Regular Contributor
timestamp: December 09, 2018, 11:06:29 am
content: Hello, EEVBlog peoples ! Always thanks you a lot for your help !now i want recive Velocity and Position from wander-azimuth mechanization.but, Books have not enough information, i think. (even every books have each different info.)anyone know detail information about it ?Please, let me know.

author: rstofer
author_rank: Super Contributor
timestamp: December 09, 2018, 04:23:27 pm
content: Have you seenhttps://apps.dtic.mil/dtic/tr/fulltext/u2/784752.pdfPage 25 has a discussion re: extracting velocityI would have to spend quite a bit of time understanding the notation. That paper is 45 years old, I would hope there is something better.

author: ammjy
author_rank: Regular Contributor
timestamp: December 10, 2018, 02:28:11 pm
content: Ow ! Mr. Rstofer.Thanks you a lot again. you are nice Man."Oldies, but goodies" - i often feeling it from books and documents.this doc written very clearly.i hope this your answer in this topic give help later also to others peoples who need a help about Wander-Azimuth Mechanization or Navigation principle thorugh this topic )))
Absolute maximum rating - Page 1
Forum section: electronics / beginners

author: tomy983
author_rank: Contributor
timestamp: February 25, 2016, 10:32:02 pm
content: Hi!I am playing with a little breakout board from Adafruit, which has on board this adchttp://www.ti.com/lit/ds/symlink/ads1115.pdfI have read the datasheet, and it is mostly clear.On the absolute maximum ratings, it states that Analog input voltage to GND must be –0.3 to VDD + 0.3On my bench I am powering the breakout board, hence the adc with a 5V supply, but the signal I am analysing comes from the output of a linear position transducer, powered at 24v with a separate supply.I am wondering, if I cut my 5V supply first, so that the output voltage of my sensor is still present I should be over the maximum ratings but the adc has no VDD...Would this damage the adc or not??

author: ataradov
author_rank: Super Contributor
timestamp: February 25, 2016, 10:46:33 pm
content: It is not recommended to do this. Even if there will be no permanent damage, your device will be powered though internal clamping diodes.Do as it says in the DS:Quote

author: tomy983
author_rank: Contributor
timestamp: February 26, 2016, 12:50:21 am
content: Thank you, Alex.
AC-AC Adapter has incorrect sticker? - Page 1
Forum section: electronics / beginners

author: Mp3
author_rank: Frequent Contributor
timestamp: September 19, 2019, 10:11:12 pm
content: Hi everyone, I bought an ac adapter from the internet and it got here today. The label is so strange. The part number and label seems to indicate it's an AC-AC adapter, but the diagram indicates the plug has polarity which implies it's DC.If i measure the plug with my my multimeter on AC mode, either way i measure with the prongs gives me ~16V ACIf I measure the plug with my multimeter on DC mode, i got 0v either way, so its safe to assume this is an AC-AC supply?Just wanted to be safe. I blew up an op-amp last time i thought i knew what was what so i wanted to ask...

author: Yansi
author_rank: Super Contributor
timestamp: September 19, 2019, 10:14:53 pm
content: Pictures of the label would really help here. "Strange label" is not enough description.However, if you have measured 16Vac there, then probably it is just a trafo in a case.

author: ledtester
author_rank: Super Contributor
timestamp: September 19, 2019, 10:21:33 pm
content: Sounds like just a transformer.You can always test with an LED and a 1K resistor. If the LED lights up no matter which way it is plugged in you have AC current.

author: Zero999
author_rank: Super Contributor
timestamp: September 20, 2019, 02:05:14 pm
content: Quote from: ledtester on September 19, 2019, 10:21:33 pmThat will work but beware most LEDs are only rated to 5V or so in the reverse direction, but I think some of that is just arse covering on the data sheets.In my experience, red, orange, yellow and greenish yellow will non-destructively breakdown at around 20V or so and conduct in the reverse direction, but pure green, cyan, blue and white LEDs can be damaged by too higher reverse voltage.The safest thing to do is to use two LEDs connected back-to-back. If it's AC they'll both light, otherwise only one connected in the correct polarity will light.In this case, it's definitely AC, because the meter measures 0V on the DC settling and the expected voltage when set to AC. It can be used to power an op-amp circuit with a bridge rectifier and smoothing capacitor.
AC - AC power supply, unregulated - Page 1
Forum section: electronics / beginners

author: beginner
author_rank: Contributor
timestamp: July 31, 2014, 05:54:02 am
content: Hey Guys,I'm putting together a kit headphone amp and have a quick question regarding the power supply. Info on the PCB calls for a max input of 20VAC. The power supply I have is 15VAC 1.5 amp and states output voltage will be higher if less than this rated current is being drawn.I'm unsure of exactly how much this little amp will draw but I'm expecting nowhere near 1.5 amps, more likely 1 / 10th of that. What I'm unsure of how much variance in output voltage to expect from the power supply, and if I should get another one.Thanks!

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 31, 2014, 06:03:09 am
content: Not really enough information to attempt any significant response.WHAT "kit headphone amp"? Do you have a URL or something where we can see what you are asking about?Does it state a MINIMUM input voltage?Do you have a meter? Can't you measure the "open-circuit" voltage of your power transformer?We could probably come up with a decent estimate if we had some information to work with,At least a schematic diagram. Without that, we are shooting in the dark.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 31, 2014, 06:23:28 am
content: It's probably fine.

author: beginner
author_rank: Contributor
timestamp: July 31, 2014, 06:26:10 am
content: Quote from: Richard Crowley on July 31, 2014, 06:03:09 amthis is the onehttp://www.jdslabs.com/products/82/objective2-diy-kit/voltage 14 - 20vacI do have a meter, open circuit reading 17.75v - does that answer my own question

author: retrolefty
author_rank: Super Contributor
timestamp: July 31, 2014, 01:00:08 pm
content: Simply measure the output voltage of your AC source when not connected to any load. If it is in excess of 20vac then don't use it with that board.
Ac adapter mod - Page 1
Forum section: electronics / beginners

author: Asavage9794
author_rank: Contributor
timestamp: August 28, 2017, 01:17:42 pm
content: Hello, I have a charger for a HP Elitebook 8760w, however it wasn't the right one that came with the laptop in the first place. Recently I have been having issues with it not being able to run my laptop. The one I have is 90w, 4.74A, and I'm supposed to have a 230w 11.8 amp charger. Would I be able to mix these 2 ac adapters with a wiring mod? One of them has a 19v 4.74A output, the other has a 19v 3.42A output. Would mixing these ac adapters be a bad idea? I was just thinking of just having it as a temporary solution til I was able to buy a real charger.Sent from my LG-VS985 using Tapatalk

author: Asavage9794
author_rank: Contributor
timestamp: August 28, 2017, 01:22:12 pm
content: One is 90w and the other is 65w. The CPU is 45w and the GPU is 35wSent from my LG-VS985 using Tapatalk

author: Benta
author_rank: Super Contributor
timestamp: August 28, 2017, 02:22:49 pm
content: Very bad idea. Get the right adapter, it can't be that expensive.

author: Kjelt
author_rank: Super Contributor
timestamp: August 28, 2017, 03:32:04 pm
content: I worked for four years with those hp laptops , well the 8560 that is and although the software tells you the charger is not right there is no problem using a 90W for now, the only drawback is that the psu runs a bit more hot and that recharging the battery takes longer. If the battery is charged you have no problems running it an entire day with a 90W charger.You do need the 200W or higher PSU for the dockingstation if you use it and use a lot of usb devices etc.Btw running them parallel does not work since the laptop senses which psu you have, there is some one wire protocol, how else do you think it can tell you that you have a wrong psu attached?

author: Asavage9794
author_rank: Contributor
timestamp: August 28, 2017, 03:50:42 pm
content: The 90w used to charge the battery but its not anymore. I'm suspecting that it was damaged cause someone left a blanket on it so therefore pairing up 2 of them would be useless anyways. I don't have any money to replace it. My grandma said she would cause she's the one who put the blanket over it in the first place for the dog. It just sucks cause I'm in the middle of trying to so college work..Sent from my LG-VS985 using Tapatalk

author: Old Don
author_rank: Regular Contributor
timestamp: August 28, 2017, 08:39:31 pm
content: A lot of 90 watt adapters on the web for under <$15 including shipping.OBTW, never use a laptop on blankets or anything that blocks the bottom vents or you'll need more than a new AC adapter PDQ.

author: Asavage9794
author_rank: Contributor
timestamp: August 28, 2017, 08:57:49 pm
content: I know that. To be honest I was pretty pissed that there was a sheet over my ac adapter anyways. I didn't put it there someone else did.Sent from my LG-VS985 using Tapatalk
AC and DC signal isolation questions - Page 1
Forum section: electronics / beginners

author: dc5e
author_rank: Newbie
timestamp: December 29, 2015, 02:21:50 pm
content: Hi all,I'm working on tapping into a smoke detector's interconnect signal and from what I've read, the interconnect system has three wires, hot, neutral, and signal. Hot and Neutral are for powering the smoke detector and the signal line supposedly is a 9v DC signal in reference to neutral. Now, my question is, why is it bad (I'm assuming it is) to connect a MCU or something similar directly to the signal line while the smoke detector is powered by AC?Assuming that the the MCU's power and AC lines were isolated, what dangers would there be in tying the MCU's ground to neutral to provide a reference for measuring the signal?If the MCU were powered through AC-DC converter that was not isolated (through AC rectification or something, right?) would there still be issues? This is assuming that they are referencing from the same neutral.I'm planning on using an optoisolator to provide isolation, but when explaining it to my dad, I couldn't come up with a good concrete explanation as to why I wanted isolation.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 29, 2015, 05:23:25 pm
content: The question is more what else is the uC supposed to do? Does it interface to something else? If, per example, you interface to a pushbutton that would become a safety hazard...

author: dc5e
author_rank: Newbie
timestamp: December 30, 2015, 05:31:47 pm
content: Quote from: Ice-Tea on December 29, 2015, 05:23:25 pmSorry, I wasn't clear enough on what the MCU does. The MCU is being used to detect if a smoke alarm went off. Currently, I'm only powering the smoke detector with the 9v battery, but may want to tap into a AC powered interconnected system later in the future. In either case, I would have the signal from the smoke detector switch a transistor. that grounds the MCU's input pin that has a pull-up resistor enabled. So while the signal isn't directly wired into the MCU, the reference would be tied together.Quote from: blueskull on December 29, 2015, 06:01:31 pmThat's a good point. I hadn't thought about that. I guess it really depends on the circuit and how things are connected and in what order.
AC BJT analysis - Page 1
Forum section: electronics / beginners

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 17, 2019, 12:12:14 am
content: If u use the Ebers-Moll model and replace the Vbe with a voltage source of Vbe, then if u had an emitter resistor, and then the (Vbe) V.S., can u do a source transformation on that into a current source if u want ? And at AC, do we treat the (Vbe)V.S. as any other DC source, so a short at AC when drawing a BJT AC model?I've watched videos on this already, but so far none explicitly said that's the case. I've only just been learning how to treat V.S. and C.S. in mesh/nodal analysis, I should have done that last year. So I'm only getting into EM BJT models and other models, and AC analysis and actually using the equations for such now....and actually remembering them. But I love it.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 17, 2019, 01:36:22 am
content: Vbe is in series with r_pi, the dynamic base resistance. This is simply dVbe/dIb = Vth / Ib, plus Rbb' if you're counting.Then it can be transformed into a Norton equivalent if you like, yes.Note that due to feedback, if there is positive emitter impedance, the base input impedance is bootstrapped even higher, to roughly h_fe * Z_e.Look up the hybrid pi model -- this is the formalism usually used with BJTs. You can apply arbitrary small-signal parameters, or derive them from device properties (N, Is, etc.) and use Ebers-Moll, or Gummel-Poon or whatever you like.Tim

author: lordvader88
author_rank: Frequent Contributor
timestamp: April 17, 2019, 10:27:35 pm
content: Well I think what I was rambling about late last night was....say if I make a 5 BJT circuit with resistors, even if it looks messy, I should be able to find all the voltages and currents using that type of model, and it's just another mesh/node problem. And indeed, at that point I'm allowed to split up the transistor just like anything else in the circuitRight now I have 5BJT amp on paper and LTspice, and I'm working backwarks through what the voltages and currents will be for the output I want.But so far I still only had to use KCL/KVL. I should try it with node/mesh analysis too for the DC, I haven't gotten near the AC yet
ac coupling for scopemeter - Page 1
Forum section: electronics / beginners

author: paulhm81
author_rank: Regular Contributor
timestamp: April 14, 2014, 09:48:53 am
content: HiI have a ut-81b and a Philips 100 MHz PM3267 and i use them for diagnostic purposes. My question is what capacitor should I use to ac couple my ut-81b. The problem is when I want to see the ripple on a dc signal I don't have a AC option on the meter to keep the signal centered and it's very limited in moving the signal up and down. The Ac option only changes the voltage measurement , not the graphic display. I tried with 0.1 uf and it seems to do the job but I'm wondering if it filters the signal. I' very new to this stuff. I could use the analog scope but it's much more convenient to use the scopemeter.Thank you!

author: Anks
author_rank: Frequent Contributor
timestamp: April 14, 2014, 12:29:12 pm
content: The ac coupling cap will create a filter based on the impedance of the scope input.

author: tautech
author_rank: Super Contributor
timestamp: April 15, 2014, 12:45:56 am
content: Normal method to measure AC ripple on DC is to use you scope. Use AC coupling.Make sure you can see the graticule and read off the divisions of ripple, then multiply by the V/div setting to get the ripple value. If you adjust the waveform vertically to line up with the graticules it can make the ripple easier to measure.
Ac Current control - Page 1
Forum section: electronics / beginners

author: rodrigopires
author_rank: Regular Contributor
timestamp: November 06, 2016, 08:47:06 pm
content: Hello everyone! I'm wondering of there's a way to control AC current without changing the voltage. I have a MOT welder and i use a triac to control it from 30 to 60v, but i wanted to use it on 60V and just control the current. I kow that a magnetic shunt is the best way but i dont have space for it. Is there a enything?Thanks!

author: Rerouter
author_rank: Super Contributor
timestamp: November 07, 2016, 07:18:37 am
content: To me it sounds like you want to current limit the output, which will change the voltage, but only when the current limit is exceeded.If not care to explain a little clearer,As for the how, wiring a bipolar constant current load inline would be one of the simplest ways, (this is an active device). Other than that would be something nastier like applying a dc bias the transformer to control the saturation current.
AC current measurement problem - Page 1
Forum section: electronics / beginners

author: Muhammad Nasar
author_rank: Contributor
timestamp: June 06, 2013, 09:46:08 am
content: I am working on a circuit to read AC voltages and AC current value through a micro controller for which i have made the following front end circuit. The voltage measurement doesn't have any problem, but the current measurement through 1 ohm shunt resistor is giving asymmetrical waveform rather than a sinusoidal one, one thing i have observed that if I place the shunt resistor at the low side then this problem does not occur!schematic is attached.suggest me a solution.

author: Andy Watson
author_rank: Super Contributor
timestamp: June 06, 2013, 10:30:51 am
content: When you put the 1R in the high side the common mode voltage exceeds the range of the op-amp (several times over). Consider the voltage that appears on the positive input of the first op-amp (pin 3?), I make it about 115 V rms, or 160 Vpeak. Under these conditions the op-amps no longer behave as you expect.

author: Paul Price
author_rank: Super Contributor
timestamp: June 06, 2013, 11:08:51 am
content: Andy has got it right, you are overloading the inputs of the op-amp because of the common-mode voltage.

author: Muhammad Nasar
author_rank: Contributor
timestamp: June 06, 2013, 12:43:40 pm
content: Thanks a lot, guys.
Ac-DC Adaptor - Page 1
Forum section: electronics / beginners

author: alamwte
author_rank: Regular Contributor
timestamp: February 07, 2022, 07:56:02 am
content: Hello,I have a question. Why my AC-DC adaptor that should just have 5v DC, it shows 10v AC when I measure it with AC mode of voltmeter too?Thanks,

author: electr_peter
author_rank: Unknown
timestamp: February 07, 2022, 12:15:17 pm
content: What multimeter do you use? Measurement may be incorrect. Some cheap DMMs may show AC voltage (and mislead you) when simple DC battery is measuredac-readings-on-dc-supply

author: BeBuLamar
author_rank: Super Contributor
timestamp: February 07, 2022, 05:28:03 pm
content: Does it measure 5VDC when you switch the meter to DC voltage?

author: bob91343
author_rank: Super Contributor
timestamp: February 07, 2022, 06:23:03 pm
content: If you measure ac it will be calibrated with the assumption that the source is ac. It's a meter issue. Don't believe what you see.

author: alamwte
author_rank: Regular Contributor
timestamp: February 12, 2022, 05:36:24 am
content: Yes, it measure 5v DC when I put it in DC mode!

author: alamwte
author_rank: Regular Contributor
timestamp: February 12, 2022, 05:37:42 am
content: Yes, I have a cheap multimeter

author: alamwte
author_rank: Regular Contributor
timestamp: February 12, 2022, 05:38:53 am
content: Ok, I got itthanks
AC-DC modules noise + ripple - Page 1
Forum section: electronics / beginners

author: VEGETA
author_rank: Super Contributor
timestamp: May 12, 2023, 08:59:18 pm
content: HelloAnyone has experience with this:https://www.digikey.com/en/products/detail/mean-well-usa-inc/IRM-30-12/7704668?? or similar form factor 25-30W 12v modules?I am interested in getting their ripple and noise as low as possible to be input for buck regulator stages (for 3.3v and 5v) to have low ripple outputs.Is the module usable directly or I should include all circuitry mentioned in datasheet? like protection, CMC, and so on?this one:https://www.digikey.com/en/products/detail/recom-power/RACM30-12SK-277/17801494seems shorter but similar.I can put large C-L-C at its output if that works.for your opinion please.

author: barshatriplee
author_rank: Regular Contributor
timestamp: May 13, 2023, 08:13:51 am
content: I think it will be wise to follow the datasheet. After seeing the capacitor, you can add filter capacitor to the output. For more answers, you can post your question to the digikey forum.

author: VEGETA
author_rank: Super Contributor
timestamp: May 13, 2023, 09:55:40 am
content: Quote from: barshatriplee on May 13, 2023, 08:13:51 amdatasheet does not say much besides maximum output capacitor valve. thus I ask if anyone tried these in a real project and measured the actual ripple and noise.

author: VEGETA
author_rank: Super Contributor
timestamp: May 18, 2023, 05:46:39 pm
content: meanwell one says internal switching frequency is 65 khz which is very low, meaning big caps and L should smooth it out nicely.i was searching for the thread where many of these modules are tested for ripple but could not find it. I hope from this thread that someone who has such data can elaborate.
AC, DC, Voltage Conversion & LEDs - Page 1
Forum section: electronics / beginners

author: pyzik
author_rank: Newbie
timestamp: July 21, 2017, 02:26:27 pm
content: I think I've been reading TOO MUCH. I had a handle on what I thought I was going to need and use but now I'm getting confused again.I have an older design motorcycle. It has a 6v system. Headlight runs off the the generator (6v coil on a stator) and the rest of the lights run off the 6v battery, (charged by another 6v coil on stator) and the ignition is powered by a third coil on the stator.I need to replace the lights. I figured I might as well go LED.Quesion Part 1:For the headlight, wouldn't a 6v to 12v "booster" work? This would be Alternating Current coming from the stator, right? So I woul need a 6v DC to 12v DC booster, or should I go 6v DC to 12v AC? Will I need a resistor?Question Part 2:The rest of the headlights are powered by the 6v battery as stated. I want to put a 12v battery in the bike. I've been reading that the generator should handle charging the 12v battery with a change of the 6v rectifier to a 12v rectifier.Correct?THANK YOU!!!

author: Zero999
author_rank: Super Contributor
timestamp: July 21, 2017, 06:52:26 pm
content: Why do you want to change to LED? It can cause problems.The voltage will probably rise, if a lower current is draw by the e LEDs, which might overcharge the battery. The indicators might flash at a higher frequency because the current through the flasher relay will be lower.

author: cs.dk
author_rank: Unknown
timestamp: July 21, 2017, 08:06:25 pm
content: I don't know about the headlights, but you can get special relays for LED's.https://www.google.dk/?gws_rd=cr&ei=c15yWcDwN4izadXJtrgD#q=flasher+relay+ledIs it to difficult to convert the whole bike into a 12V system? Maybe the stator, etc. fits from a newer model. EDIT: I think i did not read the whole thread

author: pyzik
author_rank: Newbie
timestamp: July 24, 2017, 11:33:22 am
content: Quote from: Hero999 on July 21, 2017, 06:52:26 pmSimply because something in the system isn't working and I'm going to have to track it down and fix things. I figured while I was at it I might as well throw LEDs in it, which means going 12v.I did find a rear/brake/signal combo that is 6v. IF I can find some front indicators and a headlight in 6v, I won't bother but I don't think I'm going to find them.I know I can get a new relay for the indicators.

author: pyzik
author_rank: Newbie
timestamp: July 24, 2017, 11:34:41 am
content: Quote from: cs.dk on July 21, 2017, 08:06:25 pmI initially thought I could just pay to have someone re-wrap the coils to 12v but literally NO ONE around me works on such things nowadays.

author: Benta
author_rank: Super Contributor
timestamp: July 24, 2017, 02:50:58 pm
content: From what I know about old bikes, it probably has an electromechanical voltage regulator. This will make certain that everything gets 6 Von average, but the voltage is incredibly dirty. This is no issue for incandescent lamps, but could be for LEDs.An oscilloscope on the 6 V supply might give you a hint of the potential problems.
ac fan blower no speed - Page 1
Forum section: electronics / beginners

author: fadyeid
author_rank: Contributor
timestamp: June 23, 2017, 10:53:25 am
content: hello everyoneI need to know how the fan blower inside a car woks with speeds , because inside the blower there is a circuit but welded on a metal it has two big transistors , so could I build a circuit to replace this if yes need a simple circuit by 4 speed and off ?! thanks

author: Zero999
author_rank: Super Contributor
timestamp: June 23, 2017, 12:23:48 pm
content: The metal acts as a heat sink for the transistors. You could easily use your own circuit to control them, thus the motor speed, if you want to.

author: cs.dk
author_rank: Unknown
timestamp: June 23, 2017, 07:31:58 pm
content: Quote from: fadyeid on June 23, 2017, 10:53:25 amWhy build a replacement?The module you show looks like a PSA (Peugeot/Citroën) type - I have replaced alot of these transistors. MJ11015 or MJ11016 are replacements. Some modules are PNP, others are NPN.Some modules are controlled in "opposite" direction. 0V = full speed, 12V = stop.The module it self is not with 4 steps in fan speed. The climate controller drives the fan motor at the necessary speed all time.

author: Zero999
author_rank: Super Contributor
timestamp: June 23, 2017, 09:46:13 pm
content: Quote from: cs.dk on June 23, 2017, 07:31:58 pmHow old are those cars? I'd be surprised if a modern car uses Darlington transistors, rather than MOSFETs to control the blower.

author: fadyeid
author_rank: Contributor
timestamp: June 23, 2017, 11:09:32 pm
content: yes they are for Psa cars , so you mean the two transistors play a role to change speed ? so any blower has a fault with speed caused by this transistors ?

author: cs.dk
author_rank: Unknown
timestamp: June 24, 2017, 07:53:40 am
content: @Hero999, these modules are used in mid/late 90's cars. ex. Citroën Xsara, Xantia, Peugeot 406 that i know of. They often fail short, and the blower then runs at full speed.Afaik they are only fitted in cars with AC, so the climate ECU can control the blower speed. Non AC cars have the usual resistor-pack, and 4 fixed speeds.@fadyeid, Yes if the speed can't be regulated, the transistors are shot.Note, if you replace them, there is a little disc thermistor between the heatsink and PCB, it is very easy to loose when you're busy replacing the transistors.
AC flyback has a connection that bridges the primary to the secondary. Why? - Page 1
Forum section: electronics / beginners

author: extremeodd
author_rank: Newbie
timestamp: September 08, 2020, 03:28:39 am
content: I'm needing a quick sanity check here. I aquired a couple of vintage NOS disk type ac flyback transformers off ebay a couple of months ago, coated them in several layers of super corona dope to repair the damaged insulation and put them up. Today when I went to hook one of them up to an expiremental ozone generator, I noticed both of them have a lead that connects the outer edge of the primary coil to the start of the secondary. I'm assumed this would be considered the ground lead (the only explaination I can think of) since one of the two flybacks had 2 HV leads red/black with the black one hooked up to that lead.However, while I was testing the other flyback it didn't seem to want to work when using that lead but would work great using a connection that appears to be connected near the start of the primary. Sadly due to my disorganization I've misplaced the boxes that had the factory diagram and if it isn't obvious I'm quite the novice when it comes to high voltage equipment. I'll post some pictures here in a bit, had an incident when trying the "Find the flyback's ground by seeing which connection the HV lead has the strongest arc to" and had the arc jump from the connector to the wire which almost instantly melted down into the primary windings (it wasn't the secondary) causing some damage. I brushed a ton of super corona dope onto it and now I'm waiting for it to dry, once I can touch it I'll get some pictures since I'm probably using all the wrong terms.
AC gain plot for a linear amplifier using CMOS inverter - Page 1
Forum section: electronics / beginners

author: promach
author_rank: Frequent Contributor
timestamp: January 22, 2019, 02:23:29 pm
content: how to modify theto obtain the?I am readingsome opamp loop gain testing configurationsuch as the following:

author: iMo
author_rank: Super Contributor
timestamp: January 22, 2019, 03:36:34 pm
content: The spice directive is.ac dec 100 1 1G(will do 100 points in each freq decade, from 1Hz to 1GigaHertz, for example).You have to have a Voltage source with AC=1V connected at the input.Observe the output node of choice, you should get something like Bode diagram with gain in dB and phase in degree.Note: for an AC analysis the LTspice (for example) has to create a small signal model first, based on DC analysis (done in background).When your CMOS inverter does not possess a model which includes the DC components (ie. a complete wiring with nmos/pmos transistors, Gnd, and Vcc) it may fail with an error.See below:

author: MrAl
author_rank: Super Contributor
timestamp: January 22, 2019, 11:59:58 pm
content: Hello,I checked both ways and theoretically they seem to be right.The first is obviously easier to set up but the second may give results that are simpler to interpret.Also, Beta for both circuits is Ri/(Ri+Rf). That should have been stated too i think.

author: promach
author_rank: Frequent Contributor
timestamp: January 23, 2019, 11:35:01 am
content: QuoteSomeone told me the above when he suggests to use a current source stimulus instead of voltage source stimulus.I have no idea about this. What do you guys think ?

author: promach
author_rank: Frequent Contributor
timestamp: January 23, 2019, 01:11:34 pm
content: Why do the phase plots show only 180 degrees ?

author: MrAl
author_rank: Super Contributor
timestamp: January 23, 2019, 02:00:21 pm
content: Quote from: promach on January 23, 2019, 11:35:01 amHi,There is a name for these procedures i just have to remember what it is now :-)It's the guys name who probably invented the method.
AC -> DC using Bridge diode & Capacitor - Page 1
Forum section: electronics / beginners

author: sdancer75
author_rank: Frequent Contributor
timestamp: January 18, 2020, 12:39:21 pm
content: Hi,Watching this video I was wondering how a 9VAC simple converter can output a 15VDC since9VAC X 1.4142Vrms = 12.72V.It's because of the 25V capacitor maybe?

author: MagicSmoker
author_rank: Super Contributor
timestamp: January 18, 2020, 12:44:27 pm
content: Measure the AC voltage going to the bridge - I bet it's over 10V* because the transformer is effectively unloaded. The voltage rating of the capacitor does not affect the voltage of a bridge rectifier (unless it is too low, at which point it will  fail short).* - and probably over 11V, since there are two diode drops in series with the DC output at all times in a bridge rectifier.

author: Zero999
author_rank: Super Contributor
timestamp: January 18, 2020, 01:12:46 pm
content: Yes, small transformers output a considerably higher voltage, than the rating when unloaded. Measure the AC voltage. It's got nothing to do with the voltage rating of the capacitor, which will only charge up to the peak AC voltage, minus the rectifier losses.

author: Prehistoricman
author_rank: Regular Contributor
timestamp: January 18, 2020, 03:39:51 pm
content: Quote from: Zero999 on January 18, 2020, 01:12:46 pmThis property is known as the "regulation" of the transformer. In the case of these small ones, 20% is to be expected. That is, the output when unloaded is 20% above 9V.10% can be expected from medium-size transformers.I wouldn't recommend watching channels such as this. As you can see in the comments, nobody really knows what they're on about. The video doesn't teach you why the circuit works or go into any detail, hence why you have this question. Funny how these kinds of vids get so many views.
AC Line SMPS to 12VDC PSU damaged - Page 1
Forum section: electronics / beginners

author: Cyclone1
author_rank: Newbie
timestamp: August 06, 2020, 09:15:10 am
content: I have a AC line to 12VDC SMPS power supply in my DAQ that recently damaged unexpectedly and tripped the circuit breaker. I am trying to figure out what happen, and upon disassembly I noticed on the PSU a burn mark (or arc mark) between the transformer flyback diode and the nearest rectifier GND (they are abt 1.2mm apart). I also noticed the enclosure shield (connected to chassis GND), which is abt 2.5mm away from the leads, also has a burn mark on the same spot. The fuse is also blown.Not quite sure what happen there, I have check the clearance from the PSU to the enclosure is sufficient. Another thing I found out is that the transfomer of the PSU will spike to abt 500Vpk when the transistor which control the transformer is turned off. Will this 500VDC actually cause a arc and shorted the PSU out to the enclosure ? Or did it arc over to the nearest rectifier ground and cause the air to ionize and then arc to the shield. Is 500VDC spike possibly cause all this?

author: MacIntoshCZ
author_rank: Regular Contributor
timestamp: August 07, 2020, 05:56:11 am
content: With no isolation it could happen.Check feedback loop.driving transistor, chip etc.
AC Mains, Dumb Question! - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: February 19, 2014, 11:54:12 am
content: Ok,So in EU and other parts of the world, Blue wire is Neutral, Brown is Live (or Phase) and Yellow/Green is Ground. Fair enough.So I will connect it as such to my device. But what happens when you plug the device in the wall the "other way around"? I mean, obviously your blue is now "brown" and vice versa?Does it matter?

author: Rerouter
author_rank: Super Contributor
timestamp: February 19, 2014, 12:05:42 pm
content: if its chassis is grounded likely in a fault condition, otherwise not so much,the reasoning is most products only switch and fuse the active side, so a short between the reversed active and may not trip the large circuit breaker in the house and doesn't even go near the fuse leaving the chassis at some potential (some older houses power points can have connection resistances in 10's of ohms limiting the fault current)

author: made2hack
author_rank: Frequent Contributor
timestamp: February 19, 2014, 01:35:54 pm
content: So, as long as the fuse panel is properly connected and grounded, etc, it doesn't really matter down the line?

author: cybermaus
author_rank: Frequent Contributor
timestamp: February 19, 2014, 01:48:27 pm
content: Neither wire will be connected to chassis, so nothing happens.After all, plugs in most of EU are unpolarized. German Schuko is not polarized. French plug is polarized but does not have required wiring (though they usually put life left, but then the Czeck use the same French plug and put life right). UK is an exception, they do strictly orient the plugs. I believe Switzerland also has a polarized plug, but they are not EU (arguably UK is also not really EU)So nothing happens, however on any pluggable device you should consider both wires (blue and blue/black) as potentially 'hot'.Also, a device with ground fault issues may suddenly work if you reverse the plug (you may be better of fixing it properly) and in audio it was a know trick if you got a 50Hz hum that reversing the plug could solve the issue. Before audio got all digital and stuff.
AC Mains to DC? Then to buck converter for high amp dc output? - Page 1
Forum section: electronics / beginners

author: SittingBear
author_rank: Contributor
timestamp: July 26, 2014, 12:57:05 am
content: Hey EEVBlog community,I've recently been reading through theFundamentals of Power Electronicsand was interested, due to work projects as well, in getting to understand buck-boost converters more easily. There are such a vast quantity of ranges and specifications available from DC-DC regulation ICs with feedback pins it's easy to get lost in the capabilities and in the assumptions datasheet author's make the reader will know. In the sea of all of these ICs I have only found a few which provide comprehensible equations and explanations.I'm mainly looking to understand how pre-made buck/boost converters work in order to better understand choosing one that works for my needs, or designing my own (more expensive). If it helps any my goal would be to convert some input to a solid 24V capable of feeding a <1.5A load.I've also not found out much about other safe methods with a transformer other than a full-wave rectifier with a large output capacitor. Are there any alternatives which also use a transformer which may be useful? I donotplan on going transformerless as I am not comfortable enough to design a circuit which is not isolated and live.I do not wish to use a linear regulator as they can be horribly inefficient and get extremely hot in the amount of heat they need to dissipate along with not being able to drive >1A loadstypically.Any help or advice is greatly appreciated! Thanks!

author: johansen
author_rank: Super Contributor
timestamp: July 26, 2014, 01:31:12 am
content: forward, flyback, fullwave, half wave, pushpull, all utilize a transformer to deal with the voltage conversion.in fact you can make isolated versions of the cuk and sepic converter as well.--the difference is where, and how, the energy is stored in the circuit to deal with:1)varying load (resistive losses everywhere)2) varying input and/or output voltageif you just want a 24vdc smps.. why not buy one? you are up against a lot of established technology and methodology here.the more expensive converters use a power factor boost converter to first convert rectified ac mains to 400 volts dc, then send it through the system.

author: SittingBear
author_rank: Contributor
timestamp: July 26, 2014, 01:42:14 am
content: Quote from: johansen on July 26, 2014, 01:31:12 amIt may not be used for anything and I'd rather not buy one as then I don't learn anything. Do you know of any resources online which do a good job of explaining things outside the standard oscillation? I'm talking adding a feedback comparator and clock in the circuit as most of the regulators have built in them.

author: johansen
author_rank: Super Contributor
timestamp: July 26, 2014, 02:00:24 am
content: try this websitehttp://www.smps.us/

author: SittingBear
author_rank: Contributor
timestamp: July 26, 2014, 02:04:07 am
content: Quote from: johansen on July 26, 2014, 02:00:24 amThanks!
ac motor drive Sinamics V20 - Page 1
Forum section: electronics / beginners

author: alimamzi
author_rank: Newbie
timestamp: November 30, 2023, 06:31:08 am
content: hello guys i totally frustratedto determine parameter simense ac drive because i want to rotate my motor rev or few by two switch separately ...i'm confused is it necessary to determine macro or change parameter p0700 to 2 is enough.. please kindly help me

author: Roehrenonkel
author_rank: Frequent Contributor
timestamp: November 30, 2023, 06:52:08 am
content: Hi,if you'd at least get the names right - maybe somebody can help you.

author: alimamzi
author_rank: Newbie
timestamp: November 30, 2023, 07:59:10 am
content: what is your mean? what name do you mentionedSinamics V20 1.5kw that siemense producetd it..

author: BeBuLamar
author_rank: Super Contributor
timestamp: November 30, 2023, 02:22:21 pm
content: They have preset for a number of applications. Just pick the one that fit your need. I guess you want 2 inputs. One to go forward and the other to go reverse. You also want an analog input to connect a pot for speed? Is that right? If not please decscribe what you want to do.

author: alimamzi
author_rank: Newbie
timestamp: December 02, 2023, 04:35:01 am
content: hi thanks for response... i need to two switch that make motor run reverse and forward separately and then reach to speed of motor that was set in parameter ... i don't need the pot . i set frequency motor 40 hz then i push button reverse then motor run reverse and work on forward...and i can able change time rise and decrease then change torque motor simultaneously..
Ac power adaptor on DC device - Page 1
Forum section: electronics / beginners

author: sony mavica
author_rank: Frequent Contributor
timestamp: October 29, 2016, 05:29:12 am
content: Hi I have a device that takes a adapter that has a headphone plug at the end it says on the back DC 9v 300mA could I use a 12v ac 500mA adapter with it or will it break the device

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: October 29, 2016, 05:41:29 am
content: Hi. Plugging AC power into a device asking for DC power is never a good bet. Also 12 VAC has 17 V peaks. That much overvoltage could do any amount of damage. Of course, with my luck you could try it and it might work just fine just to make me a liar. I think its a long shot, that's all. Just sayin'

author: mariush
author_rank: Super Contributor
timestamp: October 29, 2016, 07:35:48 am
content: Quote from: sony mavica on October 29, 2016, 05:29:12 amYou shouldn't. At the very least you should use another DC rated adapter, not an AC output one.But you could always open the product and see what it does with that DC input. Some products place a diode in circuit with the input jack for safety reasons, which means your AC input will be half wave rectified so it wouldn't hurt the product. others may die due to reverse / negative voltage of the AC input.If there's a bridge rectifier inside the product, or you use a bridge rectifier to convert the AC voltage of the adapter to DC before going into the product's connector .. what's after that connector... A product designed for 9v DC may use 10v or 16v rated input capacitors and a 12v AC rectified voltage can in some cases go over 16vAnd then ... the product may use a tiny linear regulator to convert those 9v into 5v or 3.3v - there are linear regulators which can only tolerate up to a certain voltage, like 10-12v ... that would exclude the 12v AC/DC adapter, because even a 12v DC adapter may output more than 12v in some cases and kill the linear regulator.And it's not just an issue of input voltage... could be a power dissipation isue. let's say there's a 3.3v 100mA linear regulator in the product. With 9v input, the regulator would waste (9v-3.3v)x0.1 = 0.57w but with 12v input you have 0.9w of heat... this may cook the regulator, may discolor the plastics around that regulator, may make the regulator to "hiccup" (work sporadically)So there's no easy answer, if you want to risk it best chance is to open the product and analyze the input, see what the product is doing with it..

author: sony mavica
author_rank: Frequent Contributor
timestamp: October 29, 2016, 07:51:28 am
content: Quote from: mariush on October 29, 2016, 07:35:48 ami do have a 9v dc adapter here but has the wrong connection

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: October 29, 2016, 07:54:47 am
content: You can cut the connector from the AC adapter and solder it to the DC one, but be careful to the polarity.
AC power connector alternative - Page 1
Forum section: electronics / beginners

author: VEGETA
author_rank: Super Contributor
timestamp: May 16, 2023, 05:17:22 am
content: Hello,I need a connector like this one:https://www.switchcraft.com/iec-320-power-inlet/rapc322x/but only one difference: I need the height to be 12 mm.I need it like this to fit in Dreamcast shell since it uses 12mm height one. I am designing a new AC power supply for it and I need this type of connector to fit perfectly.thanks

author: barshatriplee
author_rank: Regular Contributor
timestamp: May 16, 2023, 08:22:56 am
content: I think you'd better mail to Switchcraft. You can ask if they have a connector of your mentioned height.

author: Terry Bites
author_rank: Super Contributor
timestamp: May 16, 2023, 09:28:55 am
content: 1. Buy a file and make the small adjustment to the case.2. Search for "pcb C13"3. Shurter 2570-1310?

author: VEGETA
author_rank: Super Contributor
timestamp: May 16, 2023, 02:02:23 pm
content: Quote from: barshatriplee on May 16, 2023, 08:22:56 ami have mailed them but still no response. don't know if the 1mm can be considered in the margin range...Quote1- i plan to make and sell the new PSU which uses this connector. can't do that with this approach.2- mine should be c8 and searched a lot to find that switchcraft to be closest but not perfect match.3- this one is one of my consideration, its height is 16mm very far than 12mm.

author: VEGETA
author_rank: Super Contributor
timestamp: May 18, 2023, 04:33:29 am
content: I found this:https://www.aliexpress.com/item/33001358755.htmlwhich should be perfect match, but one cannot rely on aliexpress.

author: VEGETA
author_rank: Super Contributor
timestamp: May 18, 2023, 11:54:54 am
content: I found this company:http://www.dragoncity.com.hk/acso1.htmlit has this model "AS-204-005DT7" and here is the drawing:http://www.dragoncity.com.hk/dwas204005dt7.pdflooks like perfect match really, nice to have drawing.I once messaged them about scart connector and they responded, but MOQ is 1000 which was insane... don't know if this item is better.regards,EDIT: I finally found a part number for it, here:http://www.jack-zx.com/en/p_xx.asp?id=919which I saw in alibaba and talked to supplier about it... looks like it is the one. they can send sample as well. 0.25$ before negotiation xD