hybridfree/eevblog-posts huggingface dataset:
Isolation for sig gen. - Page 1
Forum section: electronics / beginners

author: chipss
author_rank: Contributor
timestamp: March 03, 2018, 06:55:13 pm
content: I am wanting to input a signal into a condenser microphone, it has 60 volts dc to polorize the capsule, I would like to not cream my new SDG2000X, I have read using a dc blocking cap, or 1/1 transformer, what would be the best way to do this? Thanks for your time.

author: danadak
author_rank: Super Contributor
timestamp: March 03, 2018, 09:20:51 pm
content: Thread here -https://www.eevblog.com/forum/beginners/floating-a-function-generator/C coupling both connector shell ground and signal would be OK. If youare real nervous about this take a couple of back to back zeners to protectoutput and add some series R between gen/zeners and mic.Transformer certainly also doable, maybe much higher ratio to keep fromunduly loading condensor. Depends on what you are trying to do, measurethe F response I would posit ?You could also consider using a pad -https://en.wikipedia.org/wiki/Attenuator_(electronics)Regards, Dana.

author: David Hess
author_rank: Super Contributor
timestamp: March 04, 2018, 01:51:56 am
content: If ground is shared which is usually the case, then a coupling capacitor together with a resistive attenuator are commonly used to do this.
Isolation Transformer - Page 1
Forum section: electronics / beginners

author: Vhsfi
author_rank: Newbie
timestamp: November 28, 2012, 02:29:34 pm
content: Hi,I need to buy an isolation transformer as i'm getting some psu and other mains connect stuff to work on,i came across a good deal on a brand new line conditioner from MGE (now EATON i think) it's aPulsar CT12, i know this does more than an Isolation transformer but it does seem to do the same in principle,plus the line correction, in the manual there is even a section on how to make the unit neutral earthedor neutral unearthed.Do you guys think this is ok to use as an isolation transformer?Here is a link to the user manual:http://pqlit.eaton.com/ll_download_bylitcode.asp?doc_id=11457thx in advance

author: jeroen74
author_rank: Frequent Contributor
timestamp: November 28, 2012, 03:00:39 pm
content: What's a good deal? Farnell has a range of isolation transformers (search for 'TIM100') that are not too expensive.

author: Vhsfi
author_rank: Newbie
timestamp: November 28, 2012, 03:10:48 pm
content: A good deal in this case is 20€.

author: ptricks
author_rank: Frequent Contributor
timestamp: November 28, 2012, 03:53:08 pm
content: That one looks like it will do the job.If you happen to have 2 transformers that are the same you can wire the secondaries together to make an isolation transformer. Works pretty well for low current applications , 12.6V or 24V secondary transformers are what I usually look for as they are fairly common.

author: SeanB
author_rank: Super Contributor
timestamp: November 28, 2012, 04:30:16 pm
content: I did that to make a 90V supply for a grain moisture meter. I have a lot of 220-12 1W transformers, so wired one to give 12VAC, and wired 2 with the 12V in series and the 220 in parallel to give me 110VAC ( actually with losses more like 90VAC) which was rectified and then dropped to 90V with a high voltage transistor ( MPSA42) and a stacked pair of 47V zeners. the filament supply was made from the 12V supply via a LM317 regulator to give 1V2 for heating ( 60mA filament hearing aid valve). Worked very well, and was cheaper than buying 10 PM3 batteries every 6 months.

author: Shock
author_rank: Super Contributor
timestamp: December 04, 2012, 06:14:33 pm
content: Isn't the Pulsar CT12 an "offline" UPS?If so it will just be running on directly connected mains voltages during normal operation, won't it?Or were you intending to disconnect the mains from the UPS and work on your equipment running under battery power?An "online" UPS may do isolation (can be more expensive).I dunno personally it sounds unsafe to me.

author: Monkeh
author_rank: Super Contributor
timestamp: December 04, 2012, 11:31:08 pm
content: Quote from: Shock on December 04, 2012, 06:14:33 pmIt's not a UPS, it's a line conditioner. There are no batteries, and the transformer is continually active. Whether it's isolating or not is another question.As an aside, my UPS (which is neither offline nor online) is isolating.
Isolation transformer - Page 1
Forum section: electronics / beginners

author: funkimunky
author_rank: Contributor
timestamp: December 16, 2012, 04:44:21 pm
content: I want to use my oscilloscope to test AC equipment but I'm worried that I blow it up connecting it to the wrong tracks. I've read that you need to isolate the equipment being tested from ground using an isolation transformer. Can I just use one from screwfixhttp://www.screwfix.com/p/portable-transformer-with-2-output-sockets-3kva/84144or do I need to get something likehttp://www.conrad-uk.com/ce/en/product/511606/VOLTCRAFT-IT-1500-1500VA-Isolation-Transformer-Lab-Bench-230Vac/2170410&ref=listI want to test everything from washing machines to TV's so the max power would need to be around 2500VA.

author: Zero999
author_rank: Super Contributor
timestamp: December 16, 2012, 11:08:26 pm
content: Quote from: funkimunky on December 16, 2012, 04:44:21 pmIt depends.What voltage does the equipment run off?The first transformer has a 110V secondary, with an earth bonded centre tap and gives two line conductors, each 55V with respect to earth. The second seems to have an unearthed 230V secondary which is probably more than likely what you want.

author: funkimunky
author_rank: Contributor
timestamp: December 17, 2012, 10:39:27 am
content: Yeah I want 240V isolated so its the second one. I thought that I could get a cheaper option using a workies transformer. Thanks for helping me out with the info you've probably saved my oscilloscope from a small fire.Sent from my GT-I9100 using Tapatalk 2

author: saturation
author_rank: Super Contributor
timestamp: December 17, 2012, 12:56:19 pm
content: For working on such tasks you are best off with a portable scope or a differential probe; there are industrial grade active probes that are relatively low cost made for checking appliance grade electronics, these are made by testec or tiepie and resold under different brand names.http://www.testec.de/tastkoepfe_25mhz.0.html?&L=1
Isolation transformer @ 133 volts - Page 1
Forum section: electronics / beginners

author: Bzonic
author_rank: Contributor
timestamp: October 12, 2016, 11:28:24 am
content: Hello all, I recently acquired this isolation transformer and have a question about the 1:1 theory of these. Is it common for them to actually be putting out 130+ volts in a unloaded state? I initially thought the thing was way out of spec but realized that maybe this is done on purpose to compensate for when a stiff load is connected. After my initial multimeter reading of 132.5 in an unloaded state I then plugged in a Wagner heat gun and turned it on for a few seconds. The 8 amp draw certainly made a difference and brought the reading down to 122v. Is this considered completely normal with how Iso's are typically designed? Any danger with using it for something that is a light load and thus likely to receive close to that 132 volts? Thanks for any insight!Brian

author: Andy Watson
author_rank: Super Contributor
timestamp: October 12, 2016, 11:57:13 am
content: It is completely normal for a transformer. The output is specified under loaded conditions. When the load is removed the output voltage goes up - it's call regulation. Larger transformers usually have better regulation - i.e. less change - than small transformers.

author: Zero999
author_rank: Super Contributor
timestamp: October 12, 2016, 12:18:04 pm
content: Yes, isolation transformers are normally wound for slightly more than 1:1 to compensate for the voltage drop when fully loaded.You'll find that if you try to make your own isolation transformer from say two 120V:24V transformers connected back-to-back, the output voltage will be less than the input, when fully loaded.

author: Bzonic
author_rank: Contributor
timestamp: October 12, 2016, 12:26:19 pm
content: Thanks - makes perfect sense. So using it on a light load with that 132V output should not be a problem? I would think the answer would be "potentially". It seems that a sensitive device might not handle the over voltage well?

author: helius
author_rank: Super Contributor
timestamp: October 12, 2016, 12:41:25 pm
content: It would be (just) within the +/- 10% specification that most devices are designed for. I wouldn't expect any issues.

author: Bzonic
author_rank: Contributor
timestamp: October 12, 2016, 12:56:04 pm
content: Thanks all!
Isolation Transformer: 2ndary Neutral bonded to Ground or not? - Page 1
Forum section: electronics / beginners

author: Zucca
author_rank: Unknown
timestamp: January 27, 2014, 06:02:22 am
content: I can not fully understand the difference between a grounded 2ndary neutral or a fully floating 2ndary. According to the www it seems to be a safety issue, but I can´t imagine when a current could flow between in the 2ndary neutral and ground connection. It is just always an open loop, may be through parasitic C and R?Thanks in advance.

author: cybermaus
author_rank: Frequent Contributor
timestamp: January 27, 2014, 07:26:21 am
content: A current would flow if you accidentally touch a lead and thus thus connect to ground via your feet. The whole idea of a isolation is that you can accidentally touch either lead and still not feel anything.IOW: If you connect secondary neutral to ground, you defeat the purpose of the isolation transformer and may as well directly plug into the wall socket.

author: Melkor
author_rank: Contributor
timestamp: January 27, 2014, 07:37:53 am
content: I think that the idea of secondary grounding comes from 3-phase transformers where is needed.I don't see a reason for doing it to an isolation transformer either.

author: cybermaus
author_rank: Frequent Contributor
timestamp: January 27, 2014, 07:49:16 am
content: Correct. If you have three phase transformers, you would re-ground the secondary neutral to avoid floating by unbalanced loads.But those are not isolation transformers. They are either step-up/down transformers, or convert between single and 3 phase. Industrial use usually.Workbench isolation transformers: Keep them isolated!

author: Zucca
author_rank: Unknown
timestamp: January 27, 2014, 03:24:31 pm
content: Thanks!So now I can confirm I´mnotcrazy and this post iswrongright:https://www.eevblog.com/forum/projects/design-for-an-apparatus-for-more-safely-experimenting-with-mains-powered-project/msg319780/#msg319780

author: Monkeh
author_rank: Super Contributor
timestamp: January 27, 2014, 03:37:19 pm
content: Quote from: zucca on January 27, 2014, 03:24:31 pmNo, that post is absolutely correct.

author: Zucca
author_rank: Unknown
timestamp: January 27, 2014, 04:25:26 pm
content: Quote from: Monkeh on January 27, 2014, 03:37:19 pmWoops

author: G7PSK
author_rank: Super Contributor
timestamp: January 27, 2014, 04:29:59 pm
content: The reason some so called isolation transformers have a centre tapped secondary is that you then only get half the volts to ground, a system used in site transformers here in the UK 240 in 110 out and 55 volts to ground. Therefore if you come into contact with one lead and the other has gone to earth you only have 55 volts rather than 110 also if either line get earthed the trip goes where if you had a live and neutral if neutral gets damaged you wont know until you touch a damaged live. But you cant really call such a system an isolation transformer.
Isolation transformer again - Page 1
Forum section: electronics / beginners

author: Bondguy
author_rank: Contributor
timestamp: September 22, 2016, 07:50:31 am
content: I bought an isolation transformer and prepared it for my need.Now it has Live, Neutral and Ground pins connected to primary side of the transformer.Live and Neutral pins to secondary side.( No Ground on secondary)Is that correct ?Now I want to measure ,with a oscilloscope ,on live side of a power supply( SMPS) adaptor.So, I connect that tested power supply adaptor to a secondary side of the isolation transformer.But must I also connect the scope to the secondary side of the isolation transformer or I not?May I connect the scope to a common wall outlet?

author: DmitryL
author_rank: Regular Contributor
timestamp: September 22, 2016, 09:16:27 am
content: Are you sure that you want to mess with mains stuff if you have no idea how it works and how to connect wires properly without killing yourself ?

author: Bondguy
author_rank: Contributor
timestamp: September 22, 2016, 09:47:25 am
content: That is a reason why I asked to understand properly

author: DmitryL
author_rank: Regular Contributor
timestamp: September 22, 2016, 09:50:29 am
content: There was a video here "how not to blow your oscilloscope"

author: madires
author_rank: Super Contributor
timestamp: September 22, 2016, 10:06:07 am
content: But it might be a better idea to get some nice differential probes, from Pintek for example.
Isolation transformer consumption - Page 1
Forum section: electronics / beginners

author: mathk
author_rank: Contributor
timestamp: December 02, 2012, 11:24:23 pm
content: HiDave often talk of isolation transformer for safety reason when you are probing a device.But I am concern about if you install such transformer will it consume power when nothing is connect to it?Thanks

author: Monkeh
author_rank: Super Contributor
timestamp: December 02, 2012, 11:45:24 pm
content: Well, yes, a little, so, y'know,turn it off.

author: TriodeTiger
author_rank: Regular Contributor
timestamp: December 02, 2012, 11:51:11 pm
content: I would have to throw in some terms such as core losses, those may draw power even though the transformer is not connected to anything.A switch may be the better way, or buying an inexpensive energy meter and seeing if it is reasonable!

author: mathk
author_rank: Contributor
timestamp: December 03, 2012, 12:00:20 am
content: Ok I see thanks for the precision. A simple switch will it work? I thought that since it is a coil, open a close circuit that have coil can generate some spike?

author: Monkeh
author_rank: Super Contributor
timestamp: December 03, 2012, 12:01:28 am
content: Quote from: mathk on December 03, 2012, 12:00:20 amSo how do you switch any transformer load?
Isolation Transformer DIY - Page 1
Forum section: electronics / beginners

author: Videng
author_rank: Newbie
timestamp: May 17, 2024, 04:03:50 pm
content: Hello-Just starting a new hobby of restoring a few vintage Sony and Teac RR tape decks as well as a Marantz receiver and amp. I’ve been slowly assembling some test gear and wanted to include an isolation transformer. I came across one that turned out to be homemade and upon testing doesn’t seem to be that isolated. The supply side has the ground attached to the metal enclosure and passes through to the outlet. Measuring the voltage on a wall outlet is 122v. Measuring the two legs of the secondary side of the transformer is 135v, then from each leg back to the wall outlet ground is 92v and 15v. I’ll pick up a Variac to adjust the output down to 120v but again wasn’t too sure how isolated and safe a DUT connected (only using a two prong non-grounded plug on these older pieces of gear) to the isolated outlet would be if I go probing with an oscilloscope. I was planning to rebuild it, hoping to salvage the transformer and incorporate a volt /current meter with a non grounded outlet. Question I had, is this transformer suitable to still use and any other tips for doing a DIY isolation transformer?Thanks

author: wasedadoc
author_rank: Super Contributor
timestamp: May 17, 2024, 05:17:51 pm
content: You don't really need an isolation transformer when working on the items you mention. Equipment with "old fashioned" 50 or 60Hz transformers is already isolated after the transformer. There is rarely any need to look at the powered-on primary side with any test equipment other than an AC voltmeter.Yes, a fault could theoretically leak from the mains input to the circuitry on the secondary side but that should be one of the very first tests you do.Having said all that, using an isolation transformer shouldn't do any harm but might lull you into a false sense of security.

author: Videng
author_rank: Newbie
timestamp: May 17, 2024, 06:35:52 pm
content: Thanks for the quick reply. I noticed the original design had both H1-H3 and H2-H4 tied together, perhaps start by separating those. So, "one of the very first steps to do", ohm out between pri and sec sides? And in theory, after all this is electrical, when measuring voltage from sec sides to house ground should be 0v or is a little leakage acceptable? Appreciate the advice and avoiding the sparks. Thanks

author: soldar
author_rank: Super Contributor
timestamp: May 17, 2024, 08:50:50 pm
content: primaries are in parallel for 115 volts and in series for 230 volts.I have several transformers like that.
Isolation transformer EMI filter - Page 1
Forum section: electronics / beginners

author: Tj138waterboy
author_rank: Regular Contributor
timestamp: November 11, 2020, 03:21:47 pm
content: Looking for input on if it would be worthwhile to have Emi filtered input for an isolation transformer for oscilloscope.

author: Gyro
author_rank: Super Contributor
timestamp: November 11, 2020, 05:17:54 pm
content: Quote from: Tj138waterboy on November 11, 2020, 03:21:47 pmThat's kind of a moot question because you should never have a scope connected to an isolation transformer. Floating a scope means that its casing, input shields etc will follow the voltage on the DUT (Device Under Test), which could then rise to dangerous levels, i.e. The scope is floating,youare not.Always have your test equipment grounded and (if necessary) the DUT powered by via the isolation transformer.

author: Tj138waterboy
author_rank: Regular Contributor
timestamp: November 11, 2020, 05:55:49 pm
content: Thanks for correcting as I didn't phrase my question correctly. So in powering d.u.t. through isolation transformer would there be any benefit or drawback?

author: Simon
author_rank: Unknown
timestamp: November 11, 2020, 06:30:14 pm
content: It depends on what you are measuring. You DUT should be connected as it normally would or why measure?

author: mag_therm
author_rank: Frequent Contributor
timestamp: November 11, 2020, 07:20:48 pm
content: If it is a purpose built isolation transformer, it might already have a grounded inter-winding shield.The capacitance of each winding to the shield is higher than their mutual capacitance,so the shield acts as a common mode attenuator, provided the "ground plane" around the DUT to the transformer ground is good.Check the name-plate / data sheet or,if you have a capacitance meter, you can measure the 3 capacitances to see if it has a grounded inter-winding shield.

author: Gyro
author_rank: Super Contributor
timestamp: November 11, 2020, 08:11:14 pm
content: Quote from: Tj138waterboy on November 11, 2020, 05:55:49 pmAh ok. That's a relief!The level of noise attenuation by the transformer is dependent on its construction - as mag-therm says, if it has an inter-winding screen, but also whether it is traditional EI split bobbin construction or is toroidal. A toroidal transformer tends to couple more high frequency noise.I suppose it would be safe to say that an EMI filter (on the primary side of course!) can't really do any harm. Whether it makes a tangible difference will depend on the mains noise environment and the sensitivity of your DUT and measurements.Edit: If it does make a significant difference, then it probably points to a weakness in your DUT design which may show up when used without an isolation transformer.Edit1: ... but any EMI filtering inside your DUT could well behave differently due to the isolated secondary of the isolation transformer. A tricky area.
Isolation transformer floating? - Page 1
Forum section: electronics / beginners

author: horle
author_rank: Newbie
timestamp: June 09, 2016, 09:45:56 pm
content: Hey guys!I got myself an isolation transformer off ebay. Toroid ISB - 100Whttps://toroid.com/Transformer-Products/IsoBox-Transformers/International-W-SeriesI just wanted someone more experienced to confirm my thoughts.I'm a bit confused about the odd number of wires. It has 2 primaries and 2 secondary windings. That's 4 wires in, 4 wires out. But there is a 9th green wire that is hooked up to protective earth that I can't find in the transformers datasheet.https://toroid.com/Portals/0/pdf/isolation_transformers/798.1202.pdfIt is neither connected to the secondary nor the primary windings.I read about isolation transformers which have the secondary bound to ground but that is not the case here.While I measure some AC voltage 180 and 40V between the output pins and mains earth there is no significant current (checked with a light bulb). So I assume that's just some stray voltage.So what is the 9th wire good for? Grounded core?And why are the output sockets protective earth pins connected to mains protective earth and chassis? what sense does that make if the power supply is floating?Due to my measurements my output should be floating right? I'm just confused because I read somewhere that medical isolation transformers are earth referenced while "technical" isolation transformers are not. So you have to mod them. But I don't see what I should mod here...Cheers!

author: retrolefty
author_rank: Super Contributor
timestamp: June 09, 2016, 11:59:28 pm
content: QuoteIt's wired to a full copper shield that helps cut down capacitance coupling of noise between primary and secondary windings and should be connected to ground. It's a extra cost item that better isolation transformers have. Very common on instrumentation grade equipment.
Isolation Transformer Question - Page 1
Forum section: electronics / beginners

author: wn1fju
author_rank: Frequent Contributor
timestamp: March 17, 2016, 11:19:43 pm
content: I'm using a Sencore PR57 (variable) isolation transformer. This one runs earth ground through to the secondary. I thought the point of such a beast was that a voltage measurement across the hot and neutral outputs will be 120 VAC (I'm in USA), but the "safety" results from the fact that both the hot and the neutral are floating (nominally at zero) with respect to earth ground.Now I plug in a piece of test equipment into the PR57, say an HP piece with a line filter. In a typical line filter are two (0.22 uF) caps from hot to earth and neutral to earth. Does that not act as an AC voltage divider and basically place the hot and neutral both about 60 VAC over earth ground? So where is my isolation safety if I'm touching the hot and the chassis at the same time?If the DUT doesn't have a line filter, would not I expect the hot and neutral to nominally be at 0 VAC over earth?

author: Zero999
author_rank: Super Contributor
timestamp: March 17, 2016, 11:31:04 pm
content: The earth shouldn't run straight through the transformer. The appliances connected to the secondary should all be unearthed but their chassis need to be connected together.
isolation transformer question - Page 1
Forum section: electronics / beginners

author: corporalspiffy
author_rank: Newbie
timestamp: August 15, 2015, 06:59:22 pm
content: this is the isolation transformer i have.can someone give me an explanation of its purpose and design.will this float the secondary circuit or will it just reduce noise from the mains supply?there is no continuity between the secondary ground and the primary ground.i plugged in an appliance to it and measured full mains voltage between its chassis and a wall receptacle which seems to indicate that it was not isolated.if i disconnect the ground on the secondary side will the whole secondary circuit then be isolated?why is there is secondary ground if it isn't grounded to the mains ground and why did i measure full mains voltage on the appliance chassis and the mains outlet receptacle.thankssecondary sideprimary side

author: IanB
author_rank: Super Contributor
timestamp: August 15, 2015, 07:21:50 pm
content: The purpose is to isolate the secondary side and reduce the risk of electric shocks caused by faults in the devices plugged into it. Since the secondary side is floating there should be no potential difference available between the secondary side and earth ground to cause electric shocks.The secondary ground may possibly be connected to a center tap on the secondary side, putting it at a potential of 60 V relative to both output conductors. This would enable a fuse to blow under fault conditions and also reduce the shock risk in the event of a person touching an active conductor and the grounded chassis at the same time. (I am not certain of this without seeing more details of the transformer.)When you measured "full mains voltage" to a mains socket, how did you measure? Did you measure between hot on the mains side and the metal chassis? When you did this measurement, did you use a "low Z" setting on the meter? It is possible you measured a phantom voltage caused by capacitance in the system.

author: retrolefty
author_rank: Super Contributor
timestamp: August 15, 2015, 07:34:44 pm
content: My understanding for using the isolation properties of such a transformer is it allows one to 'remove' the neutral to ground connection that most AC household outlets have, this connection being made at the service panel feeding the outlet. With the isolation transformer the user is allowed to remove any reference to ground for either secondary output pin of it's output outlet. There should always be a hardwired connection between 3rd ground pin from input to output as it's a safety/fault current carrier, but the user is free to have ground pin and either one but only one of the AC output pins to ground at the load end or left 'floating' from house ground.
isolation transformer toroid Mod - Page 1
Forum section: electronics / beginners

author: mike1855
author_rank: Newbie
timestamp: February 01, 2015, 06:41:09 am
content: Toroid as tested is:core: Approximately 5.5 cm tall, 11 cm across, 6.5 cmcenter hole, was best measurements I could get trying toaccount for wire and insulation.Toroid windings being used:16 awg primary winding16 awg secondary windingPowered Toroid with variac setat 120 volts out showed .01 amp current draw with no load. I thought this was kind of low.Once powered up the Toroid out put is at 125 volts with no load thendrops to 120 @ .87amp current draw loaded with 100 watt light bulb.I tested Volts per turn ratio and it is at 3 turns pervolts @ 120 volts input at primary.Ok with that said, from the above testing results would this make a good isolation 120volt -120 volt transformer, good for around 3.5 amps?It was originally a 1 kva 208-440 to 215 volt auto transformer that i removed the insulation from and separated the other sets of wires and narrowed down these two sets for my needs as an isolation transformer.My concern is , will the windings be ok with 120 volts, or are they in reality still 220 volt windings? And if they are still 220 volt windings what problems would I notice running this on 120 voltsAlso, are there any Toroid transformer calculators on line, ive searched and have not found what i was looking for.Thanks

author: SeanB
author_rank: Super Contributor
timestamp: February 01, 2015, 07:14:17 am
content: Insulation is good enough for 440VAC, so will work at 120VAC. Best though is to do a high voltage insulation test between the 2 windings, typically 1000VDC for 30 seconds, and the insulation resistance must be over about 20Mohm with no arcing. Pass that and it is fine.

author: mike1855
author_rank: Newbie
timestamp: February 01, 2015, 07:26:54 am
content: if it passes that test would this be good enough for powering the average oscilloscope? Also any ideas where i can find a toroid power transformer calculator program? thanks
Isolation Transformer - which one to get? - Page 1
Forum section: electronics / beginners

author: philwong5176
author_rank: Unknown
timestamp: September 22, 2019, 08:16:00 pm
content: Hello:I would like to hear suggestions. I plan to plug only my scope (Tek 2465B) and bench DMM (Agilent 34401A) to it.Before this posting I only know about those made by Tripp Lite, used at many hospitals.Thanks.

author: ArthurDent
author_rank: Super Contributor
timestamp: September 22, 2019, 08:28:29 pm
content: If you try to float your scope and meter with an isolation transformer you may get to see one of the Tripp Lites units in a hospital. Search the forums for isolation transformers as this subject comes up almost weekly. The only answer is don't do it.

author: philwong5176
author_rank: Unknown
timestamp: September 22, 2019, 08:50:29 pm
content: Thanks for the video link.I stand corrected on what to plug in -- the power supply I am testing has to be plugged into the transformer, not the test equipment I am using.

author: Benta
author_rank: Super Contributor
timestamp: September 22, 2019, 09:04:36 pm
content: Quote from: philwong5176 on September 22, 2019, 08:50:29 pmCorrect! Never float your test equipment, only float the DUT (device under test).I'm happy we could save your life
Isolation transformer wiring question - Page 1
Forum section: electronics / beginners

author: cincin
author_rank: Regular Contributor
timestamp: September 28, 2023, 05:45:04 am
content: I just bought a 15A used isolation transformer, which I plan to use to isolate the devices under test while using my oscilloscope.The Ground wire goes straight from the North-American 3 prong input plug to the Ground on the 3 prong outlet on the secondary side, which I'm reading is fine and may come in useful.I've confirmed that the Live and Neutral on the primary side are isolated from the Live and Neutral on the secondary side.I've also confirmed that the secondary side outputs 120V when plugged into the wall (120V).The problem is: I measure 31.5V between the Live wire of the secondary and the shared Ground, and 71V between the Neutral wire of the secondary side and the shared Ground, and I'm not sure I understand why.My understanding is that there should be no potential between the secondary and the ground.How is this possible?Thanks!

author: jonpaul
author_rank: Super Contributor
timestamp: September 28, 2023, 06:22:21 am
content: Wirign is correct but a schematic or sketch is better to understand.The voltage you see is typical for stray capacitance Pri-Sec.Place a slight load across the meter (47 k Ohm 2W ) it will go way down.Read up on transformer parasitic capacitances.Jon
isolation v variac - Page 1
Forum section: electronics / beginners

author: Dave Turner
author_rank: Frequent Contributor
timestamp: January 03, 2025, 02:50:21 pm
content: Is there a reason why an autotransformer (Variac) should not come after a true isolation transformer?

author: jwet
author_rank: Frequent Contributor
timestamp: January 03, 2025, 03:06:04 pm
content: Its fine to do this and not unusual- its actually preferred in my experience.

author: edavid
author_rank: Super Contributor
timestamp: January 03, 2025, 03:12:54 pm
content: There are some bench products that areexactly thatsimilar to that except wired the opposite way, such as B+K Precision 1655 and Sencore PR57 and PR570.Very handy if you can find one at a reasonable price.

author: bdunham7
author_rank: Super Contributor
timestamp: January 03, 2025, 03:52:34 pm
content: Quote from: Dave Turner on January 03, 2025, 02:50:21 pmYes, the autotransformer has moving parts and exposed conductors so there is greater risk of accidentally rereferencing the output voltage to ground either by short or by leakage. Although the energy will be limited, this still poses a potential shock hazard or DUT damage if you were relying on the output being isolated from ground.Quote from: edavid on January 03, 2025, 03:12:54 pmThe BK1655 and PR57, at least, are wired with the isolation transformer last, going more or less directly to the output sockets. I haven't seen a PR570, but I'd presume they haven't changed the layout.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: January 12, 2025, 07:53:36 pm
content: Thank you all for your responses.Other than bdunham7's valid comment I haven't been able to find anything definitive, of course a commercial unit would/should have to include protection against zaps of that type.I do seem to recall reading somewhere that there was a potential problem regarding impedance matching and power factor correction, though at low power consumption say max 300VA I doubt this would prove to be an issue.
Isotemp OCXO pinout question - I can't find a datasheet - Page 1
Forum section: electronics / beginners

author: alank2
author_rank: Super Contributor
timestamp: July 13, 2020, 01:45:38 am
content: It is about 2" by 1" by 1" tall and looking at it from the underside it has:Code:32 P1pins 2 and P are grounded to the case.pin 1 has 4.7K resistance to ground.pin 3 has 5M resistance to ground.Is pin 1 the VCC and pin 3 the output?Any guesses at the voltage? I'm thinking 12V, but I'm not sure I want to give it that much as a test unless I know for sure.

author: alank2
author_rank: Super Contributor
timestamp: July 13, 2020, 02:17:14 am
content: I think it is this:https://web.archive.org/web/20030608212454/http://www.isotemp.com/ocxo23.htm

author: alank2
author_rank: Super Contributor
timestamp: July 15, 2020, 07:00:46 pm
content: Could this require a load for it to work properly?The link above says "into 50 ohms".Sometimes it works great with no load except the scope, but then I've seen it snap to another frequency like 6.7 MHz. Once that happens it is only cleaned up by me putting a resistor between the output and ground. 100 ohms works, 50 ohms works, 250 ohms does not work.
Issue in low side mosfet based switch - Page 1
Forum section: electronics / beginners

author: abhishekkumar1902
author_rank: Regular Contributor
timestamp: February 12, 2020, 09:46:51 am
content: I have designed this opticaly isolated low side switch (schematic attached in the post) for driving the HORN of my car through some arduino electronics. It works flawlessley except when I turn OFF the power supply to this circuit. When I shut off the power suppy to this circuit, I notice the load (horn) switches ON for a very very short time say 100ms. Why is this happening?

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 12, 2020, 10:01:05 am
content: How do you cut off the power to the unit?

author: abhishekkumar1902
author_rank: Regular Contributor
timestamp: February 12, 2020, 10:08:47 am
content: Arduino circuit and and this circuit both are connected to the vehicle's battery through the ignition switch. The horn rings for very short time say 100ms when I turn off the ignition key, even when the arduino didn't turned ON the MOSFET previously. The only difference is arduino side has an additional 4700uF capacitor in the EMI filter design.

author: exe
author_rank: Unknown
timestamp: February 12, 2020, 10:24:50 am
content: Can it be Arduino is sending a signal just before switch off? It's easy to verify, disconnect signal lines and see if the problem still persists.

author: Vovk_Z
author_rank: Super Contributor
timestamp: February 12, 2020, 01:13:26 pm
content: Quote from: exe on February 12, 2020, 10:24:50 am+1 to previous questions. Because it is strange - if there is no power - nothing can turn horn on.

author: DBecker
author_rank: Frequent Contributor
timestamp: February 12, 2020, 01:28:22 pm
content: That seems a very complex circuit to control a horn.What is special about the signal input level that it needs to be isolated? Is there anything special about the horn?Why not use a standard automotive low-side or high-side clamping driver, with much less complexity? Why did you an extra stage rather than having the optocoupler to directly pull up the gate?

author: Wimberleytech
author_rank: Super Contributor
timestamp: February 12, 2020, 03:31:07 pm
content: Quote from: abhishekkumar1902 on February 12, 2020, 10:08:47 amIn order to troubleshoot this strange behavior, you must draw the COMPLETE circuit to understand sneak paths. What you have drawn is only part of the circuit and what you have additionally described is, at best, slightly helpful.Please show everything.

author: EEEnthusiast
author_rank: Frequent Contributor
timestamp: February 12, 2020, 06:25:17 pm
content: Just use a relay, as is done in automotive world.
Issue with LCD volt meter - Page 1
Forum section: electronics / beginners

author: jbrewton
author_rank: Newbie
timestamp: February 25, 2014, 06:48:44 pm
content: http://www.ebay.com/itm/3-1-2-Blue-LCD-Digital-Volt-Panel-Meter-DC-20V-/161045251073?pt=LH_DefaultDomain_0&hash=item257f0b8401Ok, I know I can not run off common ground supply, but can I run it off a secondary rectified supply off the same transformer with 2 bridge rectifiers separate grounds?Display will be attached to bottom supply and circuit display reading from top supply

author: SeanB
author_rank: Super Contributor
timestamp: February 25, 2014, 07:02:31 pm
content: Simple answer is the 2 supplies are not isolated at all. They have a connection of somewhat complicated impedance and will pass current from any output or ground to any other output or ground of the other side. You need 2 electrically separate windings on the transformer with separate bridge rectifiers on each to have them isolated.

author: mariush
author_rank: Super Contributor
timestamp: February 25, 2014, 07:48:45 pm
content: Or instead of buying a large transformer with two separate windings, you could buy a couple of cheap 7.5v ac adapters and then use the 7805 to regulate the output for your meters.For example :http://www.ebay.com/itm/US-DC-7-5V-1A-Switching-Power-Supply-adapter-100-240-AC-/181137467047?pt=US_Surveillance_Cables_Adapters_Connectors&hash=item2a2ca266a7orhttp://www.amazon.com/Super-Power-Supply%C2%AE-5-5x2-5mm-Certified/dp/B00EA162QQ/ref=sr_1_2?s=electronics&ie=UTF8&qid=1393357527&sr=1-2&keywords=7.5v+adapterif you want to get it faster.Hack them to remove the mains connector (remove the prongs and solder wires directly onto the pcb inside and you're in business.You may be tempted to get straight 5v ac adapters but don't, they're not regulated enough, the 7805 needs 1.5-2v above 5v to work properly so 7.5v dc from such ac adapter will be perfect.

author: Excavatoree
author_rank: Frequent Contributor
timestamp: February 25, 2014, 07:51:50 pm
content: One interesting problem I found using the current measuring version of that meter is that if two panel meters are used to measure two currents that are not isolated, they must EACH be powered from an isolated supply.That is, I am measuring currents 1 and 2 from one common supply. Each meter has to be powered separately, using two batteries in my case. I would think that one battery could be used for both.
Issue with multiple connectors - Page 1
Forum section: electronics / beginners

author: LoveLaika
author_rank: Frequent Contributor
timestamp: May 21, 2020, 02:00:56 am
content: I just have a very simple question about connectors. Odds are, the answer may be simple, but I wanted to ask in case I was missing something.Let's say I have a power supply on a PCB with 3 pins: Va, Vb, and GND. At the very least, it takes a 3 pin connector, but let's say that I also need to adapt it for a 5-pin and a 7-pin connector for some legacy connection. Would there be any problems if I have one of each pin connector on the board so that I can use it for whatever I want without having to redesign it, assuming that I'm only using it for one task at a time? If I have unpopulated locations there, wouldn't that cause issues with EMI or the unpopulated pads/holes acting as antennas, or am I overthinking things? I've included a diagram that explains what I'm talking about.

author: ataradov
author_rank: Super Contributor
timestamp: May 21, 2020, 03:20:05 am
content: You are definitely overthinking that. There is nothing wrong with having multiple connectors in parallel populated or not.

author: tkamiya
author_rank: Super Contributor
timestamp: May 22, 2020, 05:32:17 am
content: Yes, you are over-thinking this for power supply connections.You can do it if you have the need and know what connector, pin count, and voltage assignment ahead of time. It's just DC. If you are talking high frequency signal connections, it's different though.

author: Benta
author_rank: Super Contributor
timestamp: May 22, 2020, 06:23:27 pm
content: The only potential problem you could have is that someone gets hold of your PCB and uses all three connectors at the same time.You've ruled that out yourself, so don't overthink it.

author: LoveLaika
author_rank: Frequent Contributor
timestamp: May 22, 2020, 07:21:02 pm
content: Thanks for the reply. I say I ruled that out, but it's amazing how things are used in the wrong way. Worst case scenario, someone uses it in the wrong way, but with my application, it should be able to handle the extra current draw, so there's that.
issues making Windows usb bootdisk from linux... - Page 1
Forum section: electronics / beginners

author: Kilroywashere
author_rank: Regular Contributor
timestamp: March 13, 2019, 02:18:01 am
content: Hey Im having a hard time making a usb boot drive for windows 7 using Linux Ubuntu.....I use GParted to format the Fat32 drive and FuriusISO to mount but its not working it wont let me mount the ISO .... WinUSB does not seem to want to install on my computer as well... Im sort of at a loss.... I even made a virtualbox windows to try and download Rufis.exe but its too slow ....Help please ! I badly need to this laptop on windows again

author: Kilroywashere
author_rank: Regular Contributor
timestamp: March 13, 2019, 02:27:26 am
content: So just copy and past the Windows.ISO onto the Fat 32 usb? and if my computer is not super old it will run and install windows?

author: Kilroywashere
author_rank: Regular Contributor
timestamp: March 13, 2019, 02:36:00 am
content: Ok, Whats dd?Dungeons and dragons?It wont let me Extract the files...I right click the file and i click "Extract to" I pick the USB drive andAn Error occurred wile extracting filesIgnoring out-of-order file @19 (readme.text) 51200 <55296

author: Kilroywashere
author_rank: Regular Contributor
timestamp: March 13, 2019, 02:59:03 am
content: Ok thanks a bunch ... I will have to look up how to do this device dump a bit more ....I would of liked to just extract the files onto the usb .... but i dunno why its not letting me .... Maybe this disk dump might work for me ....It just seems a little confusing at the momentThank you so much for your help !!

author: Kilroywashere
author_rank: Regular Contributor
timestamp: March 13, 2019, 03:07:58 am
content: Quote from: blueskull on March 13, 2019, 02:49:43 am"first get the device path of your flash drive" /dev/sdbThen, use "sudo dd if=xxx of=/dev/sdx bs=1m; sync" So open a terminal and type sudo dd if=xxx of=/dev/sdx bs=1m; syncxxx is the full path of your ISO file So like the name of the folder i have the iso file? /home/kilroy/Downloads/Im lost right here

author: Kilroywashere
author_rank: Regular Contributor
timestamp: March 13, 2019, 03:23:52 am
content: Urg.. Im sorry to bug you.... I did it but it might not of worked ... It just said ....sudo dd if=/home/kilroy/Downloads/Windows.iso of=/dev/sdx bs=1m; syncdd: invalid number: ‘1m’

author: retiredcaps
author_rank: Super Contributor
timestamp: March 13, 2019, 03:28:47 am
content: I just used woeusb today to make a Windows 10 USB 4GB boot disk.https://github.com/slacka/WoeUSB

author: Kilroywashere
author_rank: Regular Contributor
timestamp: March 13, 2019, 03:35:20 am
content: Quote from: retiredcaps on March 13, 2019, 03:28:47 amWoeUSB also does not want to install on this computer .... its odd i tried like 3 different programs woeUSB and WinUSB did not work ... they would not open ...

author: Kilroywashere
author_rank: Regular Contributor
timestamp: March 13, 2019, 03:55:09 am
content: The dd did not work.... unless i did not do it right but i think i did ... Maybe my computer is too old? but ill have to find another way...
Issues trying to make my FOC simulation work - Page 1
Forum section: electronics / beginners

author: cadena
author_rank: Contributor
timestamp: August 01, 2020, 04:16:10 pm
content: Hi,I am having issues with making my FOC simulation work (see above image and Matlab file) but I do not understand why I am getting the error message. I am using Matlab 2017b and my simulation is using a P gain of 15 and my I gain is of 7 in both PI controllers. I am trying to control torque by just having 1 loop (not interested in speed). I am also trying to use Space Vector Modulation to modulate the 3 phase voltages before they get into the motor.I would like to an RS BLDC to model both my simulations but when trying to write down the parameters (see datasheet above). I only know the line to line resistance (but not phase resistance), line to line inductance (but not armature inductance) and the No. Of poles (4). I don´t know the permanent magnet flux, initial dq current and even less the mechanical parameters… and this is the same for other PMSM motors online. Hence, what should I include ?Thanks in advancehttps://drive.google.com/file/d/13bpjEZZvbx6kBqHe-Cm1It_O_D7DI4UB/view?usp=sharing

author: FOC_BLDC
author_rank: Newbie
timestamp: February 08, 2021, 04:33:06 pm
content: The angle to feedback from the motor should be the electrical angle and not the mechanical angle IIRC
Issues when trying to connect Brymen BM869 with sigrok-cli on OSX - Page 1
Forum section: electronics / beginners

author: tuuksijii
author_rank: Newbie
timestamp: July 29, 2020, 06:21:42 pm
content: Sorry if this is the wrong channel for asking help using Sigrok on OSX,but I didn't know where else to ask anymore. I've tried the IRC channel and sigrok-devel already.So I have a Brymen BM869 multimeter, which I bought the BC-86X USB-cable for. I heard from a friend that Sigrok supports this multimeter, but I'm having a hard time getting it to work with my OSX 10.14.6 Mac Mini.I managed to install the sigrok-cli nightly from the .dmg after a bit of fiddling with homebrew and it seems to work fine now.When using lsusb (also installed from homebrew), I get the following message indicating that the USB-cable is recognized:Superior DMM:Product ID: 0x0001Vendor ID: 0x0820Version: 86.03Serial Number: ?呐?Speed: Up to 1.5 Mb/secManufacturer: BrymenLocation ID: 0x14741000 / 19Current Available (mA): 500Current Required (mA): 100Extra Operating Current (mA): 0Also, when I installed Pulseview and tried to check that out (thought first that it would be right GUI for multimeters too), I get this as an option for serial connections:*hid/bu86x/raw=USB_0820_0001_14741000 (HID Brymen Superior DMM [0820.0001])*But when I write in terminal the command *"sigrok-cli -d brymen-bm86x --scan"*, I get the following error:sr: serial-hid: Unsupported HIDAPI path format: IOService:/AppleACPIPlatformExpert/PCI0@0/AppleACPIPCI/XHC1@14/XHC1@14000000/HS08@14700000/USB2.0 Hub @14700000/AppleUSB20Hub@14700000/AppleUSB20HubPort@14740000/USB 2.0 Hub@14740000/AppleUSB20Hub@14740000/AppleUSB20HubPort@14741000/Superior DMM@14741000/IOUSBHostInterface@0/IOUSBHostHIDDevice@14741000,0sr: serial-hid: Failed to open HID device.When changing the USB-cable to a port connected straight to the Mac Mini (no USB-hub in between) it gives the same message, the location is just shorter.I was reading about USB HID connections in the Sigrok wiki where it was mentioned that you can connect by a USB vendor and product ID pair, or bus and device address. When trying either command "sigrok-cli -d brymen-bm86x:conn=0820.0001 --scan" or "sigrok-cli -d brymen-bm86x:conn=20.20 --scan", both of them give me the following error:*sr: serial-libsp: Attempt to open serial port with invalid parameters.*What am I doing wrong here? Using "sudo" in the commands above also doesn't seem to change the error messages at all.