measuring mains with oscilloscope  - Page 1
Forum section: electronics / testgear

author: hussamaldean
author_rank: Unknown
timestamp: February 23, 2018, 11:38:40 am
content: Hi allwhat is the safest way to measure the mains with oscilloscope without ending burning my oscilloscope ?and is it possible to build differential probe ?Regards

author: joeqsmith
author_rank: Super Contributor
timestamp: February 23, 2018, 11:49:53 am
content: Depending how many harmonics out you need, maybe just a stepdown transformer. That is all I was using to measure AC power with my scope.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: February 23, 2018, 01:35:46 pm
content: Quote from: hussamaldean on February 23, 2018, 11:38:40 amI know the purists will attack me for saying this - and I caution you that this is not recommended by any manufacturer - but the safest way to ensure youdon't burn your oscilloscopeis to disconnect the ground pin from the input. If you do this, you risk electrocuting yourself!What most manufacturers do is connect the ground input pin to the ground/shield of the scope probes. The problem can be that, if a mains outlet is wired incorrectly swapping live and neutral, or if you connect the ground of the scope lead to a live mains signal you will fry the scope because the live will travel through the ground of the scope, through the PCB, and down the ground pin of the power input cord.If you disconnect the ground from the input cord, then you've effectively made the ground+signal of your oscilloscope into a differential input because neither shield or signal on your scope probe is referenced to ground.I keep a spare power cord with the ground disconnected for this very purpose.WARNINGS1. Mains voltages are lethal2. Removing the ground means that the scope ground can be at mains voltage so be very careful in touching the oscilloscope when connecting the probes to mains - in fact, don't touch the scope when the probes are connected to mains is the best advice.3. Check that your oscilloscope does isolate the power input from the scope ground - test with a meter from live and neutral in to the oscilloscope's ground / shield on front, it should be Meg Ohms4. Check that your oscilloscope can handle the mains voltages (you may need to make sure the probes are on x10)

author: hussamaldean
author_rank: Unknown
timestamp: February 23, 2018, 01:39:19 pm
content: Quote from: Gandalf_Sr on February 23, 2018, 01:35:46 pmwell, this case I will step down transformeranother questionis it possible to use this as current probe for oscilloscope ?http://statics3.seeedstudio.com/assets/file/bazaar/product/101990028-SCT-013-030-Datasheet.pdfregards

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: February 23, 2018, 02:07:40 pm
content: That can be used as a current probe but it only works up to 1 kHz. If you want to go into MHz then you need a current probe. Search eBay for "AM503B" (probe amplifier) and "A6302" which together will allow you to probe up to 20A and 50 MHz. I own this setup and I got it for around $300 on eBay.

author: hussamaldean
author_rank: Unknown
timestamp: February 23, 2018, 02:22:53 pm
content: Quote from: Gandalf_Sr on February 23, 2018, 02:07:40 pmit is little bit expensive and if I need more than 1KHz, I will use current shunt resistance with 10X probe

author: vk6zgo
author_rank: Super Contributor
timestamp: February 23, 2018, 02:44:45 pm
content: Quote from: Gandalf_Sr on February 23, 2018, 01:35:46 pmI'm not quite a purist, but I don't like this idea.Without an Earth ( ground ) connection, the external metal parts of the Oscilloscope are free to take up whatever potential is present on the probe's "ground clip".If you connect that clip to Mains "Active"( the "hot"wire), then touch the scope metalwork at the same time as you touch some other piece of equipment with an intact Earth lead you will "zap"yourself.If your Mains circuit is fitted with an RCD device, it will just be a quick shock before the device removes the Mains connection.If not, you may be badly injured or killedSometimes, all we want to do is to have a "quick look", to see if the Mains is there, & is about the right amplitude.In such cases, just remove the probe ground altogether, & rely upon the return circuit already existing via the 'scope Earth lead & the power point Earth circuit, back to where the Earth & Neutral are bonded at the building power entry.This of course, will introduce errors if you are trying to look at higher frequency artefacts upon the basic 50 or 60Hz Mains waveform.Another way is to, again without using the ground clip, use two channels as a " pseudo differential input ".(Put, say, Ch1 probe on one leg, & Ch2 probe on the other ,& set your 'scope to add the two.This does have problems, in that it is not always easy to balance the Channel gains, giving rise to errors, but it can be useful.Obviously, the best ways to do it, are a 'scope designed for such testing, with differential input circuits, or a differential probe with a conventional 'scope.

author: hussamaldean
author_rank: Unknown
timestamp: February 23, 2018, 02:46:05 pm
content: Quote from: vk6zgo on February 23, 2018, 02:44:45 pmyeahI scraped the whole idea

author: tggzzz
author_rank: Super Contributor
timestamp: February 23, 2018, 03:34:23 pm
content: Quote from: hussamaldean on February 23, 2018, 11:38:40 amWhat are you measuring and why? Frequency, amplitude, harmonics, etc?QuotePossible, yes. But if you have to ask it isnot safe!

author: nctnico
author_rank: Super Contributor
timestamp: February 23, 2018, 06:29:34 pm
content: Quote from: Gandalf_Sr on February 23, 2018, 01:35:46 pmThis is worst idea ever! There is nothing purist about not turning your test equipment into a death trap.ALWAYS MAKE SURE YOUR SCOPE IS GROUNDED BECAUSE THE GROUND IS THERE FOR YOUR SAFETY!The safe way to measure mains is to use a CAT rated differential probe which has been designed to measure the voltage levels you want to measure.

author: Gandalf_Sr
author_rank: Super Contributor
timestamp: February 23, 2018, 06:36:08 pm
content: GROUNDS ARE OVERRATED!just kidding

author: BillB
author_rank: Unknown
timestamp: February 23, 2018, 06:43:29 pm
content: You can pick up a Micsig Oscilloscope 1300V 100MHz High Voltage Differential Probe kit DP10013 for around $140 shipped. Is that too expensive?

author: tautech
author_rank: Super Contributor
timestamp: February 23, 2018, 08:22:42 pm
content: Quote from: BillB on February 23, 2018, 06:43:29 pmBill, they as cheap as shit and why most don't have one for their own protection and the same for their hard earned scope escapes me !Buying a scope is just the start, if you want to use its full capabilities AND safely, expect to have to spend more than was out-layed on the scope !It has always been this way.

author: Phil_Tech
author_rank: Contributor
timestamp: October 25, 2019, 07:14:41 am
content: I hadn't heard of the Micsig probes until I read this post - so thanks for the tip.I've just purchased one now on eBay for AUD 210 from local supplier in Melbourne, was cheaper than I could find from overseas sellers.Should be a nice addition to the test gear...

author: Terry01
author_rank: Frequent Contributor
timestamp: October 25, 2019, 09:28:26 am
content: Quote from: Gandalf_Sr on February 23, 2018, 01:35:46 pmTHE OSCILLOSCOPE WILL BE FINE.....BUT YOU MY FRIEND....WILL BE SMOKED!!We'll throw it in beside you when we bury you. Your headstone will read " he saved the scope.. but the driver is TOAST"!Too funny!

author: Gyro
author_rank: Super Contributor
timestamp: October 25, 2019, 09:34:57 am
content: Quote from: Terry01 on October 25, 2019, 09:28:26 amYou are replying (unhelpfully!) to a post that is 18 months old and has been well covered.

author: Terry01
author_rank: Frequent Contributor
timestamp: October 25, 2019, 09:45:22 am
content: And your reply to my post is helpful to the thread? It's nearly the weekend....go on...live a little!

author: Fungus
author_rank: Super Contributor
timestamp: October 25, 2019, 11:26:33 am
content: Quote from: Terry01 on October 25, 2019, 09:45:22 amNope, it's supposed to be helpful toyou, personally. Try reading what he said....

author: mansaxel
author_rank: Super Contributor
timestamp: October 25, 2019, 01:04:21 pm
content: Quote from: hussamaldean on February 23, 2018, 11:38:40 amYou need a ScopeMeter 123/124 or similar. The right tool for the right job.

author: AVGresponding
author_rank: Super Contributor
timestamp: October 25, 2019, 01:28:45 pm
content: Quote from: mansaxel on October 25, 2019, 01:04:21 pmI believe you missed out the first step in this process, which is either winning the lotto, or marrying a rich widow...

author: Terry01
author_rank: Frequent Contributor
timestamp: October 25, 2019, 02:36:10 pm
content: Quote from: Fungus on October 25, 2019, 11:26:33 amAye ok.... you win.

author: Fungus
author_rank: Super Contributor
timestamp: October 25, 2019, 03:26:39 pm
content: Quote from: Terry01 on October 25, 2019, 02:36:10 pmIt's not about anybody "winning", it's about somebody thinking to themselves, "Oh, yeah, so I did...", followed by the formation of a new neuron.

author: mansaxel
author_rank: Super Contributor
timestamp: October 25, 2019, 05:35:02 pm
content: Quote from: ThickPhilM on October 25, 2019, 01:28:45 pmHeh, no, the step is "Be present at the launch of the 123 and get one for free." That's what I did.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 25, 2019, 08:32:29 pm
content: here is what I do, when measuring stuff on a live mains:power the scope via a special low capacity isolation transformator.it was easy to make:http://webx.dk/oz2cpu/230V-trafo-isolation-low-capacity/230V-trafo.htm

author: tggzzz
author_rank: Super Contributor
timestamp: October 25, 2019, 09:32:56 pm
content: Quote from: oz2cpu on October 25, 2019, 08:32:29 pmStop thinking about how that might work, and think carefully about how it mightfail.Have a look at the safety references inhttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: nctnico
author_rank: Super Contributor
timestamp: October 25, 2019, 09:47:09 pm
content: Quote from: oz2cpu on October 25, 2019, 08:32:29 pmDon't try this at homeGet a job in a super market or flipping burgers and make money during the time spend creating dangerous contraptions so you can buy safe tools. Differential probes and current probes are very cheap nowadays. It doesn't pay to mess around.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 27, 2019, 11:51:45 am
content: tggzzz ??it is NOT going to fail, the isolation transformer I use is well made and with ultra low capacityso there is no problems at all with the test setup i explain, it is just as good as using a battery opperated scope,If the 1 ohm sense resistor brakes open, the scope prope will get full mains voltage, in 10:1 it can handle this too

author: Simon
author_rank: Unknown
timestamp: October 27, 2019, 12:04:55 pm
content: The siplest way to do it is to remove the earth clips for the probes. set the scope to math subtraction mode and and use the two probes as "differential" probes. You still have to stay withing the range of the scopes inputs relative to ground but this way you can make sure the chasis is grounded and not worry about what you do with each probe.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: October 27, 2019, 12:13:42 pm
content: There are two questions I've noticed that frequently are asked by new oscilloscope owners and users. They are : "How can I measure the mains with my (grounded) oscilloscope?" and "why does my (improperly grounded) oscilloscope keep showing me 60Hz (or 50, whatever) noise from the mains?"

author: Terry01
author_rank: Frequent Contributor
timestamp: October 27, 2019, 12:55:36 pm
content: It seems there is a couple of ways to measure the mains safely for beginners and a couple of ways to measure the mains using homebrew stuff that you should only use if you really know and understand what you are doing.I fall under the "beginner using 2 probes" category but it is also good to learn the "other" ways too. It's always good to learn new stuff.It's great how the guys who know better can teach the beginners new things on the forum and keep them from blowing themselves and/or their equipment up.

author: alsetalokin4017
author_rank: Super Contributor
timestamp: October 27, 2019, 01:14:29 pm
content: Most of the time my problem is the latter: I _don't_ want mains noise contaminating the signal I'm trying to measure. Ymmv of course!(The "line" trigger option can frequently help one to identify weirdnesses caused by mains pickup in a higher frequency signal.)But they say experience is the best teacher. Blow up one expensive scope by sticking things into places they don't belong, and you will probably never do it again.

author: tggzzz
author_rank: Super Contributor
timestamp: October 28, 2019, 01:29:29 am
content: Quote from: oz2cpu on October 27, 2019, 11:51:45 amThink about all the equipment you are connecting together, not just one bit. Include yourself in "the equipment".The failure modes can be subtle and surprising, and can catch out even professionals that take precautions. For one real life fatality, seehttps://www.eevblog.com/forum/testgear/ground-of-oscilloscope-always-connected-to-earth/msg1967150/#msg1967150

author: BravoV
author_rank: Super Contributor
timestamp: October 28, 2019, 01:47:31 am
content: Quote from: oz2cpu on October 27, 2019, 11:51:45 amIf what you claimed is true, so this millions of dollars people poured in the measurement business either the manufacturers or the users are stupid and just wasting their time and money all this time ?

author: tggzzz
author_rank: Super Contributor
timestamp: October 28, 2019, 08:35:30 am
content: Quote from: BravoV on October 28, 2019, 01:47:31 amYou can try to point people in the right direction, but the Dunning-Kruger effect is strong.That's why I will never try to remotely indicate single specific problems in topics where there are many subtle dangers.

author: Fungus
author_rank: Super Contributor
timestamp: October 28, 2019, 09:19:28 am
content: Quote from: oz2cpu on October 27, 2019, 11:51:45 amIf you meant it'sjust as dangerousas a battery-operated 'scope then I agree 100%ie. The danger isn't from the 'scope's power supply, it's from using a little crocodile clip to connect mains A/C to the chassis of a device with exposed metal all over the place.If you can't understand where the danger comes from then my only advice is to wear rubber boots and gloves while you work. And don't sit on a chair.

author: tggzzz
author_rank: Super Contributor
timestamp: October 28, 2019, 09:25:43 am
content: Quote from: Fungus on October 28, 2019, 09:19:28 amAnd work with one hand in your pocket, tied there if necessary

author: nctnico
author_rank: Super Contributor
timestamp: October 28, 2019, 09:58:29 am
content: Quote from: oz2cpu on October 27, 2019, 11:51:45 amNo it isn't. Even battery powered scopes come in two categories: expensive ones with isolated inputs (usually these have a plastic, non-conductive BNC connectors) and the cheaper ones which have a common metal chassis and metal BNCs. The latter are just as dangerous to use compared to floating a scope using an isolation transformer.

author: n3mmr
author_rank: Regular Contributor
timestamp: October 28, 2019, 11:52:11 am
content: Regarding the proper way to measure inside the mains side of a power supply, i e a high voltage diff probe, which ones are actually good enough of the diff probes offered on Ebay?I see a Micsig probe set for 5000V at about 180 USD,https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.de%2Fulk%2Fitm%2F113749875769,and used testtec 9001 probes.Are these any good? Dare one trust them?

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 29, 2019, 07:08:18 pm
content: I'm always astonished by how often this same question comes-up and even more by some of the answers given.Although I have overlooked the problems of safe probing on line referenced equipment myself in the past, it is a really important point to understand.Anyone wanting to work on live equipment should go to the trouble of first understanding how electricity is delivered to wherever they are using it, the role of each wire used up to the socket, the existing protection equipment and it's condition if something does go wrong.Beyond the financial aspect of a failure the question you want to ask when working in your lab or garage is: "If I touch this how much current will I be taking?" When "this" is your oscilloscope Ext. Trig. BNC or handle the question should become worrying.If you aren't worried at that point you may as well take the reasoning one step further and double wrist-strap yourself with a nice low impedance to the local ground, it has potential to roast your fingers off, but may at least save your chest.There are well known good solutions for probing on 220V, they do have a low cost compared to an oscilloscope or funeral.Is it really worth putting your relatives to all that bother for a bloody 9$99 power supply that should have been better designed in the first place?

author: vk6zgo
author_rank: Super Contributor
timestamp: October 30, 2019, 12:48:35 am
content: For Pete's sake, everybody, buy a bloody differential probe, & those of us with enough knowledge to do it safely in other ways can just quietly die out, without running into hundreds of iterations of this thread everytime we log on throughout our declining years!

author: Fungus
author_rank: Super Contributor
timestamp: October 30, 2019, 07:51:00 am
content: I'd like to know what information people hope to gain by poking at mains with an oscilloscope as opposed to, eg., plugging in a lamp.Quote from: vk6zgo on October 30, 2019, 12:48:35 amYou don't even need that for a quick test. Just pop the ground clips off your probes and set the 'scope to "AC" mode.(Use two probes and "difference" as necessary).

author: Simon
author_rank: Unknown
timestamp: October 30, 2019, 07:53:23 am
content: Quote from: Fungus on October 30, 2019, 07:51:00 amYep I said that way back but it's not sexy or dangerous enough.

author: maginnovision
author_rank: Super Contributor
timestamp: October 30, 2019, 08:38:24 am
content: I logged a week on an oscilloscope the mains voltage at my house. Captured large voltage dips that likely fried my refrigerator compressor and my old AC compressor. I showed the logs to SCE who paid for those failures after finding a loose connection on the pole I get power from. I then logged another week to make sure it didn't happen again.You can't do that plugging in a lamp.

author: tautech
author_rank: Super Contributor
timestamp: October 30, 2019, 08:43:21 am
content: Quote from: maginnovision on October 30, 2019, 08:38:24 amExactly !Connecting a scope to mains is not for the inexperienced but it can safely be done.Wise to use 100x probes or a differential probe for safety reasons though.

author: tggzzz
author_rank: Super Contributor
timestamp: October 30, 2019, 10:17:50 am
content: Quote from: maginnovision on October 30, 2019, 08:38:24 amJust so, but there are simple easy cheapand saferways to achieve that than connecting a scope to the mains, e.g.:use an ac voltmeter that can capture and upload the values to a PCconnect a standard 240V/12V (etc) transformer to the mains, and connect the scope to the 12V outputWith a little thought and imagination, it is usually possible to avoid the potential dangers of connecting a scope directly to the mains.

author: BravoV
author_rank: Super Contributor
timestamp: October 30, 2019, 11:46:53 am
content: I did use my HV diff. probe + scope, in measuring AC mains voltage & current (thru shunt) for capturing, and tweaking the soft start circuits that built for AC inductive load, like my bench drill, variac and other AC rotary cutting tools and etc.As these inductive loads can have nasty current spike (sometimes 10 to 50 times at rated current) at few 1st cycles when powered on at the right/wrong AC phase, and also caused serious voltage sag or trip the current breaker.In this specific case, just can't use slow AC logger like DMM (own Fluke 287) as its not fast enough to capture that events.

author: Fungus
author_rank: Super Contributor
timestamp: October 30, 2019, 12:14:38 pm
content: Quote from: maginnovision on October 30, 2019, 08:38:24 amI could point a camera at a lamp much more easily than I could record a week's worth of waveforms on my 'scope.Quote from: BravoV on October 30, 2019, 11:46:53 amie. A light bulb would flicker if it's connected to a nearby socket.

author: Fungus
author_rank: Super Contributor
timestamp: October 30, 2019, 12:20:25 pm
content: Quote from: tautech on October 30, 2019, 08:43:21 amI never said it can't be done, I even said how I'd do it a couple of posts up, ie. remove ground clips from probes (to avoid temptation), use probes.The issue at stake is floating oscilloscopes so you can attach them to mains wires without blowing your mains fuses (as ifthatshould be the thing that's worrying everybody).

author: Fungus
author_rank: Super Contributor
timestamp: October 30, 2019, 12:46:11 pm
content: Quote from: tautech on October 30, 2019, 08:43:21 amNo argument there.I'd insist on using afixed10x or 100x probe for this, if possible.(...and I'm not sure why manufacturers of multi-channel 'scopes don't supply a mixture of fixed/switchable ones as standard, it seems a much better idea to me)

author: maginnovision
author_rank: Super Contributor
timestamp: October 30, 2019, 03:37:50 pm
content: Quote from: tggzzz on October 30, 2019, 10:17:50 amThere aren't a lot of dangers when you're using a safe scope, or safe probing. I personally used a custom mains cable and an isolated(signal to ground isolation as well as channel to channel and battery powered) scope. None of my meters were able to catch the occasional dips. The one room they caught anything was the one power was being lost entirely causing the UPS's to kick in. I could have used a transformer but that's potentially more hairy than a properly designed scope or diff probe which are both easier to manage if you're thinking of people who may not be as aware of dangers.

author: tggzzz
author_rank: Super Contributor
timestamp: October 30, 2019, 03:50:24 pm
content: Quote from: maginnovision on October 30, 2019, 03:37:50 pmIndeed, but that won't be the case with OPs that are asking questions like in this thread!QuoteThat might not be OKifthere is exposed metal anywhere and the probe's shield is connected "unfortunately".QuoteIndeed, but people like the OP are highly unlikely to have that equipment.In the absence of that equipment, a 240/12V transformer (not auto-transformer!) is probably most difficult (not impossible) for newbies to use dangerously.

author: StillTrying
author_rank: Super Contributor
timestamp: October 30, 2019, 04:25:53 pm
content: I don't get this fascination withthe mains, but still, since I found how linear a LED to photo diode can be, I've wanted to get around to making anisolated mains waveform shape viewer.https://www.eevblog.com/forum/beginners/floating-probe!-for-$2-50/msg1849505/#msg1849505I've scribbled a few attempts to convert the pk-pk mains voltage into the 6mA to 12mA through a LED. If you don't mind the pk-pk isolated output being only around ~50mV to ~150mV, the isolated receiver could be just a photo diode and resistor. It wouldn't be much use for an accurate pk-pk voltage measurement or fast spikes but there's more than enough BW to see the shape of a 50Hz.

author: maginnovision
author_rank: Super Contributor
timestamp: October 30, 2019, 05:57:10 pm
content: Quote from: tggzzz on October 30, 2019, 03:50:24 pmIt will be if they have a diff probe which can easily be used to safely probe things like mains.QuoteThat's true but if your isolated scope was designed in such a way that you could be exposed to the voltages at the probe... I don't know what to tell you. My fluke and my keysight have nothing exposed, even the BNC for the probes are plastic, the probes are all plastic.QuoteI think I misunderstood this part, you were thinking something like a plug in transformer and I was thinking a loose transformer. In this case you're right it'd be difficult to misuse. A diff probe however is almost(but not quite) as easy and also provides you a useful tool in that it has many other uses. You can check a power supply and anything else it powers in any way you'd like without shorting it.Quote from: Fungus on October 30, 2019, 12:14:38 pmMaybe? I only have LED bulbs. They aren't gonna notice much other than a near power outage. In this case I'd be saving an old bulb as some sort of special tool and I'd rather have a diff probe. There is also the issue of trust with the utilities. I doubt I could even get someone to come out for a dimming bulb assuming my camera would catch it to send them a video. I'd also need a lot of video of that since to get them to pay for failures you really do need to prove it's been going on for some time.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 31, 2019, 01:59:43 am
content: Quote from: Fungus on October 30, 2019, 07:51:00 amIndeed, but you probably just generated another twenty or so postings about how inadequate this method is, & how you can only do any testing with a differential probe ---- yada, yada, yada.Back in the day, when differential probes cost as much as a small car, if I asked the Boss for such a device, he would have reacted in the mode so succinctly described in the modern abbreviation "ROFLMAO", & I would have been sent off "with a flea in my ear" to find a workaround.Now that they have become relatively cheap, differential probes have been elevated to something of a cult status,

author: tggzzz
author_rank: Super Contributor
timestamp: October 31, 2019, 09:26:16 am
content: Quote from: maginnovision on October 30, 2019, 05:57:10 pm... and if everybody had good eyesight there would be no need for spectacles!QuoteLucky you. Unlucky OP.QuoteEven a naked 240V/12V transformer would be more difficult to misuse, since most people have an intuition that 240V=dangerous and 12V=safe. They ought to instinctively put the probes on the 12V side; if not then the species has been improved.

author: maginnovision
author_rank: Super Contributor
timestamp: October 31, 2019, 03:12:38 pm
content: Well with a loose transformer the main thing I think of is someone accidentally touching the wrong leads not actually probing them. It's the same reason floating a scope isn't the recommendation most of the time, accidents happen. Purely hypothetical though because I doubt such a person would have one lying around. A plug in step down transformer can be had for things like powered PC speakers though.

author: tggzzz
author_rank: Super Contributor
timestamp: October 31, 2019, 04:15:53 pm
content: Quote from: maginnovision on October 31, 2019, 03:12:38 pmAgreed.That was behind the "(not impossible)" in my statement "In the absence of that equipment, a 240/12V transformer (not auto-transformer!) is probably most difficult (not impossible) for newbies to use dangerously."Mind you, 240V/12V transformers are nowhere near as common as they used to be!