How do I buy quality external power supplies ("Adapter"/"Wall wart") from China? - Page 1
Forum section: electronics / general

author: John_doe
author_rank: Regular Contributor
timestamp: February 20, 2022, 10:41:02 am
content: First, kindly look at the little flag next to where it says "Country" on the left. That tiny image means that I am not as privileged as someone living in some other parts of the world. Here, when you buy locally, you usually get the same cheap crap from China, only it costs about 10 times as much.I'm also asking in general but more so for a specific case: Currently I'm advising some guy on a forum about something related to electronics. He does not have any electricity or electronics knowledge or skills. He needs a low power 10V adapter. 300mW will be more than apt.AliExpress (and probably eBay too) is full of options, like this one for $2.49 USD:https://www.aliexpress.com/item/32961533195.htmlBut as someone who has had a lot of experience with these kind of adapters, I don't trust them at all. I really don't want the guy to burn down his house because of my advice.But where can I find something safe (and preferably accurate + not too noisy) in a sane price range?If I'm any judge of a good circuit (as much as you can from a photo), then this module for $2.3 is actually kind of nice (and the reviews also support my opinion):https://www.aliexpress.com/item/4000391310693.htmlBut the aforementioned man can't solder wires, nor would I want him anywhere near the "business end" of 230VAC.Right now my best option is to advise him to buy this somewhat external 12V module and hope the adjustment pot can take it down to 10V:https://www.aliexpress.com/item/1005003135918220.htmlBut I really don't like this option. For a whole slew of reasons.So... Any advice?

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 20, 2022, 12:43:57 pm
content: Quote from: John_doe on February 20, 2022, 10:41:02 amGet two cheap but good quality 5V phone chargers and make a cable to connect them in series. Show him this video explaining how to solder, an electronics hobbyist who doesn't know how to solder is not going to get very far beyond plugging together Arduino stuff.

author: John_doe
author_rank: Regular Contributor
timestamp: February 20, 2022, 01:51:51 pm
content: Not sure if you were joking or not, but I didn't mean that kind of electronics, more like consumer electronics, you know - plug sockets to jacks and such.Also aside from my current case, I'd really like to know the answer for other times I had different situations which required a good quality adapter.

author: mariush
author_rank: Super Contributor
timestamp: February 20, 2022, 02:10:42 pm
content: 10v 0.3W is very low amount. That's basically less than 50mAFor such a low power requirement there are PCB mountable transformersYou could advise him to get a 9v AC transformer, rectify it using a bridge rectifier and a capacitor to around 12v then use a generic linear regulator like LM317 to get exactly 10v.As an example, let's take this 9v 111mA (1w) transformer that costs 2$ :https://www.tme.com/il/en/details/bv302s09010/pcb-transformers/zettler/So you add a bridge rectifier or 4 diodes to rectify the 9v ac to DC, add a capacitor (if we aim for max 50mA and minimum 11v we're looking at C = Current / 2 x ac frequency x (peak dc voltage - minimum dc voltage) = 0.05 / ( 2 x 50 x (11.5v- 11v) = 0.05/50 = 0.001 Farads or 1000uF so let's go with a 1500-2200uF capacitor) then use a lm317 or some other linear regulator to get 10v.He could power it using a 12v wall wart and put a linear regulator on the board to regulate 12v down to 10v ... at 30mA or whatever, no need to worry about heatsink-ing any regulator.You can buy some wall wart power supplies for 3$ .. 3.5$ if you want them with barrel jack connector :https://www.tme.eu/en/details/zsi12_0.3-p/plug-in-power-supplies/espe/... and they have certifications and more likely to be better built than aliexpress / ebay power supplies.Alternatively, use a generic 5v phone charger and a boost (step-up) regulator to obtain 10v ... step-up boards are like 1-2$ on eBay (using super common chips that boost 3v or more to whatever voltage you set)

author: Karel
author_rank: Super Contributor
timestamp: February 20, 2022, 02:38:49 pm
content: Quote from: John_doe on February 20, 2022, 10:41:02 amFirst, kindly look at the little flag next to where it says "Track Orders" on the top right:https://il.farnell.com/https://www.digikey.co.il/en

author: John_doe
author_rank: Regular Contributor
timestamp: February 20, 2022, 03:38:09 pm
content: Thank you, mariush, but again, all the options of modifying things are out of the question, this guy is not a tinkerer.Also, the cost of shipping from the tme.eu website you linked is at least $24:https://www.tme.com/il/en/how-to-buy/7152/means-and-cost-of-transport/(probably more, but I'll have to register to find out).Your suggestion about the boost converter IS valid and is one that I did consider before, but there are also problems with this option. For example, I understand they are very noisy, however the biggest problem I had is that I thought all of the adjustable options were modules. But just as I wanted to confirm this now, I actually found an enclosed product that I didn't know existed:https://www.aliexpress.com/item/1005001297801262.htmlIf no one will know about good quality adapters from AliExpress / eBay then I will consider this a solution to my question. Thanks again.Just to be clear though, I would still love to get a recommended brand or store that is known to have good and safe adapters, preferably not as high priced and more output voltage than the well known MEAN WELL:https://www.aliexpress.com/item/1005002043298526.html

author: John_doe
author_rank: Regular Contributor
timestamp: February 20, 2022, 03:40:06 pm
content: Karel, the idea is not to find websites that ship to my country - of those there are a plethora. The idea is to find sites that do so with sane prices.

author: BeBuLamar
author_rank: Super Contributor
timestamp: February 20, 2022, 03:51:18 pm
content: How much is sane price? I would think $20 is still a sane price.

author: Karel
author_rank: Super Contributor
timestamp: February 20, 2022, 03:56:44 pm
content: Quote from: John_doe on February 20, 2022, 03:40:06 pmI guess that's because of transport costs combined with the fact that it's a small and isolated country.For example, Europe has a couple of small countries but (thanks to EU regulations) distributors can use the samewarehouse and distribution channel for all EU members.Unfortunately this is not the case for Israël.I hope you'll find an acceptable alternative or workaround.

author: janoc
author_rank: Super Contributor
timestamp: February 20, 2022, 04:09:24 pm
content: Quote from: BeBuLamar on February 20, 2022, 03:51:18 pm$20 (or rather 20€) is pretty much the standard shipping price even within EU if you order from Farnell or Mouser for less than some minimal value (50€-ish).So, OP, you are certainly not in what I would call a "small" and/or "isolated" country! Those are normal prices.And when it comes to ordering mains stuff from China - $20 shipping for a good, certified wall wart is too expensive but I wonder whether replacing whatever a crappy, poorly designed adapter from AliExpress has blown up will be cheaper? And that's still the good case, there have been plenty of fires and even electrocutions documented because of crappy wall warts.Especially so when the person in question has no clue how to spot dangerous equipment? Hint, you can't do it from pictures on a web site, so your question doesn't have an answer - there is no way to buy "quality power supplies from China" unless you are a business and/or do a lot of research and get into long term business relationship with a trusted supplier, including inspecting the goods. I.e. pretty much out of the question for buying a one-off part.When it comes to anything mains powered from places like AliExpress or Banggood, the first thing to do is to always take it apart and inspect. And fix whatever needs fixing - missing earth connection, poor insulation, lack of fuses ... Often even tossing the power supply out and replacing it with a known good one. If you can't or are not willing to do that, you are playing Russian roulette with your equipment, safety of your house and anyone living in it and really should buy a power supply from a distributor who has to sell only certified and tested equipment. Even if it costs more.BigClive has a good video on what could happen today:

author: SmallCog
author_rank: Frequent Contributor
timestamp: February 21, 2022, 02:18:26 am
content: Basic options:1) Buy from online marketplaces such as ebay/ali/bangood/wish etc. and roll the dice that you'll get what you ordered and it will be safe2) Buy the above with the skills/experience/knowledge to open the device, assess its safety, and either make the appropriate alterations or dispose of it and try again.3) Buy from a reputable retailer that does the quality checks for you, and pay a premium.There's no magic trick to buying option 1 and getting option 3. Even if you think you've received an option 3 device for $2 posted from China it may well be a counterfeit (look at all the counterfeit apple charges available) or from a batch that have failed some sort of quality inspection.My go-to suggestion for anything low power DC is to make it suitable for USB. In the case of your friends device they could incorporate a small boost module in their design and fit a micro-USB socket on their device and use it with a quality brand name adapter - either bought new or surplus from an old phone or something.

author: Karel
author_rank: Super Contributor
timestamp: February 21, 2022, 07:20:49 am
content: Quote from: SmallCog on February 21, 2022, 02:18:26 amYou can't draw more than 100 mA from USB except when you include some intelligence and even then it's not guaranteedyou can draw up to the max. 500 mA.

author: John_doe
author_rank: Regular Contributor
timestamp: February 21, 2022, 10:38:32 am
content: Quote from: BeBuLamar on February 20, 2022, 03:51:18 pmWell, I guess that for an adapter of, lets say, 30W, $20 including shipping sounds like a fair price. Not agreatprice, just a fair one. But even that price I was unable to find.Quote from: Karel on February 20, 2022, 03:56:44 pmThank you.Quote from: janoc on February 20, 2022, 04:09:24 pmI wasn't suggesting as much. My gripe is the lack of trustworthy local sources.But since you mentioned it, IMHO if Farnell or Mouser ship within Europe for $20 then they are the exception. I have seen websites that send their goods for cheaper. Also, I tried it now, and the lowest possible shipping quote was $28:Quote from: janoc on February 20, 2022, 04:09:24 pmI agree with almost everything you said, but I thought I'd try and ask. Maybe someone knows better. Also, specifically in my current situation, the problem was not so much as finding a cheap adapter, but finding ANY adapter with the non standard value of 10V.The one issue I disagree on, is USB power supplies (colloquially called "USB Chargers") - TheseCANbe bought from China for dirt cheap and still be of reasonable quality. There are people who review such chargers regularly, such as Henrik K. Jensen (lygte-info.dk). And the companies behind brands like Anker, Blitzwolf, Ugreen and Baseus do not change model internals, so if one model is proven to be safe, you can buy it with no worries.Oh, and as for Mr. Mitchell, I watch his videos in order and right now I'm about two weeks behind, so I'll watch this video when I get to it. No spoilers!!Quote from: SmallCog on February 21, 2022, 02:18:26 amYes, I have decided to do something of this sort. Thank you.Quote from: Karel on February 21, 2022, 07:20:49 amThat's not true for USB "Chargers" with USB-A ports. Actually, I'm not even sure it's true for computers anymore. I have brand name 100% genuine chargers and I don't even have to short D+ to D- (as per BC v1.2) to get 2 amps from them.

author: wraper
author_rank: Unknown
timestamp: February 21, 2022, 10:46:57 am
content: Quote from: SmallCog on February 21, 2022, 02:18:26 amUnfortunately that is not enough. A lot of them may look OK on a first glance, however transformer may easily lack any serious insulation or QC even if construction is somewhat decent. Only Hi-pot test will show if its electrically safe or not.

author: Karel
author_rank: Super Contributor
timestamp: February 21, 2022, 10:47:52 am
content: Quote from: John_doe on February 21, 2022, 10:38:32 amYou are right, I forgot we were talking about (wall)chargers. But for pc's I believe it's still true.

author: BeBuLamar
author_rank: Super Contributor
timestamp: February 21, 2022, 12:40:30 pm
content: Quote from: John_doe on February 21, 2022, 10:38:32 am300mW or 30W. 30W is a relatively big walwart.

author: tunk
author_rank: Super Contributor
timestamp: February 21, 2022, 02:01:56 pm
content: What will it be used for?If it will replace an old type PSU (transformer+rectifier+capacitor) usedto charge a battery, then an SMPS will not work (it may sort of work witha suitable resistor in series). Some equipment may work with slightlylower or higher voltages, so it may work with a 9V adapter.

author: rdl
author_rank: Super Contributor
timestamp: February 21, 2022, 03:01:38 pm
content: Quote from: tunk on February 21, 2022, 02:01:56 pmThis is a good point. What is this adapter going to be used with? For example, here in the US they love to use 9 or 12 volt adapters with things like routers, cable modems, external disk drives, etc. Then, first thing that happens inside the device is the voltage is regulated down to 5 volts or less.

author: tooki
author_rank: Super Contributor
timestamp: February 24, 2022, 06:18:13 am
content: Quote from: rdl on February 21, 2022, 03:01:38 pmThat’s not a US thing, that’s how it works worldwide. The whole reason for that arrangement is for the device itself to not require local safety certifications for each country, instead relying on an external power supply to handle that. Saves money.

author: Zero999
author_rank: Super Contributor
timestamp: February 24, 2022, 09:01:34 am
content: Quote from: wraper on February 21, 2022, 10:46:57 amI wouldn't even trust a hi-pot test for a dodgy, unknown transformer. It might pass, but that doesn't mean anything. If they used crappy insulation and too thin wire, it might get hot, melt and arc over during normal operation. The only way is to take a few to pieces, look at how it's constructed an the quality of the materials used.

author: nctnico
author_rank: Super Contributor
timestamp: February 24, 2022, 11:50:46 am
content: Quote from: John_doe on February 20, 2022, 10:41:02 amThis is probably the best option. Meanwell is a well known brand and they have datasheets for their products which show the adjustment range. 10V or 10.5V won't matter much anyway so likely this Meanwell PSU will do just fine (assuming it actually is an original PSU and not a fake one).

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: February 24, 2022, 12:41:40 pm
content: If I need a wallwort, I go to the Salvation Army Store. I then look for a heavy old one with the correct volts and proper connector pin out. (pos or neg center ??)I have never been to Israel. Perhaps you have some second hand or "charitable" stores like "Salvation Army"CB or other electronic repair stores have all sorts of 'junk' lying around, Perhaps there is one near you.The heavy wallworts or in line PS usually have an AC transformer rather than SMPS design. The device powered usually breaks rather than the PS, so there are lots lying around.RadioShack used to have a small "universal" PS that had a switch for different volts and connectors for different size and polarity devices. It is a good PS.It is extremely unfortunate the new devices are frequently of poor design and function.from China,Even if someone bought a particularly nice one there is no guarantee you will receive the same quality, or even the same device.I am in US so our AC voltages are different, of course.

author: BeBuLamar
author_rank: Super Contributor
timestamp: February 24, 2022, 02:58:52 pm
content: Actually I would want to know what kind of device he uses the walwart for. If it's something valuable it's worth the money to buy a good power supply.

author: wraper
author_rank: Unknown
timestamp: February 24, 2022, 09:43:55 pm
content: Quote from: Zero999 on February 24, 2022, 09:01:34 amI didn't call the Hi-pot test a panacea, I said that teardown by itself is not enough. Teardown without a high pot test will make apparent only the most obvious offences.

author: ve7xen
author_rank: Super Contributor
timestamp: February 25, 2022, 10:28:13 am
content: Quote from: nctnico on February 24, 2022, 11:50:46 amIt'd be a fine option from a controlled supply-chain seller, sure. On Ali I would say the chance of getting a counterfeit MeanWell product approximates 100%. It's been a popular brand for counterfeiters for ages. Stuff like this I just accept that I will need to either scavenge it from discarded consumer products or purchase it from a proper distributor, there doesn't seem to be a reasonable middle ground.I really wish you could trust trustworthy brands on Ali or eBay, but you just can't. I've even got counterfeits of some industrial stuff I wouldn't have thought has a large enough grey market volume to bother with, like specific SKUs of Omron temperature controllers and uncommon-brand SSRs. Felt a bit safe in that assumption that the effort involved in cloning the front panels, making fake packaging and documentation and sometimes plastics wouldn't be worth it to make a few pennies profit per unit, but nope, still counterfeit.There are trustworthy Chinese distributors and manufacturers too of course, but I don't think as a random English-speaking consumer we really have reliable access to them, and they probably aren't interested in selling single units. Maybe something LCSC will stock in the future...Edit: I should add that AliExpress does attempt to provide some assurance of the company's information if you go to the store Business Information link, though I'm not sure they verify it, but it can sometimes tell you if you're dealing with a fake. For the example store, 'established 2019-04-12' doesn't really jive with someone representing themselves as connected to MeanWell, and the translation of the business scope suggests the company is supposed to be trading baby supplies. Nor does the name include '明緯/明纬' (MeanWell). So rather a few red flags.If you look at the same page for Rigol's official store, for example, the information does all line up with what you'd expect.