El-cheapo 5V "LED" PSU - Yay or nay - Page 1
Forum section: electronics / projects

author: Moondeck
author_rank: Regular Contributor
timestamp: March 05, 2018, 03:29:23 pm
content: Hi everyone!Just got some el-cheapo (1$ a piece) 5V 2A modules from China, can anyone tell me if they are safe for 24h use, and won't burn down my house and kill my family when plugged in? Anything i can measure with a basic multimeter to check if its safe?I should probably send one Dave's way, i bet he knows more about these thingsPictures here:https://imgur.com/a/EupDW

author: Audioguru
author_rank: Super Contributor
timestamp: March 05, 2018, 03:59:11 pm
content: It is probably not certified to be safe so it will probably burn your house down. Cheap (cheep?) means very poor quality and many short cuts taken.

author: JanJansen
author_rank: Frequent Contributor
timestamp: March 05, 2018, 04:06:33 pm
content: It has a china export logo, then its good ?

author: Moondeck
author_rank: Regular Contributor
timestamp: March 05, 2018, 04:16:22 pm
content: Yeah, CE is there, so itmustbe safe, right?Really though, i am not going to do anything heavy with it. Just want to power a ESP8266 module with it, that's gonna sit on my wall.

author: Moondeck
author_rank: Regular Contributor
timestamp: March 05, 2018, 05:48:51 pm
content: Also, makes me wonder: How is the construction of that PSU worse than a plug-pack you get with your router/AP/whatever? I imagine manufacturers get them for a similar price, and the manufacturer isnt always the top company.Sorry if this is obvious or just a stupid question, but i would like to know *what* exactly makes it bad? Maybe there is some mods that could be done to make it not-deadly? Does a cheaply-made PSU mean a unusable (absolutely unsafe) PSU?Hope this is not too many questions

author: Peeps
author_rank: Contributor
timestamp: March 05, 2018, 06:34:25 pm
content: That thing was only $1? It honestly doesn't look that bad gum the pics.

author: Moondeck
author_rank: Regular Contributor
timestamp: March 05, 2018, 06:48:15 pm
content: Yeahhttps://www.ebay.com/itm/AC-110V-220V-TO-DC-5V-12V-24V-Switch-Power-Supply-Driver-Adapter-LED-Strip-Light/152134115704That was my thought as well, it "even" has proper spacing between the 2 transformer sides, a full bridge rectifier AND a fuse.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: March 05, 2018, 09:01:59 pm
content: The ones from ikea are not too expensive, pretty good, well made and can give up to 3.4 amps.

author: Moondeck
author_rank: Regular Contributor
timestamp: March 05, 2018, 09:22:51 pm
content: Quote from: GeorgeOfTheJungle on March 05, 2018, 09:01:59 pmYes, and i have 3 of them. Not terribly good for wiring though, and they aren't $1.35 a piece. I was asking about one specific module, not "What PSU should i get"

author: strawberry
author_rank: Super Contributor
timestamp: March 06, 2018, 12:28:55 am
content: When buying cheap chinesecheck weak solder joints to prevent cracks and arching and firesometimes they forget to trim component leads to prevent shot circuitspower supply may give HF noise and ripple and startup overshoot. essential for sensitive load and sensors

author: Terry01
author_rank: Frequent Contributor
timestamp: March 06, 2018, 12:42:24 am
content: If you have a few test one or two to destruction and see how easily or not they pop. Run it hard and see if it folds up on you before it should or doesn't even get warm. Should be a good indicator ? ? ?I'm still learning though, that's just what I would do.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 06, 2018, 12:58:06 am
content: Absolutely not!Those caps are crap, and that transformer probably is too! Probably only one piece of tape for isolation! (it's clearly not double insulated)Watch some of Bigclivedotcom's videos on these things. The transformers are nasty!

author: JanJansen
author_rank: Frequent Contributor
timestamp: March 06, 2018, 03:29:48 pm
content: Verry funny, for 1 dollar, that should cost 20 dollar normally.On the other hand i was also looking to a cheap solution to make a RGB led cube,let me know if your house burns down.

author: Stray Electron
author_rank: Super Contributor
timestamp: March 06, 2018, 03:38:20 pm
content: Quote from: JanJansen on March 05, 2018, 04:06:33 pmROFL! Does that answer your question?

author: ArdWar
author_rank: Frequent Contributor
timestamp: March 06, 2018, 05:35:32 pm
content: Quote from: Moondeck on March 05, 2018, 03:29:23 pmThey indeed looks like have decent clearance between HV and LV section (dunno with the trafo though), but the clearance between mains input is... uhh, could be better I guess.Sometimes I wonder why they lay out the circuit that way.Also, as general rule I usually don't leave untrusted, uncertified mains stuffs running unattended.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 06, 2018, 10:32:25 pm
content: Quote from: ArdWar on March 06, 2018, 05:35:32 pmPure deception. There's absolutely no isolation. Just one piece of tape inside the transformer, if the wires aren't touching somewhere in there anyway, then it would just be enamel.Seems they bothered with a Y capacitor, or is that fake too?

author: ovnr
author_rank: Frequent Contributor
timestamp: March 06, 2018, 10:45:25 pm
content: My general rule for mains stuff is that itmustbe from a reputable manufacturer (and pass a quick "is this fake or not" inspection), unless it's only used briefly under supervision - for instance, a plugpack for a battery charger; you'd be watching itanyway.Pay a bit more for quality products, just to be safe. Just like you pay for your home insurance - just to be safe.

author: Terry01
author_rank: Frequent Contributor
timestamp: March 06, 2018, 11:00:07 pm
content: Buy one of those plugs that trips if anything goes wrong with the appliance! Like a double safety feature. They're only a few quid on Ebay or whatever. Be peace of mind for you.

author: Audioguru
author_rank: Super Contributor
timestamp: March 07, 2018, 12:20:19 am
content: Cheap Unsafe Chinese Junk?My electrical utility company gave away Chinese compact fluorescent light bulbs for free to encourage people to replace their power wasting incandescent light bulbs. Some of the free ones dripped flaming plastic so they were all recalled and replaced. They discovered that the manufacturer stole the certification label number from a competitor so their product was never tested to be safe and was unsafe.

author: Terry01
author_rank: Frequent Contributor
timestamp: March 07, 2018, 12:27:47 am
content: Quote from: Audioguru on March 07, 2018, 12:20:19 amThe El-cheapo 5V "LED" PSU or the safety plug

author: Bud
author_rank: Super Contributor
timestamp: March 07, 2018, 12:43:22 am
content: @OP you should derate the specified current by half for more or less safe operation. Do not run at full load, chances are it will smoke or worse.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 07, 2018, 12:45:41 am
content: Quote from: Terry01 on March 07, 2018, 12:27:47 amDefine "safety plug". Is this going to magically stop isolation failure? If you mean a GFI, it would only trip if it contacted ground.

author: Terry01
author_rank: Frequent Contributor
timestamp: March 07, 2018, 12:57:18 am
content: I dunno....the 1 that cuts the power if the appliance fails...before it catches fire or whatever?

author: ovnr
author_rank: Frequent Contributor
timestamp: March 07, 2018, 01:19:25 am
content: Quote from: Terry01 on March 07, 2018, 12:57:18 amIt's called a fuse. And in many cases, your appliance will be merrily on fire without blowing any fuses.There's no real way to tell if an arbitrary load is faulty or not apart from exceeding a specific current - often too high to be useful - or leakage to ground. If you had a purpose-designed supervisor unit for your specific load, sure, but that's another topic entirely.

author: ez24
author_rank: Super Contributor
timestamp: March 07, 2018, 01:19:50 am
content: Nay

author: floobydust
author_rank: Super Contributor
timestamp: March 07, 2018, 01:28:43 am
content: I suggest a Koppla USB charger from Ikea 5V 3.4Aand it looks like a very good design, polymer caps, good heatsinking, good clearances, transformer construction etc.But more than $2.OP's power supply, at least it has a fuse. But cheapest electrolytic capacitors so it's not going to last. Missing CM choke and inrush PTC, flux everywhere, crappy transformer quality yeesh.

author: Moondeck
author_rank: Regular Contributor
timestamp: March 07, 2018, 07:15:12 am
content: Alright, thanks guys. I am not going to use it then, and go for a different solution (perhaps a 12V plug-pack with a regulator). I would still like to see some testing of this though, just to see. Any ideas of what i can do at home? I've checked for shorts in the transformer with a multimeter, but i guess that's not enough for isolation.

author: Moondeck
author_rank: Regular Contributor
timestamp: March 07, 2018, 08:00:27 am
content: Quote from: blueskull on March 07, 2018, 07:54:32 amThat's some expensive equipmentNot quite something i would have at hand. Maybe it's a stupid question, but would it be possible to use a electrostatic spark generation device to test if there's arcing anywhere?I guess i just won't plug it in, and go for a different solution.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 08, 2018, 02:50:59 am
content: Quote from: blueskull on March 07, 2018, 08:05:42 amThis POS is probably so bad that even an isolation tester would cause it to have a Bob Ross level of a "happy little accident" making burn art on your table.

author: Shock
author_rank: Super Contributor
timestamp: March 08, 2018, 11:32:08 am
content: I order my new and replacement power supplies from a wholesaler that supplies to quality brand manufacturers (as a local replacement) under it's own brand. They have been using the same manufacturer for many years and are locally certified.I suggest going for something like that or find a reputable brand and purchase through a legitimate re-seller. Over the years I've had several smps fail but none of the new or replacement ones I ordered.Lately I've seen some really crap supplies on cheap electronics in the country, places like dollar stores and mobile phone kiosks are the worst offenders. I still wish every power supply came with screwed enclosure, would make them easier to evaluate and keep the good ones running indefinitely.

author: Moondeck
author_rank: Regular Contributor
timestamp: March 08, 2018, 01:29:45 pm
content: Thanks for advice everyone, i know much more about PSUs now. What about a module like this one? Will THAT burn my house down too?https://www.ebay.com/itm/HLK-PM01-AC-DC-220V-230V-to-5V-Converter-Adapter-Mini-Power-Supply-Module/272811461072

author: Shock
author_rank: Super Contributor
timestamp: March 08, 2018, 02:44:41 pm
content: At least they have a website, looks like you can buy direct from them as well. I'm not sure if they are the original manufacturers of their products.This is a part of buying shit over the web you have to learn to do the research yourself. When you buy from the major (component) distributors in the EU they should have already jumped through the regulatory hoops for you. Buy from China or Ebay and anything goes it's like the wild west, for all we know the Ebay seller is making lookalike HLK Tech products.http://www.hlktech.net/product.php?CateId=10

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 08, 2018, 06:52:12 pm
content: Quote from: blueskull on March 08, 2018, 06:53:48 amI wasn't talking about the tracks, they aren't a problem with this one. I meant the transformer where the primary and secondary could be touching and only insulated by enamel. Bigclive has found this happening from ripped tape or poor winding and turns touching the output leads.