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Forum Index : Microcontroller and PC projects : Plug-pack design from China...
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9066 |
Found another one.    0.5mm between the Phase and Neutral on the PCB, 0.25mm between the rectified AC at about 325v DC, and another part of the circuit - lovely.  These were sent to me as part of a product I bought from China, that used USB to charge the battery, so these are little 5v USB charger adaptor things, but I thought I would look inside to see what it was like. This kind of design is not exactly unheard of, unfortunately.  They have used an opto for feedback, and there are some anti-creepage slots around there, but nothing at all around the incoming mains and in the area of the rectified DC once past the full-wave bridge. I would certainly not design the mains side of things to allow the phase and neutral to be THIS close to each other, to say nothing at all of the 300v potential on the other side of the bridge with it's 0.25mm clearance - yuk! I have binned all of these. You can charge up the thing on USB power anyway, so you don't really NEED the plug-pack charger, if you have a spare USB port. Smoke makes things work. When the smoke gets out, it stops! |
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GoodToGo! Senior Member  Joined: 23/04/2017 Location: AustraliaPosts: 188 |
Look on the bright side, it would be impressive to watch (from a distance) when the ergatrons finally jumped the gap......  ...... Don't worry mate, it'll be GoodToGo! |
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| robert.rozee Guru  Joined: 31/12/2012 Location: New ZealandPosts: 2291 |
an easy 'fix' would be to lift the ends of the two diodes and 1r resistor and join them together (with a thin piece of fuse wire) floating in the air. that would remove the most serious failings. with zero cost, the original designer could have corrected the clearance issues, and implemented a fuse with a fine PCB trace. cheers, rob :-) |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Ive had a real run of bad usb plugpack chargers, altho some of that might be explained by using them on my modified square wave inverter when camping(altho the one in the bedroom is 240v mains and has never been unplugged from its powerpoint and still failed in under a year) Now have several twin outlet gpo's with twin inbuilt usb charging ports in them scattered around the house (kitchen bench, 2 in lounge room, 1 in garage), so far so good plus I now have both outlets available again instead of having them tied up with a charger or two Havent bothered to pull most apart, but the first one had a cap burst and an unidentifiable IC literally blown off its legs... |
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| WhiteWizzard Guru Joined: 05/04/2013 Location: United KingdomPosts: 2794 |
When will you ever learn . . . . I take it that this is to completely power your replacement system that got taken out by your recent lightning strike?  P.S. So how much did you pay for this craftsmanship? $3 for 25 units maybe For everything Micromite visit micromite.org Direct Email: whitewizzard@micromite.o |
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palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1805 |
I bought a phone charger and not too long after my wife unplugged it and it left the two pins in the power point, the rest of it just came away. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
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| greybeard Senior Member Joined: 04/01/2010 Location: AustraliaPosts: 158 |
I'd be behaving myself if she was my missus. Sounds like she'd give you a fair wallop if you were naughty.  |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Here are some pics of the powerlead from my laptop   Another one to watch out for (I'll see if I can find the pics, not sure which computer they are on) was of a 10A marked computer IEC powercord (my old work literally had hundreds thrown in boxes out the back) which we used to replace a damaged kettle power cord- it lasted a couple of days before tripping out the main shed breaker On inspection, it had a hole about 5mm long literally blown in the side of the cable about halfway along Closer inspection showed why, despite being marked at both ends as 10A, on cutting it open and comparing against a `proper' 10A cord, it was visibly thinner on the outside, and the inner conductors on the dodgy cord were the same size for the copper and insulation combined as just the copper alone on the proper 10A cord Plugged into a 2400w fast boil kettle it was bound to fail, the copper area was tiny And the only exterior visible sign was it was a bit thinner than the real 10A cord, the extra insulation disguised mostly the fact that the wires inside were tiny, and of course it had moulded plugs both end so you couldnt see it- even the colours were incorrect (for some reason the image insert button isnt working on my firefox- edit doh was using image upload instead of image link...) |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Found the pics of dodgy IEC power cords Note both ends were marked as 10A  Cable markings  note size and incorrect colours  Hole in cable after it fused   |
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| GoodToGo! Senior Member Joined: 23/04/2017 Location: AustraliaPosts: 188 |
I've got to admit, I always find the analysis of what went wrong after an event interesting. More so in the interest of what learnings can be taken out of it, or in the case of electronics, mechanical items, etc, what modifications/improvements can be made to prevent future issues. Must be the jet engineer in me....... In the case of Boppa's laptop power supply, the pin breaking away is interesting. Overheating? Poor moulding? Either way, shouldn't happen. And the cord, I wonder if they forgot the decimal point in the middle of '10'? Cheers, GTG! ...... Don't worry mate, it'll be GoodToGo! |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Scary stuff indeed If you look closely at the remaining pin, you can see that it steps up in diameter as it enters the plastic, I suspect was the shape below and snapped at the step down that was supposed to be held by the plastic molding in the case  Whats really bad was that pin was in the active wire (altho that was purely chance as the plug is reversible) and if I hadnt noticed, could have had a live pin in my hand The cabling, thats purely criminal, intended to deceive that its adequate for the job when its woefully underspecced (presumably to save money by using a cheaper wire/ less copper |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9066 |
Hi everyone.  LOL! No, these were plug-packs supplied with pagers. The pagers themselves can charge up the battery via USB or just use a standard AA cell - or these charger things. The reason for the USB connection, is that the same socket on the pager is used to program it for the frequency and RIC code you need etc. That is pretty standard really - everything these days charges from USB power. I never even plugged these units in. I just cracked one open for a look. I would NEVER use the 230v plug-pack thing supplied from anything you buy in China. If I had to, I would replace the plug-pack with one from Jaycar, which would be certified and tested for electrical compliance you see. If I supplied that as part of a thing, and it set-fire to someone's property, my company would be in REALLY hot water, so it is pretty much my policy to never supply the factory-issue plug-packs from China if they come with one - not worth the risk. Just so everyone knows. I note also that the "Regulator" in these for the 5v side of things, is just a zener diode across the output - pretty crude. I have seen catastrophic things happen to equipment powered from a zener "Regulator" when it fails..... Zener's for a voltage reference, fine. Even for a few mA, but as for using them as a charging voltage regulator needing to supply a few hundred mA or an amp or more - nasty. Smoke makes things work. When the smoke gets out, it stops! |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I'll see if I can find it again, but even the Chinese are starting to get annoyed with the really dodgy equipment. There are chinese manufacturers that do make really good gear, and a couple of months back I saw an article where the Chinese authorities were closing down the dodgiest `manufacturers' (if they could be called that lol) because of complaints from the better quality manufacturers that the dodgy stuff was undermining confidence with their buyers I suspect that given a few more years, they will really start to lift their game- simply in order to keep selling at all We had mining gear manufactured in China, their QC was brilliant and the kit was really top notch, so they can do it, its just that the market for the shonky elcheapo stuff is more prevalent atm, plus its easier to build shonk rather than to build quality, it takes experience to build better |
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BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
Jaycar buys a lot of its gear from China. So do other stores. About 4 or 5 years back I bought a pack of 4 power boards from Bunnings. As I usually do, I pulled one apart just for a look. They were not fit for purpose. The cables had been spot welded to the socket pins but about three quarters of the conductors were not welded. That would create a hot spot if you pulled the full 10 amps. They were so cheap that the trip to the shop would have exceeded the cost of the product so I binned them. I can't recall if they had been approved but it's hard to see Bunnings sell them without approval. I suspect that the approvals process is just a quick glance and on to the next item. |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9066 |
@ Boppa - Yes, I would agree with that. MOST factories in the Shenzhen area of things seem to produce good stuff, but the scary ones seem to come from the factories setup out the back of the wop-wops somewhere.... @ BobD - Good point! I will have to crack open one of the Jaycar ones. They do have an approval number though, so one would expect that......Smoke makes things work. When the smoke gets out, it stops! |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I cant remember the exact years involved but infinity 240v tpe cables had a massive recall manufactured over several years even now they estimated that there is several thousand KILOMETERS of this stuff that had been installed and hadnt been replaced Apparently when it got too hot the insulation became brittle and literally fell off the wires at the slightest touch Scary |
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| BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
Yeah, it seems like forever since that recall was done but the date of the issue of the recall was 11 October 2013. More here and here. The crook cable was installed in 2010 thru 2013. That would be a bad job to replace all of the cable in a house. |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
I used to think that Underwriters Laboratories were a pain in the neck some of the time, but not now after hearing about this stuff. UL is owned by the fire insurance companies which are interested in not having fires. If you don't follow UL rules when building a house or installing things which could catch fire you don't get fire insurance. Furthermore, if your neighbor doesn't follow UL rules then you don't get fire insurance either. This has created a defacto private agency which is capable of superseding all laws about construction techniques and all the governments have just copied UL recommendations into the law books. UL found that 120 volts was the highest voltage which was advisable in plug in low power appliances. They specified AWG 14 wires up to 15 A and AWG 12 up to 20 A. They specified 85°C / 400V insulation. They specified conduit installation of wires which are in unprotected areas, and threaded schedule 40 pipe installation with gaskets in hazardous areas. They effectively dictate to governmental legislatures. I like them. Paul in NY |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
120v hehehe Considering most of the people in this thread have 240 (well 230VAC nowadays) as their supply voltage Anything over about 60v can be enough to kill you in the right (well wrong) circumstances |
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| robert.rozee Guru Joined: 31/12/2012 Location: New ZealandPosts: 2291 |
just 9 volts can kill under the right conditions. the problem with 120v AC is that it precludes safe implementation of many appliances. for instance, a 120v electric jug is not practical, as it would need to draw 20A to effectively boil water, and 20A mains outlets in a domestic installation are impractical. similarly, with just 120v, electric blower heaters are limited to 1.2kw (10A), which is insufficient to usefully heat a room quickly. then, of course there are clothes dryers, that need to be wired across 2 phases (240v in the case of 2-phase, 200v in the case of 3-phase) to provide acceptable drying. then there are very high load appliances such as the electric cooker that in 230v countries can draw 60A on full load. i believe that in parts of america with their 120v mains, some folks have to resort to cooking over an open fire, burning twigs and squirrels to both cook and try to keep warm. in japan (only 100v) they have to eat much of their food raw. cheers, rob :-) |
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