Re: Electricals purchased via the internet. Safety.

[sideband]

I pulled the power supply apart on Friday at work. General construction is OK and looks quite tidy. However there is not one single approved safety-critical component fitted. By safety-critical, I mean the IEC inlet, any mains filtering and capacitors, the transformer, the fuse, any capacitors across the isolation barrier and the PCB itself (should have 94-V 0 etched on it). Just on these points, it would be an automatic fail of EN60950 (power supply standard). This means there is no way of telling if any of the fitted components are actually 'up to the job'. The most critical component here is the mains transformer since this should be double-insulated and is the main source of isolation between the mains and the user.

A lot of these cheap PSUs don't have enough filtering either.

There is NO mains filtering at all so it would automatically fail EMC. If I have some time on Monday, I'd like to run it at maximum load and see if it can actually supply it's rated outputs (12V 2A and 5V 2A).

I've actually been using it with an approved mains lead and had no problems.....yet!

Rich

[Michael Watterson]

Gap between caps on fuse?

Spacing between edges of pads on the 4 diodes of Bridge Rectifier?

Live / Neutral / Earth track spacing at IEC socket looks miniscule.

The secondary / Primary PCB gap looks believable though.

[sideband]

I think the end cap spacing is OK, should be min 2.5mm for 250V BUT it should have an insulating sleeve over it.

Spacing between edges of pads on the 4 diodes of Bridge Rectifier?

.

That may be too close. I'll check these points on Monday. Good job I haven't glued the case back yet!


Rich


PS, end caps OK although only 2mm as they are not of different polarity....the 2.5mm minimum is between opposite polarities (L-N)

[sideband]

Live / Neutral / Earth track spacing at IEC socket looks miniscule.

But earth is not used so between L and N it's fine.

The secondary / Primary PCB gap looks believable though.

Yes I think that should be 5mm but you have to take into account the peak voltage across the 'barrier'. We usually measure that by using a differential probe and scope.

Rich.

[Michael Watterson]

Live / Neutral / Earth track spacing at IEC socket looks miniscule.

But earth is not used so between L and N it's fine.

Add the space of gap of tracks L to E and E to N then. Looks tiny.

[sideband]

Well I'll check the standard and the spacing on Monday if possible.


Rich.

[GlowingAnode]

Does it........MCB trip on a 20A "fused" circuit with a realistic equipment fault?

B20 marginal, C20 no, D20 definitely no.
Assuming a reasonably low EFLI at the socket, and disconnection within 0.4s, and ignoring adiabatic (thermal) constraints.
Rob.

[Michael Watterson]

Nostalgia. 1983 to 1988: The days studying CSA, VDE, UL etc when designing SMPSU for Industrial controllers and then -48V Telecom PSUs and isolated line interfaces.

Also "intrinsically" safe isolated industrial I/O boards.

Then in early 1990s the vending machine. All the electrical safety AND mechanical issues. Will it fall over and kill someone when the door is opened and the insides is emptied? Will the serving hatch cut off fingers? Will it be a source of Plague from the ice cream mix? Never mind figuring how to make Ice cream as well as serve it in "Software" so as to beat the Italian Soft Ice Cream patents.

I must write the story of the Ice Cream Machine. It did in the end make great Ice Cream and serve it beautifully, safely (in all senses), but never saw production.

We mounted a knife blade on the rotating door hatch to show how responsive the detection of a hand etc was.

[Refugee]

I have now given the cable the chop.
Internally it has blue yellow and pink insulation.
It has the feel of high temperature wire with quite a lot of strands in each conductor.
The strands are strangely springy and can't be twisted without quite a bit of difficulty.
The 3X0.6 claim is a bit fake too as can be seen in my enhanced photo on the tape measure.
The heat test took about 5 or 6 seconds with a gas lighter and it was fire retardant although not heat resistant.
It is about 1R/M so it could be stripped and used in a valve radio to replace old rubber wire as the insulation was OK and it will be OK for 100 deg C but no good for more than 0.5 amps.

[sideband]

To check the insulation quality you need to separate one of the conductors (say the blue one but it doesn't matter) for about six inches and wrap silver foil once around the outer (blue) insulation and about half an inch or so from the bared end. You then apply 1,500V (AC) at 100mA for one minute between the silver foil and inner conductor. It shouldn't flash over or break down.


Rich.

[Michael Watterson]

Well, you mean limited to 100mA! In theory there is no current or at worst microamps!

To get 100mA you'd need very high frequency or very much higher than 1500V AC if the insulation works


The "copper" (or what ever it is!) looks a lot less than 1A cable! Maybe 0.5A?

1 Ohm per meter is ghastly.

[Refugee]

I could in an extreme case get my home made high ohms range extender out and either complete it or at least fire it up as it is without the remainder of the regulator finished and shove 6000V between two conductors and the remaining conductor and see what happens
It is a long way down the to do list and will have to jump a few places.

[sideband]

Well, you mean limited to 100mA! In theory there is no current or at worst microamps!

Yes you are right....bad description on my part. Our insulation testers are automatically limited to 100mA and if the insulation cracks over, the tester cuts out with a warning buzzer.


Rich

[Michael Watterson]

PS, end caps OK although only 2mm as they are not of different polarity....the 2.5mm minimum is between opposite polarities (L-N)

If the bridge/switching transistor goes short and fuse blows it then has L & N between the caps of the fuse and between the edges of the pads of the fuse leads.

[Mike C]

Chinese stuff is ok if its battery operated but when its mains its a whole new ball game and sometimes there stuff does not meet safety standards, more so with those cheap 70s transistor radios that use a two pin shaver plug but there is a battery option on those sets and in some cases you can charge batteries with in the set if they have this feature.

When I was in Spain I visited a lot of those cheap Chinese bazar shops and some of there stuff did not look safe by our standards, there was a torch which had a mains charger with a two pin plug and I had a look at it and one of the pins fell out the plug . On the other end of the scale is in some cases with modern equipment it can be a copied fake of well known makes ie chargers that catch fire and batteries that explode. I have a few Chinese batteries in my collection and there colourful and look great but they don't last long power wise. There have been cases where fake electrical goods from china such as hair styling equipment has caused burns or fires but not all Chinese stuff is bad because a lot is made in china but to our safety standards as the labour is cheap over there.

If it sounds to good to be true it probably is but its always a case of buyer beware with some electric stuff. They are getting clever at faking stuff now. Battery stuff is ok as it wont kill you but if its mains then if it does not look right or perform well get rid of it. I would never trust mains electricals that are cheap coming from china unless it was a well known trader with a good reputation and a well known firm, sometimes saving money on such things can cost a lot more in the long run should your house burn down. I like to look at modern electricals before I buy but with vintage gear we all know the score but for modern electricals I would rather buy from a shop.

[Mike C]

Good points there, I am wondering what caused a battery to catch fire when its not on charge and the only thing I can think of is a short out as batteries can get hot when shorted out so I am thinking a manufacturing fault inside the battery when the two poles meet causing a short. Your right about it finding its way on to the legal market as I bought something from a cheap shop and it had Panasemig batteries in it, fake Panasonics that's what they were. Online you see lots of rechargeable batteries from China and there have been reports of fires caused by these.

Apple also had an issue with Lithium batteries firing up to or not lasting long on a charge. For mains electricals its a shop for me where I can see what I am buying and if faulty I can take it back, besides the safety aspect I can get an item quicker, if its something like a Tv the supermarkets sell plenty, sadly though in these cash strapped times folk will see something so cheap and buy it depending on what it is and in a lot of cases the item does not work or stops working, even cheap kids toys in some cases are a danger as parts can become loose or there badly made using small parts that break off and in some cases the paint they use to decorate them can contain lead so its not just electricals. Some Heart foundation charity shops sell electricals that have been tested. Most things such as chargers can be bought in large stores, pay that few pence extra for peace of mind I say.

[Michael Watterson]

Faulty wiring in the toy / gadget.

Retail Rechargeable packs and the new Energiser Lithium 1.5V cells can set faulty wiring on fire. Usually fully charged NiMH or new 1.5V lithium cells should vent if shorted, but that is on properly made ones.

The rechargeable Lithium especially the pouch type rather than metal cased, used in rechargeable gadgets are a serious fire risk, risk of mechanical damage causing fire.

[Mike C]

I have seen videos of those pouch type catch fire on Youtube. Most of what we buy is made in china but that does not mean its a danger because it is made to incorporate our safety standards. On the fake end of the scale then that's another matter because its made cheaply using cheap materials and worst of all not to the standard of safety that this country demands. A lot of fake electricals are badly made thus them posing a safety risk. They're cheap for that reason as they're badly made with no specification and quality checks. Sometimes the consumer does not think of this aspect when they see something cheap and they think they're getting a bargain.

[sideband]

Don't underestimate the power of even modest batteries. We've had melted mobile phones and TV remote controls (one remote had also SET FIRE to a sofa....the sofa was also Chinese and did not have fire retardant treatment). Duracel batteries have exploded because they were fitted to a chinese toy that also had a mains adaptor....the DC output of the adaptor was connected STRAIGHT ACROSS the battery. In nearly all cases, the faulty item had a CE mark.....fake of course.

At another safety lab I worked at, they had a special chamber for checking lithium button cells. If these are subject to overload or non-charge types are charged, they will explode violently. One one occasion, we had to evacuate the building because of fumes despite the extraction system.....nasty stuff!

Some interesting things to read here. You can enter the public or industrial site and have a look at the product recalls.

Rich

[Michael Watterson]

Zinc Carbon/Chloride / Alkaline are significant internal resistance it's the low internal resistance that makes the NiMH potentially dangerous to use in toys/gadgets not intended to have them.

Also shorting one coin cell is usually explosive, but shorting a stack of them certainly is and some cases "flew" over 10m!

[davegsm82]

Has Anyone noticed the Ebay adverts on their website warning against Fake/poor quality electrical goods?

Seen it a couple of times recently.

Dave.

[sideband]

I haven't noticed but it may be that Trading Standards have been on to them and fired a warning shot across their bows regarding electrical goods.


Rich.

[johntheboffin]

Another highly dodgy product is the so-called "safety cover" that is supposed to stop children fiddling with mains sockets.

Our 13 A sockets, if produced in accordance with BS1363, are the safest in the world. Yet well-known stores are selling these plastic things that are supposed to protect but instead form a tool that can easily be used to open the shutter. I saw some in Wilkinson's only yesterday.

More here, including some, er, interesting videos: http://www.fatallyflawed.org.uk/

John

[Stockden]

Not so long ago a colleague was asking around at work to see if anyone had any of those "safety covers" that they could have. Try as I might I couldn't convince them that they are a dangerous waste of money and even getting them to look at the web site made no difference. They simply couldn't accept that there could be a problem with something that was so widely available.

Hugh

[Refugee]

They are still on the shelves at Wilco.
The earth pin is the usual length but the other pins look shorter than on a regular plug making them an even better shutter opener than ever before