Counterfeit laptop chargers are bad for your box


#1

[Read the post]


#2

My guess is either they don’t know what a safe distance should be in this case so can’t, or simply don’t care.


#3

Because the existing design is in production and selling quite nicely, thank you.


#4

We need more opensource power electronics. With the clearances and safety well-described in the documentation.

Then the Chinese will have something good and safe to knock off, without having to improvise on their own, and we will get better dirt-cheap crap.


#5

I suspect that(aside from sheer shoddiness and not caring) the ‘counterfeit’ as opposed to ‘3rd party’ aspect of things is a serious problem here.

Sure, for a basic sub-100w line-lump AC adapter, you aren’t fighting for every millimeter of space; but if you want to produce a visually identical clone of one of Apple’s fetishistically compact adapters, yes you are; and you are almost certainly trying to do so with a lower bill of materials and quite possibly less competent engineers.

You would certainly still see other flavors of corner cutting, in the name of price; but if the product were a generic black box type adapter with a magsafe connector, it would be much more likely that they’d spare the few extra millimeters of FR4 required to produce a vaguely reasonable design.


#6

Ideally you want 8mm and an air gap. However, the conceptual problem for many uninstructed designers is that the gap between primary and secondary in the transformer is much less than this.


#7

Sorry, no.

Safety costs money. The fuses and microprocessors that prevent the thing from sparking or trying to charge a shorted circuit increase the cost of a device. So the cheap knock off manufacturer is always going to leave as much of that stuff out as they can get away with. And China doesn’t give a shit about regulating their industries, they only care about supressing dissent.

Sure, you could make a safe knock off charger for say $20, but then you’d be competing against the unsafe knock offs selling for $10, nobody would buy your safe ones, and you’d go bankrupt.


#8

On one hand, true. On the other hand, more space on the board costs nothing when you already have it.

So you still can get a bit better crap.

…and you can retrofit it with a Polyswitch fuse yourself.


#9

I had a knockoff Macbook power supply that melted it’s own case. There doesn’t seem to be any market for the middle ground, it’s the OEM brand or something that is dodgy.


#10

Yup. But maybe this could be addressed.

I for one would buy a $20 cheapo one instead of the $10 uber-cheapo one if the vendor shows me the schematics and the construction. Which they can easily do, double so if it is an opensource design knockoff.

A self-done commented teardown like the one done for the fakes would be one of the ways.


#11

That would require having engineers who give a damn. Creating engineers/ designers who care requires paying for such, which the companies we’re talking about won’t do, and it requires having professional societies with codes of ethics that licence engineers and instil concepts of pride of workmanship and social responsibility in their members, and that’s something that china’s government isn’t interested in fostering.

Basically china is a near perfect example of unregulated free market capitalism run amok. Libertarians take note: this is your so called utopia.


#12

Power supplies, storage, and batteries (and the devices that incorporate them) are the two electronics things Chinese engineers will tell you not to buy at a market for cheap. The quality ones are ones you can find for a consistent above average price from multiple vendors in the malls… and even then it is a risk. I’ve had a lot of success with wired electronics using USB power, AA batteries, cables of any kind, and it’s a great place to buy tools to work with electronics. I might be confident enough to buy power electronics now.

Same goes for clothing with black dye and several other goods common in these markets. The locals tend to know what materials are dangerously cheaped-out on.


#13

Yes. But you can have these with relative ease.

I for one am not a member of any professional society, nor desire to be, nor would be excited by the perspective of yet more paperwork and fees. I don’t give much damn about social responsibility. But I have a lot of tech pride so I want my designs to be good and reliable.

It doesn’t have to cost that much more.


#14

[quote=“Glaurung, post:11, topic:75331”]
Basically china is a near perfect example of unregulated free market capitalism run amok. Libertarians take note: this is your so called utopia.
[/quote]Except these are the goods marketed to foreigners, there are local brands with good engineering and regulation that mostly suffer from quality control issues.


#15

Underwriters Laboratories - founded 1894
AIEE - founded 1884
ASCE - founded 1854

I’m ok with the amount of free market capitalism appropriate to the founding and operation of these organizations.


#16

The problem there is that $20 is an awfully small increase in margin given how few people are in this cheapo-but-not-deadly power supply’s target audience - most users won’t know or care enough to get the safer version, and many of the ones who do probably won’t know enough to verify these and just buy OEM instead.


#17

There are two capacitors, but no inductor, on the DC output filter circuit. What cheeseball designed this power supply? Even I know that you need an inductor in a filter to make if be a filter.


#18

Just wrap the power cord around a table leg a few times.


#19

Eh, as long as it doesn’t actually cross zero, it’s ‘DC’, right?


#20

It’s actually AC with a DC offset.

It’s a bitch to check such mixed signals with scope. You either get DC coupling and then the offset can get the small signal out of the screen, or you get AC coupling and can make it more sensitive but then you don’t see the DC component.

What I did for rapid examination of such signals is a splitter that connects one probe to both scope channels, then set one channel to DC and the full DC range, and the other one to AC and higher sensitivity. So you then can see 100 mV signal riding on 3 V DC bias, and simultaneously see both components.

…of course then you get half the input impedance of the scope, which will screw up with the signal magnitude so the scope shows smaller voltage than what is on the probe. You have to multiply it with a factor manually. Or disconnect for a moment one of the channels.

…we need an opensource Rigol scope firmware that’d allow such functionality…