Has anyone measured a Laptop PSU from mains earth to the output 0 volt pin for continuity. Is it a real connection ?
I can't see what the problem is parelling grounds, we do it all the time with equipment, two laptops linked together don't blow up -- there is no potential between the zero volt lines.
I can't see what the problem is parelling grounds, we do it all the time with equipment, two laptops linked together don't blow up -- there is no potential between the zero volt lines.
yes, I have measured a japanese Apple Laptop PSU, its leakage current exceeds local (german) regulations.
As most SMPS, it has probable Y-capacitors from both mains to secondary ground.
I haven't seen a laptop PSU with mains ground/ safety earth yet. They are usually safe insulated without a connection to PE.
Regards
As most SMPS, it has probable Y-capacitors from both mains to secondary ground.
I haven't seen a laptop PSU with mains ground/ safety earth yet. They are usually safe insulated without a connection to PE.
Regards
I hope Ion clarifies what he means and what he considers safe.
If some computer PSUs need a Safety Earth and this is provided by the bolted/riveted connection into a Safety Earthed computer case, then omitting the required Safety Earth from the PSU is potentially Fatal.
If he means find a PSU that is built to double insulated standard and use that in it's intended way, then OK.
But, I ask the questions
are there any double insulated computer PSUs on the market, even in Spain?
If some computer PSUs need a Safety Earth and this is provided by the bolted/riveted connection into a Safety Earthed computer case, then omitting the required Safety Earth from the PSU is potentially Fatal.
If he means find a PSU that is built to double insulated standard and use that in it's intended way, then OK.
But, I ask the questions
and I'll ask a further question,
are there any double insulated computer PSUs on the market, even in Spain?
As I type this I am reading what it says on the base of my laptop PSU. "Connect only to grounded outlet". As Juergen Knoop says, it almost certainly has caps fitted L-E, N-E, L-N, to make sure nothing escapes. There may even be something like a 470 Pf cap mains earth to secondary zero line as well.
interesting, so better buy a laptop PSU like this:
An externally hosted image should be here but it was not working when we last tested it.
Regards
😀 😀 😀 Which brings to mind someone I worked with. You know what it's like, some products have as high as a 0.22 mfd across the mains. So if you unplug it at just the right time the thing is charged up to 340 volt or so. This guy always got a whack from the plug and would stand there holding the mains lead smashing the plug top against the wall or bench in revenge. 😀 😀
provided it's certified as double earthed with the double square symbol.Juergen Knoop said:
If not, then the flow or return in the connector could become "Live".
Hi Jeurgen,
A proper double insulated one. It's like with consumer AV gear. You never see an earthed DVD or TV these days.
A proper double insulated one. It's like with consumer AV gear. You never see an earthed DVD or TV these days.
of course these PSU's are certified, these certifications can't cost much in far east. 😉
regards
regards
Hello Andrew,
Providing it is certified, and even then you hear tales of "substandard" shall we say products.
Providing it is certified, and even then you hear tales of "substandard" shall we say products.
Juergen Knoop said:
All of the units I've seem here (Canada) are grounded also - three pin input. Something like 20VDC output, 2 pins.
AndrewT said:
I was refering to psu's like the one in the picture of post 105 by Juerguen Knoop. I bought them at the supermarket for $20 and, as you can see from the picture, they have a 2-pin input so there is no safety ground. I havn't encouraged anyone to "hand-disconnect" safety earth!
Whether they are safe or not, well, since laptops have metal screws and jacks i belive doing a gainclone with these supplies to be as safe as plugging them into your laptop. I don't expect things bought at the supermarket to be extraordinary dangerous, but you should not touch the wires anyways.
The couple i bought have the "double-insulated" symbol.
Nuuk said:
Yes, i placed a pair of standard dc female jacks like the ones that laptops have on the gainclone so as i don't have to cut the wire from the psu to keep the warranty! the positive from one jack goes to the negative of the other and to 0V. I did try various models and there is a zappa one which in spite of not being safety-earthed does not have the double-insualtion logo. This was the cheapest, the smallest and also the most noisy (obviously big chokes and caps don't fit there), so i suggest to go for a better one. I set them at 20V 3.2A but they can go up to 24V 2.8A. Not the most powerful thing i've seen but they do the job very well for a beginner project. I use them in 16V 4A for my class-A experiment as i've found that finding a transformer that has that current capability with so low voltage is impossible here and shipping a weighty transformer very expensive.
For "high-end" power i use "aqueduct" filtering (putting several pi-filters in series. The on-board cap should have very low impedance from 100Hz and i let the logic at the supply to take care for the bass. I've found no problem at all and the chokes i use are free as i take them from broken computer smps.
I'm very happy with the results and i belive it's a nice supply for newbies both for price and safety reasons (absolutely no construction/modification of mains-wired equipment).
I have no idea how these are designed but if it's done properly the current-limiting function should not present any more dissipation than normal operation so it would also be very safe for the circuit.
Yes, if the correct SMPS are used like you are using them, I agree, it would remove a lot of the angst (and potential pitfalls) for first-time builders!
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