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.
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.
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