Hi all,
I need to replace a laptop style (12V 7A) PSU (not for a laptop) and was wondering if the sort of thing you can get to power 12V LED lights would be suitable?
I'm talking of this sort of thing:
Is it just a 12V SMPSU or is it summat 'different'?
I find it weird that they don't mention the output voltage in the blurb, just a range of wattages (it does say 11.4V on the item itself though).
Cheers, T i m
It can't be very well regulated if it is dimmable. And it is probably quite noisy. So it very much depends on how well the item you are going to use it with can cope with that.
Transformer implies non-DC. I see others in the range on a different website actually say AC.
I would pass and purchase a true 12V DC supply, if that is what you want.
Something like this at £8.77 for 12V @ 10A:
And cheaper than the Toolsatan offering. Only concern is the output earthing arrangement. I might be wary to treat the output to be SELV without knowing more about the unit.
Of course there are others.
I think we would need to know more about the load you want to power with such a device before being committal one way or the other. Lights are one thing, sensitive electronics and chargers are quite another thing. Brian
Yes, that got me wondering and hence why I asked here.
Ok.
Good point. It was just that the world is still 'weird' because of that Xmyth thing and Toolstation are just down the road, *if* it was just a std 12V SMPSU etc.
It's to power my home server that uses a fanless Atom board, 3 x 500G laptop drives and one of those low power PSU's that take a single input voltage and fit in the mobo power connector.
A mate gave me the 12V 7A laptop type PSU a good while back but I doubt it is a good one or able to maintain 7A. I might rig up a feed using my variable bench PSU and see what it actually draws worst-case and get something that can cope with that easily.
If I get one of those semi open frame type SMPSU's I could put it inside the PSU case as that only contains the one 120mm fan atm.
Cheers, T i m
Be aware that these lighting type transformers rarely produce DC and have a minimum load usually of around half the max output before they will switch on. The output voltage quoted is often the RMS value of a non sinusoid. So ideal for lighting but not a lot else. I have used them for anti rust heating with resistive loads in the past.
Good point. I initially thought they were for LEDs but later saw they weren't. I have used one to replace similar in a floor standing lamp with a halogen light and that of course wouldn't need to be polarised
Yes, I went to them from a std 'laptop' type PSU but it would need casing up ... or fitting inside the PC PSU case than currently only holds a 120mm fan.
It was just something I could go and get locally today. ;-)
As I mentioned elsewhere, I think I might first cut the output lead off the dead laptop style PSU and connect it up to my bench PSU and remind myself what current it (my home server) actually draws (worst case) and go from there.
Cheers, T i m
Quite. My question was really 'are these Electronic transformers' really just std SMPSU's but marketed as Electronic Transformers to cater for electricians who may not know what a SMPSU was?
I think the answers so far suggest they are probably not straight SMPSU's, as in a laptop PSU and so I'll look elsewhere.
Cheers, T i m
You have probably noticed that the purpose-made ones from the computer power supply companies are inordinately expensive. Some of these Atom boards will alternatively take a standard ATX PSU. Otherwise, for economy, I agree with your plan. But get a good quality one as it is a SPOF for your server, even if you have a UPS.
That's a *lot* of power for a fanless Atom based board. My full-blown desktop machine with a (6th gen, or maybe even 5th gen) I5 and three disk drives only consumes 18 watts when idle and maybe 25/30 watts when working hard. That's a maximum of around 3 amps at 12 volts.
I doubt very much if you need anything like 7 amps.
A significant component is the starting current for the drives. If this is not specified then you really need an oscilloscope to check. Even laptop drives may draw twice their rated current when operating.
Distress purchase if you need one before the world gets back to normal, and can measure that 5A would suffice?
Thanks for the heads up Bob. From the feedback here I think I was just wishful thinking, especially with the lack of any real data presented on the Toolstation website on the things.
Back to a 'proper' SMPSU of some sort. ;-)
Cheers, T i m
So stagger the startup. Most PSUs will handle short term surges more than their rated output anyway and/or the output will droop a bit as the drives spin up.
a lighting psu is totally utterly & completely unfit for that purpose
NT
If the output droops the CPU may reset or generate unrecoverable errors causing a reboot. Although the drives may stay running and therefore the process not be infinitely repeated, this is a bad idea which could cause data corruption or electronic harm of some sort e.g. to voltage regulators.
Staggering the drive start up is easier said then done unless the hardware is designed to do this.
I have indeed. ;-(
Yes, this one was powered by such when I first built it but took it to the Pico ATX PSU when the conventional PSU fan got noisy (and a 400W PSU (needed to get a quiet / 120mm fan) was a bit of an overkill).
I think the Pico supply is 160W and I think it suggested a 15A (12V) PSU (if fully loaded etc).
Agreed ... that's why I was always a bit cautious about this 'cheap' PSU my mate gave me.
Cheers, T i m
Agreed ... and why I gave the 7A PSU a go, assuming it was only really good for 5 etc.
You may well be right and I think I'd be happy with a *quality* 5A PSU (or a cheaper 10A etc). ;-)
But, 'you can manage what you can measure' so I'll try it on my bench PSU first and 1) make sure everything is ok (Bench PSU is current limitable and goes up to 15A) and see what it actually draws on startup.
Cheers, T i m
I remember my old NW 3.12 server and it had 5 SCSI drives and hearing them all spin up on boot. ;-)
These (x3) are Hitachi 500G SATA drives from about 5 years ago FWIW.
I think it's a Dual core Atom, no optical drive, 4G RAM in 2x2 and the Pico PSU just powers the mobo, drives and the 12V 120mm low power / slow fan in the std ATX PSU case.
I fitted the DC jack socket to the case just under the PSU (Mini tower case standing behind the lounge TV). The Topfield is normally connected to the server but doesn't add any extra load, as is a 3TB powered external backup drive.
Cheers, T i m
p.s. I've bought some Arctic F12 Silent fans and may swap the one out of the server to see if it could be quieter still (you can only hear that it's on after you turn it off). ;-)
The 3 x laptop drives are suspended from silicon bands. ;-)
Hehe ..
;-)
Thanks for that Andy ... and could be a solution (even at that 'sea' price) if it's likely to be a 'good' / quality item?
It's like when you buy these replacement laptop PSUs and they weigh a fraction of the original. ;-(
Cheers, T i m
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