Hello,

I was looking for a PSU to power a child's toy but found that the CPC
web site says "not for domestic use" against all their linear power
supplies because they do not comply with energy saving regulations.
What's this about and when did that start? Are we supposed to use SMPS
for everything now? If so, why are they still selling linear power
supplies; there must be an advantage?

Thanks,
Stephen.

lid wrote:

I was looking for a PSU to power a child's toy but found that the CPC
web site says "not for domestic use" against all their linear power
supplies because they do not comply with energy saving regulations.

I did a Google search for "linear psu site:cpc.farnell.com" I didn't see
any such warning on the half a dozen or so I picked at random.

In article ,
lid writes:
Hello,

I was looking for a PSU to power a child's toy but found that the CPC
web site says "not for domestic use" against all their linear power
supplies because they do not comply with energy saving regulations.
What's this about and when did that start? Are we supposed to use SMPS
for everything now? If so, why are they still selling linear power
supplies; there must be an advantage?

I haven't bought a linear PSU for years. I always buy Switched-mode ones.
(and I do buy quite a few for the projects I build, although often
second-hand).

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"Andrew Gabriel" wrote in message ...

In article ,
writes:
Hello,

I was looking for a PSU to power a child's toy but found that the CPC
web site says "not for domestic use" against all their linear power
supplies because they do not comply with energy saving regulations.
What's this about and when did that start? Are we supposed to use SMPS
for everything now? If so, why are they still selling linear power
supplies; there must be an advantage?

I haven't bought a linear PSU for years. I always buy Switched-mode ones.
(and I do buy quite a few for the projects I build, although often
second-hand).



Wait until the green lobby find out about rf interference and mains bourn
interference from switchers and they'll be insisting we use linear psu's !

Andrew

On Sunday 05 January 2014 17:42 Andrew Gabriel wrote in uk.d-i-y:

In article ,
lid writes:
Hello,

I was looking for a PSU to power a child's toy but found that the CPC
web site says "not for domestic use" against all their linear power
supplies because they do not comply with energy saving regulations.
What's this about and when did that start? Are we supposed to use SMPS
for everything now? If so, why are they still selling linear power
supplies; there must be an advantage?

I haven't bought a linear PSU for years. I always buy Switched-mode ones.
(and I do buy quite a few for the projects I build, although often
second-hand).


Not understanding SMPSUs - do they provide complete magnetic isolation like
a simple transformer does?

TRhe beuauty of a simple linera PSU for home build projects is it's hard to
get it wrong, provided you keep the mains wiring nicely separated from the
ELV side.

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

In message , Andrew Mawson
writes
"Andrew Gabriel" wrote in message ...

In article ,
writes:
Hello,

I was looking for a PSU to power a child's toy but found that the CPC
web site says "not for domestic use" against all their linear power
supplies because they do not comply with energy saving regulations.
What's this about and when did that start? Are we supposed to use SMPS
for everything now? If so, why are they still selling linear power
supplies; there must be an advantage?

I haven't bought a linear PSU for years. I always buy Switched-mode ones.
(and I do buy quite a few for the projects I build, although often
second-hand).

Wait until the green lobby find out about rf interference and mains
bourn interference from switchers and they'll be insisting we use
linear psu's !

If the green lobby were at all interested in RF and mains-born
interference, they would have started complaining about it many years
ago.
--
Ian

On Sunday, January 5, 2014 6:44:24 PM UTC, Tim Watts wrote:

Not understanding SMPSUs - do they provide complete magnetic isolation like
a simple transformer does?

Yes, assuming you mean ones with external power output


TRhe beuauty of a simple linera PSU for home build projects is it's hard to
get it wrong, provided you keep the mains wiring nicely separated from the
ELV side.

They're quick, easy & simple. SMPSUs arent.


NT

On Sunday 05 January 2014 19:21 wrote in uk.d-i-y:

On Sunday, January 5, 2014 6:44:24 PM UTC, Tim Watts wrote:

Not understanding SMPSUs - do they provide complete magnetic isolation
like
a simple transformer does?

Yes, assuming you mean ones with external power output

OK...


TRhe beuauty of a simple linera PSU for home build projects is it's hard
to get it wrong, provided you keep the mains wiring nicely separated from
the ELV side.

They're quick, easy & simple. SMPSUs arent.



--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

On Sun, 05 Jan 2014 19:33:38 +0000, Tim Watts
wrote:

On Sunday 05 January 2014 19:21 wrote in uk.d-i-y:

On Sunday, January 5, 2014 6:44:24 PM UTC, Tim Watts wrote:

Not understanding SMPSUs - do they provide complete magnetic isolation
like
a simple transformer does?

Yes, assuming you mean ones with external power output

OK...


TRhe beuauty of a simple linera PSU for home build projects is it's hard
to get it wrong, provided you keep the mains wiring nicely separated from
the ELV side.

They're quick, easy & simple. SMPSUs arent.


I noticed lots of Christmas tree lights still come with conventional
transformers. Not much else though.


--
Graham.


%Profound_observation%

"Graham." wrote in message
...
On Sun, 05 Jan 2014 19:33:38 +0000, Tim Watts
wrote:

On Sunday 05 January 2014 19:21 wrote in uk.d-i-y:

On Sunday, January 5, 2014 6:44:24 PM UTC, Tim Watts wrote:

Not understanding SMPSUs - do they provide complete magnetic
isolation
like
a simple transformer does?

Yes, assuming you mean ones with external power output

OK...


TRhe beuauty of a simple linera PSU for home build projects is it's
hard
to get it wrong, provided you keep the mains wiring nicely separated
from
the ELV side.

They're quick, easy & simple. SMPSUs arent.


I noticed lots of Christmas tree lights still come with conventional
transformers. Not much else though.

Only a transformer gives proper isolation from the mains for safety.
110V tools on building sites are powered via transformers.

They don't kick out all the rf crud that switch modes do. I think also the
main inefficiency is in the transformer itself. The switch mode supplies use
a high frequency to aid efficiency, but in my view they do nasty things to
stuff they are used with, like crash computers etc. I really think the main
reason most manufacturers went to smpsus was weight in transit from the far
east!

Brian

--
From the Sofa of Brian Gaff Reply address is active
wrote in message
...
Hello,

I was looking for a PSU to power a child's toy but found that the CPC
web site says "not for domestic use" against all their linear power
supplies because they do not comply with energy saving regulations.
What's this about and when did that start? Are we supposed to use SMPS
for everything now? If so, why are they still selling linear power
supplies; there must be an advantage?

Thanks,
Stephen.

harryagain wrote:

I noticed lots of Christmas tree lights still come with conventional
transformers. Not much else though.

Only a transformer gives proper isolation from the mains for safety.

SMPSs have a transformer. It's just smaller than is traditional as
they're running at a frequency a lot higher than 50Hz. The rest of the
circuitry in one is then the oscillator and a some feedback control
(hence being regulated by default compared to the old
12v-on-load-20v-when-not jobs.)

There is only one caveat to this. SMPSs generally use opto-isolators to
provide the feedback from the LV side to the HV frequency generator
side. This and the transformer means they are totally isolated from the
mains. However, some of the very cheap ones skip the opto-isolators[1]
and use FETs or TRIACs or something[2] instead which ruins the mains
isolation, especially should they break down.


[1] Apparently. I've not come across one in the few that I've had apart.
I found an article on converting ordinary fixed voltage wallwarts into
variable ones that showed some like this.

[2] Can't remember exactly.

--
Scott

Where are we going and why am I in this handbasket?

On Monday 06 January 2014 09:24 Scott M wrote in uk.d-i-y:

There is only one caveat to this. SMPSs generally use opto-isolators to
provide the feedback from the LV side to the HV frequency generator
side. This and the transformer means they are totally isolated from the
mains. However, some of the very cheap ones skip the opto-isolators[1]
and use FETs or TRIACs or something[2] instead which ruins the mains
isolation, especially should they break down.

That's the bit that worries me - I would not like to have any PSU with any
sort of electrical coupling between the ELV and LV(mains) side, bar perhaps
an earth connection (that's rare now, but used to be not unheard of to bond
to earth to the -ve rail in ye olden days).



--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

On Mon, 6 Jan 2014 09:14:23 -0000, Brian Gaff wrote:

I really think the main reason most manufacturers went to smpsus was
weight in transit from the far east!

I don't think you pay by weight (within limits) for containerised
surface shipping, you pay by the container, which you stuff with as
much as will fit... Saw on the telly (so it must be true) that a 20'
container from the Far East to Europe costs about £1500. Think how
many wall warts you could get in a 20' container, shipping costs are
minimal...

The reason is that you can make a SMPSU that'll work from 60 V to 250
V AC or DC. So one single power unit will work anywhere in the world.
All you need to do is provide a selection of clip-on country specific
adapters.

I do wonder how "green", cradle to grave, a complex SMPSU is compared
to a simple linear supply. The SMPSU might be more effcient in use
but will that energy saving be more than the extra energy it took to
make?

--
Cheers
Dave.

Dave Liquorice wrote:

I do wonder how "green", cradle to grave, a complex SMPSU is compared
to a simple linear supply. The SMPSU might be more effcient in use
but will that energy saving be more than the extra energy it took to
make?


Big linear supplies are less efficient to manufacture as they require
more materials. Only the transformer and case/heatsink are recyclable.
They also mess up the 50Hz supply waveform. Linear wallwarts for low
power have better power factors as they are inherently more resistive
and inductive (lousy regulation)even when feeding a capacitative load.
Low power SMPSUs are now produced in such volume that the processes are
ultra efficient, leading to less to recycle. Just look at the selling
prices.

On Mon, 06 Jan 2014 09:43:53 +0000 (GMT)
"Dave Liquorice" wrote:

I don't think you pay by weight (within limits) for containerised
surface shipping, you pay by the container, which you stuff with as
much as will fit...

Yup, when we moved back here from the US, we hired a container, and its
ultimate weight did not matter, it was just the container that we paid
to ship.

--
Davey.

In article ,
Tim Watts wrote:
There is only one caveat to this. SMPSs generally use opto-isolators to
provide the feedback from the LV side to the HV frequency generator
side. This and the transformer means they are totally isolated from the
mains. However, some of the very cheap ones skip the opto-isolators[1]
and use FETs or TRIACs or something[2] instead which ruins the mains
isolation, especially should they break down.

That's the bit that worries me - I would not like to have any PSU with
any sort of electrical coupling between the ELV and LV(mains) side, bar
perhaps an earth connection (that's rare now, but used to be not
unheard of to bond to earth to the -ve rail in ye olden days).

If a 'normal' main transformer fails, it is possible to get a short
between the mains and LV windings. Of course there are some designs which
pretty well prevent this happening - but not likely to be used in a cheap
wall wart.

--
*Sorry, I don't date outside my species.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Tim Watts writes:
On Monday 06 January 2014 09:24 Scott M wrote in uk.d-i-y:

There is only one caveat to this. SMPSs generally use opto-isolators to
provide the feedback from the LV side to the HV frequency generator
side. This and the transformer means they are totally isolated from the
mains. However, some of the very cheap ones skip the opto-isolators[1]
and use FETs or TRIACs or something[2] instead which ruins the mains
isolation, especially should they break down.

That's the bit that worries me - I would not like to have any PSU with any
sort of electrical coupling between the ELV and LV(mains) side, bar perhaps
an earth connection (that's rare now, but used to be not unheard of to bond
to earth to the -ve rail in ye olden days).

I haven't seen any regulated ones which use anything other than opto-
couplers for last ~20 years (and I have taken apart and modified quite
a lot to convert them from constant voltage to constant current).

The 12V lighting transformers don't have any active regulation, and
only check that the input power is within an acceptable range (which
is why they have a minimum load), and rely of the much better regulation
of the HF transformer to maintain output voltage over their design range.
Philosophically, these are a different design, being plain HF transformer,
rather than being the variable energy pump design of a regulated SMPSU.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In article ,
(Andrew Gabriel) writes:
In article ,
Tim Watts writes:
On Monday 06 January 2014 09:24 Scott M wrote in uk.d-i-y:

There is only one caveat to this. SMPSs generally use opto-isolators to
provide the feedback from the LV side to the HV frequency generator
side. This and the transformer means they are totally isolated from the
mains. However, some of the very cheap ones skip the opto-isolators[1]
and use FETs or TRIACs or something[2] instead which ruins the mains
isolation, especially should they break down.

That's the bit that worries me - I would not like to have any PSU with any
sort of electrical coupling between the ELV and LV(mains) side, bar perhaps
an earth connection (that's rare now, but used to be not unheard of to bond
to earth to the -ve rail in ye olden days).

I haven't seen any regulated ones which use anything other than opto-
couplers for last ~20 years (and I have taken apart and modified quite
a lot to convert them from constant voltage to constant current).

The 12V lighting transformers don't have any active regulation, and
only check that the input power is within an acceptable range (which
is why they have a minimum load), and rely of the much better regulation
of the HF transformer to maintain output voltage over their design range.
Philosophically, these are a different design, being plain HF transformer,
rather than being the variable energy pump design of a regulated SMPSU.

One other thing - there's often a tiny capacitor between the mains
inlet (if unearthed) and the secondary. I'm not sure what it's for,
but my guess is that with the secondary floating, there's a good
chance the whole thing could be capacitively coupled to the primary
oscilating at 40kHz (and harminics) at ~160V (half the primary voltage
swing), and acting like a LW radio jammer. The capacitor would "short
out" the 40kHz (and even more so, the harmonics), which capacitively
leaks through from the primary, and prevent the output acting like a
jamming antenna.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Monday 06 January 2014 09:43 Dave Liquorice wrote in uk.d-i-y:

On Mon, 6 Jan 2014 09:14:23 -0000, Brian Gaff wrote:

I really think the main reason most manufacturers went to smpsus was
weight in transit from the far east!

I don't think you pay by weight (within limits) for containerised
surface shipping, you pay by the container, which you stuff with as
much as will fit... Saw on the telly (so it must be true) that a 20'
container from the Far East to Europe costs about £1500.

wow - cannot believe it is so cheap! I guess you add local transport (lorry)
to that too.

Think how
many wall warts you could get in a 20' container, shipping costs are
minimal...

4x4x3" box - OK... That's about 50,000 PUS allowing 10% or so for external
boxing/packaging.

So 2.8p per unit. Blimey. No wonder ebay can sell stuff so cheap!

The reason is that you can make a SMPSU that'll work from 60 V to 250
V AC or DC. So one single power unit will work anywhere in the world.
All you need to do is provide a selection of clip-on country specific
adapters.

I do wonder how "green", cradle to grave, a complex SMPSU is compared
to a simple linear supply. The SMPSU might be more effcient in use
but will that energy saving be more than the extra energy it took to
make?

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

On 06/01/2014 09:31, Tim Watts wrote:
On Monday 06 January 2014 09:24 Scott M wrote in uk.d-i-y:

There is only one caveat to this. SMPSs generally use opto-isolators to
provide the feedback from the LV side to the HV frequency generator
side. This and the transformer means they are totally isolated from the
mains. However, some of the very cheap ones skip the opto-isolators[1]
and use FETs or TRIACs or something[2] instead which ruins the mains
isolation, especially should they break down.

That's the bit that worries me - I would not like to have any PSU with any
sort of electrical coupling between the ELV and LV(mains) side, bar perhaps
an earth connection (that's rare now, but used to be not unheard of to bond
to earth to the -ve rail in ye olden days).

http://www.electricstuff.co.uk/acadapter.html


;-)


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Monday 06 January 2014 14:04 John Rumm wrote in uk.d-i-y:

On 06/01/2014 09:31, Tim Watts wrote:
On Monday 06 January 2014 09:24 Scott M wrote in uk.d-i-y:

There is only one caveat to this. SMPSs generally use opto-isolators to
provide the feedback from the LV side to the HV frequency generator
side. This and the transformer means they are totally isolated from the
mains. However, some of the very cheap ones skip the opto-isolators[1]
and use FETs or TRIACs or something[2] instead which ruins the mains
isolation, especially should they break down.

That's the bit that worries me - I would not like to have any PSU with
any sort of electrical coupling between the ELV and LV(mains) side, bar
perhaps an earth connection (that's rare now, but used to be not unheard
of to bond to earth to the -ve rail in ye olden days).

http://www.electricstuff.co.uk/acadapter.html

Fascinating - wonder how many fires those things start...

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

On Mon, 6 Jan 2014 09:14:23 -0000, "Brian Gaff"
wrote:

I really think the main
reason most manufacturers went to smpsus was weight in transit from the far
east!

Nope, blame the European Onion and Directive 2009/125/EC "Directive
on the eco-design of Energy-using Products (EuP)". The same directive
that killed the incandescent bulb. The Ecodesign Directive was
transposed into UK law under the Ecodesign for Energy Related Products
Regulations (SI 2010 No 2617).

In particular regulation (EC) No 278/2009 of 6 April 2009
"implementing Directive 2005/32/EC of the European Parliament and of
the Council with regard to ecodesign requirements for no-load
condition electric power consumption and average active
efficiency of external power supplies"

This requires a power supply to draw no more than 0.5W under no load
(reducing to 0.3W in 2015) and be of certain efficiency. Linear power
supplies cannot meet these requirements.

http://eur-lex.europa.eu/LexUriServ/...03:0010:EN:PDF

In article , Dave Plowman (News)
writes
In article ,
Tim Watts wrote:
There is only one caveat to this. SMPSs generally use opto-isolators to
provide the feedback from the LV side to the HV frequency generator
side. This and the transformer means they are totally isolated from the
mains. However, some of the very cheap ones skip the opto-isolators[1]
and use FETs or TRIACs or something[2] instead which ruins the mains
isolation, especially should they break down.

That's the bit that worries me - I would not like to have any PSU with
any sort of electrical coupling between the ELV and LV(mains) side, bar
perhaps an earth connection (that's rare now, but used to be not
unheard of to bond to earth to the -ve rail in ye olden days).

If a 'normal' main transformer fails, it is possible to get a short
between the mains and LV windings.

Never seen it happen, they are built to pretty stringent standards,
either split bobbin (LF only) or reinforced insulation which, in the
case of thin layers, is 3 layers of heat resistant insulation, each of
which is proof to 1500Vac. Overall proof test is 3750Vac.

Thermal fuse required too (on LF).

Of course there are some designs which
pretty well prevent this happening - but not likely to be used in a cheap
wall wart.

They wont get approval if they don't.

You might be saying that cheap Chinese stuff wont meet approvals but
that's a fake goods issue for Trading Standards.
--
fred
it's a ba-na-na . . . .

In article , Andrew Gabriel
writes

One other thing - there's often a tiny capacitor between the mains
inlet (if unearthed) and the secondary. I'm not sure what it's for,
but my guess is that with the secondary floating, there's a good
chance the whole thing could be capacitively coupled to the primary
oscilating at 40kHz (and harminics) at ~160V (half the primary voltage
swing), and acting like a LW radio jammer. The capacitor would "short
out" the 40kHz (and even more so, the harmonics), which capacitively
leaks through from the primary, and prevent the output acting like a
jamming antenna.

Wot, never designed a mains switcher ;-)

Yes, it shorts out the common mode pump that would otherwise have the
load and any cables connected to it jumping up and down like nobody's
business. They'd never pass EMC testing without it.
--
fred
it's a ba-na-na . . . .

On 06/01/2014 17:29, Peter Parry wrote:
On Mon, 6 Jan 2014 09:14:23 -0000, "Brian Gaff"
wrote:

I really think the main
reason most manufacturers went to smpsus was weight in transit from the far
east!

Nope, blame the European Onion and Directive 2009/125/EC "Directive
on the eco-design of Energy-using Products (EuP)". The same directive
that killed the incandescent bulb.

I think you mean winded the incandescent bulb. They seem to be making a
comeback under the name of energy saving halogen. (which is a bit of an
oxymoron but there you go)



--
Chris

On Sun, 05 Jan 2014 17:35:32 +0000, Andy Burns
wrote:

I did a Google search for "linear psu site:cpc.farnell.com" I didn't see
any such warning on the half a dozen or so I picked at random.

I had another look to make sure I was not dreaming; the warning is not
on the main product page but appears on the "further information"
page, like this one:
http://cpc.farnell.com/jsp/level5/mo...cpc/646821.xml

On Mon, 06 Jan 2014 17:29:16 +0000, Peter Parry
wrote:

This requires a power supply to draw no more than 0.5W under no load
(reducing to 0.3W in 2015) and be of certain efficiency. Linear power
supplies cannot meet these requirements.

I guess it depends on the application; if it is something that is
plugged in and switched on all the time whether it is in use or not,
may be this is beneficial, but for something you plug in when you need
and unplug when you do not, does standby current really matter?

On Thu, 09 Jan 2014 10:01:52 +0000, lid wrote:

I guess it depends on the application; if it is something that is
plugged in and switched on all the time whether it is in use or not,
may be this is beneficial, but for something you plug in when you need
and unplug when you do not, does standby current really matter?

EU directives and reality rarely have anything to do with each other.
Directives mean apparatchiks are doing "something". Doing something
is very important so they try to do a lot of it.

Achieving something is much more difficult so it isn't important and
doesn't attract much attention.

wrote
Peter Parry wrote

This requires a power supply to draw no more than 0.5W under
no load (reducing to 0.3W in 2015) and be of certain efficiency.
Linear power supplies cannot meet these requirements.

I guess it depends on the application; if it is something that is
plugged in and switched on all the time whether it is in use or not,
may be this is beneficial, but for something you plug in when you need
and unplug when you do not, does standby current really matter?

No, but most don't use them like that.

On 06/01/2014 16:01, Tim Watts wrote:
On Monday 06 January 2014 14:04 John Rumm wrote in uk.d-i-y:

http://www.electricstuff.co.uk/acadapter.html

Fascinating - wonder how many fires those things start...


Also this site,


http://www.righto.com/2012/03/inside-cheap-phone-charger-and-why-you.html

--
Adrian C

Not LED strings. They have a pair of half wave rectifiers and aren't really isolated at all.
Rusty