I recently bought in one of those 5m rolls of LED strip lighting. Great stuff for lighting awkward places - in this case a rather deep larder in which we can now find everything due to a run of LEDs for each shelf. I used a metal cased 25W transformer for this.

So that's the solution for the under-cupboard worktop lighting then too. For this I had a load of 13W, so ordered one of the plastic cased 18W transformers. This lasted for an hour before becoming so hot it smelt and was too hot to touch, and stopped working.

I had another 25W one so did the replacement - I'd opted not do use this one previously as it required an earth, and the terminals are exposed; both had to be addressed.

On looking inside the plastic cased device (I'm an electronics engineer) I was surprised by the lack of any high power devices or heat-sinking as in the metal cased equivalent. I've not been involved in switching PSU design but for something generating 1.5A everything looked horribly lightweight. The switching transformer appears to be the source of the heat.

OK it may have been a faulty one, but this makes me a bit suspicious of these plastic cased transformers.

Rob

In article ,
robgraham wrote:
I recently bought in one of those 5m rolls of LED strip lighting. Great
stuff for lighting awkward places - in this case a rather deep larder in
which we can now find everything due to a run of LEDs for each shelf. I
used a metal cased 25W transformer for this.

So that's the solution for the under-cupboard worktop lighting then too.
For this I had a load of 13W, so ordered one of the plastic cased 18W
transformers. This lasted for an hour before becoming so hot it smelt
and was too hot to touch, and stopped working.

I had another 25W one so did the replacement - I'd opted not do use this
one previously as it required an earth, and the terminals are exposed;
both had to be addressed.

On looking inside the plastic cased device (I'm an electronics engineer)
I was surprised by the lack of any high power devices or heat-sinking as
in the metal cased equivalent. I've not been involved in switching PSU
design but for something generating 1.5A everything looked horribly
lightweight. The switching transformer appears to be the source of the
heat.

OK it may have been a faulty one, but this makes me a bit suspicious of
these plastic cased transformers.

I agree with you. They all seem to run hot - too hot for my liking.

--
Please note new email address:

In article ,
robgraham wrote:
I recently bought in one of those 5m rolls of LED strip lighting. Great
stuff for lighting awkward places - in this case a rather deep larder in
which we can now find everything due to a run of LEDs for each shelf. I
used a metal cased 25W transformer for this.

So that's the solution for the under-cupboard worktop lighting then too.
For this I had a load of 13W, so ordered one of the plastic cased 18W
transformers. This lasted for an hour before becoming so hot it smelt
and was too hot to touch, and stopped working.

I had another 25W one so did the replacement - I'd opted not do use this
one previously as it required an earth, and the terminals are exposed;
both had to be addressed.

On looking inside the plastic cased device (I'm an electronics engineer)
I was surprised by the lack of any high power devices or heat-sinking as
in the metal cased equivalent. I've not been involved in switching PSU
design but for something generating 1.5A everything looked horribly
lightweight. The switching transformer appears to be the source of the
heat.

OK it may have been a faulty one, but this makes me a bit suspicious of
these plastic cased transformers.

Can you measure the actual current draw of the LEDs on that PS? I think
you may find it's rather more than the wattage stated implies.

--
*The longest recorded flightof a chicken is thirteen seconds *

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

On Tue, 01 Sep 2015 11:39:31 +0100, Dave Plowman (News) wrote:

In article ,
robgraham wrote:
I recently bought in one of those 5m rolls of LED strip lighting.
Great stuff for lighting awkward places - in this case a rather deep
larder in which we can now find everything due to a run of LEDs for
each shelf. I used a metal cased 25W transformer for this.

So that's the solution for the under-cupboard worktop lighting then
too.
For this I had a load of 13W, so ordered one of the plastic cased 18W
transformers. This lasted for an hour before becoming so hot it smelt
and was too hot to touch, and stopped working.

I had another 25W one so did the replacement - I'd opted not do use
this one previously as it required an earth, and the terminals are
exposed; both had to be addressed.

On looking inside the plastic cased device (I'm an electronics
engineer)
I was surprised by the lack of any high power devices or heat-sinking
as in the metal cased equivalent. I've not been involved in switching
PSU design but for something generating 1.5A everything looked horribly
lightweight. The switching transformer appears to be the source of the
heat.

OK it may have been a faulty one, but this makes me a bit suspicious of
these plastic cased transformers.

Can you measure the actual current draw of the LEDs on that PS? I think
you may find it's rather more than the wattage stated implies.

Just wondering if it's perhaps 13W per metre, or something.

On Tuesday, September 1, 2015 at 12:16:00 PM UTC+1, Bob Eager wrote:
On Tue, 01 Sep 2015 11:39:31 +0100, Dave Plowman (News) wrote:

In article ,
robgraham wrote:
I recently bought in one of those 5m rolls of LED strip lighting.
Great stuff for lighting awkward places - in this case a rather deep
larder in which we can now find everything due to a run of LEDs for
each shelf. I used a metal cased 25W transformer for this.

So that's the solution for the under-cupboard worktop lighting then
too.
For this I had a load of 13W, so ordered one of the plastic cased 18W
transformers. This lasted for an hour before becoming so hot it smelt
and was too hot to touch, and stopped working.

I had another 25W one so did the replacement - I'd opted not do use
this one previously as it required an earth, and the terminals are
exposed; both had to be addressed.

On looking inside the plastic cased device (I'm an electronics
engineer)
I was surprised by the lack of any high power devices or heat-sinking
as in the metal cased equivalent. I've not been involved in switching
PSU design but for something generating 1.5A everything looked horribly
lightweight. The switching transformer appears to be the source of the
heat.

OK it may have been a faulty one, but this makes me a bit suspicious of
these plastic cased transformers.

Can you measure the actual current draw of the LEDs on that PS? I think
you may find it's rather more than the wattage stated implies.

Just wondering if it's perhaps 13W per metre, or something.

60LEDs/m 5050 is likely around 15+W meter...

"robgraham" wrote in message
...

I had another 25W one so did the replacement - I'd opted not do use this one
previously as it required an earth, and the terminals are exposed; both had
to be addressed.


Care to name that one?

I refused to fit something similar a few months ago. It was bought from an
electrical wholesalers (that I do not use) by the customer.

--
Adam

On Tuesday, September 1, 2015 at 8:51:23 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...

I had another 25W one so did the replacement - I'd opted not do use this one
previously as it required an earth, and the terminals are exposed; both had
to be addressed.


Care to name that one?

I refused to fit something similar a few months ago. It was bought from an
electrical wholesalers (that I do not use) by the customer.

--
Adam

The nasty plastic one, which no doubt, Adam, you would have been comfortable fitting because it's got covered terminals and doesn't require an earth, is of the type Ebay 230843971628. I won't be buying this type again.

The better one, but does have the issue of exposed terminals is Ebay 391165796386. I've now run this one for 24 hours and it barely gets warm. I covered the terminals with a plastic cover.

Rob

On Tue, 01 Sep 2015 15:15:28 -0700, robgraham wrote:

On Tuesday, September 1, 2015 at 8:51:23 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...

I had another 25W one so did the replacement - I'd opted not do use
this one previously as it required an earth, and the terminals are
exposed; both had to be addressed.


Care to name that one?

I refused to fit something similar a few months ago. It was bought from
an electrical wholesalers (that I do not use) by the customer.

--
Adam

The nasty plastic one, which no doubt, Adam, you would have been
comfortable fitting because it's got covered terminals and doesn't
require an earth, is of the type Ebay 230843971628. I won't be buying
this type again.

The better one, but does have the issue of exposed terminals is Ebay
391165796386. I've now run this one for 24 hours and it barely gets
warm. I covered the terminals with a plastic cover.

Did you check the wattage of the entire string?

"robgraham" wrote in message
...
On Tuesday, September 1, 2015 at 8:51:23 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...

I had another 25W one so did the replacement - I'd opted not do use this
one
previously as it required an earth, and the terminals are exposed; both
had
to be addressed.


Care to name that one?

I refused to fit something similar a few months ago. It was bought from
an
electrical wholesalers (that I do not use) by the customer.

--
Adam

The nasty plastic one, which no doubt, Adam, you would have been
comfortable fitting because it's got covered terminals and doesn't require
an earth, is of the type Ebay 230843971628. I won't be buying this type
again.

The better one, but does have the issue of exposed terminals is Ebay
391165796386. I've now run this one for 24 hours and it barely gets warm.
I covered the terminals with a plastic cover.

I can find better things do in life other than install eBay Chinese LED
drivers with little or no warranty bought by a customer.


--
Adam

On Tuesday, September 1, 2015 at 11:53:37 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...
On Tuesday, September 1, 2015 at 8:51:23 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...

I had another 25W one so did the replacement - I'd opted not do use this
one
previously as it required an earth, and the terminals are exposed; both
had
to be addressed.


Care to name that one?

I refused to fit something similar a few months ago. It was bought from
an
electrical wholesalers (that I do not use) by the customer.

--
Adam

The nasty plastic one, which no doubt, Adam, you would have been
comfortable fitting because it's got covered terminals and doesn't require
an earth, is of the type Ebay 230843971628. I won't be buying this type
again.

The better one, but does have the issue of exposed terminals is Ebay
391165796386. I've now run this one for 24 hours and it barely gets warm.
I covered the terminals with a plastic cover.

I can find better things do in life other than install eBay Chinese LED
drivers with little or no warranty bought by a customer.


--
Adam

Hey, hey - guys. I bit less of the slagging please. I posted to warn others off these plastic cased transformers.

Adam - I got a full refund from the supplier and have done in cases past where Ebay items have failed; and let's be serious how do you know that the transformers you are buying aren't Chinese made too, and then you have the cost of going back to the shop when they fail.

And Bob - hardly fair to challenge a stated electronics engineer on his ability to measure current. In theory the PSU was at 80% of capacity and should have coped, but having looked inside I reckon it would never have done.

On Wed, 02 Sep 2015 04:06:27 -0700, robgraham wrote:

On Tuesday, September 1, 2015 at 11:53:37 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...
On Tuesday, September 1, 2015 at 8:51:23 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...

I had another 25W one so did the replacement - I'd opted not do use
this one previously as it required an earth, and the terminals are
exposed; both had to be addressed.


Care to name that one?

I refused to fit something similar a few months ago. It was bought
from an electrical wholesalers (that I do not use) by the customer.

--
Adam

The nasty plastic one, which no doubt, Adam, you would have been
comfortable fitting because it's got covered terminals and doesn't
require an earth, is of the type Ebay 230843971628. I won't be
buying this type again.

The better one, but does have the issue of exposed terminals is Ebay
391165796386. I've now run this one for 24 hours and it barely gets
warm.
I covered the terminals with a plastic cover.

I can find better things do in life other than install eBay Chinese LED
drivers with little or no warranty bought by a customer.


--
Adam

Hey, hey - guys. I bit less of the slagging please. I posted to warn
others off these plastic cased transformers.

Adam - I got a full refund from the supplier and have done in cases past
where Ebay items have failed; and let's be serious how do you know that
the transformers you are buying aren't Chinese made too, and then you
have the cost of going back to the shop when they fail.

And Bob - hardly fair to challenge a stated electronics engineer on his
ability to measure current. In theory the PSU was at 80% of capacity and
should have coped, but having looked inside I reckon it would never have
done.

Sorry about that! Pretty awful PSUs then.

"robgraham" wrote in message
...
On Tuesday, September 1, 2015 at 11:53:37 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...
On Tuesday, September 1, 2015 at 8:51:23 PM UTC+1, ARW wrote:
"robgraham" wrote in message
...

I had another 25W one so did the replacement - I'd opted not do use
this
one
previously as it required an earth, and the terminals are exposed; both
had
to be addressed.


Care to name that one?

I refused to fit something similar a few months ago. It was bought from
an
electrical wholesalers (that I do not use) by the customer.

--
Adam

The nasty plastic one, which no doubt, Adam, you would have been
comfortable fitting because it's got covered terminals and doesn't
require
an earth, is of the type Ebay 230843971628. I won't be buying this type
again.

The better one, but does have the issue of exposed terminals is Ebay
391165796386. I've now run this one for 24 hours and it barely gets
warm.
I covered the terminals with a plastic cover.

I can find better things do in life other than install eBay Chinese LED
drivers with little or no warranty bought by a customer.


--
Adam

Hey, hey - guys. I bit less of the slagging please. I posted to warn
others off these plastic cased transformers.

Adam - I got a full refund from the supplier and have done in cases past
where Ebay items have failed; and let's be serious how do you know that the
transformers you are buying aren't Chinese made too, and then you have the
cost of going back to the shop when they fail.


No offence meant:-)

It was the customer that bought what I thought were inappropriate drivers
from the wholesalers not me:-)

They had exposed L&N terminals and there were not IMHO fit for their
proposed use.

Cheers

--
Adam

In article ,
robgraham wrote:
Adam - I got a full refund from the supplier and have done in cases past
where Ebay items have failed; and let's be serious how do you know that
the transformers you are buying aren't Chinese made too, and then you
have the cost of going back to the shop when they fail.

You'd be hard pressed to find ones not made in China (or the components
used) - regardless of the branding, or where it claims to come from.

--
*We never really grow up, we only learn how to act in public.

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

On Tue, 01 Sep 2015 02:28:37 -0700, robgraham wrote:

I've not been involved in switching PSU
design but for something generating 1.5A everything looked horribly
lightweight. The switching transformer appears to be the source of the
heat.

Ideal transformers as you will know don't generate heat. So the heat must
be coming from the resistance of the windings. Be interesting to measure
that resistance and calculate the I^2R losses to see if they come in line
with reasonable expectations.

On 01/09/15 21:47, Cursitor Doom wrote:
On Tue, 01 Sep 2015 02:28:37 -0700, robgraham wrote:

I've not been involved in switching PSU
design but for something generating 1.5A everything looked horribly
lightweight. The switching transformer appears to be the source of the
heat.

Ideal transformers as you will know don't generate heat. So the heat must
be coming from the resistance of the windings. Be interesting to measure
that resistance and calculate the I^2R losses to see if they come in line
with reasonable expectations.


And some iron losses due to hysteresis...

On Tue, 01 Sep 2015 23:30:54 +0100, Tim Watts wrote:

On 01/09/15 21:47, Cursitor Doom wrote:
On Tue, 01 Sep 2015 02:28:37 -0700, robgraham wrote:

I've not been involved in switching PSU design but for something
generating 1.5A everything looked horribly lightweight. The switching
transformer appears to be the source of the heat.

Ideal transformers as you will know don't generate heat. So the heat
must be coming from the resistance of the windings. Be interesting to
measure that resistance and calculate the I^2R losses to see if they
come in line with reasonable expectations.


And some iron losses due to hysteresis...

True, but presumably not so much in an SMPSU. My money is on the stated
wattage of the load being incorrect.