Thinking of installing some small 15mm blue LED lights up the stair string/skirting in order to highlight each step, but most sets come with a combined transformer/plug.

As I will be hard-wiring the lights and have them controlled from a typical wall switch, the plug transformer does not lend itself to the installation coniditions. Therefore, I am thinking of chopping off the plug transformer and replace it with a new one that I can wire in and locate under the floorboards.

Assuming I can get a transformer that has all the required values for Watts, Volts and Amps to match the old one, is this a problem or am I just being over concerned?

Cordless Crazy wrote:


Thinking of installing some small 15mm blue LED lights up the stair
string/skirting in order to highlight each step, but most sets come
with a combined transformer/plug.

As I will be hard-wiring the lights and have them controlled from a
typical wall switch, the plug transformer does not lend itself to the
installation coniditions. Therefore, I am thinking of chopping off the
plug transformer and replace it with a new one that I can wire in and
locate under the floorboards.

Assuming I can get a transformer that has all the required values for
Watts, Volts and Amps to match the old one, is this a problem or am I
just being over concerned?



I see no problem with that. Just get a decent quality PSU that
won't catch fire If your are making your own up out of bits, I would
include a thermal fuse and an overcurrent fuse that's just right for the
setup. Even better, can you mount it somewhere accessible?

Cheers

Tim

Cordless Crazy wrote:

Thinking of installing some small 15mm blue LED lights up the stair
string/skirting in order to highlight each step, but most sets come
with a combined transformer/plug.

As I will be hard-wiring the lights and have them controlled from a
typical wall switch, the plug transformer does not lend itself to the
installation coniditions. Therefore, I am thinking of chopping off the
plug transformer and replace it with a new one that I can wire in and
locate under the floorboards.

Assuming I can get a transformer that has all the required values for
Watts, Volts and Amps to match the old one, is this a problem or am I
just being over concerned?

It depends.
It may be that the power supply is a bit specialised, and outputs a
constant current.
You do know about AC/DC?

In article ,
Cordless Crazy wrote:
Thinking of installing some small 15mm blue LED lights up the stair
string/skirting in order to highlight each step, but most sets come
with a combined transformer/plug.

As I will be hard-wiring the lights and have them controlled from a
typical wall switch, the plug transformer does not lend itself to the
installation coniditions. Therefore, I am thinking of chopping off the
plug transformer and replace it with a new one that I can wire in and
locate under the floorboards.

Assuming I can get a transformer that has all the required values for
Watts, Volts and Amps to match the old one, is this a problem or am I
just being over concerned?

No - LED voltages aren't critical. Unless being driven at maximum current.

Don't go for a much oversized transformer as the voltage may be higher
when not much loaded and remember the nominal AC output will not be the
same at DC due to rectifier losses.

But there's no reason why you can't break open the wall wart and fit its
electronics inside a suitable enclosure for under floor use. I'd use a
steel adaptable box rather larger than the wall wart to allow for heat
dissipation.

--
*i souport publik edekashun.

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

The message
from "Dave Plowman (News)" contains these words:

Don't go for a much oversized transformer as the voltage may be higher
when not much loaded and remember the nominal AC output will not be the
same at DC due to rectifier losses.

And if you're going to regulate the output remember...

If the LEDs are in series, regulate the current. That way if one fails
as a short the others won't all follow.

If the LEDs are parallel (which is how I'd do it), regulate the voltage.
That way, if one fails as open the others won't all follow suit. Though
of course, if one fails as a short things might get a bit smokey.

--
Skipweasel
Pay no attention to that man behind the curtain.

Guy King wrote:
The message
from "Dave Plowman (News)" contains these words:

Don't go for a much oversized transformer as the voltage may be higher
when not much loaded and remember the nominal AC output will not be the
same at DC due to rectifier losses.

And if you're going to regulate the output remember...

If the LEDs are in series, regulate the current. That way if one fails
as a short the others won't all follow.

If the LEDs are parallel (which is how I'd do it), regulate the voltage.
That way, if one fails as open the others won't all follow suit. Though
of course, if one fails as a short things might get a bit smokey.

LEDS are more or less constant voltage devices. Its extremely difficult
to control them by applying a particular voltage. The current to voltage
is a sharp exponential, whose exact location depends on the doping
levels and may vary between devices in different batches.

The only way to drive them at similar brightnesses is either in one long
chain with a ballast resistor or in parallel with a ballast resistor EACH.

Blue/white ones are fairly high voltage IIRC...about 4v, so any more
than 12 or so and you may fall foul of high voltage regulations.

I would personally use a toroidal 12v LV (halogen) transformer and a
bridge rectifier, and then a simple resistor of about 300 ohms in series
with each one.

In article ,
The Natural Philosopher wrote:
LEDS are more or less constant voltage devices. Its extremely difficult
to control them by applying a particular voltage. The current to voltage
is a sharp exponential, whose exact location depends on the doping
levels and may vary between devices in different batches.

They are extremely easy to dim by using a variable series resisor (pot) in
series with the current limiting one which sets the maximum current
allowed. They will dim to extinction in much the same way as a tungsten.
Or rather all the types I've used do.

--
*It is easier to get older than it is to get wiser.

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

Guy King wrote:

If the LEDs are parallel (which is how I'd do it), regulate the voltage.
That way, if one fails as open the others won't all follow suit. Though
of course, if one fails as a short things might get a bit smokey.

dont do that


NT