IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.

They are very bright and eminently suitable for repacing 10W halogen
capsules to illuminate double/single glass fronted display cabinets
which fails often and offer severe difficulty in replacement.

However they are powered by 3 AAA batteries.

I've measured the current consumption, they draw 56 mA from 3 AAA
cells in series. So I rekon they'll last one day or thereabouts.

So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.

I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

Any better ideas from the panel ?

DG

On Mon, 04 Jun 2007 22:38:19 +0100, Derek Geldard
mused:

IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.

They are very bright and eminently suitable for repacing 10W halogen
capsules to illuminate double/single glass fronted display cabinets
which fails often and offer severe difficulty in replacement.

However they are powered by 3 AAA batteries.

I've measured the current consumption, they draw 56 mA from 3 AAA
cells in series. So I rekon they'll last one day or thereabouts.

So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.

I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

Any better ideas from the panel ?

Solar power.

I'd just stick a power supply in, if the lamps last longer then the
environmental impact will be less anyway.
--
Regards,
Stuart.

Derek Geldard wrote :
I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

The voltage of the 3x none rechargeables is 4.5v and the 3x
rechargeables 3.6v, so the light output would be considerably less.
There is also a good chance that simply charging the cells without any
sort of sensible control on the charger would quickly destroy the
cells.

Ideally what you need is a 4.5v DC regulated output wallwart, then just
turn it on when you want the light on. One of the general purpose ones
designed to power battery powered devices with a (3, 4.5, 6v etc.)
voltage switched output should do - but be wary of the cheap PSU's, not
all have a regulated output - some just rely on being fully loaded to
pull the voltage down.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On 4 Jun, 22:38, Derek Geldard wrote:
IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.

They are very bright and eminently suitable for repacing 10W halogen
capsules to illuminate double/single glass fronted display cabinets
which fails often and offer severe difficulty in replacement.

However they are powered by 3 AAA batteries.

I've measured the current consumption, they draw 56 mA from 3 AAA
cells in series. So I rekon they'll last one day or thereabouts.

So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.

I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

Any better ideas from the panel ?

DG

Ick. Just use a wallwart that delivers apx 4.5v. So one rated at
around 3.5v or so will give around 4.5 @56mA.


NT

In article , Harry Bloomfield
writes

Ideally what you need is a 4.5v DC regulated output wallwart, then just
turn it on when you want the light on. One of the general purpose ones
designed to power battery powered devices with a (3, 4.5, 6v etc.)
voltage switched output should do

Bung a 7805 in the output and a diode in series with the output to drop
the voltage to 4.4v?

--
(\__/) Bunny says NO to Windows Vista!
(='.'=) http://www.badvista.org/
(")_(") http://www.cs.auckland.ac.nz/~pgut00...ista_cost.html
http://www.schneier.com/crypto-gram-0702.html#8
http://www.theinquirer.net/default.aspx?article=39051
http://www.theinquirer.net/default.aspx?article=39087
http://www.theinquirer.net/default.aspx?article=38926
http://www.theinquirer.net/default.aspx?article=37091
http://www.theinquirer.net/default.aspx?article=36653
http://www.annoyances.org/exec/forum/winvista

In article ,
Derek Geldard wrote:
IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.

They are very bright and eminently suitable for repacing 10W halogen
capsules to illuminate double/single glass fronted display cabinets
which fails often and offer severe difficulty in replacement.

However they are powered by 3 AAA batteries.

I've measured the current consumption, they draw 56 mA from 3 AAA
cells in series. So I rekon they'll last one day or thereabouts.

So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.

I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

Any better ideas from the panel ?

LEDs aren't concerned about voltage as such but the current passing
through them. So you could use any DC supply with a suitable series
connected resistor or better one resistor per actual LED.

There's a formulae to calculate the resistor value for a single LED. It
is:-

VS - VF
R = ----------
I

Where R is the required resistance value in ohms
VS is the supply voltage
VF the forward voltage drop of the LED
I the current required in amps

So if we take 12 volts, a current of 20mA (about yours per LED), and a
forward voltage drop of 2 volts which is an average, we get a figure of
500 ohms per LED. Use the nearest available resistor value as it's not
critical.

However, white LEDs often have a VF rather higher than others and it could
be 4 volts. Or anything from approx 1 to 5 volts. ;-)

You can run an LED directly off a low voltage DC source like a battery,
but in practice off a ready made wall wart it's easier to get a readily
available one (cheap) and add a series resistor.

You can also run them off a low voltage AC source (things like modem wall
warts are usually AC) by adding a diode in parallel, but inversely
connected, to the LED, and doing the above calculation then halving the
value of the resistor.

LEDs are polarity sensitive and the negative connection (cathode) is
usually indicated by a flat on the body at the base. Reverse connection at
the higher end of their current range will usually knacker them.

--
*What are the pink bits in my tyres? Cyclists & Joggers*

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

Derek Geldard wrote:
IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.

Do you mean like these:
http://www.shinyshack.com/product.ph...=Dot-It-Lights
?



So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.

I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

Any better ideas from the panel ?


Find a suitable 4.5V or 5V adapter (surely you have a box of those
somewhere). Old phone chargers etc, just find one that's the right
voltage, rated at 60mA or more, and you're away.

--
Grunff

On Jun 5, 9:53 am, "Dave Plowman (News)" wrote:
In article ,
Derek Geldard wrote:





IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.
They are very bright and eminently suitable for repacing 10W halogen
capsules to illuminate double/single glass fronted display cabinets
which fails often and offer severe difficulty in replacement.
However they are powered by 3 AAA batteries.
I've measured the current consumption, they draw 56 mA from 3 AAA
cells in series. So I rekon they'll last one day or thereabouts.
So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.
I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.
Any better ideas from the panel ?

LEDs aren't concerned about voltage as such but the current passing
through them. So you could use any DC supply with a suitable series
connected resistor or better one resistor per actual LED.

There's a formulae to calculate the resistor value for a single LED. It
is:-

VS - VF
R = ----------
I

Where R is the required resistance value in ohms
VS is the supply voltage
VF the forward voltage drop of the LED
I the current required in amps

So if we take 12 volts, a current of 20mA (about yours per LED), and a

Assuming they are connected in parallel.

forward voltage drop of 2 volts which is an average, we get a figure of
500 ohms per LED. Use the nearest available resistor value as it's not
critical.

However, white LEDs often have a VF rather higher than others and it could

s/often/always/

be 4 volts. Or anything from approx 1 to 5 volts. ;-)

Show me a white LED datasheet that specifies a Vf anywhere near 1V ;-)

MBQ

On Jun 4, 10:55 pm, Harry Bloomfield
wrote:
Derek Geldard wrote :

I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

The voltage of the 3x none rechargeables is 4.5v and the 3x
rechargeables 3.6v, so the light output would be considerably less.

Unless a white LED driver chip is being used, in which case the
voltage will be nowhere near as critical.

MBQ

On Jun 5, 12:05 am, wrote:
On 4 Jun, 22:38, Derek Geldard wrote:





IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.

They are very bright and eminently suitable for repacing 10W halogen
capsules to illuminate double/single glass fronted display cabinets
which fails often and offer severe difficulty in replacement.

However they are powered by 3 AAA batteries.

I've measured the current consumption, they draw 56 mA from 3 AAA
cells in series. So I rekon they'll last one day or thereabouts.

So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.

I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

Any better ideas from the panel ?

DG

Ick. Just use a wallwart that delivers apx 4.5v. So one rated at
around 3.5v or so will give around 4.5 @56mA.


Still feeling tired when you wrote that? Depends if it's regulated or
not.

MBQ

On Jun 5, 1:27 pm, "
wrote:
On Jun 5, 9:53 am, "Dave Plowman (News)" wrote:





In article ,
Derek Geldard wrote:

IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.
They are very bright and eminently suitable for repacing 10W halogen
capsules to illuminate double/single glass fronted display cabinets
which fails often and offer severe difficulty in replacement.
However they are powered by 3 AAA batteries.
I've measured the current consumption, they draw 56 mA from 3 AAA
cells in series. So I rekon they'll last one day or thereabouts.
So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.
I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.
Any better ideas from the panel ?

LEDs aren't concerned about voltage as such but the current passing
through them. So you could use any DC supply with a suitable series
connected resistor or better one resistor per actual LED.

There's a formulae to calculate the resistor value for a single LED. It
is:-

VS - VF
R = ----------
I

Where R is the required resistance value in ohms
VS is the supply voltage
VF the forward voltage drop of the LED
I the current required in amps

So if we take 12 volts, a current of 20mA (about yours per LED), and a

Assuming they are connected in parallel.


Which, of course, they almost certainly are. Brain fart.

MBQ

On 5 Jun, 13:32, "
wrote:
On Jun 5, 1:27 pm, "
wrote:
Assuming they are connected in parallel.

Which, of course, they almost certainly are. Brain fart.

MBQ

Not always though. I have just been looking at using LEDs as a row of
lights on the stairs and the data sheet shows them connected in series
with a constant current power supply. I am assuming that the PSU will
up its voltage as more LEDs are connected to maintain the current.

Andrew

On Jun 5, 4:30 pm, Andrew wrote:
On 5 Jun, 13:32, "
wrote:

On Jun 5, 1:27 pm, "
wrote:
Assuming they are connected in parallel.

Which, of course, they almost certainly are. Brain fart.

MBQ

Not always though. I have just been looking at using LEDs as a row of
lights on the stairs and the data sheet shows them connected in series
with a constant current power supply. I am assuming that the PSU will
up its voltage as more LEDs are connected to maintain the current.

Andrew

But the OP specifically stated they're run from a 4.5v source so
either they are in parallel (Vf for 3 white LEDs is 4.5V) or
there's a controller chip boosting the voltage. Most white LED
controller chips are, however, designed for parallel operation.

MBQ

On 6 Jun, 13:26, "
wrote:


But the OP specifically stated they're run from a 4.5v source so
either they are in parallel (Vf for 3 white LEDs is 4.5V) or
there's a controller chip boosting the voltage. Most white LED
controller chips are, however, designed for parallel operation.

MBQ

I didn't intend to imply that these were in series. I was merely
pointing out that I had also assumed LEDs were always wired in
parallel but had just come across some in my search for recessed stair
lights where the manufacturer explicitly stated that they were in
series. There particular ones being driven by a 350mA constant current
supply.

Andrew

On 5 Jun, 13:30, "
wrote:
On Jun 5, 12:05 am, wrote:
On 4 Jun, 22:38, Derek Geldard wrote:

IKEA have *New*-ly started offering a light module with 3 very bright
white LED's in a single plastic capsule "Grosby" £2.99.

They are very bright and eminently suitable for repacing 10W halogen
capsules to illuminate double/single glass fronted display cabinets
which fails often and offer severe difficulty in replacement.

However they are powered by 3 AAA batteries.

I've measured the current consumption, they draw 56 mA from 3 AAA
cells in series. So I rekon they'll last one day or thereabouts.

So what is needed is a means of efficiently powering them from the
mains, that avoids the high power consumption and failure of the old
10W halogens.

I'm considering such tricks as powering them from 3 AAA rechargables
and charging them via a timeswitch or an electronic substitute so
that they charge only (say) 10% of the day (which surely should be
enough) to save energy. Given the heat losses in "Wall Wart" type
transformers.

Any better ideas from the panel ?

DG

Ick. Just use a wallwart that delivers apx 4.5v. So one rated at
around 3.5v or so will give around 4.5 @56mA.

Still feeling tired when you wrote that? Depends if it's regulated or
not.

MBQ

few warts are regulated.


NT