So, I completed putting LEDs on my trailer. (LEDs are used to
indicate power and braking status) They are current limited by simple
500 ohm resistors, to approximately 25 mA. No big deal.

That made me think: most of the power to LEDs is wasted worthlessly in
those resistors. Only a small fraction of it is used to make
light. (my guess is about 85% of power is wasted)

Are there any LED driver kinds of chips that allow LEDs to be used in
a low power usage kind of situation (as opposed to running from a
truck alternator). That replace those resistors with something smarter.

The reason for my question is that I have a mailbox that used to be
often hit by vehicles. I have changed it to a higher visibility,
swingaway mailbox:

http://igor.chudov.com/projects/Mailbox/

but I would like to also add solar powered LEDs to it based on a WHY
NOT principle. (why not do it)

For this thing to work properly, it has to use as little power as
possible, so, I would like to know how LEDs are used in low power
situations.

i

So, I completed putting LEDs on my trailer. (LEDs are used to
indicate power and braking status) They are current limited by simple
500 ohm resistors, to approximately 25 mA. No big deal.

That made me think: most of the power to LEDs is wasted worthlessly in
those resistors. Only a small fraction of it is used to make
light. (my guess is about 85% of power is wasted)

Are there any LED driver kinds of chips that allow LEDs to be used in
a low power usage kind of situation (as opposed to running from a
truck alternator). That replace those resistors with something smarter.

The reason for my question is that I have a mailbox that used to be
often hit by vehicles. I have changed it to a higher visibility,
swingaway mailbox:

http://igor.chudov.com/projects/Mailbox/

but I would like to also add solar powered LEDs to it based on a WHY
NOT principle. (why not do it)

For this thing to work properly, it has to use as little power as
possible, so, I would like to know how LEDs are used in low power
situations.

So, I completed putting LEDs on my trailer. (LEDs are used to
indicate power and braking status) They are current limited by simple
500 ohm resistors, to approximately 25 mA. No big deal.

That made me think: most of the power to LEDs is wasted worthlessly in
those resistors. Only a small fraction of it is used to make
light. (my guess is about 85% of power is wasted)

Are there any LED driver kinds of chips that allow LEDs to be used in
a low power usage kind of situation (as opposed to running from a
truck alternator). That replace those resistors with something smarter.

The reason for my question is that I have a mailbox that used to be
often hit by vehicles. I have changed it to a higher visibility,
swingaway mailbox:

http://igor.chudov.com/projects/Mailbox/

but I would like to also add solar powered LEDs to it based on a WHY
NOT principle. (why not do it)

For this thing to work properly, it has to use as little power as
possible, so, I would like to know how LEDs are used in low power
situations.

i
There are some chips made for the purpose but they tend to be hard to

So, I completed putting LEDs on my trailer. (LEDs are used to
indicate power and braking status) They are current limited by simple
500 ohm resistors, to approximately 25 mA. No big deal.

That made me think: most of the power to LEDs is wasted worthlessly in
those resistors. Only a small fraction of it is used to make
light. (my guess is about 85% of power is wasted)

Are there any LED driver kinds of chips that allow LEDs to be used in
a low power usage kind of situation (as opposed to running from a
truck alternator). That replace those resistors with something smarter.

The reason for my question is that I have a mailbox that used to be
often hit by vehicles. I have changed it to a higher visibility,
swingaway mailbox:

http://igor.chudov.com/projects/Mailbox/

but I would like to also add solar powered LEDs to it based on a WHY
NOT principle. (why not do it)

For this thing to work properly, it has to use as little power as
possible, so, I would like to know how LEDs are used in low power
situations.

i

So, I completed putting LEDs on my trailer. (LEDs are used to
indicate power and braking status) They are current limited by simple
500 ohm resistors, to approximately 25 mA. No big deal.

That made me think: most of the power to LEDs is wasted worthlessly in
those resistors. Only a small fraction of it is used to make
light. (my guess is about 85% of power is wasted)

Are there any LED driver kinds of chips that allow LEDs to be used in
a low power usage kind of situation (as opposed to running from a
truck alternator). That replace those resistors with something smarter.

The reason for my question is that I have a mailbox that used to be
often hit by vehicles. I have changed it to a higher visibility,
swingaway mailbox:

http://igor.chudov.com/projects/Mailbox/

but I would like to also add solar powered LEDs to it based on a WHY
NOT principle. (why not do it)

For this thing to work properly, it has to use as little power as
possible, so, I would like to know how LEDs are used in low power
situations.

i

A switching power supply would be the way to go. I doubt that any are
made specifically for LED supplies, a

Tim Wescott wrote:

A switching power supply would be the way to go. I doubt that any are
made specifically for LED supplies, a


Readily available from a dozen manufacturers.

So there are. A quick web search got me many relevant hits.

Igor, juvenile hoodlums will thank you. Leaning out of a car window
clutching a baseball bat while going fast in the dark makes it very hard
to see mailboxes. Having one lit up by LEDs would be a blessing.

So much for bad humor:

A switching power supply would be the way to go. I doubt that any are
made specifically for LED supplies, and finding one that'll be efficient
at the low power levels you're looking at will be a challenge. So you
have your work cut out for you -- but you're known to be energetic.

On a sunny day (Mon, 12 Feb 2007 12:02:25 -0600) it happened Ignoramus21592
ignoramus21592@NOSPAM.21592.invalid> wrote in
jeSdnbCtStMsNk3YnZ2dnUVZ_vyunZ2d@giganews.com>:

So, I completed putting LEDs on my trailer. (LEDs are used to
indicate power and braking status) They are current limited by simple
500 ohm resistors, to approximately 25 mA. No big deal.

That made me think: most of the power to LEDs is wasted worthlessly in
those resistors. Only a small fraction of it is used to make
light. (my guess is about 85% of power is wasted)


Well, you could have put some LEDs in series on that 12V, and create a
constant current source with some FET or transistor.
This is the classic low component count LED constant current source:

k a k a k a k a
|
|---
| |---
| | select
| [ ] R for 25 mA
| |

http://igor.chudov.com/projects/Mailbox/

but I would like to also add solar powered LEDs to it based on a WHY
NOT principle. (why not do it)

Well light at night, sun during the day, you need at least a battery of sorts.

Well, you could have put some LEDs in series on that 12V, and create a
constant current source with some FET or transistor.
This is the classic low component count LED constant current source:

k a k a k a k a
|
|---
| |---
| | select
| [ ] R for 25 mA
| |



That's a great idea, very simple and elegant. Thanks.

Ignoramus21592 wrote:


Well, you could have put some LEDs in series on that 12V, and create a
constant current source with some FET or transistor.
This is the classic low component count LED constant current source:

k a k a k a k a
|
|---
| |---
| | select
| [ ] R for 25 mA
| |



That's a great idea, very simple and elegant. Thanks.


Also very wrong.
The efficiency would be negligible.

Ignoramus21592 wrote:

Well, you could have put some LEDs in series on that 12V, and create a
constant current source with some FET or transistor.
This is the classic low component count LED constant current source:

k a k a k a k a
|
|---
| |---
| | select
| [ ] R for 25 mA
| |

That's a great idea, very simple and elegant. Thanks.

Also very wrong.
The efficiency would be negligible.

Ignoramus21592 wrote:
....
For this thing to work properly, it has to use as little power as
possible, so, I would like to know how LEDs are used in low power
situations.

Igor, juvenile hoodlums will thank you. Leaning out of a car window
clutching a baseball bat while going fast in the dark makes it very hard
to see mailboxes. Having one lit up by LEDs would be a blessing.

So much for bad humor:

A switching power supply would be the way to go. I doubt that any are
made specifically for LED supplies, and finding one that'll be efficient
at the low power levels you're looking at will be a challenge. So you
have your work cut out for you -- but you're known to be energetic.

On Mon, 12 Feb 2007 10:12:28 -0800, Tim Wescott <tim@seemywebsite.com

Igor, juvenile hoodlums will thank you. Leaning out of a car window
clutching a baseball bat while going fast in the dark makes it very hard
to see mailboxes. Having one lit up by LEDs would be a blessing.

I know what you mean, but so far, all my mailbox accidents were NOT due to
juvenile hoodlums. They were due to people not knowing how to drive. Once
it was a snow plow, and another time it was some odiot who left his or her
car mirror lying next to the mailbox.

So much for bad humor:

A switching power supply would be the way to go. I doubt that any are
made specifically for LED supplies, and finding one that'll be efficient
at the low power levels you're looking at will be a challenge. So you
have your work cut out for you -- but you're known to be energetic.

Thanks Tim... I am still hoping that this is a standard problem...