LEDs that are visible in sunlight

J

Jason Hsu

Guest
What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,
the LEDs should be at least 2000 mcds in brightness, have at least a
60-degree viewing
angle, and have clear or diffused lenses.

But for all the sources of LEDs, the >=2000 mcd LEDs have viewing
angles that are no larger than about 20 degrees. I realize that
there will be some trade-off due to energy issues (analogous to
highly directional antennas vs. omnidirectional antennas), but I'd
like to hear your real world experiences.

What do you suggest? Should I trade off viewing angle to get the 2000
mcds? Should I trade off the mcds to get the 60 degree viewing angle?
Do I simply need to look harder and be prepared to pay more?

Jason Hsu, AG4DG
http://www.jasonhsu.com/ee.html
http://groups.yahoo.com/group/eeham/
http://groups.yahoo.com/group/resume_hyperinflation_fighters/
http://groups.yahoo.com/group/gmu-ece-control/
 
Jason Hsu wrote:

What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,
the LEDs should be at least 2000 mcds in brightness, have at least a
60-degree viewing
angle, and have clear or diffused lenses.

But for all the sources of LEDs, the >=2000 mcd LEDs have viewing
angles that are no larger than about 20 degrees. I realize that
there will be some trade-off due to energy issues (analogous to
highly directional antennas vs. omnidirectional antennas), but I'd
like to hear your real world experiences.

What do you suggest? Should I trade off viewing angle to get the 2000
mcds? Should I trade off the mcds to get the 60 degree viewing angle?
Do I simply need to look harder and be prepared to pay more?

Jason Hsu, AG4DG
http://www.jasonhsu.com/ee.html
http://groups.yahoo.com/group/eeham/
http://groups.yahoo.com/group/resume_hyperinflation_fighters/
http://groups.yahoo.com/group/gmu-ece-control/
Click to expand...
Perhaps you should think about using an LCD? More involved to drive,
but certainly visible in sunlight!

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,

Perhaps you should think about using an LCD? More involved to drive,
but certainly visible in sunlight!
Click to expand...
Uhhh...

Take a walk through the strip in Las Vegas some time, count the LED
billboards. Count the plasma billboards. Count the LCD billboards.
You'll be able to count LCDs on the fingers of one elbow.
 
Luxeon emitters -- quite expensive, big and brite

Agilent has a whole series of ultra-brights on their website.

Note -- an LED's brightness is inversely related to temperature --

"Jason Hsu" <jason_hsu@my-deja.com> wrote in message
news:f7d9a152.0404302033.907106b@posting.google.com...
What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,
the LEDs should be at least 2000 mcds in brightness, have at least a
60-degree viewing
angle, and have clear or diffused lenses.

But for all the sources of LEDs, the >=2000 mcd LEDs have viewing
angles that are no larger than about 20 degrees. I realize that
there will be some trade-off due to energy issues (analogous to
highly directional antennas vs. omnidirectional antennas), but I'd
like to hear your real world experiences.

What do you suggest? Should I trade off viewing angle to get the 2000
mcds? Should I trade off the mcds to get the 60 degree viewing angle?
Do I simply need to look harder and be prepared to pay more?

Jason Hsu, AG4DG
http://www.jasonhsu.com/ee.html
http://groups.yahoo.com/group/eeham/
http://groups.yahoo.com/group/resume_hyperinflation_fighters/
http://groups.yahoo.com/group/gmu-ece-control/
Click to expand...
 
Tim Wescott wrote:
Jason Hsu wrote:

What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,
the LEDs should be at least 2000 mcds in brightness, have at least a
60-degree viewing
angle, and have clear or diffused lenses.

But for all the sources of LEDs, the >=2000 mcd LEDs have viewing
angles that are no larger than about 20 degrees. I realize that there
will be some trade-off due to energy issues (analogous to highly
directional antennas vs. omnidirectional antennas), but I'd like to
hear your real world experiences.

What do you suggest? Should I trade off viewing angle to get the 2000
mcds? Should I trade off the mcds to get the 60 degree viewing angle?
Do I simply need to look harder and be prepared to pay more?

Jason Hsu, AG4DG
http://www.jasonhsu.com/ee.html
http://groups.yahoo.com/group/eeham/
http://groups.yahoo.com/group/resume_hyperinflation_fighters/
http://groups.yahoo.com/group/gmu-ece-control/


Perhaps you should think about using an LCD? More involved to drive,
but certainly visible in sunlight!

There certainly are led's bright enough to see in daylight. Many of the
Click to expand...
new traffic signals actually use leds! Not to mention the brake lights
on many trucks. But these are clusters of smaller leds packed into a
tight bundle and housed in reflector.
 
Tim Wescott <tim@wescottnospamdesign.com> wrote in message news:<1096ap5ov6ece5d@corp.supernews.com>...
Perhaps you should think about using an LCD? More involved to drive,
but certainly visible in sunlight!
Click to expand...
The application is an SWR/wattmeter for amateur radio. An LCD would
not be suitable because the power level fluctuates many times per
second during voice transmissions (AM or SSB modes). This would
render the numeric readout useless. True, there are ways to smooth
out the fluctuations, but that would make the SWR/wattmeter less
responsive. On the other hand, an LED display in dot mode would
simply appear to be in bar graph mode during these voice
transmissions.

Jason Hsu, AG4DG
http://www.jasonhsu.com/ee.html
http://groups.yahoo.com/group/eeham/
http://groups.yahoo.com/group/resume_hyperinflation_fighters/
http://groups.yahoo.com/group/gmu-ece-control/
 
The application is an SWR/wattmeter for amateur radio. An LCD would
not be suitable because the power level fluctuates many times per
second during voice transmissions (AM or SSB modes). This would
render the numeric readout useless. True, there are ways to smooth
out the fluctuations, but that would make the SWR/wattmeter less
responsive. On the other hand, an LED display in dot mode would
simply appear to be in bar graph mode during these voice
transmissions.
Click to expand...
It's not such a worry. I have SMD leds from chicago miniature, in a product
with light pipes, that are quite visible outdoors in full sun.
www.mobilecommand.net
 
Should I trade off viewing angle to get the 2000 mcds?
Jason Hsu, AG4DG
Click to expand...
As Tim said, do think about a different (reflective) technology.
If you're stuck on LEDs, recess them into a black substrate.
 
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message news:<RPCdncfCgPFbIA7dRVn-uQ@comcast.com>...
It's not such a worry. I have SMD leds from chicago miniature, in a product
with light pipes, that are quite visible outdoors in full sun.
www.mobilecommand.net
Click to expand...
What are the specs? How many mcds? What is the viewing angle?

Jason Hsu, AG4DG
http://www.jasonhsu.com/ee.html
http://groups.yahoo.com/group/eeham/
http://groups.yahoo.com/group/resume_hyperinflation_fighters/
http://groups.yahoo.com/group/gmu-ece-control/
 
Lewin A.R.W. Edwards wrote:

What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,

Perhaps you should think about using an LCD? More involved to drive,
but certainly visible in sunlight!


Uhhh...

Take a walk through the strip in Las Vegas some time, count the LED
billboards. Count the plasma billboards. Count the LCD billboards.
You'll be able to count LCDs on the fingers of one elbow.
Click to expand...
Take a walk through the electronics department of your local store.
Count the LED calculators. Count the plasma calculators. Count the LCD
calculators.

Maybe I'm wrong but I thought the OP was talking about handheld, battery
powered equipment.

If he's building stoplights, yes LED's are the right choice.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
In article <f7d9a152.0404302033.907106b@posting.google.com>, Jason Hsu wrote:
What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,
the LEDs should be at least 2000 mcds in brightness, have at least a
60-degree viewing
angle, and have clear or diffused lenses.

But for all the sources of LEDs, the >=2000 mcd LEDs have viewing
angles that are no larger than about 20 degrees.
Click to expand...
30 degree ~5,000 mcd (at 20 mA) and 45 degree 2,000-3,000 mcd (at 20 mA)
are now available in orangish red, reddish orange, green and white.

60 degrees is less common for high brightness LEDs and usually made with a
diffused package, but should be able to exceed 1,000 mcd.

There are rectangular flat-tip packages with a nominal viewing angle of
100-120 degrees and those get around 500 mcd, maybe somewhat more
nowadays (at least for green and white).

- Don Klipstein (don@misty.com)
 
"Jason Hsu" <jason_hsu@my-deja.com> wrote in message
news:f7d9a152.0405011626.6ad4861f@posting.google.com...
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:<RPCdncfCgPFbIA7dRVn-uQ@comcast.com>...

It's not such a worry. I have SMD leds from chicago miniature, in a
product
with light pipes, that are quite visible outdoors in full sun.
www.mobilecommand.net

What are the specs? How many mcds? What is the viewing angle?
Click to expand...
CMDA5-1 is the part number.
The MCD rating is not spectacular, but they are surprisingly bright, and
quite visible in full summer sun.
 
"Jason Hsu" <jason_hsu@my-deja.com> wrote in message
news:f7d9a152.0405011626.6ad4861f@posting.google.com...
"Dave VanHorn" <dvanhorn@cedar.net> wrote in message
news:<RPCdncfCgPFbIA7dRVn-uQ@comcast.com>...

It's not such a worry. I have SMD leds from chicago miniature, in a
product
with light pipes, that are quite visible outdoors in full sun.
www.mobilecommand.net

What are the specs? How many mcds? What is the viewing angle?

Jason Hsu, AG4DG
http://www.jasonhsu.com/ee.html
http://groups.yahoo.com/group/eeham/
http://groups.yahoo.com/group/resume_hyperinflation_fighters/
http://groups.yahoo.com/group/gmu-ece-control/
Click to expand...
Jason -

Time to visit your local auto supply store for the latest stop and turn
indicators (which are slowly replacing bulbs)
... of course largely 12 vdc

gb
 
What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,

Perhaps you should think about using an LCD? More involved to drive,
but certainly visible in sunlight!

Take a walk through the strip in Las Vegas some time, count the LED

Maybe I'm wrong but I thought the OP was talking about handheld, battery
powered equipment.
Click to expand...
Yes... but actually that's not where your thinking and mine diverged.
I'm not sure why, but I was thinking of transmissive LCDs (i.e.
backlit color TFTs and STNs), which by and large are totally
unreadable in sunlight.
 
Lewin A.R.W. Edwards wrote:

What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,

Perhaps you should think about using an LCD? More involved to drive,
but certainly visible in sunlight!

Take a walk through the strip in Las Vegas some time, count the LED

Maybe I'm wrong but I thought the OP was talking about handheld, battery
powered equipment.


Yes... but actually that's not where your thinking and mine diverged.
I'm not sure why, but I was thinking of transmissive LCDs (i.e.
backlit color TFTs and STNs), which by and large are totally
unreadable in sunlight.
Click to expand...
I have a radio from Tandy Aerospace in my truck. It's an otherwise
cheap piece of crap (the radio, the radio), but it _does_ have an
always-on LCD clock that's reflective when the truck's off and backlit
when the truck's on. Very nice. Doesn't make up for the sound when
it's turned on, though...

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
OK, I built a small 4 digit score board for use outside, and I used LEDS
I salvaged from clusters I bought on E-Bay. The clusters were red/green
mix, and the red ones really are bright in sunlight. Oddly enough the
guy e-mailed me recently to say he had more of 'em for sale.

Here's the web addy he gave me;

http://www.evaluecomp.com
(The clusters are on page 5 of the LED list)

It takes a fair amount of effort to get the leds out of the clusters. I
just cut the case off, and used a blow torch and heated the base until
the solder got hot enough to pull the pcb off the back, then I just
broke apart the expoxy or glue or whatever and retrieved the leds. I had
about 93% success rate, with the other 7% damaged or failed after they
were removed.

Works nice, even at the beach, but the green ones can be hard to see
sometimes.

- Tim -


In article <608b6569.0405030713.5f0ff15@posting.google.com>,
larwe@larwe.com says...
What LEDs do you use for a display that needs to be readable in
sunlight?Obviously, regular LEDs are too dim. From what I have heard,

Perhaps you should think about using an LCD? More involved to drive,
but certainly visible in sunlight!

Take a walk through the strip in Las Vegas some time, count the LED

Maybe I'm wrong but I thought the OP was talking about handheld, battery
powered equipment.

Yes... but actually that's not where your thinking and mine diverged.
I'm not sure why, but I was thinking of transmissive LCDs (i.e.
backlit color TFTs and STNs), which by and large are totally
unreadable in sunlight.
Click to expand...
 
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