"Mike Harrison" <mike@whitewing.co.uk> wrote in message
news:u2n7n215v9l98td6p4c0oaaei3a9utu9d7@4ax.com...
> On 3 Dec 2006 07:58:44 -0800, "Viktor" <vkesler@gmail.com> wrote:
>
>>
>>
>>On Dec 3, 2:00 pm, Mike Harrison <m...@whitewing.co.uk> wrote:
>>> On 2 Dec 2006 10:07:55 -0800, "Viktor" <vkes...@gmail.com> wrote:
>>>
>>> >Is there such a thing?
>>> >All I can find on the net are smallish alphanumeric and graphical
>>> >displays.
>>>
>>> >Thanks,
>>>
>>> Viktor
>>>>Why OLED instead of conventional LED?
>>
>>Power consumption.
>
> Are OLEDs actually any more efficient than standard LEDs for the same
> light output? I suspect
> probably not.
> OLEDs typically compete with LCDs, which throw away at least 50% of th
> backlight light in the
> polariser, and then about 60% mode in the RGB filters. Not hard to compete
> with that with a
> light-emitting product.
>
>>>From what I've seen in the alphanumeric OLED datasheets, you get decent
>>visibility without backlighting. I was hoping to find single or several
>>digit displays to make a large clock module with only a few W
>>consumption.
>
> A few W will run a bunch of (carefully chosen) normal LEDs pretty darn
> bright.
> And it will last longer - OLEDs still have some lifetime issues ISTR.
Reply by Spehro Pefhany●December 4, 20062006-12-04
On 4 Dec 2006 10:27:10 -0800, the renowned "Viktor"
<vkesler@gmail.com> wrote:
>
>
>On Dec 3, 7:46 pm, Jim Granville <no.s...@designtools.maps.co.nz>
>wrote:
>
>>
>> How large a display are you after, on what power budget ?
>>
>> -jg
>
>Thanks for the answers everybody.
>I must admit, I've never actually seen a real live OLED so all my
>information is hazy at best. I imagined it to be something like an LCD
>with its own light source. So, I thought that in bright light it would
>have a reflective component like LCDs (I've worked with some big LCDs
>for petrol station pump displays and they are very good at high ambient
>light.)
>
>The largest 7-segment LED display I found (LITEON) had a 76mm digit
>height and was stated at 30mcd/20mA.
>With four digits, and about 20 segments, that would be about 5W. I can
>just about manage that, but it wouldn't be at its brightest and it
>would probably be poor in daylight.
>
>So, is it just wishful thinking or do OLEDs have a reflecive function
>like LCDs?
>
>Viktor
No, they don't.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by Mike Harrison●December 4, 20062006-12-04
On 4 Dec 2006 10:27:10 -0800, "Viktor" <vkesler@gmail.com> wrote:
>
>
>On Dec 3, 7:46 pm, Jim Granville <no.s...@designtools.maps.co.nz>
>wrote:
>
>>
>> How large a display are you after, on what power budget ?
>>
>> -jg
>
>Thanks for the answers everybody.
>I must admit, I've never actually seen a real live OLED so all my
>information is hazy at best. I imagined it to be something like an LCD
>with its own light source. So, I thought that in bright light it would
>have a reflective component like LCDs (I've worked with some big LCDs
>for petrol station pump displays and they are very good at high ambient
>light.)
>
>The largest 7-segment LED display I found (LITEON) had a 76mm digit
>height and was stated at 30mcd/20mA.
4" seven-seg displays are pretty common - I think I've also seen 6 & 8"
>With four digits, and about 20 segments, that would be about 5W. I can
>just about manage that, but it wouldn't be at its brightest and it
>would probably be poor in daylight.
If you need best readability for minimum power, you may want to look at using slim lines of discrete
LEDs ( e.g. PLCC-2/4 types) as the segments , so the light is more concentrated & contrast is
maximised.
Reply by Arlet●December 4, 20062006-12-04
Viktor wrote:
> On Dec 4, 7:40 pm, "Arlet" <usene...@ladybug.xs4all.nl> wrote:
> >.5W for 20 segments @ 20mA doesn't sound right. At 1 Volt forward
> > voltage, the power is 20mW/segment, or 400 mW total. I don't know the
> > LITEON specs, but even if Vf is somewhat higher, you don't get close to
> > 5 W.
> >
> > Of course, if you add in the dissipation in the series resistor, total
> > power will be higher, but you can reduce that by using a lower drive
> > voltage made from a switching power supply (use a SimpleSwitcher for
> > instance), in combination with a smaller resistor.
> >
> > If you multiplex the displays, you can use a higher peak current, so
> > the resistor can be even smaller, resulting in lower losses.
>
> Six LEDs in series for each segment. The chart gives 20mA If @ 12V Vf.
Ah, I see.. that makes sense.
However, at 30mcd/20mA, these aren't the most efficient. There are
single LEDs that are a few thousand mcd, at lower power. Perhaps you
can make your own display by taking some state of the art LEDs, and
mount them behind some diffusing plastic yourself ?
Reply by Viktor●December 4, 20062006-12-04
On Dec 4, 7:40 pm, "Arlet" <usene...@ladybug.xs4all.nl> wrote:
>.5W for 20 segments @ 20mA doesn't sound right. At 1 Volt forward
> voltage, the power is 20mW/segment, or 400 mW total. I don't know the
> LITEON specs, but even if Vf is somewhat higher, you don't get close to
> 5 W.
>
> Of course, if you add in the dissipation in the series resistor, total
> power will be higher, but you can reduce that by using a lower drive
> voltage made from a switching power supply (use a SimpleSwitcher for
> instance), in combination with a smaller resistor.
>
> If you multiplex the displays, you can use a higher peak current, so
> the resistor can be even smaller, resulting in lower losses.
Six LEDs in series for each segment. The chart gives 20mA If @ 12V Vf.
Reply by Arlet●December 4, 20062006-12-04
Viktor wrote:
> On Dec 3, 7:46 pm, Jim Granville <no.s...@designtools.maps.co.nz>
> wrote:
>
> >
> > How large a display are you after, on what power budget ?
> >
> > -jg
>
> Thanks for the answers everybody.
> I must admit, I've never actually seen a real live OLED so all my
> information is hazy at best. I imagined it to be something like an LCD
> with its own light source. So, I thought that in bright light it would
> have a reflective component like LCDs (I've worked with some big LCDs
> for petrol station pump displays and they are very good at high ambient
> light.)
>
> The largest 7-segment LED display I found (LITEON) had a 76mm digit
> height and was stated at 30mcd/20mA.
> With four digits, and about 20 segments, that would be about 5W. I can
> just about manage that, but it wouldn't be at its brightest and it
> would probably be poor in daylight.
5W for 20 segments @ 20mA doesn't sound right. At 1 Volt forward
voltage, the power is 20mW/segment, or 400 mW total. I don't know the
LITEON specs, but even if Vf is somewhat higher, you don't get close to
5 W.
Of course, if you add in the dissipation in the series resistor, total
power will be higher, but you can reduce that by using a lower drive
voltage made from a switching power supply (use a SimpleSwitcher for
instance), in combination with a smaller resistor.
If you multiplex the displays, you can use a higher peak current, so
the resistor can be even smaller, resulting in lower losses.
Reply by Viktor●December 4, 20062006-12-04
On Dec 3, 7:46 pm, Jim Granville <no.s...@designtools.maps.co.nz>
wrote:
>
> How large a display are you after, on what power budget ?
>
> -jg
Thanks for the answers everybody.
I must admit, I've never actually seen a real live OLED so all my
information is hazy at best. I imagined it to be something like an LCD
with its own light source. So, I thought that in bright light it would
have a reflective component like LCDs (I've worked with some big LCDs
for petrol station pump displays and they are very good at high ambient
light.)
The largest 7-segment LED display I found (LITEON) had a 76mm digit
height and was stated at 30mcd/20mA.
With four digits, and about 20 segments, that would be about 5W. I can
just about manage that, but it wouldn't be at its brightest and it
would probably be poor in daylight.
So, is it just wishful thinking or do OLEDs have a reflecive function
like LCDs?
Viktor
Reply by Mike Harrison●December 4, 20062006-12-04
On 3 Dec 2006 07:58:44 -0800, "Viktor" <vkesler@gmail.com> wrote:
>
>
>On Dec 3, 2:00 pm, Mike Harrison <m...@whitewing.co.uk> wrote:
>> On 2 Dec 2006 10:07:55 -0800, "Viktor" <vkes...@gmail.com> wrote:
>>
>> >Is there such a thing?
>> >All I can find on the net are smallish alphanumeric and graphical
>> >displays.
>>
>> >Thanks,
>>
>> Viktor
>>>Why OLED instead of conventional LED?
>
>Power consumption.
Are OLEDs actually any more efficient than standard LEDs for the same light output? I suspect
probably not.
OLEDs typically compete with LCDs, which throw away at least 50% of th backlight light in the
polariser, and then about 60% mode in the RGB filters. Not hard to compete with that with a
light-emitting product.
>>From what I've seen in the alphanumeric OLED datasheets, you get decent
>visibility without backlighting. I was hoping to find single or several
>digit displays to make a large clock module with only a few W
>consumption.
A few W will run a bunch of (carefully chosen) normal LEDs pretty darn bright.
And it will last longer - OLEDs still have some lifetime issues ISTR.
Reply by Jim Granville●December 3, 20062006-12-03
Viktor wrote:
>
> On Dec 3, 2:00 pm, Mike Harrison <m...@whitewing.co.uk> wrote:
>
>>On 2 Dec 2006 10:07:55 -0800, "Viktor" <vkes...@gmail.com> wrote:
>>
>>
>>>Is there such a thing?
>>>All I can find on the net are smallish alphanumeric and graphical
>>>displays.
>>
>>>Thanks,
>>
>>Viktor
>>
>>>Why OLED instead of conventional LED?
>
>
> Power consumption.
>
>>From what I've seen in the alphanumeric OLED datasheets, you get decent
> visibility without backlighting. I was hoping to find single or several
> digit displays to make a large clock module with only a few W
> consumption.
>
> I don't know if it's just a matter of time before these appear or if
> there's a technology constraint in making large OLED segments.
It's more likely simple economics - the market for jumbo LEDs is
relatively tiny, (and primitive) and anyone developing OLED displays
will chase the larger revenue streams first.
How large a display are you after, on what power budget ?
-jg
Reply by Arlet●December 3, 20062006-12-03
Viktor wrote:
> On Dec 3, 2:00 pm, Mike Harrison <m...@whitewing.co.uk> wrote:
> > On 2 Dec 2006 10:07:55 -0800, "Viktor" <vkes...@gmail.com> wrote:
> >
> > >Is there such a thing?
> > >All I can find on the net are smallish alphanumeric and graphical
> > >displays.
> >
> > >Thanks,
> >
> > Viktor
> >>Why OLED instead of conventional LED?
>
> Power consumption.
>
> From what I've seen in the alphanumeric OLED datasheets, you get decent
> visibility without backlighting. I was hoping to find single or several
> digit displays to make a large clock module with only a few W
> consumption.
>
> I don't know if it's just a matter of time before these appear or if
> there's a technology constraint in making large OLED segments.
>From what I've read, current OLEDs have lower efficiency than
conventional LEDs, so at the same brightness, a conventional LED should
have lower power.