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'[EE] What's a "bright" LED?'
2008\07\05@094016 by Tomás Ó hÉilidhe

picon face

Here's what I'm looking for:
   * A bi-colour two-lead LED which consists internally of two LED's in
parallel facing in opposite directions
   * The forward voltage of both colours must be less than 2.5 V
   * 20 mA should be enough to have it very lit
   * Extremely bright because I'm multiplexing them in a 30 stage
multiplexer and I want them to be visible in daylight

First thing I want to ask is:

Can someone suggest to me a minimal candela rating I should aim for? I
know 1 candela is the light given off a candle, but I haven't got much
of a clue how I should compare this to LED light.

2008\07\05@095254 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> Can someone suggest to me a minimal candela rating I should aim for? I
> know 1 candela is the light given off a candle, but I haven't got much
> of a clue how I should compare this to LED light.

There is no substitute for experience for this.  I guess this means you
*still* haven't done the LED tests I told you to do a week or two ago.  No,
I'm not just going to give you answers if you continue to refuse to do any
work on your own.  In this particular case any answer you get via email
won't be that useful anyway.  You're going to have to see this for yourself.
And yes, that means doing a little work on your own.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\05@122259 by Tomás Ó hÉilidhe

picon face


Olin Lathrop wrote:
> Tomás Ó hÉilidhe wrote:
>  
>> Can someone suggest to me a minimal candela rating I should aim for? I
>> know 1 candela is the light given off a candle, but I haven't got much
>> of a clue how I should compare this to LED light.
>>    
>
> There is no substitute for experience for this.  I guess this means you
> *still* haven't done the LED tests I told you to do a week or two ago.


Sorry Daddy, no I haven't done the tests. If I thought they'd be
productive I'd do them.


> No,
> I'm not just going to give you answers if you continue to refuse to do any
> work on your own.


Maybe next time I want to pick a resistor value I should take out my
breadboard and test what current I'll get through it when I apply a
certain voltage.


> In this particular case any answer you get via email
> won't be that useful anyway.  You're going to have to see this for yourself.
> And yes, that means doing a little work on your own.

No have LED's. No can do tests.

2008\07\05@125305 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> Sorry Daddy, no I haven't done the tests. If I thought they'd be
> productive I'd do them.

You don't have the experience to know what will be productive and what not.
I suspect the real reason however is that you'd actually have to do some
work, which you clearly have a aversion to.

> No have LED's. No can do tests.

Of course you can.  LEDs are are both cheap and available.  Your project
relies on them heavily, so you really should get some and play around with
them.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\05@133846 by Tamas Rudnai

face picon face
Another subject to the old topic.... ehhh

> Maybe next time I want to pick a resistor value I should take out my
> breadboard and test what current I'll get through it when I apply a
> certain voltage.

No, this is not the same. With a LED you already know what current source
you need, it's in the datasheet of the LED. What you do not know is if the
LED is bright enough or not - bright enough for YOUR application for YOUR
eyes... Olin keeps telling you this, but you do not seems to understand: See
how the LED is working for you - different LEDs, different current sources,
different frequencies / duty cycles.

With a resistor you may can have experience of capacitivness and
inductiveness of that resistor for example. Or measure the resistance with
high frequency - you'll be surprised...

Tamas


On Sat, Jul 5, 2008 at 5:22 PM, Tomás Ó hÉilidhe <spam_OUTtoeTakeThisOuTspamlavabit.com> wrote:

{Quote hidden}

>

2008\07\05@134102 by Tamas Rudnai

face picon face
> LEDs are are both cheap and available.

Yes, just go to Maplin and pick up a lucky bag for LEDs, you'll have enough
for playing for a while.

Tamas



On Sat, Jul 5, 2008 at 5:55 PM, Olin Lathrop <.....olin_piclistKILLspamspam@spam@embedinc.com>
wrote:

{Quote hidden}

>

2008\07\05@145331 by Tomás Ó hÉilidhe

picon face


Tamas Rudnai wrote:
>> Maybe next time I want to pick a resistor value I should take out my
>> breadboard and test what current I'll get through it when I apply a
>> certain voltage.
>>    
>
> No, this is not the same. With a LED you already know what current source
> you need, it's in the datasheet of the LED. What you do not know is if the
> LED is bright enough or not - bright enough for YOUR application for YOUR
> eyes... Olin keeps telling you this, but you do not seems to understand: See
> how the LED is working for you - different LEDs, different current sources,
> different frequencies / duty cycles.
>  

This applied to when the voltage source was very close to the forward
voltage of the diode. Since my source voltage is well above the diodes'
voltage drops, I don't need to worry about them being dim; I just pick
the right resistor and I'm good to go.

Theory will have to suffice for now because I haven't got the LED's to
test out practically.

Of course, if I was working with a lower voltage voltage source, there
might be some merit in the experiment.

2008\07\05@170854 by Gerhard Fiedler

picon face
Tomás Ó hÉilidhe wrote:

> Theory will have to suffice for now because I haven't got the LED's to
> test out practically.

I'm the first one to look into datasheets and calculate something before
trying it out -- but there are some things (especially when you don't know
what the number in a datasheet mean for you) where you /have/ to do some
experimenting and figure that out for yourself. It wouldn't help you if I
told you that 1 cd is good for me... you may want a different viewing
angle, or want it brighter or be happy with less bright, or whatever...

In what end of the world are you that LEDs are difficult to get by? You
don't need bicolor LEDs; you just need some LEDs for which you have
datasheets.

Gerhard

2008\07\05@173734 by Tamas Rudnai

face picon face
> In what end of the world are you that LEDs are difficult to get by? You
> don't need bicolor LEDs; you just need some LEDs for which you have
> datasheets.

I believe he's from Ireland too (same as me). Actually there is only one
shop so far I could find here in Dublin where you just go in and buy some
components: Maplin. Unfortunately Maplin is UK based and many times they do
not have in stock all of those components that is on the catalog. I'd say
too many times... Sometimes hard to get 100nF... However, a pack of LED is
easy, as they have that lucky bag which contains many LEDs different
colours, shapes and sizes. Also Radionics delivers in 2 days in my
experience. Fairchild and Digikey also good source here. So yes, end-of-the
world (next stage is America if you go a bit further to the west) but even
here he could have get those LEDs very easy.


Tamas
PS: Maplin is open at Sunday too...



On Sat, Jul 5, 2008 at 10:08 PM, Gerhard Fiedler <listsspamKILLspamconnectionbrazil.com>
wrote:

{Quote hidden}

>

2008\07\05@175123 by Tomás Ó hÉilidhe

picon face


Tamas Rudnai wrote:
> So yes, end-of-the
> world (next stage is America if you go a bit further to the west) but even
> here he could have get those LEDs very easy.

Try searching for two-pin LED's that have a certain minimal candela
rating. Impossible on Farnell's website. Might try Radionics, but I
think I've tried them already.

2008\07\05@181603 by Tamas Rudnai

face picon face
ie.farnell.com/jsp/search/browse.jsp?N=500008+1000125&Ntk=gensearch_001&Ntt=led&Ntx=


On Sat, Jul 5, 2008 at 10:50 PM, Tomás Ó hÉilidhe <.....toeKILLspamspam.....lavabit.com> wrote:

{Quote hidden}

>

2008\07\05@182226 by William \Chops\ Westfield

face picon face

On Jul 5, 2008, at 10:40 AM, Tamas Rudnai wrote:

>> LEDs are are both cheap and available.
>
> Yes, just go to Maplin and pick up a lucky bag for LEDs, you'll  
> have enough
> for playing for a while.

Um.  Useless, unfortunately.  Find an LED you like, and THEN what?  
It looks just like all the other LEDs, you don't know who made it or  
what its part number is, and in general, even if you've decided that  
it's the BEST LED IN THE WHOLE WORLD, you can't count on being able  
to buy any more of them!

Frankly, for high brightness, you're in trouble.  For some reason it  
seems to be quite uncommon for manufacturers to put together their  
brightest LED chips in this configuration.  High brightness 4-lead  
RGB leds are pretty common, and three-lead two-color aren't TOO hard  
to find, but the two-lead bipolars are rare...

BillW



2008\07\05@184042 by Tomás Ó hÉilidhe

picon face


Tamas Rudnai wrote:
> http://ie.farnell.com/jsp/search/browse.jsp?N=500008+1000125&Ntk=gensearch_001&Ntt=led&Ntx=
>

Congratulations you can search for an LED.

Now try searching for a bi-polar, bi-colour, bi-lead LED that has one
dome and that's above 50 mcd.

2008\07\05@185652 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> Now try searching for a bi-polar, bi-colour, bi-lead LED that has one
> dome and that's above 50 mcd.

First, the exercise was to find out how bright is bright enough, so
individual LEDs are just fine, even easier to use.  Since you don't know how
bright you need, you don't know whether 50mcd is enough or not.

Second, two-lead bicolor LEDs being so hard to find should tell you it's
probably a bad idea to rely on them in your design.  There are lots of
alternatives, like using separate LEDs, common anode or common cathode, or
even RGB LEDs.  Some of these solutions simplify the drive requirements and
even get around the problem of using color to convey information, which is
not a good idea as has already been discussed.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\05@192513 by Tomás Ó hÉilidhe

picon face


Olin Lathrop wrote:
> Since you don't know how
> bright you need, you don't know whether 50mcd is enough or not.
>  

I was hoping somebody with experience could tell me. If someone hadn't
got a clue about guitar strings and asked me what ones to get for a
beginner, I'd be able to tell them to get 8's or 9's. In similar vein, I
was hoping someone could cut it with a simple "You'd want about half a
candela at least".

> Second, two-lead bicolor LEDs being so hard to find should tell you it's
> probably a bad idea to rely on them in your design.  There are lots of
> alternatives, like using separate LEDs, common anode or common cathode, or
> even RGB LEDs.

Separate LED's wouldn't really do the trick for the game I have in mind.

I don't have enough pins on the 887 to work with 3-pin LED's.


> Some of these solutions simplify the drive requirements and
> even get around the problem of using color to convey information, which is
> not a good idea as has already been discussed.

The Connect4 game is well established as using colour to indicate the
players' chips. Of course a pattern could work instead of colour, but I
haven't seen any pattern LED's.

2008\07\05@193215 by William \Chops\ Westfield

face picon face

On Jul 5, 2008, at 9:22 AM, Tomás Ó hÉilidhe wrote:

>>> Can someone suggest to me a minimal candela rating

Ok.  1Cd (1000mCd) is sort of the beginning of the range that truely  
qualifies as "ultrabright."  That's for narrow viewing-angle LEDs;  
for your app you may want to consider wide-angle LEDs, even  
"diffused" domes, which will cut the Cd rating WAY down.
If you have a datasheet that talks about "lumens" rather than  
Candela, that's a better rating of overall "brightness."
The way I look at it, Cd is more relevant of you're shining the LED  
on something and want to know how bright the "spot" is, while Lumens  
is more relevant if you're looking AT the LED (NOT shining the LED in  
your eye!) and what to know how bright it looks.

BillW

2008\07\05@193637 by Jinx

face picon face
> Try searching for two-pin LED's that have a certain minimal candela
> rating. Impossible on Farnell's website. Might try Radionics, but I
> think I've tried them already.

What happened with these people I posted the other day ? Blue and
yellow superbright bi-colours

http://www.lc-led.com/Products/department/27

http://www.lc-led.com/View/itemNumber/411

http://www.lc-led.com/products/n500tby4d.html



2008\07\05@194951 by Tamas Rudnai

face picon face
> In similar vein, I was hoping someone could cut it with a simple "You'd
want about half a
> candela at least".

In similar vein what would you say if I'd ask you which string shall I buy
for my guitar - you don't know what do I have, do you? I can't play and
never ever get a guitar in my hand but I would even telling you certain
parameters of that string. And then if you tell me what string shall I buy I
will keep saying it is not good, does not sound good to me or broke off the
head machine.

Actually I found couple in Farnell (just have to use the right searching
phrase) but as you answered arrogant I just do not feel showing the link for
you. Other thing is that you still do not know about 50mcd - that's quite
high in my opinion, and it also indicated by the fact that you could not
find it easily. Once I almost got blind looking at the led directly - for an
indicator of your game board you'd probably enough much less - but back to
Olin's standard sentence: Try those leds out, see how bright are they...

Good luck,
Tamas



On Sun, Jul 6, 2008 at 12:24 AM, Tomás Ó hÉilidhe <EraseMEtoespam_OUTspamTakeThisOuTlavabit.com> wrote:

{Quote hidden}

>

2008\07\05@195201 by Tomás Ó hÉilidhe

picon face


Jinx wrote:
> What happened with these people I posted the other day ? Blue and
> yellow superbright bi-colours
>
> http://www.lc-led.com/Products/department/27
>
> http://www.lc-led.com/View/itemNumber/411
>
> http://www.lc-led.com/products/n500tby4d.html

Thanks for those links Jinx, I went through every one of them one by one
the other day. Unfortunately, they're 3-pin LED's but I'm looking for
2-pin ones.

2008\07\05@201147 by Jinx

face picon face
> No have LED's. No can do tests.

If you intend to sell this project, you are no longer a hobbyist and
need to be building circuits. If this involves a lot of searching and
scraping parts together with mail-order, so be it. You don't have
a monopoly on being at the/an arse-end of the world

People who probably know most about component sourcing are
contract assemblers. I suggest you get in touch with one. You
might also get their opinion on through-hole assembly

LEDs with ostensibly the same specs are likely to be different, so
you need at least to find the most reliable source and have s/w that
can adapt

Be aware of course that not all LEDs have excellent life-times,
so be prepared for extensive soak-testing of whatever you get


2008\07\05@202050 by Tomás Ó hÉilidhe

picon face


Tamas Rudnai wrote:
> In similar vein what would you say if I'd ask you which string shall I buy
> for my guitar - you don't know what do I have, do you? I can't play and
> never ever get a guitar in my hand but I would even telling you certain
> parameters of that string. And then if you tell me what string shall I buy I
> will keep saying it is not good, does not sound good to me or broke off the
> head machine.
>  


My supply voltage is 3 V, I'm multiplexing in 20 stages and I want the
LED's to be visible in daylight. There's your guitar.

> Actually I found couple in Farnell (just have to use the right searching
> phrase) but as you answered arrogant I just do not feel showing the link for
> you. Other thing is that you still do not know about 50mcd - that's quite
> high in my opinion, and it also indicated by the fact that you could not
> find it easily. Once I almost got blind looking at the led directly - for an
> indicator of your game board you'd probably enough much less - but back to
> Olin's standard sentence: Try those leds out, see how bright are they...


Nearly blinded looking at a 50 mcd LED? Is that not half the light of a
candle? How could nearly blind you? Do I misunderstand?

2008\07\05@202054 by Jinx

face picon face
> Since you don't know how bright you need, you don't know
> whether 50mcd is enough or not

Exactly right. The10mcd/10mA HP LEDs I've used are perfectly
bright at way less than 10mA

I've bought LEDs supposedly many times 10mcd and thought,
well they're pretty crap actually, even with the light off


2008\07\05@202710 by Jinx

face picon face
> Separate LED's wouldn't really do the trick for the game I have in
> mind

Why not ? 2 SMDs will fit into less space than a 5mm dome, and you
can use any colours you like. My assembler chose H150UR red for
power and tick indicators and they're plenty bright enough to be seen
with a light pipe

2008\07\05@202958 by Jinx

face picon face
> I believe he's from Ireland too (same as me). Actually there is only
> one shop so far I could find here in Dublin where you just go in and
> buy some components: Maplin

RS aren't represented in Ireland ? Nothing like Dixons ?

2008\07\05@203716 by Jinx

face picon face
> I believe he's from Ireland too (same as me)

Tamas, Ireland (or rather Eire) is often touted to New Zealanders
as an example of how a country of similar size and population can
have a successful technology sector. If that's true, it seems surprising
that there is no component supply infra-structure to support it, even
at retail level

2008\07\05@204051 by Jinx

face picon face
> Nearly blinded looking at a 50 mcd LED? Is that not half the
> light of a candle?

Correct. That's not half the light of a candle

> How could nearly blind you? Do I misunderstand?

Candles generally don't have lenses

2008\07\05@205457 by Tomás Ó hÉilidhe

picon face


Jinx wrote:
>> Nearly blinded looking at a 50 mcd LED? Is that not half the
>> light of a candle?
>>    
>
> Correct. That's not half the light of a candle
>  

Wups I meant one twentieth the light of a candle.

2008\07\05@224113 by William \Chops\ Westfield

face picon face

On Jul 5, 2008, at 4:34 PM, Jinx wrote:

> What happened with these people I posted the other day ? Blue and
> yellow superbright bi-colours
>
> http://www.lc-led.com/Products/department/27

two-color, but not "bi-polar" (2-lead)
Also rather depressingly expensive!

So does anyone know of any pre-made LED matrix displays that are  
bright enough to be daylight visible?  That might be another  
solution, and they're more likely to be bi-polar.

It might be better to redesign for three-lead LEDs; you'd have a lot  
more flexibility, including the ability to use the (relatively  
common) 4-lead RGB leds in various configurations (using only two of  
the three chips...)

BillW

2008\07\06@034343 by David P Harris

picon face
You might be interested in a matrix:
http://www.sparkfun.com/commerce/product_info.php?products_id=681

I don't know how bright they are.

David

William "Chops" Westfield wrote:
{Quote hidden}

2008\07\06@060656 by Tamas Rudnai

face picon face
> My supply voltage is 3 V, I'm multiplexing in 20 stages and I want the
> LED's to be visible in daylight. There's your guitar.

You need 20 LEDs, not 1:20 multiplexing, right? Did you see the piclist
techref link I have sent you in the other day?

Tamas




On Sun, Jul 6, 2008 at 1:20 AM, Tomás Ó hÉilidhe <toespamspam_OUTlavabit.com> wrote:

{Quote hidden}

>

2008\07\06@061435 by Tamas Rudnai

face picon face
> RS aren't represented in Ireland ? Nothing like Dixons ?

Yes, they are. They have a web shop and you can order it, and RS (alias
Radionics) are quite fast actually. What I meant is that there is no
component shops for hobbyists, only Maplin. You cannot just enter to the
shop and ask some LEDs and out it into your bag. In Hungary (my home
country) you have quite a few of these shops and the price is not that high
- higher than if you were buying in 1k pcs of each but definitely not that
expensive as in Maplin. In Dixons here AFAIK they do not have components,
only whole sale - correct me if I am wrong.

Tamas



On Sun, Jul 6, 2008 at 1:27 AM, Jinx <@spam@joecolquittKILLspamspamclear.net.nz> wrote:

> > I believe he's from Ireland too (same as me). Actually there is only
> > one shop so far I could find here in Dublin where you just go in and
> > buy some components: Maplin
>
> RS aren't represented in Ireland ? Nothing like Dixons ?
>
> -

2008\07\06@062228 by fred jones

picon face


>
> I was hoping somebody with experience could tell me. If someone hadn't
> got a clue about guitar strings and asked me what ones to get for a
> beginner, I'd be able to tell them to get 8's or 9's. In similar vein, I
> was hoping someone could cut it with a simple "You'd want about half a
> candela at least".

If that person told you they wanted to learn jazz, would you still direct them to 8s or 9s?  I certainly wouldn't!  What if this was a classical guitar, would you still direct them to 8s or 9s?  I certainly wouldn't.  I'd give them a starting place based on their needs and my experience.  Then I'd tell them to buy several and try them out and see what works for their needs.  I think you'll be hard pressed to find someone here who has thought of an LED in terms of candelas, just like trying to find someone here who has thought of batteries in terms of milliwatt/hours.  As has been said, buy some LEDs and try them.  They aren't that much money.

On my last project, I ordered 3 different color LEDs all from the same product line.  When I tested my circuits, I found that 2 of them, the red and the blue, were considerably brighter than the green...way too bright.  I raised their resistance values until they were toned down and matched the green LED.  Done, finished, that was that.  Not five threads on the PIClist about it.  Maybe that scenario doesn't work for you, so buy some and try them.

You have more threads here in the last 2 weeks than I've had in the 9yrs I've been on the PIClist.  That's ok, that's what the PIC list is for.  One thing I do is read, buy, experiement.  
FJ  
_________________________________________________________________
The i’m Talkaton. Can 30-days of conversation change the world?
http://www.imtalkathon.com/?source=EML_WLH_Talkathon_ChangeWorld

2008\07\06@062815 by Tamas Rudnai

face picon face
> Tamas, Ireland (or rather Eire) is often touted to New Zealanders
> as an example of how a country of similar size and population can
> have a successful technology sector. If that's true, it seems surprising
> that there is no component supply infra-structure to support it, even
> at retail level

In Ireland people speak English, plus they have a strong leg to Europe. Plus
Ireland gave a huge tax relief to companies if they put their subsidiaries
here. It was just perfect for US companies, so Microsoft, Apple, IBM, Xerox,
Symantec and loads of others are here. But now the picture changed a bit,
many of them are moving to India or China.

Anyway, you have web shops - not just for components but for many other
things. And even if they have shops many times they have to back order from
the UK. And many things are more expensive than in the UK - maybe have to
pay for the shipping or higher taxes or because you have no other choice I
do not really know the reason to be honest.

Anyway, Ireland is a nice place to live, just have to understand that is
highly dependent on the UK economy.

Tamas



On Sun, Jul 6, 2008 at 1:36 AM, Jinx <KILLspamjoecolquittKILLspamspamclear.net.nz> wrote:

> > I believe he's from Ireland too (same as me)
>
> Tamas, Ireland (or rather Eire) is often touted to New Zealanders
> as an example of how a country of similar size and population can
> have a successful technology sector. If that's true, it seems surprising
> that there is no component supply infra-structure to support it, even
> at retail level
>
> -

2008\07\06@073929 by Jinx

face picon face
> And even if they have shops many times they have to back order

Sounds like you need a friend to go shopping for you outside Ireland

How about Irish eBay ?

http://www.ebay.ie/

Quick search for diode, found eg Buy Now 50 ultrabright 3mm red
for E6.25. First similar listing I see at Radionics is E13.50 / 50. Not
a customer in Europe, obviously, but imagine the two would have
similar freight



2008\07\06@075339 by Tomás Ó hÉilidhe

picon face

Tamas Rudnai wrote:
> In Ireland people speak English

Don't forget about the likes of Inis Oírr; I'm hoping to head over there
for a week or so this summer: http://www.inisoirr-island.com/

"Feicfidh tú bealach saoil traidisiúnta á chleachtadh ag an bpobal de
252 atá ar an oileán seo agus is í an Ghaeilge a dteanga labhartha"

"You'll see a traditional way of life being practised by the community
of 252 people on the island and their spoken language is Irish"

2008\07\06@075559 by Tomás Ó hÉilidhe

picon face


Jinx wrote:
>> And even if they have shops many times they have to back order
>>    
>
> Sounds like you need a friend to go shopping for you outside Ireland
>
> How about Irish eBay ?
>
> http://www.ebay.ie/
>
> Quick search for diode, found eg Buy Now 50 ultrabright 3mm red
> for E6.25. First similar listing I see at Radionics is E13.50 / 50. Not
> a customer in Europe, obviously, but imagine the two would have
> similar freight

You're a genius thanks! They're dirt cheap too :-D

2008\07\06@083612 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> The Connect4 game is well established as using colour to indicate the
> players' chips. Of course a pattern could work instead of colour, but
> I haven't seen any pattern LED's.

I have no idea what a Connect4 game is, but it sounds like you want to
indicate three states for each of a number of positions in a rectangular
grid.  What about two discrete LEDs physically close to each other?  They
could still be different colors to add to the distinction.  Sortof like a
traffic light per game square.  Or modulate brightess so you have off medium
and bright?  I've used brightness and flashing patterns to indicate a number
of states with a single LED on several products, but I could see how this
could get confusing or annoying with a whole array of these.

As for driving them, that can be arranged.  Find LEDs and a display strategy
that works first, then have that decide your driving circuit, not the other
way around.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\06@084005 by olin piclist

face picon face
Jinx wrote:
> What happened with these people I posted the other day ? Blue and
> yellow superbright bi-colours

You didn't go out and actually buy them, then deliver them to his door?

********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\06@084645 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> Nearly blinded looking at a 50 mcd LED? Is that not half the light of
> a candle? How could nearly blind you? Do I misunderstand?

See, this is exactly why someone just can't give you a number.  You got a
number, and now you're asking more details.

You need to SEE FOR YOURSELF.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\06@085215 by olin piclist

face picon face
Jinx wrote:
> Tamas, Ireland (or rather Eire) is often touted to New Zealanders
> as an example of how a country of similar size and population can
> have a successful technology sector. If that's true, it seems
> surprising that there is no component supply infra-structure to
> support it, even at retail level

It's a evil plot by the leprechauns.  They also intercept packages with
electronic parts and change all the values a little.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\06@090053 by Jinx

face picon face
> They're dirt cheap too :-D

Compared with mail-order, that's an achievement that doesn't
require a lot of effort !!

If you're serious about getting a quantity of LEDs, it would be
worth getting in touch with a volume distributor like Arrow

http://www.arrowuk.com/

I've no idea of bulk pricing in Europe but I might expect perhaps
around NZ$15 (or less) / 100 (E7.25 / 100 -> E3.62 / 50) for
'average' utility LEDs, and upwards for higher performance.
E6.25 / 50 sounds like a reasonable deal but a distributor may
have a better price, especially for 100. And often it's more
economic in the long run to get 100 rather than 25 or 50

2008\07\06@090802 by Tamas Rudnai

face picon face
> It's a evil plot by the leprechauns.  They also intercept packages with
> electronic parts and change all the values a little.

Exactly! :-)



On Sun, Jul 6, 2008 at 1:54 PM, Olin Lathrop <RemoveMEolin_piclistTakeThisOuTspamembedinc.com>
wrote:

{Quote hidden}

> -

2008\07\06@144501 by Sean Breheny

face picon face
Tomas,

You are right to put a lot of emphasis on figuring out things
beforehand using a theoretical basis, but designs always require
iteration. In other words, you work out a basic scheme, then you test
it out, then you refine your calculations based on the results of the
test, and then you try it out again.

When it comes to LED brightness, there are many factors involved in
determining how bright an LED needs to be:

Candelas are a unit of light intensity, as in watts per solid angle,
except that they are also adjusted for the spectral response of the
human eye.

Lumens are a unit of total light output, similar to watts, but also
adjusted for the eye's response to color.

A certain LED will have a range of total output at a given current
(due to manufacturing differences). This range can be specified in
Lumens. The output will vary linearly with the current through the
LED.

This same LED will output this light in a non-uniform way (that is, it
has a radiation pattern due to the lensing effect of the case). The
Candela rating is the light intensity at the peak of the LED's pattern
(usually looking straight into it). The points where the light
intensity is cut in half (I think) are referred to as the LED's
viewing angle.

The human eye's response to brightness is close to logarhythmic so
unless you are going to put several LEDs next to each other and want
them to look identical, you normally do not care about changes in
intensity which are less than, say, 50%.

You stated that you want these LEDs to be easily visible in daylight.
You need to specify the range of angles for which you want this to be
true. I think that the packaging around the LEDs will also greatly
affect this.

I suspect that designing your LED light to look bright in full
sunlight will make it painfully bright indoors. You may even want to
be able to vary the drive and have a photosensor which detects the
ambient light and adjusts the LED drive accordingly.

Roughly, here's what you would need to do to try this mathematically
(but be prepared for the results to be wrong enough to require
iteration):

1) Determine the maximum background illumination level you need to
operate in (full sun you said)
2) Determine the range of angles you want someone to be able to see the LED from
3) Determine how uniform you want the illumination to be (i.e., the
original Connect4, I think, had large plastic buttons which lit up
rather than point sources like LEDs)
4) Take the entire surface area which the LED will light (i.e., the
"button") and compute the number of lumens of sunlight which might, at
max, fall on this area.
5) Determine how much of the light incident on that surface will be
reflected. Now call this Lc, as in light you have to compete with.
6) Assume that this light reflects back over the same range of angles
which your LED will. Under this assumption, your LED needs to emit Lc
lumens.
7) You can then convert the LED's radiation pattern to solid angle,
divide Lc by this solid angle in steradians, to get the required
intensity in Candela.

Sean




On Sun, Jul 6, 2008 at 8:48 AM, Olin Lathrop <spamBeGoneolin_piclistspamBeGonespamembedinc.com> wrote:
{Quote hidden}

>

2008\07\07@060312 by Alan B. Pearce

face picon face
>> http://ie.farnell.com/jsp/search/browse.jsp?N=500008+1000125&Ntk=gensearch_001&Ntt=led&Ntx=
>
>
>Congratulations you can search for an LED.
>
>Now try searching for a bi-polar, bi-colour, bi-lead LED
>that has one dome and that's above 50 mcd.

What is your fixation with a 2 pin LED? I would have thought the type of
drive circuit you were using would have been better with a 3 lead LED, if
using a bi-colour one.

And did you actually try using the selector that came up on the above link?
Scrolling down through it there are a fair number of bi-colour and
tri-colour LEDs, although I haven't gone looking at each to see what their
respective output light levels or pin configurations are.

Which ones came closest to your requirements, just looking at the selector?
I am sure someone here could come up with an item that would meet your
requirements, but I am also sure that the cost of it would shock you.

Have you actually been through the list to do a price/performance
comparison? As you are essentially looking at producing a toy, price is
going to be a major factor in how well it does in the market, so you need to
be looking at the price/performance figures early on to decide if it is
viable to go ahead.

2008\07\07@062318 by Alan B. Pearce

face picon face
>Tomás Ó hÉilidhe wrote:
>> The Connect4 game is well established as using colour to indicate the
>> players' chips. Of course a pattern could work instead of colour, but
>> I haven't seen any pattern LED's.
>
>I have no idea what a Connect4 game is, but it sounds like you want to
>indicate three states for each of a number of positions in a rectangular
>grid.

His YouTube video, at the link posted about a week ago, showed a pretty good
example of the project he is doing.

2008\07\08@085432 by M. Adam Davis

face picon face
On 7/6/08, Olin Lathrop <TakeThisOuTolin_piclistEraseMEspamspam_OUTembedinc.com> wrote:
> Tomás Ó hÉilidhe wrote:
> > The Connect4 game is well established as using colour to indicate the
> > players' chips. Of course a pattern could work instead of colour, but
> > I haven't seen any pattern LED's.
>
> I have no idea what a Connect4 game is

http://en.wikipedia.org/wiki/Connect_Four

It's a fairly common game in the US, could be thought of as vertical
tic tac toe where the winner needs to get four in a row, and pieces
are introduced at the top and fall down to the bottom or onto the last
piece played in a given column.  Can be had for $15 at nearly every
toy store.

http://www.amazon.com/Hasbro-4430-Connect-Four/dp/B00000IWI1

-Adam

<sarcasm>comment about doing your homework before commenting on
something you don't know much about</sarcasm> ;-D ;-D ;-D

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