Need same color bi-directional LED 3mm

On Sunday, 28 October 2018 19:22:17 UTC, Jeff Liebermann  wrote:
> On Sun, 28 Oct 2018 11:58:15 -0700 (PDT), tabbypurr wrote:
> >On Sunday, 28 October 2018 17:37:01 UTC, Jeff Liebermann  wrote:
> >> On Sun, 28 Oct 2018 03:53:39 -0700 (PDT), tabbypurr wrote:
> >> 
> >> >sounds like there just isn't room for what you want, unless 
> >> >you buy an unobtanium led. Unless you put a green LED behind the 
> >> >relay in the machine.
> >> 
> >> Putting the LED on the back side of the relay would probably be usable
> >> if I had the room.  If you look at the photo of the way these are
> >> mounted, the side facing the door is the bottom of the solenoid coil,
> >> which is facing the bottom of the LED.  One might think that it's not
> >> very visible in that position, but the LED lights up most of the clear
> >> plastic case and is therefore easily visible from most directions.
> >> Putting an LED on the opposite side would probably work equally well.
> >> 
> >> Also, at 24VDC and 5K series resistor, that's only 4.5ma.  I could
> >> probably lower the resistor value somewhat and improve the brightness.
> >> 
> >> >I'll skip the joke about going over an LED with a green pen.
> >> 
> >> Also, thank you for NOT suggesting replacing the LED with a 24V
> >> incandescent lamp.
> >> <https://www.eiko.com/category/77/2176>
> >
> >With a 36v lamp that might even work. Not 24v. You won't even need 
> >a colour filter. 
> 
> Y'er right.  The light bulb might also last longer if I run it
> undervoltage.
> 
> >Why don't you just accept there being no LED in there?
> 
> As I mumbled in my original posting, no LED would be perfectly
> acceptable, but I want something better.  Summerizing:
> 1.  All the 4PDT 24VDC relays I can buy from stock today include an
> LED indicator.
> 2.  All these relays have the diode inserted backward from the way the
> CNC vertical mill Bandit controller socket is wired.  However, I can
> buy reversed polarity relays from Omron, but really don't want to have
> two relays on the shelf.  Datasheet:
> <https://www.mouser.com/datasheet/2/307/my_ds_e_7_3_csm59-940997.pdf>
> 3.  I can reverse the LED, but there are some sockets on later
> controllers that are wired using the standard polarity.  With a
> maximum reverse voltage of 5VDC for the green LED, I don't like
> running with reverse polarity although a shorted LED in series with
> 5.2Kohms won't do much damage.
> 4.  Since I have to do the work, I want to keep the rewiring to a
> minimum.
> 5.  The operators and maintenance people are accustomed to green is
> good, red is bad.  Therefore replacing the LED with a bi-color LED
> will surely inspire midnight phone calls.  Very high on my list of
> design priorities is to prevent the phone from ringing.
> 6.  Various combinations of back to back LED's, SMD LED's, diode
> bridges, and incandescent lights are not acceptable because they won't
> fit, require too much wiring, reduce the solenoid to contact
> insulation, 
> 7.  The world market for bi-directional green-green 3mm LEDs seems to
> have been cornered by evil forces intent on ruining my day.
> 8.  Whatever else I forgot.
> 
> 
> Drivel:  Why is it that I have few headaches with complexicated
> problems, while the simple little things, like finding a usable LED,
> seem to be what is driving me insane?

Can you not find green/yellow, or something else without red? Purple stripes perhaps?

I don't think you'll like this, but it just might be worth a mention. Incandescents work for many years when heavily dimmed.


NT

On Sunday, October 28, 2018 at 6:08:11 PM UTC-4, Jeff Liebermann wrote:
> On Sun, 28 Oct 2018 13:26:14 -0700 (PDT),
> gnuarm.deletethisbit@gmail.com wrote:
> 
> >I gave you a link to a usable green/green bicolor LED.  What more do you want? 
> >Rick C. 
> 
> Perhaps free samples?  About 100 pcs will suffice.
> 
> I replied to your post with:
> <https://groups.google.com/forum/#!msg/sci.electronics.design/2NCYlHgUQy0/SiFwYL7gAQAJ>

Wrong post. Try this one. 

https://groups.google.com/d/msg/sci.electronics.design/2NCYlHgUQy0/6AC5FYjjAQAJ


> Since then, I've done some additional digging for Lite-On LTL-10CGJ
> (green-green) LEDs without much luck:
> <https://www.findchips.com/search/ltl-10cgj>
> I did find some surplus parts jobbers who claim to have stock, but
> these tend to have rather high prices.  I'm not that desperate for the
> parts:
> <https://www.electronics-distributor.com/components/Lite-On,Inc/LTL-10CGJ.html>
> <https://www.usa-global-chips.com/chips/lite-on/ltl-10cgj__overview.html>
> 
> Thanks again for the link.  At least I now know that the part exists.

You can order parts from these guys.  Here is the link again. 

https://www.lc-led.com/View/itemNumber/726

Rick C. 

On Sun, 28 Oct 2018 17:47:57 -0700 (PDT),
gnuarm.deletethisbit@gmail.com wrote:

>On Sunday, October 28, 2018 at 6:08:11 PM UTC-4, Jeff Liebermann wrote:
>> On Sun, 28 Oct 2018 13:26:14 -0700 (PDT),
>> gnuarm.deletethisbit@gmail.com wrote:
>> 
>> >I gave you a link to a usable green/green bicolor LED.  What more do you want? 
>> >Rick C. 
 
>> Perhaps free samples?  About 100 pcs will suffice.
>> 
>> I replied to your post with:
>> <https://groups.google.com/forum/#!msg/sci.electronics.design/2NCYlHgUQy0/SiFwYL7gAQAJ>

>Wrong post. Try this one. 
>https://groups.google.com/d/msg/sci.electronics.design/2NCYlHgUQy0/6AC5FYjjAQAJ

That points to:
<https://www.lc-led.com/View/itemNumber/726>
That 3mm LED has 3 leads with a common anode.  How am I suppose to
wire that for for back to back diode operation that will light up with
either polarity?  There were plenty of 3mm green-green 3mm LED's with
either common anode or common cathode available such as:
<https://www.ebay.com/itm/123452852566>
I couldn't figure out how to wire them, so I ignored those.  I
couldn't find any that had 2 LED's in series which could easily be
wired back to back.

Anyway, thanks for the suggestion.

-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On Sun, 28 Oct 2018 16:03:23 -0700 (PDT), tabbypurr@gmail.com wrote:

>Can you not find green/yellow, or something else without 
>red? Purple stripes perhaps?

No.  I've found red-green and red-blue but nothing else.  I couldn't
use it anyway because the convention that green means things are
working, and red means problems.  There are 2pin 3mm RGB LED's in
red-green-blue that look interesting, but I don't think anyone would
appreciate watching a color cycling light show.

>I don't think you'll like this, but it just might be worth a 
>mention. Incandescents work for many years when heavily dimmed.

Yep.  One of these perhaps:
<https://www.aliexpress.com/item/36v-50mA-3x8x25-miniature-lamp-bulb-light-a336/297910999.html>
The price is a bit high, but tolerable.  At 24v my guess(tm) is that
the 36v light will dissipate about 1 watt, which isn't horrible but
might be high in an unvented plastic cover.  By comparison, the
solenoid uses 83mw.  I'll need to make some temp measurements, but I
think it might work without melting.

If the red-green LED is unacceptable, I would probably go with gluing
two SMD 0805 green LED's together, wiring them back to back, and
living happily ever after.

I'll take back my previously having thanked you for NOT suggesting an
incandescent lamp.


-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On Monday, 29 October 2018 02:13:45 UTC, Jeff Liebermann  wrote:
> On Sun, 28 Oct 2018 16:03:23 -0700 (PDT), tabbypurr wrote:

> >Can you not find green/yellow, or something else without 
> >red? Purple stripes perhaps?
> 
> No.  I've found red-green and red-blue but nothing else.  I couldn't
> use it anyway because the convention that green means things are
> working, and red means problems.  There are 2pin 3mm RGB LED's in
> red-green-blue that look interesting, but I don't think anyone would
> appreciate watching a color cycling light show.

lol

> >I don't think you'll like this, but it just might be worth a 
> >mention. Incandescents work for many years when heavily dimmed.
> 
> Yep.  One of these perhaps:
> <https://www.aliexpress.com/item/36v-50mA-3x8x25-miniature-lamp-bulb-light-a336/297910999.html>
> The price is a bit high, but tolerable.  At 24v my guess(tm) is that
> the 36v light will dissipate about 1 watt, which isn't horrible but
> might be high in an unvented plastic cover.  By comparison, the
> solenoid uses 83mw.  I'll need to make some temp measurements, but I
> think it might work without melting.

1w is in the typical ballpark for a relay, so is fine in your average relay sized box. How much that surrounding bit of plastic impedes airflow is another question.

> If the red-green LED is unacceptable, I would probably go with gluing
> two SMD 0805 green LED's together, wiring them back to back, and
> living happily ever after.
> 
> I'll take back my previously having thanked you for NOT suggesting an
> incandescent lamp.

Lol.

How you might make a back to back 3 leg green work: Wires to the outer legs. An smd diode across each half, sandwiched between its legs. If you solder the inner lead to the smds first the outers should not be hard to do. That just might be a solution.


NT

On Sun, 28 Oct 2018 19:23:57 -0700 (PDT), tabbypurr@gmail.com wrote:

>How you might make a back to back 3 leg green work: Wires to 
>the outer legs. An smd diode across each half, sandwiched between 
>its legs. If you solder the inner lead to the smds first the 
>outers should not be hard to do. That just might be a solution.

Good idea.  I'll try it later tonite if I can find some green SMD
LEDs.  I may need to scrap some boards for parts.

The center to center lead spacing on a 3mm LED is 2.54mm.  The wire
spacing on a 0805 SMD LED is 2.0mm, so I think I can make it fit and
work.  It would be nice if I could get the light emitting "top" of the
SMD LED directly against the bottom of the existing 3mm LED for
maximum light transmission.  If it's not bright enough, one SMD LED to
light up the existing 3mm LED and another in parallel pointed the
opposite direction.  This may actually work.

My preliminary tentative thanks and undying gratitude if it works.  

-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On Sunday, October 28, 2018 at 9:42:16 PM UTC-4, Jeff Liebermann wrote:
> On Sun, 28 Oct 2018 17:47:57 -0700 (PDT),
> gnuarm.deletethisbit@gmail.com wrote:
> 
> >On Sunday, October 28, 2018 at 6:08:11 PM UTC-4, Jeff Liebermann wrote:
> >> On Sun, 28 Oct 2018 13:26:14 -0700 (PDT),
> >> gnuarm.deletethisbit@gmail.com wrote:
> >> 
> >> >I gave you a link to a usable green/green bicolor LED.  What more do you want? 
> >> >Rick C. 
>  
> >> Perhaps free samples?  About 100 pcs will suffice.
> >> 
> >> I replied to your post with:
> >> <https://groups.google.com/forum/#!msg/sci.electronics.design/2NCYlHgUQy0/SiFwYL7gAQAJ>
> 
> >Wrong post. Try this one. 
> >https://groups.google.com/d/msg/sci.electronics.design/2NCYlHgUQy0/6AC5FYjjAQAJ
> 
> That points to:
> <https://www.lc-led.com/View/itemNumber/726>
> That 3mm LED has 3 leads with a common anode.  How am I suppose to
> wire that for for back to back diode operation that will light up with
> either polarity?  There were plenty of 3mm green-green 3mm LED's with
> either common anode or common cathode available such as:
> <https://www.ebay.com/itm/123452852566>
> I couldn't figure out how to wire them, so I ignored those.  I
> couldn't find any that had 2 LED's in series which could easily be
> wired back to back.
> 
> Anyway, thanks for the suggestion.

O----+---|>|---+---|<|---+----O
     |         |         |
     +--/\/\/--+--/\/\/--+

Won't this do it? 

Rick C. 

On Sun, 28 Oct 2018 20:11:31 -0700 (PDT),
gnuarm.deletethisbit@gmail.com wrote:

>On Sunday, October 28, 2018 at 9:42:16 PM UTC-4, Jeff Liebermann wrote:
>> On Sun, 28 Oct 2018 17:47:57 -0700 (PDT),
>> gnuarm.deletethisbit@gmail.com wrote:
>> 
>> >On Sunday, October 28, 2018 at 6:08:11 PM UTC-4, Jeff Liebermann wrote:
>> >> On Sun, 28 Oct 2018 13:26:14 -0700 (PDT),
>> >> gnuarm.deletethisbit@gmail.com wrote:
>> >> 
>> >> >I gave you a link to a usable green/green bicolor LED.  What more do you want? 
>> >> >Rick C. 
>>  
>> >> Perhaps free samples?  About 100 pcs will suffice.
>> >> 
>> >> I replied to your post with:
>> >> <https://groups.google.com/forum/#!msg/sci.electronics.design/2NCYlHgUQy0/SiFwYL7gAQAJ>
>> 
>> >Wrong post. Try this one. 
>> >https://groups.google.com/d/msg/sci.electronics.design/2NCYlHgUQy0/6AC5FYjjAQAJ
>> 
>> That points to:
>> <https://www.lc-led.com/View/itemNumber/726>
>> That 3mm LED has 3 leads with a common anode.  How am I suppose to
>> wire that for for back to back diode operation that will light up with
>> either polarity?  There were plenty of 3mm green-green 3mm LED's with
>> either common anode or common cathode available such as:
>> <https://www.ebay.com/itm/123452852566>
>> I couldn't figure out how to wire them, so I ignored those.  I
>> couldn't find any that had 2 LED's in series which could easily be
>> wired back to back.
>> 
>> Anyway, thanks for the suggestion.
>
>O----+---|>|---+---|<|---+----O
>     |         |         |
>     +--/\/\/--+--/\/\/--+

>Won't this do it? 
>Rick C. 

I had thought of that but also noticed that the maximum LED reverse
voltage and current might be exceeded.  That's why I preferred the
back to back diode approach.

Assuming 24VDC operating voltage and a 2.0V forward voltage drop on
the LED, that puts 22VDC reverse voltage on the unlit LED which is
rated at 5V reverse maximum.  I don't know exactly how the LED with
react when it enters the reverse breakdown region, but if it
avalanches and conducts somewhere above 5V, there may be a problem.  I
found some vague references suggesting that the reverse avalanche
voltage is about 20V or more, which might eliminate the problem.

Looking at some typical specs,
<https://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTL-42x1,42x2.pdf>
it seems (not sure) that it will zener at something above 5VDC and
will tolerate no more than 100 microamps.  At a voltage of
   24v - 2.0v - 5.6v = 16.4V    (the 5.6v is my guess)
the existing 5.2K resistor will produce:
   16.4V / 5200ohms = 3.2ma
which greatly exceeds the 100 microamp reverse current limit.  

The maximum dissipation for green is 100mw.  With this arrangement,
the reverse polarized LED will dissipate:
   2.0V * 0.0032A = 6.4mw
which is much less than 100mw.  So, it just might survive reverse
conduction.  I don't know exactly what will happen, so it's probably
worth my time bench measuring the reverse breakdown voltage and
testing the idea.

"What destroys a LED in the reverse direction?"
<https://electronics.stackexchange.com/questions/173283/what-destroys-a-led-in-the-reverse-direction>
  "In my experience the standard 3mm and 5mm red LEDs can block 
  12V easily so I have used them as reverse polarity protection 
  in 12V systems where current is about 10 mA DONT use them on 
  a 24 Volt system some LEDs died at approx. 30V"

Thanks much for the suggestion.


-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On Sun, 28 Oct 2018 21:10:02 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

>On Sun, 28 Oct 2018 20:11:31 -0700 (PDT),
>gnuarm.deletethisbit@gmail.com wrote:
>>O----+---|>|---+---|<|---+----O
>>     |         |         |
>>     +--/\/\/--+--/\/\/--+

>>Won't this do it? 
>>Rick C. 

>I had thought of that but also noticed that the maximum LED reverse
>voltage and current might be exceeded.  That's why I preferred the
>back to back diode approach.
>
>Assuming 24VDC operating voltage and a 2.0V forward voltage drop on
>the LED, that puts 22VDC reverse voltage on the unlit LED which is
>rated at 5V reverse maximum.  I don't know exactly how the LED with
>react when it enters the reverse breakdown region, but if it
>avalanches and conducts somewhere above 5V, there may be a problem.  I
>found some vague references suggesting that the reverse avalanche
>voltage is about 20V or more, which might eliminate the problem.
>
>Looking at some typical specs,
><https://media.digikey.com/pdf/Data%20Sheets/Lite-On%20PDFs/LTL-42x1,42x2.pdf>
>it seems (not sure) that it will zener at something above 5VDC and
>will tolerate no more than 100 microamps.  At a voltage of
>   24v - 2.0v - 5.6v = 16.4V    (the 5.6v is my guess)
>the existing 5.2K resistor will produce:
>   16.4V / 5200ohms = 3.2ma
>which greatly exceeds the 100 microamp reverse current limit.  
>
>The maximum dissipation for green is 100mw.  With this arrangement,
>the reverse polarized LED will dissipate:
>   2.0V * 0.0032A = 6.4mw
>which is much less than 100mw.  So, it just might survive reverse
>conduction.  I don't know exactly what will happen, so it's probably
>worth my time bench measuring the reverse breakdown voltage and
>testing the idea.
>
>"What destroys a LED in the reverse direction?"
><https://electronics.stackexchange.com/questions/173283/what-destroys-a-led-in-the-reverse-direction>
>  "In my experience the standard 3mm and 5mm red LEDs can block 
>  12V easily so I have used them as reverse polarity protection 
>  in 12V systems where current is about 10 mA DONT use them on 
>  a 24 Volt system some LEDs died at approx. 30V"
>
>Thanks much for the suggestion.

Looks like it just might work.  I took a green 3mm LED, wired it in
series with a 2.2K resistor, and connected it to an HP6235A variable
voltage power supply.  I connected a DVM across the LED.  There was no
indication of any reverse conduction or voltage limiting to 40V.  So,
it just might work.  I don't have any of the 3 pin LED's in stock, so
I'll order some immediately.  Meanwhile, I get to ponder over why the
LED manufacturers specify a maximum of 5V reverse voltage when it
seems to be much higher.  Any clues?

Thanks again.

-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On Sun, 28 Oct 2018 21:48:31 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:
>Meanwhile, I get to ponder over why the
>LED manufacturers specify a maximum of 5V reverse voltage when it
>seems to be much higher.  Any clues?

"Failure modes for LEDs"
<http://lednique.com/technology-basics/failure-modes-leds/>
   Almost all LEDs can withstand 5 V reverse voltage. (We rely 
   on this to avoid damaging LEDs in Testing unknown LEDs.) If 
   you try your own reverse voltage limit testing you may find 
   that most have higher actual reverse voltage breakdown 
   voltages of 12 to 70 V. It would be unwise to depend on this 
   in a design project, however, as it is not guaranteed by the
   manufacturer and could change from batch to batch or vendor 
   to vendor.

"what is the reverse breakdown voltage of a red or green 5 mm led ?"
<https://www.eevblog.com/forum/beginners/what-is-the-reverse-breakdown-voltage-of-a-red-or-green-5-mm-led/>
   The breakdown voltage has been about 170V for the last 40 
   years at least for generic ones. You will see Chinese designs 
   that connect them to the mains without a diode for 120V 
   operation.  I've been testing them periodically since then, 
   placing them on the line for a couple weeks with a 47K resistor.
   There are some newer ones that have a really low breakdown 
   voltage.
   (...)
   Various red, yellow and green: they seem to cluster around 
   30-40V, and >110V (some over 150V).  Probably some die
   manufacturers / designs have softer doping profiles?
   (...)
   My understanding of the situation is that under reverse bias 
   below the avalanche breakdown threshold, the leakage current 
   is concentrated around existing lattice defects in the 
   junction depletion layer and if the bias voltage is high 
   enough, the resulting hot carriers cause the defects to grow.

<https://www.eevblog.com/forum/beginners/what-is-the-reverse-breakdown-voltage-of-a-red-or-green-5-mm-led/msg1114021/#msg1114021>
   And in summary
   red (N)        mean 50.2 V   std  3.2V
   green (N)      mean 89V      std 12.3V
   blue (N)       mean 50.8V    std 21.7V
   red (OS)       mean 27.3V    std  7.7V
     N = New LED's   OS = Old Stock

Looks like high brightness red will be a problem at 24VDC, but green
and ordinary red are will work:
<https://www.eevblog.com/forum/beginners/what-is-the-reverse-breakdown-voltage-of-a-red-or-green-5-mm-led/?action=dlattach;attach=287840;image>

Argh!



-- 
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558