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'[OT]: 3 colors from an LED'
2000\06\26@140049 by Dan Michaels

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Andy wrote:
>I need to generate Red, Amber-ish, and Green from a single LED body (standard
>T1.75 size).
>
>I am limited to a common-cathode device with two anodes to select the desired
>color.
>
>The P391 from Digi-Key doesn't blend the colors well when both LEDs are turned
>on, it's obviously a red and a green LED in the same package.
>

Try pulsing red and green on opposite phase, with various duty cycles
for different amber hues. To trick the eye, ie, to get persistence of
vision, use pulserate >> 25 hz.

2000\06\26@141129 by Bennett, Matt

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I have not seen any device that mixes the colors perfectly- I can always see
where the green die is and where the red die is.  You might have some luck
if you use a light-pipe, which should mix the colors a bit more.  Also a
more opaque, less focused package could help too.

Matt Bennett

{Original Message removed}

2000\06\26@142350 by Andrew Kunz

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Did that.  You still see a red side and a green side.

Good idea, though.

Andy









Dan Michaels <spam_OUToricomTakeThisOuTspamLYNX.SNI.NET> on 06/26/2000 01:59:44 PM

Please respond to pic microcontroller discussion list <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>








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Subject: [OT]: 3 colors from an LED








Andy wrote:
>I need to generate Red, Amber-ish, and Green from a single LED body (standard
>T1.75 size).
>
>I am limited to a common-cathode device with two anodes to select the desired
>color.
>
>The P391 from Digi-Key doesn't blend the colors well when both LEDs are turned
>on, it's obviously a red and a green LED in the same package.
>

Try pulsing red and green on opposite phase, with various duty cycles
for different amber hues. To trick the eye, ie, to get persistence of
vision, use pulserate >> 25 hz.

2000\06\26@142353 by Andrew Kunz

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We are using external diffusers as well, with little improvement.

Andy









"Bennett, Matt" <.....Matt.BennettKILLspamspam.....ANDREW.COM> on 06/26/2000 02:10:09 PM

Please respond to pic microcontroller discussion list <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>








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cc:      (bcc: Andrew Kunz/TDI_NOTES)



Subject: Re: [OT]: 3 colors from an LED








I have not seen any device that mixes the colors perfectly- I can always see
where the green die is and where the red die is.  You might have some luck
if you use a light-pipe, which should mix the colors a bit more.  Also a
more opaque, less focused package could help too.

Matt Bennett

{Original Message removed}

2000\06\26@150747 by Dan Michaels
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Andy wrote:
>Did that.  You still see a red side and a green side.
>
>Good idea, though.
>

Huh??? Hold voltage1 --> red. Hold voltage2 --> green.
Pulse opposite phases --> amber. ????????????????

- Dan
=====


>Try pulsing red and green on opposite phase, with various duty cycles
>for different amber hues. To trick the eye, ie, to get persistence of
>vision, use pulserate >> 25 hz.
>
>

2000\06\26@151415 by Andrew Kunz

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Yup, that's the idea.  It works a _little_ on these LEDs, but it doesn't cover
the whole body of it.

Currently driving them at 1KHz, 50% duty cycle, first red, then green.

If the body diffused the light better it might work.

Andy








Dan Michaels <@spam@oricomKILLspamspamLYNX.SNI.NET> on 06/26/2000 03:07:07 PM

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Subject: Re: [OT]: 3 colors from an LED








Andy wrote:
>Did that.  You still see a red side and a green side.
>
>Good idea, though.
>

Huh??? Hold voltage1 --> red. Hold voltage2 --> green.
Pulse opposite phases --> amber. ????????????????

- Dan
=====


>Try pulsing red and green on opposite phase, with various duty cycles
>for different amber hues. To trick the eye, ie, to get persistence of
>vision, use pulserate >> 25 hz.
>
>

2000\06\27@110508 by Bill Colville

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Date sent:              Mon, 26 Jun 2000 13:49:02 -0400
Send reply to:          pic microcontroller discussion list <spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU>
From:                   Andrew Kunz <TakeThisOuTakunzEraseMEspamspam_OUTTDIPOWER.COM>
Subject:                3 colors from an LED
To:                     RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU

Andy,
I have used bi-color red/green LED's from Hosfelt Electronics that I
think blend the colors well. They are in a diffused milky case.
Unfortunately they don't list the manufacturer. Hosfelt part number
is 25-308

Bill



> I need to generate Red, Amber-ish, and Green from a single LED body (standard
> T1.75 size).
>
> I am limited to a common-cathode device with two anodes to select the desired
> color.

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