EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Richard Crowley on January 28, 2019, 06:45:36 pm
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I have an application (low-profile video switcher control panel) where I would like to use these Panasonic EVPADK04K switches.
(https://www3.panasonic.biz/ac/e/control/switch/thumbnail/3478_01.png)
I need R/G lighted indication (industry convention: Red = on-air, Green = preview)
These switches are nice low-profile and provide a 4.1mm "hole in the middle" to deploy the lighting.
But I am trying to find a nice bright R/G LED solution that would fit into that 4.1mm dia space constraint.
I fear that the ordinary SMD LEDs that will fit within the 4.1mm diagonal are not bright enough to shine through the button cap.
Unless I can find molded buttons, I am fabricating my own from white translucent acrylic.
There are SMD LEDs that mount from the back-side of the PCB, and shine through a hole in the PCB.
But I don't know what is the proper name for that style?
Ideally I would like something like a fully-controlled RGB component with integrated controller (what AdaFruit calls "NeoPixel")
But those are much to large to fit within the 4.1mm dia space.
I suppose, worst-case I could simply use ordinary 3mm RGB (or RG) LEDs poked in from the back-side of the PCB,
and fold over the leads to create a DIY surface-mount kludgy solution.
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If you really want RGB, what about a second PCB with the LEDs mounted behind the first with the buttons? You may need a light pipe or lens to get better light coupling, there are a number of simple cylindrical light pipes that might work.
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2x2mm RGB LEDs are readily available and fairly bright
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A RGB PLCC4 might also fit in there ( 3.2 x 2.8 ) but they tend to be extremely bright.
Edit: stupid emotes
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I have used Cree 2mm x 2mm PLCC4 in small/tight spots.
These ones are pretty bright.
They were too bright in my particular application and I ended up using them with 35% PWM.
Datasheet here: https://nz.mouser.com/datasheet/2/90/1273-CLMVC-FKA-1519109.pdf (https://nz.mouser.com/datasheet/2/90/1273-CLMVC-FKA-1519109.pdf)
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They are called reverse mount LEDs.
https://www.digikey.com/en/product-highlight/s/sunled/reverse-mount-rgb-plcc-smd-led (https://www.digikey.com/en/product-highlight/s/sunled/reverse-mount-rgb-plcc-smd-led)
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It somewhat depends how you're planning to cover them, you need some diffusion to avoid a bright point source anyway, but even standard 0603 indicator LEDs run at full power are almost certainly brighter than you'd ever want if you use modern parts.
Red & Green are on the dimmer end for LEDs, but at 5-10mA should be plenty bright enough, even through a lossy diffuse layer. (For blue < 1mA can still be obnoxiously bright)