LED selections

[MannyDay]

I am building a CTC control board for my model railroad layout. I am looking at using 5mm LEDs to indicate switch position and signal status on the control board, specifically the Adafruit 5mm LEDs with the #2176 LED holders. I have these questions before making the purchase:
1. What is the maximum panel thickness that these LED holders can be installed on?
2. I see only #299 diffused red 25-pack and #298 diffused green 25-pack available. Are yellow/amber 5mm LEDs available?
3. At what voltage level can these LEDs be applied? My system voltage is 12VDC.

Thank you, Manny Day, Plymouth MN

[dastels]

1) The length is stated at 12mm but there's no indication of what the includes, but I assume it's end to end. which gives a threaded space of about 3/4 of that (judging from the photos) .. so ~9mm. Take a couple mm for the washer and nut and you can likely comfortably fit on a 6 or 7mm panel.

2) There doesn't seem to be. However, there is a variety pack https://www.adafruit.com/product/4203 as well as diffused 5mm RGB https://www.adafruit.com/product/302 and NeoPixel https://www.adafruit.com/product/1938 options.

3) That depends on the LED. The red you mention has a forward drop of 1.85v-2.5v (as the nominal 20mA). The green has a drop of 2.2v-2.5v. You'll need a resistor in series with each one to drop the remainder of the voltage (e.g. 12v - 2.5v = 9.5v) at 20mA. In this example that would be 9.5v/0.020A = 475 ohms.

See https://learn.adafruit.com/all-about-leds for more about LEDs.

Dave