LED on / off circuit that slowly brightens and turns off?

[psychepool]

Hi.

I am trying to install an indicator lamp on my DIY tube amp.
I would like the LED to gradually light up or go off, like a vacuum tube or antique lamp.

Can you give me some information about the circuits that can achieve this effect?
Or can you recommend me a search term for these kind of circuits?

I plan to use 12VDC (or 9VDC) power inside the amplifier.

[xtian]

Programmable RGB LED will do the trick. I did this ages ago...let me find the thread...

https://ampgarage.com/forum/viewtopic.p ... 2&start=15

https://youtu.be/gg72VGxTO-0

[Lauri]

If it doesn´t need to be anything too fancy you could just use a resistor and a capacitor. For example something like 2.2k resistor and 10000µ/16V capacitor.

[jcool666]

2 * pi * R * C is the formula to figure out how big your resistors and capacitors need to be. Its the inverse of the freq. cutoff for high and lowpass filters. You just need to keep your resistor small enough to deliver the full voltage your LED needs. You could probably power this off a half-wave rectifier from your filament winding. I doubt any LED you'd use would consume more than 30mA, and that would be a super-bright.

[psychepool]

OK, Thanks everyone!
The Programmable RGB LED method is not familiar to me.
I'm going to test the R / C method first and watch the results.
Thanks for your advices.