Very Slow Fading LEDs

Other Hardware LEDs and Multiplexing
1

Hi:

I am very new to electronics and have recently been bitten by Audrino. I have a good programming heritage but the physical aspects I struggle with.

I am trying to run a 6x6 grid of high power LEDs. I want to be able to 'trigger' them individually and when this happens they flash on and very slowly fade over 5-30 mintues.

I have a prototype with a few LEDs working using analogue connetions but understand I need to move to digital and use a 595 shift register etc to control it correctly.

People seem to use capacitors for this sort of task but are there capacitors suitable for my required fade duration? Are there any other approaches open to me?

Many thanks for your patience...

John

2

I think that fading over 30 minutes would take a heck of a capacitor. :confused:

I think your best bet is using PWM to fade each LED in software. I don't know if there is an easy way to do PWM and driving a matrix at the same time. It will probably be easiest to use an external multi-pin PWM controller with a serial interface (SPI).

3

I think that fading over 30 minutes would take a heck of a capacitor. :confused:

And it wouldn't fade evenly...