LED flash/sequencer

Hi guys:
Seems like I'd be looking at a project to do some decorative coloured LED sequencing/flashing as a hilite for picture outlines, perhaps legal size or so.


I expect perhaps 16 to 32 LEDS in all.

I'm just looking for some advice or to get pointed in the right direction as to a cost effective approach as this may end up commercial if it's cost effective. Basically I have to do a working prototype and see if it gets accepted.

Perhaps a time based random sequence picker would be nice as well.

My initial thoughts are to use flash 'DT" bit patterns for the sequencing with circular/reversible rrf/rlf commands to get the LEDs moving etc. Coupled with a few PWM rotatable PWM bit patterns to influence LED intensity as an additional effect.

Using regular multiplexing I can see 16 LED's will take 4x4 for 8 bits/pins of control, 36 would be 6x6 @ 12 bits/pins. Hopefully I'd like to use a 3V button cell and do away with LED resistors if that's possible. So an MCU that can run on 3V is needed with a sleep mode for energy savings. Perhaps a single tactile can wake from sleep and put to sleep. The watchdog timer can do double duty by starting a new random sequence every few seconds.

The 3V will likely run 2 LEDs in series. So I wonder if by doing so and placing the 3V Led pairs with max separation on the picture outline (180deg phase shift) I can fudge the control matrix down by half and cut out the limiting resistors at the same time.

Thanks for your suggestions.

For simply flashing and sequencing, check my PIC tutorials.

Individual fading is a very different matter though.

You cannot run 2 LEDs in series on 3v.
You are jumping around all over the place.
Settle down to a requirement and use a PIC12F629 if you want to drive a number of LEDs but remember that multiplexing reduces the brightness. You can get 8 LEDs on a PIC12F629 with 12mA through each LED. A PIC16F628 will give a 30 LED display at 12mA.

colin55 said:

You cannot run 2 LEDs in series on 3v.
You are jumping around all over the place.
Settle down to a requirement and use a PIC12F629 if you want to drive a number of LEDs but remember that multiplexing reduces the brightness. You can get 8 LEDs on a PIC12F629 with 12mA through each LED. A PIC16F628 will give a 30 LED display at 12mA.

Click to expand...

You can drive 12 with a pic12f629 the pickit1 came with 8 on it but you could solder on the 4 they didn't install and it worked fine.

You can actually get up to 10 LEDs on a PIC12F629 with 12mA - but not 12.

Any configs available that don't require thecurrent limiting resistors?