Hi, I am attempting to use the above, common anode device with a Bela Mini. I am using digital outputs to sink the current for the 7, (actually 8) segments. This works fine if I use the 3.3 volt line on the board but I need to activate each of the 3 led blocks separately. Is it OK to use digital output pins as a current source? For instance D6 to power one 7 segment led, D8 for the next and D10 for the third? I gave it a go and the LED's are quite dim but I'm worried about pushing the unit too hard and bricking it. Thanks

    psychonaught Is it OK to use digital output pins as a current source?

    The pins can do up to 6 mA or 8 mA each, same for sinking and sourcing.That's enough for one LED but not for more than one. Even shorting the pins to ground or Vcc shouldn't damage them. Maybe you could try connecting multiple digital pins to 10, 8 and 6 so that they can sink more current? The proper way would be to add a transistor for each, of course.

      10 days later

      Hi, I wonder if you can point me in the right direction for a chip that can take the strain off the digital pins. I have no idea where to start.. Thanks very much..

      4 days later

      see this page on controlling motors with power transistors ... pretty much the same principles apply to driving LEDs although you only need a fraction of the current, probably less than 100mA for the 7 LEDs, so lower powered, commonly available transistors such as 2N3904 or BC548 should work pretty well.