Hi all,
I'm building this larg-ish scale digital clock using a series of six inch incandescent tube lamps positioned in the form of several seven segment displays. Clear-case relays will be controlling the 120v lights (dimmed of course), and some Toshiba TLP621 opto-isolators will be controlling the relays. Finally, an Arduino Mega will be in charge of the opto-isolators.
There will be a seconds unit on this clock, and with that being said, 43 I/Os will be used. However, while only for a few seconds, a maximum of 32 pins will be powered high at any given time.
My concern is whether or not the Arduino will be able to power that amount of opto-isolators (32). Each opto requires 5-10mA, and from what I found, the MEGA can only supply a collective current of up to 200mA.
Another thing I have to mention was that my original plan included the use of 20mA LEDs wired in parallel with the LED side of each of the the 43 opto-isolators (220 ohm resistor included with each LED). I have since omitted these since it would most certainly exceed the current draw of the Arduino. I still have some other indicator ideas for the other side of the optos, but that would require me to order more parts. Let me know of your opinion about this indicator idea.
Anyway, I simply ask whether or not the Arduino will be happy when powering all those opto-isolators. It's also worth noting that, a 220 ohm resistor will be in series with each one.