I took apart a LED-waving toy. It has 7 LEDs. There are 8 wires coming out of it. I assumed one was a common ground, and the rest were the positive leads.
It's actually the other way around, though. They share a common positive connection, with a different ground wire for each LED. I can turn each LED on individually by putting the common positive lead through a resistor into a +5V terminal, then touching the LED's ground onto GND.
I'm hoping to control these through the digital I/O pins. Normally one would apply either 0V or +5V to the pin. That would correspond to off and on (normally).
In this case, if I put the common positive wire in the +5V and an LED's ground into a digital I/O pin, the LED is on when the pin is low, and off when the pin is high.
Is it okay for a i/o pin set high to be connected to the +5V pin? They're the same voltage (more or less), which means very little electromotive force(right?) (and not much current with a resistor in the way). Is that okay?
When the LED is on, the i/o pin would be low, which means the current is flowing "backwards." (It seems that the +5V pin would be essentially 0V, and the 0V i/o pin would be essentially -5V). I don't know if I'm getting that right. Is it okay to do that?
If these things are okay, then I'm worried about running multiple LEDs when there's a common ground. That means the current per LED goes down as the number of LEDs lit at once increases? How's my logic there?
Thanks for your time. I'm quite new to this and I appreciate any help.