I'm powering my SparkFun 1602 LCD from a 7805, powered by a +12v adapter. I'm also powering my Uno from the +12v adapter. So the ground is common to the Uno and the LCD.
My question, if my voltage into the Uno goes to the Vin and Gnd pin right next to it, can I safely use the ground pin next to D13 to ground my LCD, and LCD backlight?
In simpler terms, the voltage my LCD uses has to get it's ground by going back to and through the 2 ground pins on each side of the Uno board. This should not be a problem for the amount of current an LCD uses should it, nor will it cause any type of inductance or something that I don't know about?
My question, if my voltage into the Uno goes to the Vin and Gnd pin right next to it, can I safely use the ground pin next to D13 to ground my LCD, and LCD backlight?
SouthernAtHeart:
Thanks, I thought so, but wanted to be sure.
There are two ways to always be sure; both should be used and understood together. If you are unfamiliar with either, you are going to find electronics a very difficult hobby to say the least:
Learn to read a schematic
Learn to properly use a multimeter
Had you followed the above, you could have referenced the design material (schematics and PCB layout) of the Uno, then applied your multimeter to the proper points to determine whether or if the grounds shared the same path. Note that without that knowledge, you can't (in good faith) trust any circuit, PCB, or its markings otherwise. There are circuits which have wholly separate grounds (typically for power and signal), and while points on a PCB or such may both be marked "GND" or some equivalent, they may not be connected (though to be fair, a good PCB design and schematic will point this out with proper and clear labeling).
Learn to read schematics, learn to use your multimeter (if you have one - if you don't, buy one) - both skills will be valuable to you as you progress.
