Forgive the newbie question, fairly new to Arduino and have a basic question about injecting 5V power into my project. I'm running several 5V devices, a WS2812B RGB strip, 8x8 RGB LED Matrix and 4 line LCD Display (and possibly others) which pull more power than the Arduino Nano I'm using can provide from being powered by USB. I already have a 5V DC power supply in my project - I believe I see from schematics that I should not only connect the 5V +/- to the devices but also back to the Arudino itself, is that correct? That feels wrong to me as it feels like I might damage the Arduino by sending it power on what seems to be an output channel but am I just thinking about it incorrectly? My RGB lights seem to work fine without thee 5V only going to them but the LCD display doesn't, I'm guessing it has something to do with grounding and the circuit being open, etc.
So is that correct, I should be just injecting the power into the circuit as it would be wired without the 5V power supply such that it would be connected to both the Arduino 5V/GND as well as the devices? Using a 5V/2Amp PSU BTW.
Just join the GND of your external power for the leds with the GND pin of your USB powered arduino.
If there is no motor / inductive load involved you should be just fine
Thanks so much guys, I appreciate it. I figured I was right from all the schematics I was seeing but being new to this I also worried that feeding power in to what I felt like was an out was going to do bad things. I really appreciate the help and for not giving me any crap for being a noob!
I always try to build a kind of powersupply bar on my projects where I connect the Arduino processor and all devices and loads which I have on my project. That looks like on my draft. I suppose there is no problem with this or some better experianced people can correct me ?
If you don't need the USB connection to the computer you can power the whole thing from the same 5V power supply.
And it's generally OK to connect them both at the same time, but that might depend on which Arduino you're using or if you are paranoid about damaging your computer (or just want to be cautious) you can run the Arduino from USB power when it's connected to the computer and only use the external supply when it's running stand-alone.
I'm not a hardware guy but I heard many times that if you want to minimise GND issues, it's best to connect all the GNDs to the same physical point rather than chaining them. (star topology)
Star topology is especially important for large currents. Not so important when the currents are relatively small for the conductor size in use. When they share the same conductor, it's usually rated for the total current, but may only take into account conductor current capacity, and not necessarily the effects of current induced voltage drops on other devices sharing the same supply. Then, the design is insufficient and has to consider those.
this is actually a great hint. Is it possible that a current induced voltage drop caused by a device like a servomotor resets the processor ? On some of my projects I have some effects like this when the arduino lets a Servomotor start working. Can I eliminate this effect just by changing the GND wirering ?
That is because it's mainly a beginner forum, at the start it's presented as a different problem. Or a vague problem, "my servo doesn't work...".
They can't understand that a reset is even occurring until we request they put a Serial debug statement as the first line. Then they see an output like
begin
starting servo
begin
starting servo
begin
starting servo
...
OK, I don´t understand what you mean with debug statement but actually my issue is not the topic here so I think I need to open a new one. Thanks anyway so far