FAQ: How to use two power supplies.

[IoT_hobbyist]

Newbie usually runs into trouble when using two power supplies. A lot of people asked on the forum about the same issue.

1. Two power supplies use cases:
- one for Arduino, one to provide the extra power for motors (Servo motor, stepper motor, dc motor)
- two power supplies for two Arduino, which communicated to each other (via I2C, UART, SPI...)

2. How To
It's very simple, just connect GND from one to the other.
Example: This post showed a wiring diagram for using the extra power supply for multiple servo motors.

NOTE 1: In the case of you connect two Arduino to the same PC, GND of two Arduino has been connected to each other via PC.
NOTE 2: If you use some motor drivers, GND may be internally connected.
NOTE 3: The above does NOT apply for the case of using the Relay

[lastchancename]

A diagram would help newbies, many of them can't read instructions.

[ballscrewbob]

Such as this

[lastchancename]

@bsb, where did you find that?
I often suspect I can't see graphics posted in some threads...?!

[ballscrewbob]

Tee Heee....There are a few good arduino forum sourced pics.

Let Google be your friend but just get specific with it.
Use the magnifying glass and do a forum search for "common ground" then hit the PICS in google.

I think there was a better one so you can outdo that pic easily LOL

Bob.

[lastchancename]

no, I get it
i understand, but you suggest that the image you posted is related to the OPS question, and I didn't see any image or link before your post...

I've seen other threads where people discuss some code or i,age, but there is no prior code or image in the thread!!

Maybe I'm just getting old!

[ballscrewbob]

AH...I get it now...

Yes possibly not the very best example I could have picked.
That's why I suggested you topple it with a better one.

Bob.