I've got a Uno (Elegoo UNO R3) running with - Ethernet shield (Kuman K15), - 4 relay board (Elegoo 4 Channel DC 5V Relay Module with Optocoupler ) - Matrix Orbital 2041 LCD connected via I2C (11mA typical, 90mA with backlight) - A series of buttons connected
The Uno is currently running plugged in via USB to my macbook pro.
All of these devices are powered by the 5V pin on the Arduino.
The LCD goes wonky from time to time, and other times will work fine, it starts flashing the backlight, and just behaves oddly, sometimes even rebooting, when buttons are pushed (which activate the relays).
I'm wondering if this a power issue, perhaps the Uno isn't able to supply enough current to run everything.
My reading indicates that the USB port should be able to provide ~400mA, and when on an external supply I should able to draw 900 mA when using an external power adapter. However even with on an external supply (12v, 2A) I still have these issues.
Any thoughts would be much appreciated. Thanks