How to Power Arduino and its External Devices with single USB Power Supply

Question

I’m building a Warning Display with Bluetooth interface. The ‘Bluetooth Module’ and ‘Buzzer Control’ won’t consume much current so decided to connect them directly to the Arduino and they are working fine. But the ‘Lamp Control’ has a lot of LED’s and it needs an external power source. The ‘USB Power Supply’ I’m using is able to source the current required for the ‘Lamp Control’ (and Arduino too).

So this is my plan (see the picture) to wire the ‘Lamp Control’ and everything else.

Info:

1. Green Lines are Data lines
2. Red is for +5v
3. Purple is for +3v3
4. Black is for GND

The questions are:

1. Is this OK?
2. Do I need to connect an extra ground line (Dotted Line?) to the ‘Lamp Control’ for data link?
3. Or what is the best option to power all these with a single ‘USB Power Supply’?

Thank you, Please help.

Answer 1

All devices connected to the same power source should share the same ground line. Connecting the Lamp control to the USB GND bin will not differ from connecting it Arduino bin GND, since they are connected internally by nature.

Answer 2

The questions are:

1. Is this OK?

Yes, all looks good.

2. Do I need to connect an extra ground line (Dotted Line?) to the ‘Lamp Control’ for data link?

No, you don't really need any additional ground line. I would expect that all GND pins of the Arduino board are connected together. Also, of course with the GND of the USB port. If you have a multimeter you could measure all GNDs together. It should show only a couple of Ohms.