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I’m building a Warning Display with a Bluetooth interface. The ‘Bluetooth Module’ and ‘Buzzer Control’ won’t consume much current so I decided to connect them directly to the Arduino and they are working fine. But the Lamp Control has a lot of LEDs 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 the Arduino too).

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

enter image description here

Info:

  1. Green lines are data lines
  2. Red is for +5 V
  3. Purple is for +3.3 V
  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 the data link?
  3. What is the best option to power all these with a single USB power supply?
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  • \$\begingroup\$ Why not be OK? What is your concern? \$\endgroup\$
    – nickagian
    Commented Jun 23, 2017 at 6:38

2 Answers 2

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The questions are:

  1. Is this OK?

Yes, all looks good.

  1. 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.

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  • \$\begingroup\$ So do i connect the GND line for the Lamp control to the power supply or to the Arduino GND? \$\endgroup\$
    – john smith
    Commented Jun 23, 2017 at 6:58
  • \$\begingroup\$ Its the Ground Loop I'm worried about... \$\endgroup\$
    – john smith
    Commented Jun 23, 2017 at 7:01
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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.

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