Fritzing circuit overview


I am a complete amateur when it comes to electronics so forgive me for any misconceptions.

I am trying to design a circuit that will power an RGB LED Strip (here depicted by a single RGB LED), an Arduino Uno (Rev 3), and an HC-06 SPP Bluetooth module.

You probably already guessed that i want to control the color of the LED Strip using the SPP Bluetooth protocol on a smartphone / other SPP capable device. In the picture you can see the circuit i have come up with.

I have a few questions:

  • The HC-06 requires 3.3V to work. Is the Arduino Uno supplying 3.3V on the 3V3 rail when the arduino itself is powered off of a 9V Source? I hear the arduino comes equipped with a voltage regulator, so I think the answer is yes.
  • Is it a problem that the HC-06 Module running on 3.3V is connected to the shared ground connection of the 9V power source? If i were to use a standalone voltage regulator I would connect it to the GND of output side of the regulator, so just connecting it to a shared ground like this is sounding some alarm bells in my head.
  • Is the RGB LED as depicted in this picture common cathode or common anode? In chemistry i learned that Cathodes are positive and Anodes are negative. However, in chemistry we talk about the flow of electrons from negative to positive. In electronics lingo, it flows from positive to negative. Does that mean it is common anode in electronics lingo?
  • 1
    \$\begingroup\$ Hello, there is an embedded schematic drawing tool on the site and you can edit your question, so please add a proper schematic instead of this image. \$\endgroup\$ Jul 22, 2016 at 16:44
  • \$\begingroup\$ What is the current draw of the RGB LED strip? How is it wired? What is the required terminal voltage (anode-to-cathode voltage)? \$\endgroup\$
    – FiddyOhm
    Jul 22, 2016 at 17:28

1 Answer 1


Yes. It will. Keep in mind that the 3.3V regulator is limited, and the bluetooth module may take too much current. Most bluetooth modules that work at 3.3V tend to come with their own 5V to 3.3V regulator on board.

Yes, you connect the grounds together. That is expected and required.

It is common Anode or positive pin. While electrical theory is that electrons flow negative to positive, conventional electrical engineering shows positive to negative. The led here has three individual cathode and are low side switched.

That said, 9V tends to be too low for common 12V led strips to turn on at all in my experience, and a 9V battery will not last long at all in this setup. They just arnt meant for high current draws.


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