I am trying to connect my bluetooth module to my Arduino but it takes 3.3 volts (the bluetooth module HC-05, The Arduino mega takes 5v) and the tutorials online say to connect the RX pin to the Ground through a voltage divider.


i'm not sure how it works but i don't understand because if i'v learned anything by playing around with electronics it would be that you should never connect positive voltage to GND. I mean it's technically not connecting 5v to GND but it seems like a bad idea im not sure. If someone could explain this that would be quite helpful. Could i just use a resistor from the RX from the Arduino to the HC-05?

  • Your right it's nothing like connecting 5v to Ground. "Could i just use a resistor from the RX from the Arduino to the RX to the HC-05." - Nope; You need two in order for it to work; You seem 100% sure that you actually need a voltage divider, "through a voltage divider or something.", do you need a voltage divider or "something" edit your question
    – Ramhound
    Jan 15, 2017 at 2:13
  • Don't connect resistors to the voltage source, the video, is clear about that
    – Ramhound
    Jan 15, 2017 at 2:18

2 Answers 2


Why do you have to use a voltage divider with HC-05 bluetooth module ?

If you won't use level shifter you will damage 3.3v device.

You can build it (voltage level converter, not divider) yourself, it just one MOFSET transistor per line, schematics is here, but I advise you just get one on ebay, they are extremely cheap, look for keyword "voltage level converter shifter", it should looks like that.

The purpose of voltage shifter - is to bi-bidirectionally convert voltage 3.3<->5 volts to get compatible voltage level between devices.

  • Sorry i got confused i meant to post this on the Electrical engineering stack exchange site, thank you for your help despite my mistake.
    – techset
    Jan 15, 2017 at 19:37

Please show me your real schematic circuit. Please attach here. I will discuss with you if you want to know about the circuit. What i got is the schematic that you share the link to me but i need the real schematic diagram if you have one. enter image description here

You connect RX to pin ground because you have to complete the circuit. Using just two series resistors and an input voltage, we can create an output voltage that is a fraction of the input.

Why you must connecting 5v to ground? It doesnot make any sense since the circuit flow is not equal to anything. Voltage start from positive and it must flow to other component and the other component need to connect to ground to complete the current. V=IR

He connect the resistor to the power that comes from Receiver,RX while Tranmitter,TX connected directly. You want to use 2K resistor from arduino to connect to HC-05? It is already in series circuit.

  • ok that is my schematic just i haven't connected EN to 5v what's that do? It seems like every tutorial is completely different, how is it that they all work the same?!?!.
    – techset
    Jan 15, 2017 at 19:23

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