In this Project I will try to bring my HC 05 Bluetooth module to life and control a LED with commands.

The HC 05: Wireless Bluetooth Transceiver Module for Arduino

But before I dive into the project, I need to write some words about the HC 05. It is a pretty old Serial Communication Bluetooth Module. It supports dynamic switching between Master and Slave mode – in contrast to its cheaper brother the HC 06. Both modules only support Bluetooth 2.x. That’s why it will not work with iOs devices – they need Bluetooth LE 4.0 support at least. I will buy a different module in the future. For the time being the HC 05 is ok for the first steps.

Don’t get me wrong. The Hc 05 is a cool module if you are using Android phones. They are not as picky as iPhones and i’ve seen cool projects in the web. But for iPhone users it is simply the wrong module.

But back to the facts: The HC 05 supports EDR (Enhanced Data Rate for tripple speed) on a 2,4-GHz band.

Pinning of HC 05

State: Do not know yet; I will post this asap

RX: Receive pin; DO NOT CONNECT TO 5V! If seen many projects on the web where the RX pin is connected to 5V, like one of Arduino’s digital pins. It will work, but it will harm the board. You should either use a Logic Level Shifter with 3.3V on one side and 5V on the other side. Or you use a simple voltage divider (see picture below).

TX: Transmit pin

GND: Connect with Arduino’s GND

VCC: +5V

EN: The enable pin for AT mode; must be high during powering the HC 05 to enter AT mode

Connecting the HC 05 using a voltage divider