Bluetooth 4 Relays Control Pro is an Android application developed by Hobbyprojects.com. This app allows users to control up to four relays or devices using an 89c2051 Micro-controller and an HC-05 Bluetooth Module.

To get started, users need to pair their mobile device with the HC-05 Bluetooth Module. The default password for pairing is "1234" or "0000," which can be found in the module's manual.

Once paired, users can control the relays or devices by pressing the respective ON or OFF buttons in the app. When the ON button is pressed for a specific device, the app sends the corresponding data (A, B, C, D) to the Bluetooth Module, which then activates the corresponding relay. Conversely, pressing the OFF button sends the corresponding data (a, b, c, d) to the module, turning off the relay.

Bluetooth 4 Relays Control Pro provides a simple and convenient way to remotely control multiple devices using Bluetooth technology. Users can download the circuit and hex file from the Hobbyprojects.com website to set up their own control system.