Bluetooth-Based Remote Control System
The author showcases a Bluetooth-based remote control system on his website titled ‘AVR Blue Remote.’ This system features six output relays and six sensor inputs, providing a versatile solution for various applications. The website offers Smartphone software (avrblueremote.exe) and microcontroller software (avrblueremote.hex) essential for implementing projects like a short-range remote garage door opener or a remote lighting controller. The software is freely accessible for private individual use, allowing enthusiasts to explore its potential.
Transmitter and Receiver Components
To operate this system, any Smartphone running the Windows Mobile 5.0 operating system can function as the transmitter. The receiver employs the compact Blue Ice Corn III Bluetooth module, equipped with an integrated chip antenna from Amber Wireless. This tiny module, based on the LMX9220A from National Semiconductor, decodes messages and communicates them through a UART-like interface (TX and RX signals) with an Atmel AVR ATMega8L microcontroller.
Microcontroller Outputs and Circuit Elements
The microcontroller’s outputs are linked to a ULN2803 octal driver, capable of efficiently handling the current necessary for powering relays. The circuit incorporates a 3 V voltage regulator (type LP2950-3V) and an ISP (in-system programming) connector, ensuring seamless functionality. Furthermore, the system includes four LEDs serving as indicators: LED1 signifies successful data reception by the microcontroller, while LED2 alerts users about any timeout occurrences. The Bluetooth module’s LEDs also play crucial roles, with LED3 indicating the link status and LED4 denoting the transmit mode, enhancing the overall user experience.
Printed Circuit Board Layout Considerations
Designing the printed circuit board layout for this circuit involves adhering to specific constraints. To maximize the range, it’s crucial to maintain a distance of 8 mm between the antenna and any ground plane, conductors, components, or other metal parts. Detailed requirements are outlined in the module’s manual. Additionally, the microcontroller can be programmed through the ISP interface. Ensuring compatibility between the connector’s pinout and the programmer is essential. Numerous programmer circuits can be found online and in publications like Elektor Electronics, with additional resources available on Atmel’s website.
Programming the Microcontroller
Once the hardware is assembled, the focus shifts to configuring the accompanying Smartphone software. Firstly, it’s necessary to install the appropriate version of Compact Framework 2.0, conveniently accessible for download from Microsoft’s official website. This step lays the foundation for integrating the software with the hardware setup, facilitating seamless communication between the Smartphone and the circuit.
- Windows Mobile 5.0 Pocket PC and Smartphone: wm.armv4i.cab;
- Pocket PC 2003 and 2003 SE: NETCFv2.ppc.armv4.cab;1
- Windows XP: netcfsetupv2.msi.
Transferring and Pairing Bluetooth Devices
To initiate the system, transfer the avrblueremote.exe file to the designated platform, like an SD card compatible with the Smartphone. The next crucial step involves pairing the two Bluetooth devices – the Smartphone and the receiver board. This pairing process is a one-time requirement. Once paired, launch the program. By clicking on the upward and downward arrows, the COM port is configured effortlessly. The central square opens the interface, establishing a connection with the receiver. Subsequently, the arrows enable toggling the outputs on the receiver board, while the space key activates the sixth output.
Interface Control and Signal Feedback
On the interface display, the six sensor inputs are depicted as LEDs located near the top section. Moving out of the receiver’s range causes these LEDs to extinguish, accompanied by the appearance of a timeout bar. If the timeout period elapses without receiving a valid signal, the interface will be automatically closed, ensuring efficient management of the connection.