REMOTE-CONTROLLED REAL-TIME CLOCK WITH DEVICE CONTROLLER

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Circuit description

1 shows the block diagram of the
remote-controlled real-time clock with
device controller. It comprises six sections,
namely, IR detector remote control
sensing and decoding unit, realtime
clock, LCD interface, device
switching unit, microcontroller and
power supply unit
The microcontroller unit integrates
all the sub-systems and system software
operates the system. Fig. 2 shows
the circuit of the device controller.
Remote control section. This circuit
makes use of a Philips TV remote for
device switching and RTC parameter
setting. It uses RC5 coding format,
which is also known as ‘biphase coding.’
In RC5-coded signal, each bit has
a uniform duration.



Software
The system software is used to achieve
integration and functionality. The software
for this project is written in ‘C’
language and compiled using
WINAVR. WINAVR is available free
of cost for Windows and Linux operating
systems. It is capable of handling
all the AVR functionalities like UART,
timer, ADC, interrupts, etc and offers
the facility of writing the program in
‘C.’ The finally obtained Intel hex code
file was burnt into AVR’s flash memory
using a suitable programmer. The
microcontroller uses a 4MHz internally
generated clock. To activate, fuse bytes
have to be programmed as follows:


Remote control operation
The entire device operation is controlled
through keys of the Philips remote
control. The remote keys are used
as shown in Table II. The functions of
these keys are given below.
Key 0 is used to change the setting
of the RTC. When the RTC is functioning
normally, it can be switched
to setting mode by pressing the ‘0’ key
and immediately the cursor will blink
on the hour field, indicating that this
value can be changed through ‘volume
up’ and ‘volume down’ keys to a desired
value.