BUILD THE RTC OSD FOR
By Kelly Lewis
A real time clock-based on-screen display for
closed-circuit television camera recording.
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Closed circuit television (CCTV) camera systems have been in use for years
in commercial areas such as banks and supermarkets, but with camera prices
being more affordable, CCTV is now used more and more to protect homes
and private property. Unfortunately, recording systems such as DVRs and
time-lapse VCRs can be expensive, so an old VCR is sometimes used instead.
However, without time stamps on the recordings, it can be difficult to
determine when an event occurred.
I installed two affordable CCTV cameras with
infrared for night vision around our yard to deter any
potential troublemakers. An old Sharp VCR was put into
service as a time-lapse VCR using a circuit that I built to
switch between the two cameras and control the VCR
using IR signals, but I had no way of knowing when
events had happened because the VCR does not write
the date/time on the video recording. So, I built the RTC
OSD (real time clock on-screen display) to provide an
accurate time-stamp for the recordings.
The circuit is made quite
simple through the use of
function-specific chips and a
Microchip PIC to tie them
together. Video display can be
very tricky to get right, but the
MAX7456 makes displaying
■ FIGURE 1. MAX7456 mounted
on a 28-pin SSOP to DIP adapter.