Miniature Black and White TV System
(C) G. Forrest Cook 2005
Mini camera (in vise jaws), modulator and Sony Watchman
Close-up photo of miniature B&W camera
INTRODUCTION
August 30, 2005
Incredibly small video cameras have recently become available
at reasonable prices. Small televisions are
available for very little money at online auction sites such as eBay.
It is now possible to build a miniature short-range wireless video system
with off-the-shelf parts. This wireless nature of this circuit is
not suitable for long distance operation, the video modulator just
provides a simple method for interfacing the video signal to a
standard TV. Transmission distance is limited to a few feet.
Theory
The 12VDC supply provides power for the camera and video modulator
circuits. The video from the camera is fed into the video input of
the modulator circuit. The modulated RF from the modulator is fed
into a small antenna. Use of a dipole antenna that is resonant at the
frequency of the modulator can extend the signal range.
The RF travels across a short distance to the Sony Watchman TV receiver.
A black and white image magically appears on the TV screen.
Construction
The camera's video signal is connected to the video modulator with an
RCA jumper cable. Power to the camera and video modulator is connected
to the 12V power supply. Be careful with polarity, reversing the leads
may damage the modulator. The camera that was used had reverse polarity
protection built in. The modulator's RF output signal is connected to a
small antenna, the antenna can be made with two short lengths of #16 gauge
solid wire.
Alternately, for long distance wired operation, the RF signal can be fed into
a length of 75 ohm coax cable with a 75 ohm terminating resistor across the
far end of the cable. Connect the remote center conductor of the cable
to the TV antenna through a 330 ohm resistor.
Use
Turn the power for the camera and modulator on, turn on the TV.
Tune the TV to the channel of the RF modulator, fine-tune the TV
for the best picture. For full-time operation, use the appropriate
AC adapter for the watchman. If battery operation is desired, run
the TV from its internal batteries and use a 12V battery for powering
the camera and modulator. A rechargeable lead acid battery with a series
fuse (and a recharging circuit) is recommended.
A fun use for this system would be to create an engineer's view of
a model train layout. A loop of wire near the track would make a good
receiving antenna. Power could be pulled from the engine motor
circuit using a bridge rectifier feeding into an electrolytic capacitor,
just make sure not to exceed the camera's 12V maximum supply voltage.
Parts
- Miniature black and white video camera, 12VDC, Model PC-206XP
- Video modulator block, Jameco 141639CJ or equivalent
- Sony Watchman miniature TV
- 12V DC power supply, beware of wall-warts - they often have inaccurate voltage ratings.
- Miscellaneous wires and cables
The PC-206XP camera is available from
Super Circuits for around $80.00 They also sell a 1" Mini-Monitor
for $100.00
Video modulators can be purchased from
All Electronics and Jameco
for a few bucks.
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