A = regulator 7809, or 7806, or 7805, which respectively
delivers 9V, 6V, ou 5V.
When combining the two resistances,
the tension can be very precisely adjusted.
Get an old camcorder, out
of order, but with viewer still working.
identify the connections:
Open it, and give access to the
connecting wires of the viewer. Disconnect each wire one
by one, and each time, put the camcorder on, and check the
action on the viewer. Thus, identify the "plus",
minus" or ground, and video signal connections.
Other connections may be used for
incrustations, led alarm, etc...
When one of the + or - wire is
disconnected, the viewer is entirely off. When the video
signal is disconnected, there is no image and the viewer
is still lightened; however, on some, the viewer stops when
there is no signal.
With a control device, check the
polarity + and - directly on the camcorder connectors and
measure the voltage value.
Electric feeding for viewer:
The feeding voltage of the viewer
must be precise to 0.1V. Such module is easy to make. When
modifying one or other resistance, the voltage can be exactly
With R1 = 0, the tension is 9,
6, or 5V related to the regulator; and with R2 very great,
the tension is the primary one, e.g. 9,6, or 5V
With R2 between 0 et 10 ohms, the
tension may go down to 1 V.