Mechanical TV System

Posted on Feb 4, 2014

Build a two-color camera and a three-color monitor. You can build your camera to pick up any two of the additive primary colors. Just install the proper color filters over the phototransistors or photodiodes. With a matrix circuit and an inverter, you will derive the third color. The trick You might not have thethird color, but you can create its complement.

Mechanical TV System
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A bit of electronics turns the complement back into the "missing" primary color. At the monitor, connect a potentiometer to the red and green LED driver outputs. This potentiometer is your resistor matrix. Some point on the pot`s resistance element corresponds to yellow, the complement of blue. The red signal is at one end of the potentiometer. The blue signal is at the other end. With the wiper at the center position, you get a mix of red and blue, or magenta. This magenta signal is what you want. Center the wiper. Run the wiper of the pot to the base of a new transistor (or an op amp input). With the transistor or op amp, invert the magenta signal. The inverted signal is your green drive signal. Derive Red. Now you want red, but only have green and blue. Cyan is between green and blue. With a transistor, invert the cyan signal and you have your red. Inverting mixer. An inverting mixer is an easy way to derive a third color. (See the schematics above. ) For experimental use, use the circuits as-is. The phasing is only approximate. For better phasing, add level-adjustment pots to the transistor inputs. Theory. Each transistor is an inverting phase-splitter. After a 180-degree phase shift, the input signals mix at the common collector resistor. Neither amplifier has any voltage gain. Yet each amplifier offers an 11. 8-times power gain. You can take the in-phase signal off the emitter of each transistor. The emitter signal...

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