|Hawes Mechanical Television Archive||
Colorize Your Mechanical TV System, Part 2
Option: Derived Color (D/C)
Following the instructions above, 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 the third color, but you can create its complement. A bit of electronics turns the complement back into the "missing" primary color.
Another way to derive a third color: An inverting mixer.
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 includes the power gain.
Option: Pseudocolor (P/C)
The simplest pseudocolor system outputs two colors. This method requires no quantizing and no digital circuits. A two-ended analog amplifier will serve excellently. You can achieve very effective pseudocolors by applying the monochrome signal to the inputs of a difference amplifier. The inverted signal then drives one color output. The non-inverted signal drives the other color output.
In the nearby schematic, the collector of transistor Q1 provides the inverted or orange signal. The cyan, non-inverted signal appears on the collector of transistor Q2. The two collector signals are 180 degrees out of phase with one another.
The output resistors may be fixed or variable. Using variable resistors and a maximum signal, you can adjust the white balance. When the output appears white, you've achieved balance.
If you desire a third color, it could be the midrange or difference signal between the two output signals. (For example, the midpoint of a 50K pot VRZ that connects between the Q1 and Q2 collectors.) The third signal is 90 degrees out of phase with each of the other two signals. If VRZ is smaller than 33K, it introduces crosstalk between the Q1 and Q2 outputs. The crosstalk alters the phase relationship of the three signals.(This is how a matrix in a color TV works.)
Amplifier. In most cases, the third color requires its own amplifier after VRZ.
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♦ WARNING. This is your project. Your achievement is entirely yours. I assume no responsibility for your success in using methods on these pages. If you fail, the same is true. I neither make nor imply any warranty. I don't guarantee the accuracy or effectiveness of these methods. Parts, skill and assembly methods vary. So will your results. Proceed at your own risk.
♦ WARNING. Electronic projects can pose hazards. Soldering irons can burn you. Chassis paint and solder ar8:39 PM 12/4/2011e poisons. Even with battery projects, wiring mistakes can start fires. If the schematic and description on this page baffle you, this project is too advanced. Try something else. Again, damages, injuries and errors are your responsibility.
♦ CAUTION. Values in the figures above are for reference only.
The circuits are theoretical. No one has built or tested them.
Your application will likely differ from the examples. If you use circuits like
those on this page, test and modify as necessary. Safety first!
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