This video is part oftheTechXchange:Oscilloscope Techniques
You always hear about them, but they are hard to find: Tech talks on YouTube that are fun and interesting. Well, stop searching for test and measurement titles and check outAlan Wolke's channel.
Alan is a ham in more ways than one. His call sign is W2AEW. He also has a knack for presenting technical topics in an entertaining way. The video above is just one example. I actually remember building my first monitor using logic similar to this. Of course, turning an oscilloscope into a TV is more of an engineering exercise than a practical application, but it's one of many videos he has on his channel that's subscription-worthy.
This particular video uses the Z-axis input on an analog oscilloscope. The input is composite video that's used to create X and Y sawtooth ramp signals from the vertical and horizontal sync pulses.
For this hack, he used an LM1881 Composite Video Sync separator to easily extract the sync pulses from the composite video, then a couple of transistors to create the sawtooth waveforms, and finally a simple inverting amplifier to invert the video signal so that the resulting image on the scope isn't a negative image.
"Then, I take a little lab equipment tour, using the scope video monitor to show the equipment (just for fun!). Note: I made a little tweak to the circuit to enhance the vertical linearity and video contrast. The 10-µF cap in the vertical ramp circuit was changed to 0.1 µF, and the corresponding 680-Ω resistor in the current source feeding that cap was increased to 68 kΩ. And, I changed the 39-nF cap that creates the horizontal ramp to 22 nF to increase the amplitude of it a bit. More careful power supply decoupling got rid of a lot of the noise on the ramps, and sharpened the video.
“此外，我降低了视频逆变器中收集器电阻的价值，以降低对比度的对比。这种'增益'更改将取决于范围，以根据需要获得所需的增益，以使您想要的对比度基于您所需的对比度您的视频振幅和范围z轴灵敏度。
“再进行一些调整……我为复合视频放大器添加了一个可调节的增益阶段，以便它可以适应不同范围的z轴增益差异。我还为X轴坡道信号添加了一个逆变器，以便我不必将其倒在范围上。我的旧485将CH2用于X，而CH2具有反转开关。但是，许多其他范围将CH1用于X输入，因此通常不会具有反转功能。”
链接
- Alan Wolke's website, W2AEW
- Alan Wolke's channelon YouTube
- Schematic for the project(updated PDF)
