VGA to X-Y-Z scope converter

This is fun project I found on Jon’s antique radios web-page. He has managed to convert VGA output signal from PC to X Y X oscilloscope signal. Converting VGA RGB signal to synchronized oscilloscope input signal is pretty easy because VGA has two sync signals separate from RGB signals. Look at pin-out of VGA cable:

vga15_pinout.gif

Sync signals makes things much easier as there is no need for additional sync signal generators – thus circuit becomes pretty simple without any programmable components:

vga_to_scope.gif

The sync signals taken from VGA cable triggers sweep tooth signal (555 timer) generators. These generators generates ram signals for oscilloscope, that enable creation of raster pattern. The vertical generator frequency is around 75Hz and horizontal about 35kHz is used as horizontal sync pulses. Output sync (75Hz) is fed to oscilloscope Y-axis and and 35kHz sync signal is fed to X-axis of oscilloscope. The circuit is ready for 800 x 600 at 75Hz refresh rate. For different configurations you might need to adjust horizontal and vertical sync 555timers RC circuits.

RGB signal is converted to monochrome signal and fed to Z-axis of oscilloscope as intensity.

vgascope1.jpg

Inside the box:

soldered_vga_to_oscilloscope.jpg

Be sure that you turn PC before switching oscilloscope ON otherwise without PC sync signal you will get bright dot on Oscilloscope screen what can burn the phosphor. When turning off – turn oscilloscope first before turning off PC.

Circuit is sensitive to voltage swings. Be sure that you have stabile +5V.

PC desktop image:

PC_desktop.jpg

The image on oscilloscope:

oscilloscope_desktop.jpg

References: Jon’s antique radios.

2 Comments:

  1. This is great project :-). I wouldn’t believe ordinary oscilloscope is capable of displaying fast VGA signal in XY mode.

    btw, you might be interested in some VGA Microcontroller projects at http://www.tinyvga.com

  2. smirdiigs tev tas suuds sanaacis, es no govs suudiem labaaku vareetu uztaisiit

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