Cathode Ray Tube (CRT) Controller
Massachusetts Institute of Technology
CRT displays are not rendered just once, like plots and meshes, but constantly refreshed at least 30 times a second, creating cyclical patterns when recorded over time. Sean Cubitt writes that in video display on modern TVs “time becomes material”. The same is true with earlier display technologies like the CRT. As a space to explore the temporality of computer representation in real time with physical circuits, the CRT display is ideal.
The CRTC1 allows for variation of several display parameters:
-By turning on and off switches in the two Dual In-Line (DIP) switch sets, bits can be removed from the bytes being sent from the microchip to the ADCs where they are converted into voltage levels.
-Two flip switches allow for the X or Y channels to be individually turned ‘on’ or ‘off.’
-Two potentiometers allow for varying of the low-pass filter’s time-constant (RC), the factor which slows the movement of the beam between points to produce lines on our CRT screen.
-Finally, a potentiometer which is polled by the microchip is used to vary the delay time between the sending of bytes to the ADC to be converted into voltages. This knob functions as the refresh rate control, changing the overall speed at which the CRT screen is redrawing over the same image.
Full description in my thesis document here: http://dspace.mit.edu/handle/1721.1/118575?show=full
A Cathode Ray Tube screen controlled by the CRTC.
The CRTC circuit diagram. Based on the CRTC design from “The Art of Electronics.”
A series of time-lapse CRT renders controlled by the CRTC.