Op Amp Challenge: How late is your monitor?

In the days of CRT displays, precise synchronization between source and screen meant that the time between a line of video appearing at the input and the point writing it to the screen was constant and very short . Today's display technologies offer unimaginable resolutions compared to the TV your family had in the 1970s, but they do so at the expense of all their signal processing imposing a much longer delay before a frame is displayed. This can become a problem for gamers, but also with normal viewing, as in some circumstances the delay can be long enough to be audible in a disconnect between the movie and the soundtrack. This is something that [Mike Kibbel] solved with his video input delay counter, and it makes for a very interesting project.

At its heart is an FPGA, and in the video below, he describes in detail its programming. It generates both a DVI output to drive the monitor and performs the measurement. The analog-to-digital converter side of the circuit is interesting, it has a photodiode and an op-amp driving a comparator to form a simple 1-bit converter. He walks us through the design process in detail, with little gems as useful as the small amount of hysteresis applied to the comparator.

There are probably many ways this project could have been implemented, but this one is both technically elegant and extremely well documented. Definitely worth a visit!