Video Clock Superimposer

David B. Thomas
March, 1999

About the Project

As a followup to my VCR Pong project, here is a gadget that is actually useful in the Real World! It superimposes the time of day, in "HH MM SS" format, in the bottom right-hand corner of an existing video signal. My friend Scott uses it with his home security system.

In keeping with the tradition of my previous hacks, I use few parts and lots of tricks. All timing signals, including the timebase for the time of day and the clock for the microprocessor, are derived from the incoming video signal. That means if you lose power, or lose video, it loses the time... but in this home security application, that didn't matter. Lost power would mean the VCR stops recording and starts flashing 12:00 (1:00 during daylight savings).

Project Files

Here is the schematic, a parts list and circuit description, and most importantly the PIC source code.

The code uses the Parallax instruction syntax, so you'll either need to use Parallax's SPASM.EXE (available for free on Parallax's web site) or Tech-Tools's CVASM16.EXE (available for evaluation on Tech-Tools's web site), or here is a preassembled object file, in INXH8M format, for use with any device programmer.


If you have trouble getting something to work, feel free to email me. I get lots of emails so please be understanding if I am slow to respond.

I don't have ready-made PC boards (yet), but I can send pre-programmed controllers. For more information, see the parts list.

Another Video Overlayer

Check out this far more flexible video overlayer (different maker) elsewhere on the web.

Go back to -DeeT's PIC Page.

David B. Thomas (