Another Ebay deal where the sum of the parts seems like a pretty good value. Must trigger at an adjustable DC level of reflected IR since the 4093 IC is just NAND gates, so this isn't a high tech sensor. A 38 kHz sensor & circuit would be more reliable, but who am I to look a gift horse in the mouth.
If nothing else, it looks like a nice PCB, so soldering the non-SMT parts may be fun for us old Heathkit lovers, or an intro to electronics for someone's budding young scientist. Win the whole science fair when your kid turns on a lamp or something else when you or Rover is detected.
"When you make a thing, a thing that is new, it is so complicated making it that it is bound to be ugly. But those that make it after you, they don’t have to worry about making it. And they can make it pretty, and so everybody can like it when others make it after you."
- Pablo Picasso