My dog walking through it.What is the beam detecting?
That's a great start. Thank you very much!OK, so a board something like this: https://www.amazon.com/Gikfun-avoidance-Reflective-Photoelectric-Intensity/dp/B07FJLMLVZ/ used with a retro reflector (like a small white bicycle reflector, for example).
With a module something like this: https://www.amazon.com/dp/B07DFT2WDS/
And you can get latches that release when turned on, which is better in general to keep it turned on full time.
Interfacing these two will requite a few components, so if you are up for learning something, an Arduino would be a better way to go than the delay module, and there are plenty of people here who would love to help you learn how.