Need to circuit design a red light detector which will raise alarm on detection. What will be the tentative cost for the elements.
This forum/Community is for Samsung SmartThings home automation hubs and devices, as well as many other devices that work with our hubs.
Your question is very open ended, and subjective to hundreds of possibilities; plus, it’s not really relative to this community unless you plan on integrating with ST one day in the future. I suggest researching electronics forums, web sites, kits, etc.