Small AC Zero Cross Board

I needed a small zero cross detector to switch SSR's efficiently and properly in my DIY reflow oven so I designed these in KiCad, and built them.   They are optically isolated (5000V Isolation) and Low power (less than 120mW) so are safe to hook up to any board supported by Armbian (or any other SBC) (provided you safely wired them to the mains) and produce a nice open drain low going pulse for 1ms (50Hz AC) centred dead around zero cross. (about 0.83ms for 60Hz AC).  On the digital side they will interface to any logic level between 1.8V and 5V. 

The thing is I only need 2, and I have spares because I had to get 10 PCB's minimum.  I have decided to build them all up, So, if anyone would like one, let me know I am happy to sell my spares.  Useful for any project involving the switching of mains power, load monitoring, etc.  I am not thinking about going into production of these, so once these are gone I likely won't be making any more.  I designed the board to be hard wired to the mains and then heatshrinked so that no High voltage is exposed in operation.  However they can take a screw terminal if one is so inclined.  Send me a PM if your interested in getting one, and otherwise I am happy to discuss the boards here in this thread. 

Obviously these are connecting to mains which can be lethal if you are careless or stupid, so anyone doing this sort of project needs to take the appropriate precautions, and know what they are doing.  That said, once these are safely wired up to the mains, and then encapsulated, they should be quite safe and present no danger to connected equipment.