For my Year 12 project I have 15mm round dog treats rolling down 18mm PVC piping.
I plan to have a solenoid (extruded when off, pulled in when on) blocking the pipe. I want the solenoid to be active when it senses there is no dog treat sitting on the LDR (LDR active when light hits).

I have a 12V solenoid, 12V LDR and veroboard to build the circuit on.

I need to know what size resistors, transistors, ... I will need and how to set the circuit up. I also want there to be a delay between the LDR and the Solenoid (e.g. senses light, 5 minutes pass, solenoid pulls in and releases treat).

I need about 15 of ^^^ circuits and I want to connect all of them to a single 12V digital programmable relay timer along with a few other components such as a bubble machine.

I can follow plans to build circuits but in school we have not had to design circuits so far, so my experience is rather minimal

 

Solenoids, LDR's, programmable relay timers, bubble machine... Way too much stuff going on for no pictures. Please draw a sketch of the overall wiring or signal flow with boxes for the circuits you need help with. If you draw in every input and output wire it will be messy, but will help keep things clear.

ak