I wonder if anyone has had thoughts on an alternative design for the AC to AC supply, rather than needing a separate mains outlet. i have used this design in several projects in the past. see diagrams. theres also a zero cross detector.
Oscilloscope reading attached too
tony
Re: Alternative approach to the AC to AC supply
Your circuit requires a direct connection to the supply and therefore needs to be double-insulated or in an earthed metal case, with all the attendant difficulties and safety precautions required when working on live equipment. There can be no external connections that do not have the appropriate isolation.
Having said that, I agree that the danger is small given that the failure of one or even two components would not result in a dangerous current flowing (though it might well damage anything connected) but as I understand that many kits go into schools, and I assume many kits are built by people with no experience of safe working around live equipment, it's not something that can be generally advocated. If you want to do it, fine, so long as you take sufficient precautions to prevent danger to yourself or anyone else who might become involved.