This small project was a box which would be opened by voice activation. In fact the ‘box’ would ask a question and only if the correct answer was given would it unlock.
The starting point was an electromagnetic lock which could be controlled by a microcontroller, a module to play speech (i.e. the challenge questions) and a voice recognition module (to recognize the correct answers.
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One major consideration is to provision an emergency ‘unlock’. What if the program crashes ? the battery goes flat etc. etc.
The electromagnetic lock has a mechanical override which is probably the best solution. So a hole in the box to access this with a rod or screwdriver.
What I did was to wire the lock to two bolts on the box, so I just had to apply 12v between the two screw heads, to unlock the box.