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Positive affirmation box Answered

I am trying to make a positive affirmation machine so that when my students turn in homework it will either give an audio message or display a message that says something good.  I know I need to build an optical sensor but I was wondering if there is a build that you can suggest that I can modify?  I have moderate skills with building electronics and access to plenty of materials but I am lost as to how to start.


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6 years ago

If they're posting it through a letter-box, just have a micro-switch that is pushed by the paperwork and trips an electric door-bell.

The diagram isn't anything like to scale, but I think you'll get the idea: