This is a continuation of the tangle and out of filament sensor project. I used a CMOS 555 to conserve power , I measured 110µa while in standby, I considered not adding a power switch but one dead battery later changed that. I did something on this project that I thought I would never do and that was use a protoboard as the permanent substrate for my project. I used 9 volts because I wanted the sonalert to be loud so I could hear it a couple rooms away. The tangle sensor was simple, Just a magnet on a Reed switch basically. Move the magnet and then re switch pops open, which causes the alarm to sound. Having The alarm sound when one switch was open and the other switch was closed presented a minor issue, Fortunately a 555 chip only needs around 1 Volt on the reset pin to be active. I used this property to good advantage.
I created a battery compartment as part of the box print.
the cap.stl file has covers for the screws for the wire binding posts.
