Extreme Doorbell

The Project

An electronic project for kids in grades 4-6, the Extreme Doorbell is a customizable electronic doorbell built on a breadboard. Ringtones are RTTTL format that are entered at compile time. Extra equipment for device programming and ringtone demonstration was built as required.

Design Constraints

  • Cost – A very limited budget was available per kit was available so a strategy of low parts count & donated parts and a greatly simplified amplifier was pursued.
  • Ease of Assembly – As the kits were to be assembled by children on breadboards the circuit had to be as simple as possible.
  • Fun – The final product had to be worth the effort for the kids.

My Role

  • Research into initial concept. Included finding an ultra low cost Amplifier design, locating the information necassary to play RTTTL tones and finding an existing parser.
  • Programming. An existing parser had to be ported to a new compiler (C18) and chip (PIC18F1320).
  • Parts Layout. A template for the breadboard was required, and revised with experience from observing assembly.
  • Troubleshooting. As very young children built the kits, many unique construction problems were encountered.
  • Training and Documentation. Counsellors had to be trained in how to build and customize the project.
  • Support Hardware Concept, Design and Execution. Support hardware was developed as needed and included a ZIF programming adapter / device tester, and a demo unit capable of playing 8 different tones.

Lessons Learned

  • Designing for childrens’ kits – The kids had a great deal of difficulty with the breadboards, often inserting wires too far in, thus causing shorts and leading to overheating and exploding batteries. Also, parts were very frequently installed incorrectly making troubleshooting much more difficult.
  • Designing Musical Equipment – When creating oscillators for tone generation at a certain note, tolerances must be VERY tight as to output vs. intended frequency.