| This project was aimed at year 8 and developed from a mechanical toy project to include some electronics. It has proved very successful and students have produced very high quality results.
The musical toy must have some part that moves to activate a microswitch. This powers the circuit to play a tune.
The circuit uses the UM66 melody IC range, which unfortunately is becoming more limited as time goes on. Rapid sell 4 types as do Maplins but I recommend Rapid for price.
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The model is made from 6mm MDF. The lever has to be attached behind the model to activate the microswitch. A 4x1/2 japaned wood screw was used to secure the lever. Students were encouraged to add relief to their toy to enhance certain features - such as arms, feet, eyes etc.
The battery box made from MDF holds the 2xAA battery holder which is wire ended, not the snap type.
The circuit board is very basic and small enough to be supported on wires attached to the speaker. The speaker is screwed to the back using 1/2" screws. The microswitch is screwed into place from the front of the model using countersunk screws then the heads painted over to hide them.
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Circuit consists of IC and transistor amplifier. Any TO92a case transistor with a collector current of around 150mA will do.
PCB
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Circuit Diagram
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| DOWNLOADS
PCB and circuit details
Lesson plans, 7 weeks
A more comprehensive version is being prepared
PCB sheet - 25 PCB's
Assembly details - powerpoint (140K)
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Components and Materials
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UM66 melody IC
BC183L transistor
10uF elect. capacitor
1K resistor
8ohm 38/50mm speaker
Lever microswitch
2xAA battery holder
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6mm MDF
PVA glue
PVA paints
4x1/2 japanned screws
4x1/2" countersink screws
Stranded wire 7/0.2 |
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