how does this tea container work?

my parents have had it for as long as i can remember, and then a bit more, its branded by Tetley, and as i recall, it is some sort of limited edition container, there is no date stamped on it anywhere, its made by Royal Winton.

when you poen the lid, the container will play a tune, and its only when there is light visible by the bottom of the lid, if you set the lid on a flat surface or turn off the lights, it stops singing.
which brings me to the question:
how does it know its open, how does it make noise, and, most confusing, how has it managed to keep working even though its at least 20 years old? surely if it ran off of a battery it wouldve burnt out by now, right?

Picture of how does this tea container work?
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lemonie6 years ago

There's a photo-sensitive semiconductor device embedded in the white plastic insert in the lid.
The plastic disguises it but lets enough light through to activate the tune.

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zack247 (author)  lemonie6 years ago
hm.

thanks for helping me figure it out, ive never known how it worked and i suppose it bugged me enough to try and find out.
+1... and batteries CAN last that long when the circuit isn't drawing much power. I just had the battery give out on a 30-year-old watch.

If you had let it play for an extended time you would probably kill the battery... but you generally wouldn't, right?
+1
Kiteman6 years ago
See everybody else's posts, plus remember that the circuit draws only a tiny amount of current for a few seconds at a time.

I had a Tetley's mug that played music like this - the circuitry is embedded in the ceramic, but the ceramic is translucent.

Eventually, as the battery dies, the music will be played in random snatches, no matter what you do with the lid. You then need to put the caddy out of annoyance's way for a few months until the battery is completely dead.

 
+1 to the explanations.

One of my sons had a 'singing mug' until my wife heated something up in it in the microwave. Then we had a smoking mug for a few seconds. Now it's just a mug.
lemonie Kiteman6 years ago
I knew someone who had a similar mug, eventually the thing fell out of the bottom of the cup...

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