This is something of a mandatory donation meter. If you don’t feed it with coins it sounds a very loud alarm continuously.

[Piet De Vaere] built the device for a free festival in Ghent, Belgium. The intent is to help raise awareness that although free of an admission price, the success of the event depends on donations. It works much like a parking meter. When you feed it coins time is added to the meter. When it runs all the way down that large loudspeaker on the right side of the case sounds the alarm.

In the video after the break [Piet] walks us through a demonstration, followed by a tour of the hardware. The pointer on the meter is a piece of cardboard connected to a servo. An Arduino board controls the servo, adding time in two-minute intervals whenever a coin enters the chute and passes by an optical sensor. There is no distinction between types of coins.

The use of a pizza box as a prototyping board shows that you don’t have to be fancy to build something neat.

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