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Analogue hourglasses have become rare. If you want to use your soldering iron again, you can put together a kit that represents a digital version of an hourglass. The electronics control 30 LEDs that simulate the running sand. The running time is controlled by a potentiometer. Supplied with 5V voltage, the LED sand always trickles down, controlled by a toggle switch. https://www.az-delivery.de/products/b...