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Vintage rotary phone becomes stylish kitchen timer

Arduino TeamMay 28th, 2024

It seems like everything that happens in a kitchen requires exact timing. Whisk the batter for three minutes, knead the dough for 15 minutes, bake for 30 minutes, and so on. A timer is a necessity for cooking and baking, but there is no reason you need to use your phone or a boring egg timer from the dollar store. You can follow Scott-28’s lead and convert an antique rotary phone into a stylish kitchen timer.

This looks like a very old rotary phone, but it is actually a versatile kitchen timer that counts down from as little as one second or as much as 99 hours and 99 minutes. Users enter the time by spinning the rotary dial, which is good fun. Then, when the countdown ends, the old school ringer bells start chiming. A four-digit seven-segment display is a bit anachronistic, but makes the timer more usable by showing the countdown. Lifting and then dropping the handset turns off the timer. 

This all happens under the control of an Arduino UNO Rev3 board, which reads the pulses from the rotary dial and the singular input button. It also sets the seven-segment display and the LED indicators.

The only tricky part was sounding the ringer, which requires AC power to function. To provide that from a DC power supply, Scott-28 used a LS057020 Black Magic Sine Wave Generator. That works like a power inverter, turning 5VDC into 70VAC (at 20Hz) to drive the ringer. 

The result is a timer that will impress anyone that walks into the kitchen.