The sys admin's daily grind: Charly's doorbell Pi

Ring, Ring

Article from Issue 186/2016
Author(s):

When Charly puts on his headphones at home, he often fails to hear the doorbell. So, he dreamed up a solution with a Raspberry Pi Zero, a noise detector, and a power outlet with a LAN connection.

Sometimes I sit in my home office using a headset, listening to some good old electric guitar music or taking part in a teleconference – which is naturally slightly less invigorating. As a consequence of my acoustic escapism, I tend not to hear anyone who rings the doorbell.

To restore my social presence, I opted for the smallest version of the Raspberry Pi, the Zero. The Pi needs to detect the bell circuit closing and output a visual alert. In Germany, doorbells use 8 to 12V alternating current. You could convert this to DC and tune it down to a Pi-compatible voltage, but this would involve a mess of wire in the doorbell housing.

So, I went for a noise sensor. These things are very simply made, need a supply voltage of 5V, and send a signal via the output pin when they pick up a noise [1]. A blue rotary potentiometer lets me set the noise level. The sensor and the Raspberry Pi both fit into the doorbell housing (Figure 1).

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