n-teller is an IoT device that displays the number of checked in participants and visitors at the hackerspace called Revelation Space (or RevSpace).

n-teller

I built a desk display that mirrors the RevSpace headcount live. n-teller joins the space's WiFi, listens on the MQTT server, and shows the number of checked-in visitors on an old-school 7-segment display.

Parts and prints

ESP8266 plus a MAX7219 LED driver on a custom PCB, a 0.36-inch 4-digit 7-segment common-cathode display, a 3D-printed stand, and an optional USB-C socket for power
Gerbers, schematic and PlatformIO firmware included

Reading the feed

The ESP8266 subscribes to `revspace/doorduino/checked-in` on the RevSpace MQTT server. Each message updates the shown number; a separate `revspace/state` topic drives the open/closed state. Double-reset the button to open the WiFi config portal.