How to run a countdown timer on a Raspberry Pi

Almost any Pi works — a browser showing a timer page is light work. A newer model just makes the desktop snappier.

The list:

• A Raspberry Pi — a Pi 4 with 2 GB of RAM or a Pi 5 is comfortable; older boards work too.
• A microSD card (16 GB or larger) with Raspberry Pi OS with desktop — the Lite image ships neither a desktop nor Chromium.
• Power supply, HDMI cable, and the display you want the countdown on. Use a supply rated for the board — an underpowered Pi reboots at random and drops Wi-Fi.
• Network: Ethernet or Wi-Fi with internet access.
• A keyboard and mouse for the first setup — removable afterwards. No spare keyboard? Enable SSH in the Raspberry Pi Imager's advanced settings before flashing and do the setup from another computer.
• A MaestroTimer room with a timer in it, created in the browser.

Raspberry Pi OS with desktop ships with Chromium, and that is the entire display stack.

The steps:

The viewer scales itself to whatever resolution the screen runs. If the digits look too small from the back of the room, lower the display resolution in the Pi's screen configuration and the timer grows with it.

1. ✓Boot the Pi to the desktop and open Chromium.
2. ✓Enter the room's viewer URL — every view in MaestroTimer is a link, and the viewer is the clean output meant for screens.
3. ✓Press F11 for fullscreen. Only the countdown remains.
4. ✓Set a wrap-up threshold on the timer so the display changes color as time runs low — visible across the room without anyone touching the Pi.

For a permanent installation, the Pi should power straight into the fullscreen timer with no desktop and no clicks. Chromium's kiosk mode does exactly that.

First set the Pi to log into the desktop by itself: in raspi-config, under System Options → Boot / Auto Login, choose Desktop Autologin. Then add a kiosk entry to your desktop session's autostart: on current Raspberry Pi OS (labwc) that is a line in ~/.config/labwc/autostart; on older Bookworm releases running Wayfire it is an [autostart] entry in ~/.config/wayfire.ini. The command is chromium, followed by the viewer link and the flags --kiosk --noerrdialogs --disable-infobars --disable-session-crashed-bubble — the last one stops a crashed session from parking a "restore pages?" bar over your countdown. Use chromium, not chromium-browser; the old name is a transitional shim. Give the script a few seconds' delay so the desktop is up before the browser launches.

One finishing touch for a set-and-forget display: disable screen blanking in the Raspberry Pi configuration so the screen never sleeps mid-event. To hide the mouse cursor, use the compositor's own cursor setting — the old unclutter tool is X11-only and does nothing on the Wayland desktop current Raspberry Pi OS ships.

The Pi never needs a keyboard again once the kiosk boots. Open the room's controller view on any other device — start, pause, and adjustments appear on the Pi's screen immediately, and messages arrive next to the countdown as bold, colored, or flashing notes.

The timer itself runs in the room, not on the Pi. A power cut, a network drop, or a browser reload does not lose the countdown: the viewer reconnects and shows the current state. Before an event, open the room's live connections view — the Pi appears in the list when its viewer is attached, so you can confirm every screen is receiving without walking the venue.

The same three-part recipe — Pi, screen, viewer link — covers most timing installations.

Common ones:

• A confidence monitor at the foot of the stage showing speakers their remaining time.
• A permanent countdown in a studio, church, or meeting room, mounted behind the display it drives.
• A portable production kit: Pi, small screen, and power bank in one case.
• A timer feed into a video switcher — the Pi's HDMI output works as an input source like any computer.