I am a film photographer and do some darkroom printing and always wanted one of the proper, advanced f-stop timers, but never really wanted to spend a couple hundred dollars on one. Eventually I figured my phone was already perfectly capable of doing the timing, it just needed a way to switch the enlarger.

So I built Darkplug around a cheap smart plug. The app controls the enlarger over the local network and does regular timing, f-stop timing, test strips, has an intuitive dodge/burn workflow, split grade (2 timing channels) and paper development timing.

I’ve been using it for a few months in my improvised bathroom darkroom.

Fair warning: the app was blindly vibe coded using Codex and Xcode.

Very cool. Is it controlling the plugs via direct Bluetooth connection? Or zigbee via a hub, or wifi (direct or via service)?

I always assumed, probably incorrectly, that there would be too much jitter in the actual timing so I had built a few prototypes of e.g. an esp8266 controlled relay, where you would give the MCU a duration rather than separate on/off commands. But I guess that was wildly over-optimizing. In your case, how stable is the delay from the app sending a command until the switch operates?

I'd add voice mode for color printing in total darkness.

Good idea. I wonder if the iPhone's camera would be able to measure the projected negative and guide exposure time?