Show HN: I turned my iPhone and a $20 smart plug into an f-stop timer
peterszentkiralyi.euI 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.
I was curious about timing accuracy too, has any testing been done on this? Is it accurate to 1s, 0.1s, 0.01s? How dependent is it on the smart switch hardware?
I played with development photos in a darkroom a long time ago. I don't think one second actually makes much difference.
Good idea. I wonder if the iPhone's camera would be able to measure the projected negative and guide exposure time?