Show HN: I turned my iPhone and a $20 smart plug into an f-stop timer
I am a film photographer and do some darkroom printing and always wanted one of the proper, advanced f-stop timers, but never really wanted to spend a couple hundred dollars on one. Eventually I figured my phone was already perfectly capable of doing the timing, it just needed a way to switch the enlarger. So I built Darkplug around a cheap smart plug. The app controls the enlarger over the local network and does regular timing, f-stop timing, test strips, has an intuitive dodge/burn workflow, split grade (2 timing channels) and paper development timing. I’ve been using it for a few months in my improvised bathroom darkroom. Fair warning: the app was blindly vibe coded using Codex and Xcode.
Discussion Highlights (8 comments)
arnarbi
Very cool. Is it controlling the plugs via direct Bluetooth connection? Or zigbee via a hub, or wifi (direct or via service)? I always assumed, probably incorrectly, that there would be too much jitter in the actual timing so I had built a few prototypes of e.g. an esp8266 controlled relay, where you would give the MCU a duration rather than separate on/off commands. But I guess that was wildly over-optimizing. In your case, how stable is the delay from the app sending a command until the switch operates? I'd add voice mode for color printing in total darkness.
sailingcode
Good idea. I wonder if the iPhone's camera would be able to measure the projected negative and guide exposure time?
mmmlinux
25$ to unlock all the features...
pimlottc
I get that red-on-black color scheme is a nod to the red lighting of a dark room, but the contrast is so low I can hardly read the example screenshots.
Sarkie
I had no idea what an enlarger was.
dofm
Nice. I have been meaning to do this with an e-ink device but other distractions keep getting in the way.
s0rce
25 years ago my dad built me a darkroom timer with a relay and a PIC 16F84A. It only had one button that you used a combination of short and long presses to adjust the time (read on a 7 segment LED display) and trigger the exposure.
nottorp
I'd like to endorse the plug choice :) Shellys can be configured to connect to your wifi and are not dependent on any cloud service.