Home & IoT

Turn your phone and a $20 smart plug into a darkroom timer

A film photographer vibe coded an iOS app with Codex that drives his enlarger through a cheap smart plug, replacing a $300+ dedicated timer.

By Peter Szentkiralyi on Hacker News · Posted · Added Oct 15, 2026 · 2 sources

Difficulty
IntermediateOur rating
Time to build
Not reportedOur estimate
Monthly cost
Sourced: one-time ~$20 smart plugFrom the source
Revenue
Not reportedWe only show revenue the source states
Result
Sourced: under $50 vs $300+ for a hardware timer

What they did

Peter Szentkiralyi built Darkplug, an iPhone app that switches the enlarger through a local-network smart plug and handles f-stop timing, test strips, dodge and burn, split grade and paper development timing. He says it was 'blindly vibe coded using Codex and Xcode'.

How it went

He has used it for a few months in a bathroom darkroom. He puts the cost at under $50 for the app and plug versus $300+ for a boutique hardware timer.

Worth knowing

Relies on a compatible smart plug on your local network. Hands-free control in the darkroom is traditionally a foot switch, which came up in the discussion.

Builder recipe

Our own starting point, written from the source. Adapt it to your setup.

Stack

  • Codex
  • Xcode
  • A smart plug with a local API

Steps

  1. Confirm your smart plug can be switched over the local network.
  2. Ask Codex for a minimal SwiftUI app that toggles the plug for N seconds.
  3. Add f-stop math and test strips one feature at a time.
  4. Test with the enlarger before trusting it with paper.

Starter prompt

Build a SwiftUI iPhone app that turns a smart plug at [IP] on for an exact number of seconds over the local network. Add f-stop timing (base time × 2^(stops)), a test-strip mode, and a big red stop button.

Tags

Agent Codex
Industry Photography

Read the original

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