Turning a dumb AC unit smart (without losing my security deposit)

Overall reaction to the AC/PTAC hack

• Many find the stepper-motor-on-the-knob solution clever and surprisingly reasonable given the “no damage, no deposit loss” constraint.
• Some call it “hella jank” but acceptable jank: author explored safer options first and is clearly aware of trade‑offs.
• Main practical weakness noted is the fragile mounting (binder clips, cardboard) causing motor sag, friction, and stalls.

Mechanical mounting suggestions

• Replace binder clips with 3M Command strips or removable adhesive for stronger, residue‑free mounting.
• Use a snug wood block, aligned via the shafts, with screws into the block (or discreetly into the unit, then patched on move‑out).
• Several people suggest 3D‑printed brackets as the “right” long‑term solution.

Control strategies & firmware

• Multiple suggestions to use ESPHome instead of custom firmware; it has built‑in support for the ULN2003 stepper and thermostat logic.
• Some argue adding Home Assistant/Linux dependence introduces failure modes; others note ESPHome can run useful local logic even when HA is down.
• Alternative approaches:
  • Use PTAC thermostat terminals with a commercial thermostat (e.g., Ecobee, Mysa, smart 20A outlet).
  • Smart plug / relay in the power path plus enforced compressor restart delay, though OP’s article explains why a simple smart plug is problematic.
  • More invasive electronic options like vactrols or digital potentiometers to emulate the knob electrically.

Safety, reliability, and lease issues

• Concerns about servos/steppers leaving switches half‑thrown or stressing components, potentially a fire risk.
• Some are comfortable hacking cables or outlets; others are uneasy doing this in multi‑unit buildings because mistakes affect neighbors.
• Debate over whether such a non‑destructive add‑on is even a lease violation; enforcement is seen as unlikely if everything is removed cleanly.

HVAC and building context

• PTACs are criticized as noisy, leaky, and outdated, but popular in NYC due to cheap retrofit costs and no ducting requirement.
• Landlords optimize for install cost; tenants pay the power bill, so efficiency gets less weight.
• Discussion compares PTACs, mini‑splits, and portable (especially dual‑hose inverter) units, with conflicting claims about which is more efficient.
• Compressor behavior is debated: abrupt power‑off is generally fine; key requirement is a delay before restart to avoid high head pressure and stalls.

Smart devices, APIs, and DIY philosophy

• Strong sentiment against manufacturer “smart” ecosystems and abandoned apps; preference for simple, documented physical or electrical interfaces.
• Desire for standardized low‑level control pins across appliances, similar to thermostat terminals, so users can choose their own controller.
• Commentary extends to TVs (wanting HTTPS APIs instead of proprietary AV stacks), smart washers/dryers, and even phones.
• Some note that many commercial smart devices internally are just ESP32‑style boards with the same “janky” mechanics, but in nicer enclosures.

Infrared and other retrofit solutions

• Separate subthread: how to control ACs with IR remotes. Suggestions include ESPHome + IR LED/receiver, Broadlink IR blasters with temp/humidity probes, Sensibo, and Mysa mini‑split controllers.
• Others report wiring ESP32s directly into heat pump interfaces or PTAC UART ports for more robust control.
• One commenter uses an AC that resumes after power loss, leaving it always “on” and controlling it via a smart plug and external temp sensors.

Miscellaneous

• Some would gladly pay for an off‑the‑shelf, renter‑friendly solution to this exact PTAC‑knob problem.
• Minor ethical/environmental note: criticism of returning small misordered parts to Amazon due to waste, versus cost justification.