from Hacker News

Automating My Air Conditioner

by dguo on 10/9/21, 8:56 PM with 25 comments

  • by glitchc on 10/9/21, 10:13 PM

    A general note: Arbitrarily cutting and restoring power is a bad idea for a compressor. See the first answer at this link for a detailed explanation:

    https://diy.stackexchange.com/questions/145791/how-bad-is-it...

    In a nutshell, it takes time for the refrigerant pressure to equalize. An AC with a thermostat will have a timer to prevent an immediate restart after a stop.

    Another option is to introduce hysteresis into your control loop as the TFA author has done: Use a distinct power threshold from your off threshold. By setting the power on a couple of degrees higher than the cutoff, it will give the refrigerant pressure time to settle.

    To the author: I agree with the other posters. Looks the AC already has a thermostat, just no automatic fan control.

  • by ultrarunner on 10/9/21, 10:24 PM

    Mentioning it just because I didn't see it addressed in the article: AC compressors & fans can be a significant current draw. If you want to replicate this project, it's probably worth checking the amperage ratings for whatever smart plug you use. Something intended to switch lights or a room fan may not be up for the task of repeatedly starting a compressor. Even if the AC unit only draws 15 amps (an so is fine to plug into a wall), inrush current could be an issue for an traic or SSR-based smart plug.

  • by sxp on 10/9/21, 9:50 PM

    > If the temperature is above 75°F, the job turns the smart plug on. If the temperature is under 73°F, the job turns the smart plug off.

    Would turning on/off a high current A/C like this have any negative consequences? Some A/C units have a cooldown period after you turn them "off" via their button since they need to remove some condensation and perform other normal maintenance. Would that issue apply to cheep window A/Cs?

  • by snthd on 10/9/21, 10:55 PM

    https://github.com/ct-Open-Source/tuya-convert is useful for re-flashing some widely available smartplugs without opening them up. Then you can use MQTT or HTTP.

    Unfortunately some newer plugs are incompatible with the hack (different chipset - https://github.com/ct-Open-Source/tuya-convert/issues/484 ).

  • by cereal_console on 10/9/21, 11:07 PM

    Check out Home Assistant. I use Home Assistant to control about 35 TP-Link Kasa devices via local control. Home Assistant supports both local and cloud control of Kasa devices.

    I use a mix of ESPHome (using ESP8266 devices) and BLE sensors (feeding back through ESPHome ESP32 based gateways) to gather home air quality data.

  • by sokoloff on 10/9/21, 10:08 PM

    It sure looks like that thing has a thermostatic control. I’ve got similar window shaker units and they have a distinct click when the thermostat turns on or off and they do an ok job of controlling the temp in the bedrooms.

  • by syntaxing on 10/9/21, 10:21 PM

    Love the spirit of the idea and execution! I would guess the “temperature” knob ties to some sort of trigger relay downstream. You would probably be able to tie in a microcontroller of some sort to control it and maintain the process function like ramp up and cool down. But at the expense of requiring to open up that panel.

  • by avh02 on 10/9/21, 10:09 PM

    In university I had an air conditioner that would turn off when the power went out (regular occurrence, few minutes), so I'd wake up sweltering or otherwise needing to get up/interrupted in order to switch it back on (it had a cabled remote/controller)

    The automation was a clothes peg on the power button.

  • by mcbishop on 10/10/21, 4:54 AM

    Is anyone aware of an open-source smart plug or smart outlet with a public API? ...That doesn't assume a big-tech integration?