Brainstorming - Detect if "dumb" AC is on

Hi all,

If have a central AC in my apartment that can be controlled by an IR remote. Unfortunately there is no separate On/Off buttons only a single Power button toggle.
Would love to hear any suggestions on how I might be able to detect if the AC is actually running or not.

Appreciate all ideas :slight_smile:

Temperature sensor :wink:

Most AC indoor units have some sort of flap or swing at the air exhaust which opens/closes when you power it on/off and which also directs where the cold air is blown (often with a ‘swing’ setting or something like that). If your AC has such a flap, you could use a door/window sensor to dectect whether it’s currently powered on or not.

Here’s a picture of what I mean:

1 Like

Don’t think it didn’t cross my mind… :slight_smile:

That’s not a bad idea but I have a central AC not

Does it have a power LED?

If so, you have a couple of options:

Use a light dependant resistor to test if the LED is on or off. Or if you are feeling a bit more adventurous, open it up and and connect an optocoupler in series with the LED.

Getting that signal back to HA can be done a number of ways. Probably the simplest and cheapest would be with an ESP module of some description.

1 Like

Ah, okay - then it’s a little more difficult. :sweat_smile:

Those central AC units are not so commonly seen here in my country. I don’t think that fetching the IR signal with a reciever would work well in this case if you only have one button to toggle the power state, because it will go out of sync if the signal isn’t detected correctly every time. Using a temperature sensor on the air outlets isn’t the best option either, because you can only detect if the AC is blowing out cold air right now or not. Maybe a combination of these two solutions would deliver a reasonable result.

Nevertheless, I guess it’s pretty hard get the accurate power state into Home Assistant with these units. :thinking:

If you are able to make modifications, an inline power monitor to the AC like the sonoff pow would give you the state

1 Like

What about a wind speed sensor?

1 Like

Not sure if this would work, but maybe you could put a temperature sensor in front of the vent and do a mathematical comparison between the detected temperature and the outside temperature?

An in-wire Sonoff, good one. Or if you can access the power plug: just use a smart power plug. E.g. Neo Coolcam Smart Power Plug does power measurement. Using it to detect if my set top box is on or off.

I’ve wired little temperature sensors to ESPs running espeasy to measure my pool temp.
Air temp would be easier, but I’m not sure how you would put a sensor in front of the vent without it looking bad.

Here’s some info on wiring the sensor
temp sensor

audio sensor/microphone to listen for the air flow might work, but I expect the detection algorithm may be tricky.

Someone already suggested power sensor on the ac power lines. Could also maybe put a vibration sensor on the ac unit if you have access to it, depending on how much it moves during operation.

Thanks for all the ideas! Some might be tricky as the AC can go into “snooze” once it hits appropriate temparture which would stop wind / noise / power consumption but it’s still on (and will kick in eventually again) but that’s still better than nothing :slight_smile:

How do you tell now whether it is on or off? If something is observable it is recordable.

Out of the box suggestion.
See if you can find on/off codes for your AC. There are ir databases online, and your ac might support discrete on/off codes even if your remote doesn’t.

Then make an ir blaster to control your AC
I recently made one
ir blaster

There is a control button with an indicator light… But I couldn’t think of a good elegant solution for observing this…

That would be ideal but I couldn’t find any indication an off code exists nor did I find any online (doesn’t mean it doesn’t exist but I didn’t find any :))

I happened to be reading this earlier

Someone said he used it to detect washing machine status.
So you might be able to read the indicator light, on off should be pretty easy with a little tweaking.

Is the control button a wall-mounted unit? Something like this ? If yes, then you might want to peek behind the unit. You should be able to find power cables. You can then tap into the power cable and use an inline Sonoff POW(2nd Gen). Stating the obvious, but don’t forget to switch the mains off when doing this.

Lastly, I hope it is not a rented property. :slight_smile: (which makes any modifications tricky due to legal/contractual requirements)

Maybe an HEM in the circuit breaker box to determine power usage. Can watch it for a while to determine your low limit (on/off) then create automation to turn virtual switch on or off based on the power. I have something similar for my washing machine.

- alias: Washer Turn On
    - platform: numeric_state
      entity_id: sensor.washing_machine_power
      above: 10
        seconds: 60
    - service: input_boolean.turn_on
      entity_id: input_boolean.washer_status

- alias: Washer Turn Off
    - platform: numeric_state
      entity_id: sensor.washing_machine_power
      below: 30
        minutes: 3
    - service: input_boolean.turn_off
      entity_id: input_boolean.washer_status