Looking for a creative hack to check AC unit ON/OFF

Hey Blynkers,

Need your creative thinking.

I have this monster at home.

I hacked the IR signals from it’s remote, and now it’s a bit smarter, thanks to Blynk. It’s built on Photon as a control module, and I use another Photon with Temp sensor which acts as a thermostat.

But, there is an issue. Sometimes my wife ignores the convenience of having an app and switches it on and off manually. Which, of course, can’t be reflected in the app. Overall, having a feedback that device is On or Off is really crucial.

I’m looking for a creative hack to check the status of the unit. I don’t want to get inside the machine’s electronics (not my best skill)

Some early ideas:

  • use a light material (like paper) with a tilt sensor, which will check if there is an air flow. Somehow fix it near the vent…
  • installing another temp sensor inside the vent and measure the difference with a thermostat
  • suggest yours

It’s getting really hot in NY, so I need to fix it before August :slight_smile:


hmmm why not to put a photodiode (general speaking a photo detecting device) at the Power on led of the A/C (I hope there is such indication or display…)? You need to shadow the rooms light tho… What do you think?

The other more expensive idea is to monitor the power consumption of the A/C…

Power monitoring sounds great in general! This monster doubles our electricity bills.

Photoresistor is cheap and straightforward if i stick it with black tape. Like it! Thanks.

maybe http://sensing.honeywell.com/products/current-sensors?Ne=2308&N=3027 ??


Ahh I love me some HVAC monitoring! :slight_smile:

That is quite the monster! Now this is much different than my cooling unit, but I has originally started with a 120/220V relay to create a dry contact. Then I moved to using the 24VAC control signal, also closing a relay to create a dry contact.

I thought about proving airflow with a sail switch or differential pressure sensor, but I’m honestly less concerned about watching for failure (I feel I can trust the motor running).

I sadly never sorted out CTs, current sensing, etc. But that’s a great route for evaluating what you’re spending on power.

So enough of that… is this unit (relatively) loud? I once considered using a sound sensor inside or very close to the unit. And then maybe some code to weed out incidental loud noises… something looking for consistent (or maybe steady) noise… like a running AC unit!

Never heard about sail switch before… this is something I was thinking about when talking about a paper with a tilt sensor.[quote=“structure7, post:5, topic:7156”]
So enough of that… is this unit (relatively) loud?

Yes, it’s terribly loud. On hot nights we prefer to sleep with earplugs (well, it’s NY, after all :slight_smile:

Maybe wind sensor like;

You can also use Non-invasive current sensor like this

I would try a Hall Effect Sensor measuring the magnetic field the motor of your unit creates. See:

@NickM, thanks. looks interesting for another project I’m working on. Might be a bit expensive for this one, though

@Lavan: I can’t find a reasonably well documented tutorial on how to connect everything. If you know any - please post a link. Thanks. Majority of them don’t explain how to actually connect it.

@mrohner: Do you know how close the sensor should be to the motor? Sounds like a dirty cheap solution.

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@Pavel, Please refer this Link for more details.

I just tried and the hall effect sensor. It needs to be very close. another low cost module (also hall effect sensor) is the ACS712 that is used to measures current AC or DC.

There are several models ranging from 5 Amps to 30 Amps. You have to check your Air conditioning unit. A disadvantage is that you have to cut one wire open. Be careful.

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There is one more brutal solution - change wife :smile:.
Also widget on home screen may force your wife to use Blynk!


Sorry… couldn’t resist! :sunglasses:


I’ll pass her your idea, @Dmitriy :wink: And I’m not sure that “changing” will resolve the issue :joy:

BTW, she is on iOS and, in general, sometimes it’s just faster to press the button on the unit.
But Blynk won’t know that, which excludes some nice scenarios, like using IFTTT to determine that there is nobody at home, but AC is working - so turn it off and some other nice ones.

I’ve seen this, but I’m having hard times to understand how physical connection should look like. Still searching. Need a Dummies giude to…)

@mrohner - thanks for sharing. Might be my option.

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something like this…

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You could consider adding a physical button to the Photon so that one pushes that button instead of the one on the unit itself. Placed in a bit of a decent enclosure and put in a location at least as convenient as walking to the machine itself this still be simpler than always finding one’s phone, running the Blynk app, turning off the virtual power button.

You might have to make the device look a lot better than a raw photon hiding under a table or whatever if you want to add the physical button. When pressed, the button sends the Power Toggle IR signal to the unit and updates the Blynk virtual pin state to reflect the change. By always using your device either manually or via cloud, it should keep track of the state of the device. Of course this will only work if you use the new button on the photon, but if as quick and convenient as the machine button…

I used a photo resistor to monitor “Power ON/OFF” by looking at the power LED of my cable company box. I am using a hall sensor to determine if the power is on at a remotely controlled stereo – I taped a magnet to the volume knob that physically rotates and positioned the Hall sensor to detect zero volume. Sensing the power ON by using the fan to trigger a change of state of a Hall sensor / magnet pair would be interesting to try but has to be wired to photon and you may not have your unit that close by…ditto with a photo resistor. Let us know what solution worked for you.


Try a slotted photo diode with something light in betwren like this

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Hi, nice problem, I would resolve it by using an accelerometer, and since you use a Particle Photon you could find some hint there: https://build.particle.io/libs/5494bbacd2378603370001ce/tab/MMA8452-Accelerometer-Library-Spark-Core.cpp
I never try it so I let you look at it.

+1 for @mikekgr’s idea, I would go with a mini photocell like this guy did on his washing machine:

good luck!

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