How to monitor when a circuit is on?

Been looking around on the forums to figure the best way to monitor when a circuit comes on. The specific circuit is the buzzer in my clothes dryer. The buzzer is actually a 120v buzzer with two prongs .


In researching, i saw a CT clamp sensor based on ESPHome, but since i don’t really have any ESP home devices i figured i would ask if anyone has any other ideas on how to monitor when this gets power? i do have zwave and zigbee in the home, so a solution that integrates that way would be preferred.

EDIT: This is in the US, the dryer circuit is 240v and 30amp, which is probably the reason i can’t find any plugs that i can use. I believe the draw on the dryer is only 24 amp. Inside the dryer, it splits out a 120v leg for some of the accessories (like the buzzer). I was hoping i could just splice into one leg of the buzzer with something like a relay switch and whenever the circuit for the buzzer is energized (when the cycle is done), i could send an alert.

I have no clue what this does but adding a clamp or other device seems a bit overkill / expensive (I have no clue how important it is for you to be aware of on/off of course). You could measure the clothes dryer by adding a power-measuring plug in between socket and buzzer?

sorry, guess i left some info out of the first post. The dryer is a 240v appliance, i could not find any plugs that would work with that. All i am trying to do is to monitor when the dryer is done so we can go get the clothes. The dryer is at the far end of the house and we can’t hear the buzzer. My thought was that when the cycle is done, it energizes the circuit for the buzzer. if i can sense power to the circuit, i can then send a notification to the speakers near us.

There are plenty of plugs that measure power and many many more people who are asking the same question: for their coffee maker, their washing machine, etc. …i.e. how to determine when a cycle is ‘done’…you should search this forum a bit more as each machine has different cycle behavior but as soon as you know what…then you know how to do this

I was not able to find a single plug that supports 240v, believe me, i have searched high and low. If you have, please share as it would be a fantastic find for a bunch of people

You found nothing searching for “smart plug with power meter”?

Here’s a good one: https://shelly.cloud/products/shelly-plug-smart-home-automation-device/.

The fundamental problem with this thread is that the original poster hasn’t told us where in the world he lives. The says he has a 240v device, but also refers to a 120v buzzer. I suspect the totally bizarre US system, but who the hell knows.

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Correct, US system. The dryer is 240v from the receptacle, but the internal components (the buzzer) run at 120v.

What does the power socket look like?

It’s a 3 prong outlet.

Really hard to tell from that pic, but it may be compatible with AU/NZ plugs https://www.athom.tech/blank-1/esphome-au-plug

Going back a step, what about putting a opto-isolator in parallel to the buzzer, with the other side of the opto attached to an esp.

sorry for the poor image, i dug another one out of the interwebs…

Not certain what an opto-isolator is, but i will do some research

No, not compatible with NZ/AU plugs.