The Monoprice shock/vibration sensor is absolutely worthless for this purpose. I did put it on a spring (surprisingly enough just like @john.hart3706) with some double sided tap and it did work a little better. The reason it doesn't dampen always is because eventually you have basically constructive energy where the spring is moving slightly in a direction and the it gets a boost in the same direction from the dryer.
At any rate, it wasn't reliable because the Monoprice sensor, even set to most sensitive and on a spring, would not trigger and stay triggered.
What I eventually did was got these (one for my dryer and one for my oven). These essentially support an external dry contact sensor aka a sensor that doesn't require voltage but on it's own either completes or interrupts the circuit.
At that point you just have to get a dry contact amp sensor. (My dryer is electric. I'm assuming yours is too or you should just get a power metering 110V plug and watch the power spike to know when it's on.)
*edit: By the way, dry contact amp sensors are called current transformers or CTs. There are two types: split core and solid core. Split core means that they act like clamps and you don't have to disconnect the wires because you can clamp them on around a wire. Solid core mean that you have to disconnect the wire so that you can slide them on from one of the wire ends.
You have to choose the amperage at which you want them to trip or the "trip point." I choose .5 amp CTs because (from looking at my HEM) I could see that the dryer always pulled an amp or more when it was running. This was one of the cheapest I found so I went with them. They don't come with contact wires, just the CTs. I have wire laying around.
I am trying to use my aqara vibration sensor in some way to notify me when washing machine is completed. I am trying to follow your rule but my rule screens do not look like yours. maybe that is an old version of hubitat?
I had a question about more specifics related to my setup so I will answer them here.
I used the CT-800 (solid core) because I am cheap. The solid core CTs are always cheaper than the split core ones. The 805 is the same CT but split core. With a dryer that means you have to probably move the dryer out to get at the terminals on the back.
I removed the terminal block cover and loosened the cord strain relief so I could easier work with it. My cord is a 3-wire cord which means (I think) that 1 leg of the 220v (110v) is on the left and the other leg is on the right with neutral in the middle. I tugged on each of the individual wires to separate them from the bundle to give me some slack,
I disconnected one of the 110v legs (probably the left) and pushed it through the CT-800 and hooked it back up. The CT-800 in my case was small enough to sit inside the dryer behind the terminal block cover. Also, I got lucky and choose the correct one 110V leg becase I later discovered that that one of the legs powers the heating element while the other leg powers the motor. I ended up on the motor which is what you want so that you get off-on-off instead of off-on-off-...[millions of repeats]...on-off-on-off for light or tumble dry loads. I used a bit of extra fluorescent ballast wire to hook the CT up to the sensor. I command strip mounted the sensor to the back of the dryer, tightened the cord relief and covered the terminal block again.
In HE it's a little weird to use because that Monoprice Sensor (for this purpose) then uses the "Generic Z-Wave Contact Sensor" driver. And because the CT is normally open and when current passes it closes it means that dryer off == contact open and dryer on == contact closed. Then you just use it like a contact. I will eventually write a driver that treats the Monoprice sensor like a switch that makes sense but I haven't gotten around to it yet.
Thanks for the explanation Ben and for the suggestion to use the leg that goes to the motor instead of the heating element. You confirmed my suspicion that you only went around one leg. Take care and be safe.
