Sewer Pump Alarm?

I don’t think we’re talking about the same thing here. :thinking:

A contact sensor typically detects a “closed” event when the magnet piece is moved close enough to the other piece that the magnet can pull the thin metal “reed” inside the other piece of the sensor into position.

”Dry Contacts”: on the other hand, are connecting points on a device which complete a circuit when an external device is electrically active. The device with the dry contacts can be pretty much anything: one very popular one is the Mimolite. Which doesn’t do anything else: it’s designed specifically as a bridge to add zwave communication to dumb devices.

As it happens, there are a couple of contact sensors which also have dry contacts, but that was just a manufacturer decision. Because these typically cost quite a bit less than the mimolite, people often use them for simple on/off reports, particularly for low voltage devices like a doorbell.

The mimolite is a much more robust device. Not only can it handle somewhat higher voltage, you can set it to detect with a range rather than just on/off. Or to count pulses. And you can use it as a relay to turn off a 120v device as well, something you can’t do with the ecolink sensor, for example.

So it’s just a coincidence that there are “contact sensors” with “dry contacts”— the word “contact” is being used two different ways there. :sunglasses:

For the OP:

As to what happens if the bridge device fails…the dry contacts attachment is just a physical loop spliced into the existing circuit. That part can’t really fail unless the wire becomes physically detached from the contact post, so it shouldn’t be an issue even if the radio communication fails.

The mimolite or other control devices could be more of a problem if they randomly open or close the relay. But that’s an optional feature.

In any case, I’d still recommend trying the Fibaro multisensor first. No wiring required, so even total failure shouldn’t change the pump’s function in any way. :sunglasses:

2022 update

The mimolite is no longer being sold at retail, but there are a number of other devices now available. See the faq:

FAQ: List of devices with dry contact input from external sources

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