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Small Project to connect two dry contact sensors to one signal. Is it possible?

DSF360

Mar 16, 2024
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Mar 16, 2024
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Hey there,

I've got a little project going on and could really use your expertise.

Here's the scope: In my septic system, we've got a high water float that operates as a dry contact using a reed-style switch. It's Normally Open (NO), and when the float reaches a certain level, it closes the circuit, triggering an alarm (a Rhombus Tank 1 alarm, to be precise).

The float switch has two wires that are connected to the alarm.

Now, I'm looking to add another layer of monitoring by incorporating a second sensor that's Wi-Fi compatible.

The goal is for this new Wi-Fi sensor to send me an alert whenever the alarm is triggered along with the original alarm. I realize I could buy a whole new Wi-Fi-based Rhombus Alarm for three hundred, but I have a feeling this can be done with a twenty-dollar Wi-Fi sensor.

Here's what I've done so far: I ran an additional set of wires from the Rhombus alarm, branching them off ("Y" configuration) (Parallel), and connected them to a Wi-Fi dry contact sensor (DWZWAVE2.5-ECO), which boasts two dry inputs.

However, I'm encountering an issue with this setup.

The Eco Wi-Fi sensor seems to be behaving oddly. It initially reports as open, as it should, but when I trigger a test alarm, it closes and remains closed even after the circuit is opened again. It worked fine when not connected to this system as I tested the ECO by shorting the two dry contact. The Rhombus is working fine in this setup; only the ECO sensor remains closed.

My suspicion is that power is back-feeding from the Rhombus alarm to the Eco Wi-Fi dry sensor, causing it to act up. This setup currently works per say, in that when the circuit closes, it triggers the ECO, and I get an alert on my phone. It's just not resetting itself after the alarm is cleared, and that requires removing the battery on the ECO and resetting it each time it's triggered.

So, my question is: Is there a way to connect this second ECO Wi-Fi sensor on those two wires, piggy-backed from another sensor, but somehow removing the backfeed of power? or does it not work like that.

My understanding is the Rhombus alarm is sending some sensing voltage down the line to "watch" if the switch is closed and that voltage may be causing the issues on the second ECO sensor.

Additionally, I'm curious if using a diode or reversed diode on one of the inputs on the ECO might work? or some sort of multiplexer, allowing input from the two wire float switch and outputting to multiple dry contacts, keeping them isolated.

If a diode would work, which wire would it go to? or do I need to try both and see which one solves the issue?

I really appreciate your help with this.
Thank you!

Cheers
 
Last edited:

Delta Prime

Jul 29, 2020
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Welcome to Maker Pro.
:)
If you have a multimeter check to see if you have 12 VAC across the secondary input float switch connection terminals.
The float switch itself must present an 1 amp, 12 VAC load for proper operation.
 

Bluejets

Oct 5, 2014
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Oct 5, 2014
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One cannot willy nilly add extra circuitry to existing without knowing the possible effects.
Start with supplying a circuit diagram of existing and then what you plan to add.
Otherwise it's just a wild guess at best.
 

DSF360

Mar 16, 2024
3
Joined
Mar 16, 2024
Messages
3
Welcome to Maker Pro.
:)
If you have a multimeter check to see if you have 12 VAC across the secondary input float switch connection terminals.
The float switch itself must present an 1 amp, 12 VAC load for proper operation.
Hey there,

Thank you! I measured the AC across those two wires, and I got about 13.8 volts. It's the same reading regardless of polarity on the meter leads.
 

DSF360

Mar 16, 2024
3
Joined
Mar 16, 2024
Messages
3
One cannot willy nilly add extra circuitry to existing without knowing the possible effects.
Start with supplying a circuit diagram of existing and then what you plan to add.
Otherwise it's just a wild guess at best.
Thank you. I don't have the schematics for either of the two retail devices used in this setup, so I would not have that level of detail.

I was talking with the support guy with the Wifi sensor, and he suggested:

I could use a 4000 series diode to isolate the buzzer from the Eco DW wifi sensor and eliminate the voltage coming into the Eco that is causing the misbehavior.

He suggested connecting the diode's anode side to one of the leads to the wifi sensor to remove voltage going into that device.

He goes on to say: 'Connecting a diode in line like this (attached image) should still allow any voltage that the control module uses to monitor its own input from your float switch to continue to do so but keep the voltage out of your Eco wifi contact yet still allow a trigger to occur for both the buzzer and the dw contact when the float is engaged."

If I do try his suggestion, will it hurt anything? It's either going to work or not?
 

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Delta Prime

Jul 29, 2020
2,071
Joined
Jul 29, 2020
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Hey there,

Thank you! I measured the AC across those two wires, and I got about 13.8 volts. It's the same reading regardless of polarity on the meter leads.

Alternating current has no polarity.
This is your septic tank; bad things happen to human beings
Along with their loved ones living in the household around septic tanks. I know you don't wish to spend the money but it will cost a lot more if you get sick.
I would if possible eliminate the septic tank altogether ,if practical.
 
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