A simple trick to connect traditional alarm systems (like a water sensor) to your Tuya smart lights and sirens. No advanced degree required.

It’s a feeling many homeowners know and dread: the thought of a hidden leak or a sudden flood in the basement. You might have a trusty, old-school water alarm down there, ready to scream its head off. But what if you’re not home to hear it? That simple, reliable alarm feels a bit lonely and disconnected from the rest of your modern smart home. What you really want is to trigger a Tuya device—like a smart siren upstairs or a notification on your phone—the second that alarm senses trouble.

The good news is that you don’t need to be an electrical engineer to make this happen. I’m going to walk you through a surprisingly simple way to connect your standard alarm system to your Tuya-powered smart home. It’s a fantastic trick that works for more than just water sensors.

Your Alarm Speaks a Different Language

So, what’s the actual problem here? Most traditional alarm systems, whether for water, motion, or a door opening, use something called a “zero voltage” or “dry contact” signal. You might see terminals labeled NO (Normally Open), C (Common), and NC (Normally Closed).

Think of it like a simple light switch. When the alarm is triggered, it doesn’t send out a blast of electricity. Instead, it just closes a circuit between two of those terminals—it metaphorically flips a switch from “off” to “on.” It’s an incredibly reliable system, but it’s a completely different language from the Wi-Fi signals your Tuya smart plugs and bulbs understand. Your Tuya siren is waiting for a command from the cloud, not for a simple switch to be flipped in the basement.

The Perfect Translator: How to Trigger a Tuya Device with a Relay

The hero of this story is a small, inexpensive gadget called a smart relay module or a dry contact switch. This little box is the perfect translator between your old alarm and your new smart home.

Here’s how it works:
1. The relay module is wired directly to your alarm’s dry contact terminals (usually the NO and C ports).
2. The relay itself is also connected to your home’s Wi-Fi and paired with your Tuya or Smart Life app.
3. When your water alarm goes off, it closes the circuit. The relay module detects this “switch flip” as a trigger.
4. Because the relay is connected to your smart home, it instantly tells the Tuya app, “Hey, the thing I’m connected to just went off!”

From there, the Tuya app can execute any automation you can dream of. It’s the missing link that makes your dumb alarm smart.

Step-by-Step: Connecting Your Alarm to Trigger a Tuya Device

Ready to give it a try? It’s easier than you think.

What You’ll Need:

• Your alarm system with a dry contact output.
• A Tuya-compatible Wi-Fi Inching/Self-Locking Relay Module. You can find these easily on sites like Amazon or other electronics retailers. They are often sold for garage door openers but work perfectly for this.
• The Tuya or Smart Life app on your smartphone.
• Basic tools like a small screwdriver.

Let’s Get It Connected:

1. Safety First! Before you touch any wires, please make sure the power to your alarm system and the outlet you’ll be using for the relay are turned off. Safety is everything.
2. Connect the Signal Wires: Take two small wires and connect one to the “NO” (Normally Open) terminal and the other to the “C” (Common) terminal on your water alarm. Connect the other ends of these wires to the dry contact input on your Tuya relay module. The module’s manual will show you exactly where these go.
3. Power Up the Relay: Plug the Tuya relay module into a mains power outlet. Your basement likely has one nearby.
4. Pair with the Tuya App: Open the Tuya app on your phone. Follow the instructions that came with your relay to put it into pairing mode (this usually involves holding down a small button for a few seconds until a light starts blinking). Add the device in the app.
5. Build Your Automation: This is the fun part!
   • In the Tuya app, go to the “Scene” or “Smart” tab and tap the “+” to create a new automation.
   • For the “If” condition (the trigger), select your newly added relay module. Choose its state as “On” or “Closed.”
   • For the “Then” action, choose what you want to happen. You can trigger a Tuya device like a smart siren to sound, have all your house lights flash red, or simply send a push notification to your phone that says, “BASEMENT FLOODING!”
6. Test Your Setup: Now for the moment of truth. Carefully test your water alarm (you can often do this by shorting the sensor pins with a screwdriver or a drop of water). If you did everything right, your smart home automation should spring to life! For more on the technical side of relays, this explanation from SparkFun is a great resource.

More Than Just Water Alarms

Once you understand this simple principle, you can apply it to all sorts of things. You can use this exact same method to connect:

• A driveway motion beam: Have your porch and hallway lights turn on automatically when a car pulls in.
• A physical push-button: Create a smart doorbell or a panic button for an elderly relative.
• A garage door sensor: Get a notification if your garage door is left open after 10 PM.

By bridging the gap between simple sensors and your smart ecosystem, you unlock a whole new level of creative and practical home automation. For more ideas, the official Tuya Smart platform showcases a huge range of compatible devices and automation possibilities. You’re no longer limited by what’s “smart”—you can make almost anything smart.