How To Inexpensively Convert Any Light Switch Into A Smart Switch

As I expand my home automation system, I find myself wanting to be able to turn my lights on and off remotely or via voice control. There are a million great products out there that would allow me to integrate my light switches, but I wanted to select something that will be scalable (read: affordable) if I decide to convert all light switches to smart switches throughout my home.

When automating their homes, many folks look to replacing their light switches with smart ones such as this Leviton Decora. The cost per switch can be intimidating, however, when you want to talk about adding 10 or 20 smart switches.

Luckily, there is an affordable line of products that can be installed with the same basic electrical skills needed to install a smart switch: wireless relays for home automation.

What is a wireless relay or smart relay?

A relay, in a general sense, is a device that has an input circuit and an output circuit. When the input circuit is closed, the relay closes the output circuit. In many cases, it is used to allow a low-voltage or low-amperage signal circuit to activate a higher-voltage or higher-amperage output circuit.

In this context, a wireless relay or smart relay is a device that is wired in with your existing light switch. The wireless relay then connects to your Wi-Fi network (or other home automation network depending on the relay you purchase). Just like other smart home products, once the relay is on your network, you can then control it through its proprietary app or through other hubs or assistants, such as Google Home or Amazon Alexa products.

What are some popular wireless relays?

One of the most popular wireless relays for home automation enthusiasts is the Sonoff Basic. An incredibly affordable smart relay, the Sonoff Basic is typically available for only a few dollars! While this is an excellent product and well-loved in the smart home community, I’m going with what I regard as its big brother, the Shelly 1:

The Shelly 1, a smart switch or wireless relay used for home automation. The Shelly 1 is only around $12, making it a very affordable option.
The Shelly 1 smart relay

Shelly is typically just a few more dollars than the Sonoff Basic. Here’s why I’m willing to shell out the extra few bucks for a Shelly 1:

  • The Shelly 1 is -very- small for what it does. The common saying is that Shelly 1 is about the size of two Oreo’s stacked together
    • Because it’s so small, it can easily fit in the gang box behind your existing light switch
    • In comparison, the Sonoff cannot fit in a gang box without modification
  • When converting your light switch into a smart switch, you can easily wire in your existing light switch output to the Shelly’s SW port. This way, when you set Shelly 1 to its “edge switch” mode, your light switch will work normally
    • You won’t have to reach for your phone or ask Alexa any time you want to turn the light on or off
    • You won’t frustrate your guests with switches that don’t behave as they expect
  • The Sonoff Basic is a 10A switch, while the Shelly 1 is a 16A switch. This means that during an electrical fault, a 15A breaker should pop before the 16A Shelly 1 is damaged
  • For the real tinkerers of the home automation world, you can flash Shelly 1 with a custom firmware load without opening the case or soldering. Shelly 1 has an external port for communicating with its ESP8266 chip

How do I install a smart relay?

If you can replace a light switch, you can install a wireless relay. Simply connect the wiring from your home to the correct ports of the wireless relay, and you’re off to the races. Let’s look at wiring in a Shelly 1:

Shelly 1’s Ports:

  • N – Neutral (neutral in from your breaker box)
  • L – Line (hot in from your breaker box)
  • SW – Switch (the output of your physical light switch)
    • This allows the physical switch to continue to turn the lights on and off
  • I – Input (line in) for the relay side
  • O – Output for the relay side (the new power source for your lights)

Converting a traditional light switch into a smart switch using a Shelly 1

To use a Shelly 1 to convert a traditional light switch into a smart switch, you would do the following:

Setup

  • Kill the breaker for the circuit on which you’re working, and then verify that the circuit is safe (not energized)
  • Remove the light switch that you want to automate (except for its load-side black wire), making note of which wires come in from your breaker box and which provide power from the switch to the light
    • “Line-side” (in from breaker box) wires are typically wired into the bottom of a light switch
    • “Load-side” (out to light) wires are typically wired into the top of a light switch

Wiring in your Shelly 1 smart relay

  • Wire in the Shelly 1 as follows (use wire nuts and electrical tape to secure the wire nuts. You may have to go up a size on your wire nuts if you have to add wires):
    • Neutral – Add a short segment (a few inches, enough to reach the Shelly 1 comfortably) of white (neutral) wire into the bundle with the other white wires and connect this wire to Shelly 1’s N port
    • Line-side – Use the black wire that was providing power to the bottom (line side) of the light switch. In a wire nut, bundle three short segments of black wire with this wire
      • Connect one of these short segments to Shelly 1’s L port
      • Connect one segment to Shelly 1’s I port
      • The final short segment goes to the line-side (bottom) screw or port on your light switch
    • SW – Cut the load-side black wire coming out of the light switch so that a few inches of wire are hanging out of the switch. Strip both sides of the cut wire. Connect the short segment hanging out of the switch to Shelly 1’s SW port
    • O – Use the other side of the load-side wire that goes off to the light itself (that you cut to connect SW) and connect it to Shelly 1’s O port

Fire it up!

Sounds like a deal to me!

For the goal of automating my home without interrupting any “traditional” functionality, Shelly 1 is an awesome fit. Using Shelly, I can convert “dumb” light switches into smart switches that I can then control via:

  • An app on my phone – from anywhere that I have Internet access
  • A home automation solution like Home Assistant
  • With my voice through Amazon Echo or Google Home

Best of all, I can do all of this without cleaning out my bank account.

For the ability to convert any light switch into a smart switch at a low price, how could you say no?

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