I’ve been tinkering with DIY smart devices for a while, and one thing that always bothers me is how complicated some platforms make it. There is always a steep learning curve and if you just want to have a DIY smart device online, you need a ton of other supporting systems.
Recently, I stumbled on a simpler solution: the KME Smart Platform. It lets you build and control devices from your phone without writing a single line of code. Best part? It’s free, and you can control your gadgets from anywhere. Here’s how I set up a cloud-controlled relay with it.
What You’ll Need
For this project, I used a NodeMCU (ESP8266), a 5V relay, a push button, a transistor (2N2222), and a status LED with a resistor. You’ll also need the KME Smart Windows app (to configure the device) and the KME Smart mobile app (for control). The relay is powered separately at 5V since the NodeMCU runs on 3.3V, and the transistor acts as a switch to safely control it.
Below are some links from where you can purchase the required parts.
- NodeMCU (ESP8266) - AliExpress - Temu
- 5V Relay - AliExpress - Temu
- Assorted Transistors - AliExpress - Temu
- Tactile Switches - AliExpress - Temu
Setting Up the Hardware
First, I wired the relay to the NodeMCU through the transistor—collector to 5V via 10k resistor, emitter to ground, and base to a 10k resistor connected to a GPIO pin (D1 in my case). The push button goes between ground and another GPIO pin (D7), and the status LED connects between ground and pin D6 with a 1k resistor. This setup lets me control the relay manually with the button or remotely via Wi-Fi.
Installing KME Smart and Configuring the Device
After downloading the KME Smart Windows app, I connected the NodeMCU via USB and selected the right COM port. When you first connect the NodeMCU, you will need to upload the basic firmware, and with it you can then upload the configuration after it is set. I added a relay configuration entry, where I set:
- Relay control pin GPIO5 (D1, active high)
- Button input on GPIO13 (D7, active low since it’s grounded)
- Status LED on GPIO12 (D6)
The app lets you save these settings as a file, so you can reuse them later.
Once you are happy with the configuration, you can upload it to the device and it is then ready to be paired with the mobile app.
Pairing with the Mobile App
Once the firmware was uploaded, I opened the KME Smart mobile app and held the NodeMCU’s flash button for 2 seconds to enter pairing mode. The onboard LED starts to blink with an interval of 1 second and the device can then be added to the app. After selecting my Wi-Fi network it detected the device and gave me an option to name it. Once paired, it appeared on the dashboard and I could control it from anywhere—even on mobile data—because it uses cloud connectivity.
Adding Automations (Like Timers)
The app supports creating automations and I think this is where it truly shines. I set up a rule: "Turn off the relay 20 seconds after it’s turned on." This mimics an irrigation system that shuts off automatically to avoid overwatering. In reality, this timer should be set to about an hour or so but I used the 20 seconds as an example for easier testing. You could also add conditions like "Only turn on if soil moisture is low" if you add a sensor later.
In a previous project, I made a similar irrigation controller for my back yard, but that one uses my Home Assistant setup to add in such automation features. With KME Smart, you don't need anything else, but you are dependent on having an internet connection.
Final Thoughts
KME Smart is a great alternative to platforms like Arduino Cloud—especially if you want zero coding and remote control. The downside? It relies on cloud access, so if your internet drops, automations might not work. But for quick projects, it’s surprisingly flexible.
If you try this, let me know what you build! Got questions? Drop them in the comments—I’d love to help.
