Bellfire home automation project

This article provides you with an overview and links of all articles published around the Bellfire fireplace (Mertik Maxitrol controller) project that was presented during the Home Assistant Conference 2020.

Although this solution is presented around Home Assistant you can easily use the same solution in OpenHab, Domoticz or any other open home automation platform.


View Automate Everything! How to make your stupid device smart on Notist.

Introduction articles

The steps

Shopping list

  1. The ESPboard: ESP8266 board or ESP32 if you also want to use Bluetooth features on, Banggood, Amazon
  2. The 4 channel relay board. Make sure you select the 5V version The relay: 5v relay board or Banggood, Amazon
  3. If you don’t want to solder order:
    – Mini breadboards or Banggood
    – Dupont cables male-female or Banggood

Optional tools

Step 3: Wiring the ESP to the relay

This article is part of the Make your Bellfire fireplace smart project that I presented during the Home Assistant Conference 2020.

It’s time to execute the third step, you can find all steps in the overview how it all going to work article.

To control the relay we need to provide high or low power to the IN ports of the board. This board has four relays. In my example I only need to use three relays.

Wiring the relay board to the ESP is easy. I always use Dupont cables and mini breadboards, this way soldering is not required.

Powering the relay board

The relay board needs 5v power. We will power the relay board directly from the ESP using the 5v VIN pin.

Controlling the relays

Pin D5, D6, and D7 will be used to control the three relays on the board.

See wiring image below for more details.

The wiring is now ready, let’s expose three switches to Home Assistant to control the relays. Read the next article.

Introducing Relays

This article is part of the Make your Bellfire fireplace smart project that I presented during the Home Assistant Conference 2020.

In previous article I addressed a way to make a Bellfire fireplace smart using the pins of the controller. To do this we need to use relays.

What is a relay?

In really short; A relay is an electrically operated switch.

How does it work?

A relay has two circuits:

  1. The control circuit.
    This circuit is used to control the switch, switching the control circuit will change the state of the load circuit switch
  2. The load circuit.
    The load circuit is where you connect the device that you want to interact with.

Both circuits are separated circuits, there is no direct connection or current flow between the control and the load circuit. This makes using relays very safe.

There is multiple variations of switching the load circuit. For usage with the ESP boards and 5v I prefer using Optocoupler relays. The switch is controlled using light and a photosensor to control the switch. Ensuring 100% separation of circuits.

For this solution, I’m using one board with 4 relays on it. You can buy it for a few dollars on AliExpress.

On the left we have IN top control the board; this is where you provide it with Power and one input to control every relay.

For OUT there are three outputs per relay:

  • Normal Close (NC)
  • Common, to close the circuit
  • Normal Open (NO)

You always connect the Common, but you need to choose between Normal Open and Normal Close. The difference between NO and NC is the default behavior for the relay if it is not power/switched on. If you select Normal Open the circuit will be not closed in a default state, when you use the Normal Close the relay will have a closed load circuit in a default state. 

Now we know we can use relays as a solution for the switches. But how are we going to control the relays? We need a solution to switch the controller circuit using high with voltage to close the control circuit and low voltage to open.  We need a controller for the relay, this is where the ESP boards come in.

The next article will introduce the ESP boards.