Arduino OPTA as a simple smart home solution

Hardware Opta
1

Hi.

I have a simple smart home use case, I need to:
-read temperature from a few temperature sensors,
-turn on/off heaters (1.5 kW)
-turn on/off ventilation.

I assume that the number of Relays and inputs in Opta is enough in my case.
I wanted to set up Home Assistant on my PC and connect it (via Ethernet) with OPTA. On Arduino setup MQTT to control devices via HA.

I have a few questions:

  1. Can Relays in Arduino OPTA handle 1.5kW heaters?
  2. What temperature sensor will be easy to set up? I read that there are problems with DS18B20
  3. Can I program OPTA in C (Arduino) as a normal Arduino?
2

Hi @trojek.

There is information about the OPTA's relays here:

https://docs.arduino.cc/tutorials/opta/user-manual#relays

Yes. You can learn how to install support for the OPTA in Arduino IDE from this section of the documentation:

https://docs.arduino.cc/tutorials/opta/user-manual#opta-core-and-libraries

Please let me know if you have any questions or problems while following those instructions.

3

It depends on whereabouts in the world you are.

If you live in a territory where the mains voltage is 220-240V, then a 1.5kW heater will draw a current of around 6-7A.

The contacts are rated at 10A.

However if you live in a territory where the mains voltage is 110-120V, then a 1.5kW heater will draw a current of around 13-14A.

Edit:
Having thought about it, the inrush current when switching on a cold heater (and hence lower resistance) is likely to be above the 10A rating even for the 220-240V territory.

4

Thank you for your answer.

I live in a territory where the mains voltage is 230V. I know that 6.5A should be enough, but I read that sometimes the relay contacts can welded and It's not recommended to use classic relays for heaters. I assume that it depends on the relay's quality - that's why I asked.

As far as there are problems with connecting the thermal sensor (even Arduino Team member avoid answering this question) I think that it is better to go with an ESP32 device or Shelly Pro (also ESP32-based).

5

The reason I didn't answer the question is because I don't happen to know the answer. I'm not an expert on temperature sensors and even an expert on the subject might have difficulty answering based on the limited information you provided.

It was not a situation where I "avoided" answering it due to knowing of some "problems" using a sensor with the Opta as you insinuated.

7

never a good idea to control large loads with a PLC’s output regardless of its ratings. Use interposing relays.

I can guarantee you that an ESP32 ADC will not be better or as accurate as the OPTA’s ADC. Any sensor will work good and easy just the same as any other board. Just has to be a 0-10v or 4-20mA output

Just my 2cents.