Looking for hardware advice

Projects General Guidance
1

Hi,

Could you please recommend Arduino hardware for a HVAC system that I would like to develop by myself? So far I have tried only RPI but I am considering moving to Arduino for its open nature.

Here are the requirements:

  • at least 10 input/output lanes
  • Ethernet connectivity
  • capable of running a HTTP server and servicing requests (<10 per minute)
  • output control of 10 mechanical-electric valves (only 5 logical outputs)
  • 5 input temperature sensors

The valves are 24V/3W and I will be grateful if you can recommend a relay (or something).

-- thanks in advance

2

Ethernet is rather unusual now unless you need the PoE (Power over Ethernet), but not impossible to find. WLAN connectivity is more usual. However, here is an example solution with an *ESP32 Enabling Ethernet On The ESP32 | Hackaday

The valves could be driven by something like a TPIC6B595 power shift register (5 volt logic) or logic level N channel mosfets (or even simple NPN transistors).
What temperature sensors are you looking at ?

*ESP32 is loosely an "Arduino" in that it is compatible with the Arduino IDE

3

Thanks a lot for the reply, @6v6gt! It will be control of a room temperature and I am considering DS1812. If there is no easy available Arduino - Ethernet solution, I can start with WiFi.
Hardware is lots of fun, but I'm a programmer so wiring the whole thing will be a challenge. The challenge will be to wire DS1812 using a 20m twisted pair as well as controlling the valves. I like the NPM tranistors idea but I will have to put those in working mode which I only studied in the past.

4

I guess you have a typing error in the sensor type. That DS1812 appears to be a power supply monitor.
Here a link for a DS18B20 project: Guide for DS18B20 Temperature Sensor with Arduino | Random Nerd Tutorials

You are right to identify a possible issue with long wires. The data sheet is quite intimidating https://datasheets.maximintegrated.com/en/ds/DS18B20.pdf so you are best looking for sample projects which successfully use these devices at a distance from the main processor.

As for the NPN transistor, google for "Low Side Switch transistor". Your current requirements are small because the voltage is quite high. You'll need a flyback diode across the valve coils. I'm assuming, incidentally, that the valves are DC driven. If not, you have to look at other solutions.

1 Like
5

AC or DC?

6

Both are supported at 24V.

7

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