MAX31865 RTD100 on Arduino

Hi All,
I'm running NodeRed to control my home brewery. Currently running an Arduino Mega that controls a relay board using the Arduino Node (Arduino like loaded with StandardFirmata script) to control relay board (working) and solid state relays.

I'm struggling to work out how I can read my 3 temperature probes. These are standard RTD PT100 probes with the MAX31865 amplifier boards. All of the nodes that I have seen so far are for Raspberry Pi.

Is there any way I can read the analogue value on the Arduino and convert that to temp?

I'm fine with adding a second Arduino if absolutely needed as a dedicated temp reader, as long as I can get the values into NodeRed



Welcome to the Forum

No idea where you are seeing this reference, but generally a sensor is MCU/SoC agnostic, aside from possible voltage limits.

Those seem to output via SPI, not analog... I haven't worked with Firmata for Arduino yet, so no idea if it can handle SPI input or not (EDIT - Nope)

Personally, I would just run a normal Arduino script with MQTT client (PubSubClient.h), and then you can load whatever sensor libraries and code you need, and control all inputs/outputs via MQTT to your Node-Red setup... Of course you would also need a MQTT broker (mosquitto is a good choice), but easy enough to add to whatever is running your Node-Red

On that note, how are you running Node-Red?

Sorry, I meant that the only premade flows or nodes that I had come across all seemed to be based on the raspberry pi and I hadn't seen any specifically for the Arduino.

Currently running NodeRed on a Windows PC, connected to the Arduino.

I'll look into your suggestions, but looks like I'll need to run an additional Arduino if I want to keep the other one running Firmata (unless I can get all what I need one the one Arduino).

Thanks for your suggestion.

No reason to have multiple Arduinos... Firmata is a very simplistic interface and nowhere capable of handling what the Mega could with standard programming/libraries etc.

The effort to get another Arduino to work with those sensors and send the data back to Node-Red would be 90% of the effort to do it all on your existing Arduino.

And it is not difficult to program either... lots of existing libraries for everything you need. Then connecting to Node-Red via MQTT is very simple.

Again, that is usually because the RPi itself is usually running Node-Red, thus those nodes expect that.

But with MQTT handling the Arduino <--> Node-Red interface, then you can get all the control and display functionality you need with other dashboard nodes.

See here for MQTT Broker. Just one of many explanations out there.

And finally if all you want do so is add temp sensor to your existing setup... then you need to find a simple sensor (thermistor) with analog output.

One example of such is here... but the programming details are not relevant for your use case becasue of Firmata, so you just need the thermistor and all the "processing" would have to be done in Node-Red. Accuracy is unknown.