I’d like to measure the temperature of a plant’s leaf over time relative to the air surrounding it. I know that the temperature readings need to be very sensitive to detect meaningful differences over the noise. I am thinking of connecting thermocouples to a thermocouple amplifier (such as the MCP9600 Thermocouple Amplifier Breakout) and then connecting this to an analog-to-digital converter (ADC), such as the ABELECTRONIC’s ADC Differential Pi, and then running this all and storing data on a Pi.
I would like to take measurement from multiple plants at a time, so I was thinking of using the Breakout Garden to increase my sample size.
Will these components be compatible together? I think I should be able to connect the Breakout Garden (with thermocouples) to the ADC via I2C. What would be the best/easiest way to do that?
Also, if I wanted to further increase my sample size, can I stack 2 or more breakout gardens together (maybe on a HAT stack), or would I run into issues of the same pins being used? If so, how can I increase my sample size?
If sensitivity and noise are a concern, I would neither use thermocouples nor a Pi. The accuracy of thermocouples are limited, and the Pi is a heater. Go for a MCU (like the Pico-W) and operate it and your sensors in on/off mode.
I would also suggest that you take a look at DS18B20-sensors. They are very cheap and in my testings they show a great consistency. And since they use the 1-wire interface, you can even chain many of them together and still only use a single pin for all of them.
Thanks for getting back to me.
Between the time I posted my question and now, I’ve also come to the conclusion that the Pico is definitely the way to go.
In terms of temperature-sensing, though, I can understand the value of a digital probe in terms of less noise. However, from what I can find, the size of the probes is prohibitively large for the small plants I’ll be working with. Perhaps there are smaller ones out there that are similar in size to a thermocouple probe?
Could you say more about operating the Pico/sensors in ON/OFF mode? My desire is to take measurements approximately every 30 seconds. Would this be possible in ON/OFF mode?
Thanks again.
DS18B20 are available from TO92 (about 5mm) down to 8-pin MSOP (2.8x2.9mm which is already a challenge for manual soldering). And you can skip the ADC and all the support electronics and calibration you would need otherwise. The very big argument for the DS18B20 is that you can just put them in series and take all the measurements of multiple plants at once.
Running a Pico in on/off mode in a 30sec interval is no problem. Have a look at Adafruit TPL5110 Low Power Timer Breakout
That breakout basically controls the enable-pin of the Pico and turns it on. You then signal “done” to the breakout with a digital-IO and that turns power off again.