Suitable Arduino for a portable 3 channel ratiometric pressure datalogger

Projects General Guidance
1

Hi,

I've recently completed my single channel data logger which consists of:

Uno R3 driven by x6 AA batteries
0.5v - 4.5v ratiometric Pressure Transducer - 15ma Max current
16x2 LCD I2C
Adafruit data logger shield ( SD and RTC)

All is fine and dandy.

I'd like to develop it further and miniaturise it somewhat.

I intend to use a 3v Nano / Zero powered by an Adafruit 2500mah Li-po battery and DC buck the transducer supplies to 5v then use a voltage divider on each of the 3 transducers to bring it back to 3v. I suppose I could also use a 5v nano and boost the voltage which leaves negates the need for voltage dividers on the analog inputs.

The transducers are Honeywell PX3's:

I need to be logging at 250ms intervals and taking 64 samples to smooth to readings on all 3 transducers. I would like to use an OLED I2C 128x64 to display the resultant pressure in real-time.

Also I'd like to explore the serial plotter so I could see the transducer output in real-time. Im not interested in running serial print on this new unit as I have access to a Druck pressure calibrator and use a seperate small sketch with serial print for zero and max pressure calibration and just copy the values into my main sketch.

I think I may be asking way too much from a Mini-Pro or Nano but I'd like to be told otherwise.

Any pointers to the right Arduino for the job would be most welcomed.

Thanks !

2

The Uno, Pro mini and Nano all use the same AT328 chip so they can all do the same things. It sounds totally doable since you only need 3 analog inputs for your sensors, i2c for your display. If you are sticking with your data logger shield, you aren't really saving much by making the arduino smaller and then have to wire it to the shield vs. plugging it in directly to the Uno.

3

An 8 MHz Pro Mini will do fine on a LiPo battery, no need for converters or regulators.

Do check how your pressure transducer reacts to different voltages. Does the output scale accordingly?

4

For miniaturization, check out the Sparkfun OpenLog: complete Arduino/datalogger a bit over 1 cm square.

With some care, you could attach wires to the ADC pins and use it directly.

5

blh64:
The Uno, Pro mini and Nano all use the same AT328 chip so they can all do the same things. It sounds totally doable since you only need 3 analog inputs for your sensors, i2c for your display. If you are sticking with your data logger shield, you aren't really saving much by making the arduino smaller and then have to wire it to the shield vs. plugging it in directly to the Uno.

Sorry, I should have stated that I intend to use a separate SD pcb & DS3231 RTC pcb rather than a shield.

6

jremington:
For miniaturization, check out the Sparkfun OpenLog: complete Arduino/datalogger a bit over 1 cm square.

With some care, you could attach wires to the ADC pins and use it directly.

Wow, that is small.
I didn't even know this was an option to be honest. I have also been looking at the Adafruit Feather M0 data loggers in Atmel 32u4 and Cortex flavours as the onboard JST Li-Po connector with 100mah charger is tempting but this one is definitely a smaller footprint !

7

Works out of the box, too. Just send it text via a serial line, and it automatically records it on the microSD card.

I use them all the time, as they are extremely reliable.

8

wvmarle:
An 8 MHz Pro Mini will do fine on a LiPo battery, no need for converters or regulators.

Do check how your pressure transducer reacts to different voltages. Does the output scale accordingly?

I will set up a bench supply with pressure calibrator to confirm the output scale at 5v then 3v, it will be interesting to see what happens

9

The datasheet of your sensor should contain clues as well. That's what I'd start with. See whether it'll work at the lower voltage to begin with.