Analog sensor breakout board for arduino uno

Projects General Guidance
1

Sorry in advance for lack of competance, I am new to arduino and this type of electronics overall.

I'm working on a school project that requires a specially shaped PCB (donut shaped) with a oxygen level and humidity sensor, as well as electrodes controlled by a potentiostat (on same PCB but not controlled by arduino)

(data sheets)
oxygen sensor data sheet

humidity sensor data sheet

Currently stuck on creating the schematic for the pcb, I have come to understand through plenty of research that the output current of the oxygen sensor through the recommended load resistor is very small (as low as 0.25 mV) so trying to create a schematic with an operational amplifier. from what i know if i use a cmos amplifier here it doesn't matter that my -ve rail of the amplifier is just ground. The gain on the non inverting amplifier in the image is ~400 which would put my voltage range at about 0.1-2 V.

Here is the schematic i have so far

image
image2895×1575 87.6 KB

For the Humidity sensor, from my understanding, if i just follow this sample schematic from the data sheet i can just wire "OUT" to an analog in pin on the arduino.

image
image1652×342 24.5 KB

Current questions are:

  1. Is this oxygen sensor schematic correct and would work? can i just wire the amplifier out to an analog in pin of my arduino?

  2. Is there a specific amplifier you recommend? i was looking at the MCP6002, not sure what most of the specs mean.

  3. Should i use 3.3 or 5 volt rail? is there a difference other than the resolution and maximum voltage?

Thanks in advance

2

  • You have the sensor driving a 100 ohm load, that is very very small. :thinking:

  • At first glance, the OP amp looks reasonable.
    Pass the signal through a low pass filter say a gain of 20, then to a 2nd amp with a gain of 20.

  • I would use 5v from a low noise linear voltage regulator.

3

Thank you for the response,

Im using a 100 ohm because that is what the data sheet suggests, i think because the sensor can only generate a certain amount of power.

Why use a low pass filter and then an additional amp? because of the large gain?
to implement this i can just change the existing op amp to have gain of 20 and then put the low pass filter between it and the sensor?

does the 5V from the arduino work also?

thank you again

4

It says 47 to 100, I think that is very likely to mean 47K to 100K. 47000 to 100000 ohms.

The lower the resistor value, the greater the current the sensor would have to provide to establish a meaningful voltage.

100 ohms seem unusually low for a sensitive device output load.

minutes later...

... googling for as long as I am going to seems to support the 47 ohm to 100 ohm "suggestion" as stated in the data sheet.

a7

5

lol, i think because the sensor is small, but very limited on vertical size for this pcb. Thanks anyway

6
  • I have no experience with these sensors.
    Appears the sensor produces a voltage/current.