I am in the process of developing a temperature sensor module with 4 MAX31865 (PT100) modules communicating with Arduino Micro via SPI. The setup will be battery powered. The readings from the sensors needs to be monitored with an internal to 15 minutes, therefore I can keep the MCU in sleep mode so that it consumes low power of about some 200-300 uA. I also want the MAX31865 to stay in very low power mode. I figured out that in an inactive mode these modules consumes about 2-3 mA which is contributing to the maximum current consumption. As a solution to this I am planning to power the MAX modules with the build in 3.3V. supply from the Arduino, so that I can shut off the supply itself to these the MAX modules, so that they completely stay in the dead state, during this 15 min interval, after that once the MCU is in active state it will activate the power to these modules and obtain the readings. Is this a feasible solution? Can anyone please guide me on this. The datasheet for MAX31865 is attached with this post.
Firstly, wire everything up and check what the maximum current is drawn by the chips
(while idle, while measuring, while SPI transfer).
If it is small enough, you might even get away with powering the chips directly from one or more of output pins
(the same way you would power up an LED).
A more reliable way is to use a mosfet or transistor from this kit:
I would try P-channel low-Vgs MOSFET, similar to: Learn And Build A High Side Switch | Hackaday
It is easy to understand how it works, and you can try to light up an LED+resistor with it first.
But make sure you are not accidentally sending power or providing ground through the SPI pins! Turn SPI off
when done and put the pins into INPUT state.
Thanks for the reply. I think MOSFET might be the best solution. But also the modules consume about 2.5 mA in ideal state and about 4-4.5 mA while measuring, therefore I think I can directly power the modules.
Hi Tom,
I have already attached the data sheet in my first post.
Have you got the Interagated Circuit on its own, like in the datasheet you provided, OR haved you got the module in the image below.
There is a difference how you use them.
I went through this adafruit module, I think this contains the same IC as the data sheet I have uploaded. I am planning to develop the circuit on my own. So basically I would be developing a similar module based on the IC.
