Powering sensors through GPIO Pins

Posted by: @sven

Good day,

I am a Electrical Engineering student currently working on my own project which involves creating a wine bottle storage quality sensor. These questions might seem trivial but I am not very experienced when it comes to MCU's and any assistance will be greatly appreciated! This device will be powered using a CR2032 3V coin-cell battery. The aim is to run the device for over a year on this single coin-cell battery. Measurements will be taken once every hour and the device should be as small as possible (hence the coin-cell). I've chosen I2C sensors that are low power with minimum current draw. All these sensors have a minimum operation voltage of around 2V (the end-of-life voltage for the coin-cell). In-between sensor readings, the MCU will be put into sleep mode. The questions I have are concerning the power draw of these sensors while the MCU is in sleep mode.

Some of the questions I have are:

• What are the advantages/disadvantages of powering the sensors (granted they do not exceed the current limit) through the GPIO pins? Would this minimize power consumption or is it bad practice?
• Is a better alternative powering the sensors through the 3.3V rail of the MCU and then make use of a switch to power the loads? Is it appropriate to connect the gate of the transistor to a GPIO pin to switch the loads on and off?

If interested, the components I am using are:

• Ambient I2C light sensor
• SHT21 Humidity and Temperature sensor
• Temperature sensor (This temperature sensor will be used as fail safe and used to ensure the main temperature sensor is functional) 
• Accelerometer (used to check whether the bottle is being stored vertically or horizontally)
• Seeed Studio Seeeduino XIAO MCU
• Battery

If anyone has any experience in projects of this nature, your help will be greatly appreciated! 

Thank you.

 

I think you would be better off with a seperate battery for the MCU and each sensor. More redundancy.