I’m making a battery powered air quality sensor node using Adafruits Feather M0 LoRa MCU. I have a MH-Z19 carbon dioxide sensor that requires 5V (datasheet says 3.6 ~ 5.5 V DC, and average current draw < 18 mA). The M0 only provides 3.3V. There is a BAT pin which gives ~3.7V straight from the Li-Po battery, but it is apparently not enough for the MH-Z19. I also tried using a Pololu 5V step-up regulator (U1V10F5) after both the BAT and 3V pins on the MCU. It did not work at all with the 3V pin. It worked with the BAT pin, but only when the battery was pretty full. When the voltage dropped it first started making noises, and then stopped working.
So my current solution is using 3 AA batteries for just the MH-Z19. Now I want to shut the 3 AA battery and sensor circuit off when the MCU is in “sleep mode”. Shut it off like with a mechanical switch, except I want to control the switch using the MCU. Can I use load switches for this? Can they effectively stop the circuit so that the batteries power is not wasted. I guess I need something that defaults to not being shortened since the controller is going to sleep. Is this possible with a Load Switch?
I have been looking at these following Load Switches.
Would it be better to use something like a relay or a MOSFET?