I am making an eultrsonic sensor to determine the amount of liquid left in a drum. I am planning on using a 3.3v arduino board, a 3-5 volt ultrasonic sensor (HC-SR04P) and an lcd screen. I was planning on running this on (3) AA batteries. Should I power this through VIN or the RAW pin? I think all the components are tolerant of the range of 4.5v at full charge down to 3v or so. I know voltage may effect range of the ultrasonic sensor but I don't think it will effect accuracy. Any thoughts?
If you are wrong in your thinking you may be purchasing additional units. Use a simple SEPIC converter and set it to 3v3 as the electronics per your statement will work at that voltage. Side benefit you can use a higher voltage battery, some go over24 volts, if you want. Disadvantage that will allow your battery to discharge to about 1.2 volts depending on the SEPIC converter you use.