I am using a Moteino (8Mhz) for a project I am working on and I have a question regarding how to power the Moteino. I am using 2 AA batteries and I initially connected power to GND and 3v3. The reason I did this is on the Moteino (8Mhz) page there is the following statement:
The VIN and 3v3 pins are connected and can be considered the same
When I connected power to GND and 3v3 the Moteino works as expected, but the battery life is such that it would only run for a few weeks max. When I power the Moteino via GND and VIN I am seeing the battery life that I would expect. Should I assume that the correct way to power a Moteino (8Mhz) and get good battery life is GND and VIN?
Thanks
That resistor connects the pads of the input and output of the LDO (which is not there).
You can see the traces are connected together through the 0-ohm resistor. Also if you take a continuity tester VIN and 3V3 will beep.
I would expect the same behavior either way.
Do you just "wait" to measure the battery life?
I suggest doing an actual measurement through a current meter instead so we know we're comparing apples 2 apples (and for instance potential code bugs that keep mcu awake after some event don't interfere). That would also help reveal such bugs if any.
I performed a continuity test between VIN and 3v3 and there is less than an ohm between the two. I should have been a bit more precise about the pins I used to power the moteino. I used GND and 3v3 that are on the opposite side of where you hook up the FTDI adapter. There are 3 pins: GND, 3v3 and AREF. I did a continuity test there between 3v3 and VIN and there is less than an ohm between the two pins.
I am measuring the voltage in the sketch once every 10 min and sending that off to my Pi Gateway. The sketch spends all of its time sleeping. I am measuring bandgap voltage by using the technique WhiteHare published here: https://lowpowerlab.com/forum/projects/a-solar-supercap-powered-moteino/msg18027/#msg18027
I can post the code if you wish. Like I said, switching things around to how I normally power a moteino resolved the issue, GND and VIN. I just thought I would ask the question.
Both 3v3 pins are connected through traces and vias. That said, I would not use the 3v3 on the 3 pin header on far right of the board as INPUT, only as output.
I would power the Moteino 8Mhs through GND and VIN (or 3v3 next to it, same thing).
Very good. That is what I'm doing and I'm getting much better battery life.