Hi!
There are 2 pins mentioned on Lilypad USB for "external power": 3.8 - 5 V - in some places; 3.3 V in other places.
I plan to use 3 AAA (4.2 V - I measured) on those 2 pins. Will the board work safely and reliably?
Sorry for bothering you with such trivial questions. I could not find detailed info on the internet.
Thank you!
Have a look at the schematic of the board.
The + and - pins will have 3.3 V supplied to them so you can power external sensors if you are powering the lilypad from the battery connector or powering the lilypad from the USB port.
If you are not powering the lilypad from the battery connector or USB port, you can power it using those + and - pins. You can power it with 2.7 to 5.5 volts. Be aware when you supply power through those pins there is no regulator between your power source and the ATmega32u4, and the logic level of all the pins will be the same as your supply voltage. If you connect any sensors that have a max voltage or max logic level of 3.3 V you could damage them.
I recommend study the schematics of whatever board you are working with, and study the data sheets of the components on the board, especially the MCU.
4.2v open circuit from 3 alkaline batteries? Those batteries are dead, bro. 3S alkaline configuration should be giving you minimum 4.5 open circuit, up to 5.4 with fresh high end batteries. Rechargeable AAAs have 1.2-1.3 open circuit voltage per cell,
Thank you!
I just forgot about logical levels - this is my first Lilypad. I use old Arduino Nano (a brilliant board for education purposes, in my opinion), so those rounded electronics look - well- exotic to me. No excuse for my lack of attention, though.
Then the safe way is to mount a 3.3 V regulator from my 3xAAA.
Reason why playing around this +_ separate pins is that the JST socket on the board is a different standard from the 1 cell Lipo I connector I have in hands.
OT: The vendors better state the standard than just write "JST". I think I waste 10% of my time to fit connectors.
+++
I agree my Alkalines are stating their last wish- but I thought that as long as they are above 3.7 V, that is sufficient for the Board. It is going to work for just 10-20 minute maximum (girls students first contact with coding and Arduino :-).
