jhuebotter:
Hello Fellas,
I hope this request is under the correct topic. I have a few Arduino Fio Microcontrollers and I would like to attach them to a 7.4 V power source.
On the official Website (https://www.arduino.cc/en/Main/ArduinoBoardFio) it shows th following:
Operating Voltage 3.3 V
Input Voltage 3.35 -12 V
Input Voltage for Charge 3.7 - 7 V
Yesterday I tried to connect a 7.4 V battery to the BAT + and - holes right behind the LiPo dock. It fried my Microcontroller. After looking it up online, I also came across this request:
ARDUINO FIO input voltage +12 - IDE 1.x - Arduino Forum
It's 4 years old and doesn't really come up with a propper solution. I really don't need the advice "just take a 3.3 or 3.7 V battery". Also a voltage converter would be unhandy for my application. I actually bought the Fio expecting to be able to cope with 7.4 V as is.
Thank you, Justus
QUOTE from the URL you posted ...
Power
The Arduino Fio can be powered with an FTDI cable or breakout board connected to its six pin headers (as marked on the bottom side), or with a regulated 3.3V supply on the 3V3 pin or a Lithium Polymer battery on the BAT pins.
To me, it clearly states ...
a) OR ... with a regulated 3.3V supply on the 3V3
b) OR ... or a Lithium Polymer battery on the BAT pins
I do not see where is states it is OK to put 7.4 Volts on the BAT +/- Terminals.
Then I looked up the SPEC for the MAX1555 chip.
The MAX1555 has a maximum Input rating of 7 Volts on PIN 4.
PIN 4 & Ground are attached to JP6, which is labeled as "USB VIN" on the schematic.
The MAX1555 then supplies BAT+ at 4.2 volts on PIN 5 (output) which...
a) Charges the Li-Ion Battery
b) Energizes U2, a 3.3 Volt Voltage Regulator, when the On/Off switch is closed.
EDIT:
IF "U2" on your motherboard is a MIC5219-3.3 then it can accept a 12 Volt Input MAX.
But, I am not 100% sure the MAX1555 can handle 12 Volts on its output PIN 5?
But when the On/Off Switch is OPEN ...
the Power Input pin of the MIC5129-3.3 is disconnected
from the 4.2 Volt Output Pin 5 of the MAX1555.
Or is there a PAD to PIN 5 that needs to be CUT to isolate the MAX1555 Li-Ion Charging Chip when a Power Supply is connected to BAT+ instead of a Li-Ion Battery?
Are you 100% sure you didn't connect your power supply voltage backwards?
Is the PTC SMD FUSE F1 still good?
This is the best that I can figure out.
I agree with you, the the Input voltage Specs are confusing
Also, Schematics are subject to change without notice.