board, a maximum of 4.2V will appear at this connector as the charger attempts to charge the
missing battery.
Regulated 3.3V source
If you have an external regulated 3.3V source, you can use it by connecting it to the 3.3V sew tap.
Note that this will not charge an attached Lipo battery. You can also pull regulated 3.3V out of this
sew tap to power other items in your project.
Current requirements
Because the amplifier chip can pull quite a bit of power at full volume, ensure that any external
supply you use can supply up to a few hundred mA. With lower volume levels, you can get away
with 50-100mA.
Changing the charge rate
If you would like to use a battery smaller than 500mAh, you can do so by soldering a new charge-
rate resistor to the board. A through-hole footprint is provided in the white box marked R1 near the
power switch.
You will need a through-hole resistor of the proper resistance. The formula to use is R =
1000/amps. For the given 500mA charge rate, the provided resistor is 1000/0.5 amps, or 2000
ohms. For a 110mAh battery, the resistor would be 1000/0.4 or 9090 ohms. (There is no standard
9090-ohm resistor, so use the next larger standard size which would be 10k.)
Before soldering on the new resistor, remove the existing surface-mount resistor within the white
box. You can remove it by carefully heating it up with a soldering iron and nudging it off the pads
when the solder softens.
Hacking for FTDI power
We said earlier that you can't power the LilyPad MP3 Player solely from a 5V FTDI board or cable.
This is because the FTDI connector is used to charge the battery, and the limited current isn't
enough to run the whole system including the amplifier (which can draw quite a bit of power).
However, you
can
modify the board to allow it to be powered via FTDI. Note that if you do this, you'll
be bypassing the charge circuitry, so you won't be able to connect a Lipo battery to the board. If
you'd rather run the board from an FTDI than a battery, here's how to modify the board.
NOTE: once you make this modification, do not connect a Lipo battery to the board. This
modification sends 5V to the battery connector, which would overcharge an attached
battery. Damage or fire may result.
To modify the board for power from the 5V FTDI header, solder a jumper wire between the VIN sew
tap (you can use the small header hole directly behind it) and the "+" header on the JST battery
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