Pololu Balboa 32U4, Руководство пользователя

Страница: 21 / 97

3.6. Power
The Balboa 32U4 control board includes battery terminal connections that provide access to power
from the Balboa chassis’s six-AA battery compartment. We recommend using rechargeable AA NiMH
cells, which results in a nominal voltage of 7.2 V (1.2 V per cell). You can also use alkaline cells, which
would nominally give you 9 V.
The negative battery voltage is connected to GND. The positive battery voltage is designated VBAT .
VBAT feeds into a reverse protection circuit and then a power switching circuit controlled by the on-
board pushbutton or slide switch. The output of the power switching circuit is designated
VSW .
VSW provides power to the motors through the on-board DRV8838 motor drivers, so the motors can
only operate if the batteries are installed and the power switch circuit is on.
The reverse protected and switched battery voltage on VSW can be monitored through a voltage
divider that is connected to
analog pin 1 (PF6). The divider outputs a voltage that is equal to one third
of the battery voltage, which will be safely below the ATmega32U4’s maximum analog input voltage
of 5 V as long as the battery voltage is less than 15 V (though the maximum voltage for the board
is still limited to 10.8 V by the DRV8838 motor driver). The
readBatteryMillivolts()
function in the
Balboa32U4 library can be used to determine the battery voltage from this reading.
Power switch circuit
The Balboa 32U4 control board uses the patented latching circuit from the Pololu pushbutton power
switch
[https://www.pololu.com/product/2808]
, which provides a solid-state power switch for your robot
controlled with the on-board pushbutton. By default, this pushbutton can be used to toggle power: one
push turns on power and another turns it off. Alternatively, a separate pushbutton can be connected
to the
PWRA and PWRB pins and used instead. Multiple pushbuttons can be wired in parallel for
multiple control points, and each of the parallel pushbuttons, including the one on the board itself, will
be able to turn the switch on or off.
The latching circuit performs some button debouncing, but
pushbuttons with excessive bouncing (several ms) might not function well with it.
For proper pushbutton operation, the board’s slide switch should be left in its Off
position. (Sliding the switch to the On position will cause the board power to latch on,
and the switch must be returned to the Off position before the board can be turned off
with the pushbutton.)
Alternatively, to disable the pushbutton, you can cut the button jumper labeled Btn Jmp ; this transfers
control of the board’s power to the on-board slide switch instead. A separate slide or toggle switch can
be connected to the
GATE pin and used instead.
Pololu Balboa 32U4 Balancing Robot User’s Guide © 2001–2019 Pololu Corporation
3. Balboa 32U4 in detail Page 21 of 97