There are a few things that can be done with the power board, namely current and voltage sensing, and beeping. As there is only one power board, it is not accessed like a list like motors and is instead accessed directly, for example:


Power Outputs

Each of the power board’s controllable outputs has a constant whose name closely matches the name of the output:

  • H0 : OUT_H0
  • H1 : OUT_H1
  • L0 : OUT_L0
  • L1 : OUT_L1
  • L2 : N/A (Not Controllable)
  • L3 : OUT_L3

Both of the 5V outputs are controlled simultaneously.

While they are all turned on when your code starts running, you can control whether each output is turned on or off like so:

from sr.robot3 import *

# Turn output H0 off
R.power_board.outputs[OUT_H0].is_enabled = False

# Turn output L0 on
R.power_board.outputs[OUT_L0].is_enabled = True

# Find out whether L3 is enabled

# Find the current (in Amps) being used by L3

An exception is raised if you try to set an output index which doesn’t exist.

You can also control all the outputs together:

If you turn off the power output which is powering another of your boards, then they will appear to be missing and your code will break if you try to control them.

Battery Status

The power board can report both the battery voltage, in Volts, and the current being drawn from it, in Amps. You can access these values like so:

# Print the battery voltage and current to the log

A fully charged battery will measure 12.6V. The power board will turn off and signal a low battery at 10.2V. The discharge curve is roughly linear between 11.4V and 10.4V.


The power board has a piezo buzzer which can beep.

The buzz function accepts multiple parameters, depending on what you want to play. The first argument is the duration of the beep, in seconds. The later arguments are either the note you want to play, or the frequency of the buzzer (in Hertz). You have to specify which of note or frequency you’re passing using a keyword argument, your code will fail otherwise.

Theoretically, the piezo buzzer will buzz at any provided frequency, however humans can only hear between 20Hz and 20000Hz.

The Note enum provides notes in scientific pitch notation between C6 and C8. You can play other tones by providing a frequency.

Calling buzz is non-blocking, which means it doesn’t actually wait for the piezo to stop buzzing before continuing with your code. If you want to wait for the buzzing to stop, use the blocking argument!

from sr.robot3 import Note

# Beep for 0.5s in D., Note.D6)

# Beep for 2s at 400Hz, 400)

# Beep for 3s at 250Hz and wait for it to finish, 250, blocking=True)

ValueError is raised if the note is not recognised or the frequency is not an integer.