Power Board

A photo of a power board The Power Board distributes power to the SR kit from the battery. It provides eight general-purpose power outputs, with port L2 reserved for powering the Brain Board. You can control the state of these outputs from the Power Board API.

It also holds the internal On|Off switch for the whole robot as well as the Start button which is used to start your robot code running.

Board Diagram

A diagram of a power board


There are six power output connectors on the board, labelled L0–L3, H0, and H1. These are enabled when your robot code is started, supply around 11.1V (±15%) and will turn off when your robot code finishes. These may be referred to as 12V ports elsewhere in the docs. They should be used to connect to the motor and servo board power inputs. The “H” connectors will supply more current than the “L” connectors.

When connecting the brain board, the "L2" port must be used. This ensures the Brain Board can turn on before the rest of the power outputs. Your Brain Board will not power on unless it's connected to "L2".

The 5V connectors can be used to connect low-current devices that take 5V inputs.

There is also a Micro USB B connector which should be used to connect the Brain Board for control of the power board.

Finally, there are connectors for external Start and On|Off switches. You may connect any push-to-make latching switch for the On|Off button, or a push-to-make button for the start button.

If you intend to use only the internal On|Off switch, you must connect a CamCon to the On|Off connector with a wire connecting one pin to the other pin on the same connector.


LED Meaning Initial power-up state
PWR|FLAT Green when powered
Flashing red and green when the battery is low
5V Green when 5V is being supplied Green
H0-1, L0-3 Green when the output is on 1
Red when the output’s current limit is reached
RUN|ERROR Orange on power-up, or USB reset
Flashing green when ready to run
Solid green when running or booting

On power-up, the Power Board will emit a beep.

If the Power Board starts beeping (and all the outputs turn off) then this means that the whole board’s current limit has been triggered.


Control Use
ON|OFF Turns the power board on, when used in conjunction with an external switch
START Starts your program


The power board has a fan to keep the board cool when it is under high load. The fan will only begin to spin when the board gets hot.

Case Dimensions

The case measures 83×99×24mm. Don’t forget that the cables will stick out.


Parameter Value
Main battery fuse current 40A
Overall current limit2 30A
High current outputs (H0-1) 20A
Low current outputs (L0-3) 10A
Motor rail output voltage (nominal) 11.1V ± 15%
Maximum output current per 5V channel 1A


You can access the schematics and source code of the firmware for the power board in the following places. You do not need this information to use the board but it may be of interest to some people.

  1. The outputs only turn on when your program runs (specifically, when the Robot object is created). 

  2. If overall current limit is exceeded, the Power Board will turn off and start beeping.