Schematics PDF

The LTC2950CTS8-1 converts the signal from a momentary push button, into a latched signal, which is then used by the LTC4231CMS-2 hot swap controller, to turn the power to the robot on and off. For ease of use, the on/off button also has a pin header, which allows us to connect an external push button, which can be positioned anywhere in the robot. This functions the same as the button on the PCB. The microcontroller can also send a kill signal to the chip, which will turn off the robot aswell.

The hot swap controller also has a resistor network to set the acceptable battery voltage range. Outside this range, the robot will not turn on. The accepted voltage is from 20.7V to 27.6V. There is also an overcurrent protection, which was set to 16A. Once the robot draws more than this limit, for at least 240ms (set by the timing capacitor), the robot automatically shuts down. This limit was, however, doubled to 32A (by placing 2x 5m ohm shunt resistors on top of each other) to not have the robot turn off, every time we accelerate.

The power board also has an INA232BIDDFR power monitor chip, to measure the battery voltage and the supplied current. This is connected to the MCU with an i2c interface.

To convert the battery voltage into 5V, which is used by the PCBs, a TPS54332DDA buck converter is used.

The child lock switch can be used, to disconnect the hot swap controller, from the on/off controller, thus making the on/off button useless. Why would you want this? I have no idea, but this was left in for some reason.

The second switch disconnects the microcontroller from the kill pin on the ON/Off controller, which allows us to disable this feature and prevent bricking the powerboard. (By setting the kill pin at boot, which turns off power and not being able to reprogram the chip)

In normal use, make sure both these switches are flipped the correct way. (Child lock to the right, Kill lock to the left)

There are 6, 8-pin power connectors on the board, which can supply 24V to other boards. (4 pins 24V and 4 pins GND). The 24-pin connector is used to send 24V and 5V to the top board. The 6-pin connector is for the CAN-bus.

For debugging, there are 2 programmable LEDs on the PCB. There is also a reset button, to reset the microcontroller.