Schematics PDF

The charging of the capacitor is based on a flyback transformer, controlled by an LT3751EFE#PBF chip, to charge the capacitor up to 250V. The charging can be initiated, by setting the CHARGE pin to high. Once the capacitor reaches the desired voltage, the DONE pin will be pulled to LOW, to notify the MCU that the charging is done. In case there are any faults, the FAULT pin is pulled low. When the FAULT pin is active, the charging is stopped. When running the robot off a power supply, the FAULT pin is often triggered, as the power supply can not deliver enough current. The chip can be restarted, by turning off and on the CHARGE pin. The high-voltage part of the circuit is isolated from the low-voltage side.

When turning off the robot, it is important to discharge the capacitors, as these could be dangerous when handling the robot. When the robot is turned off, the discharge circuit will cause the capacitors to discharge through a resistor. This feature is hardware-based and can not be disabled.

An IGBT(basically a MOSFET) is used to kick and chip. By opening one of these, a current will flow through the corresponding solenoid and thus kicking or chipping. To drive these IGBT's fast enough, a two-channel gate-driver (UCC21520ADWR) is used. The gate driver is also used to isolate the low-voltage, the digital signal coming from the microcontroller, from the gate voltage of the IGBT (which is reverenced to HVGND).

For safety, the high-voltage side is isolated from the low-voltage side. The capacitor charging chip already does this, and the gate driver as well. The gate driver needs to be powered from both the low and the high voltage side, so to generate an isolated 12v rail, referenced to the HVGND, an LT8301IS5#TRMPBF is used. On the HV side, there is also an AZ1117CH-5.0, which generates 5v from the 12v.

To be able to measure the voltage on the capacitors, while keeping the HV isolated, an AMC1100DUB isolation amplifier is used. This transmits the voltage from the HV side to the LV side while keeping the isolation. On the LV side, it is powered by the 3v3 rail, and on the HV side, it uses the isolated 5v.

To be able to see if everything is working correctly, there are a few red LED's on the kicker board. There are 3 LEDS used to see whether the three voltage rails are on (3v3, 5v and 24v). There is one LED, which shows whether the capacitors are charged or not (Capacitor voltage is above 37V). There are also two LED's which can be programmed to do anything in software.