Voltage stabilizer

The problem

With 18 motors on the robot, the 12V battery could sag to about 6V under load.

The solution

A supercapacitor bank carries the protected loads at 12V through harsh brownouts. The design is fail-safe: every power switch fails off and the bank discharges by default, so a crash or an unprogrammed board stays safe.

Power sequencing

• An eight-state power state machine runs the whole sequence: idle, precharge, bypass, boost, output, ride-through, shutdown and fault
• The bank is precharged with PWM to limit inrush, and the boost output is verified before the 12V output switches on
• When the input returns, the board recovers directly, with no second precharge

Telling a brownout from its own charge current

The firmware polls input voltage every 2ms and enters ride-through when it stays below 9.75V for 15ms, but only if the bank is at least 500mV above the input. That check separates a real input loss from the bank's own charge current pulling the input down.

Faults and protection

• Four latched fault types: precharge timeout, boost start failure, overcurrent and out-of-regulation. The fault LED blinks the fault code
• A charge lockout above 15.5V input protects the capacitors, and cell imbalance raises a warning
• An independent watchdog of about 1s resets a hung board into its safe state, and a watchdog reset is reported in telemetry

Tooling

• Live telemetry over USB at about 3Hz
• Reflashing over USB without touching a BOOT0 switch, using a 1200-baud touch to enter the bootloader
• A Python tool handles building, flashing and monitoring

Status

Commercial sale through Wirx Systems is pending, awaiting FIRST approval.