The shunt regulator can protect power supplies from voltage spikes generated by motor controllers they are connected to. This version has a fixed set point of 33.0 V, a shunt resistance of 4.00 ohms, and twelve SMT shunt resistors populated on one side of the PCB (this is the lower-power version). An external potentiometer can also be added to change the set voltage.
Pololu’s shunt regulators are designed with fixed values available with ±3% accuracy for some common voltages, and adjustable versions available to accommodate any voltage from approximately 5V to 35V. To use the shunt regulator, install it across (in parallel with) your power supply. Under normal conditions, the supply voltage should be below the set point of the shunt regulator, and the regulator should only draw its quiescent current of less than 0.5 mA. However, any voltage spikes above the set point will cause the shunt regulator to draw substantially more current, dissipating energy and limiting the extent of the voltage change.