When turning an inductive load (e.g., a dc motor) on and off, high-voltage and high-current spikes are generated, propagating across the circuit and potentially causing problems. To avoid damaging spikes, robotics and mechatronics designers must exercise much care.
Decoupling capacitors must be included at all points where current or voltage spikes can be present and threaten the stability of the circuit. Some points of the ciruit are especially important When looking for a place to add a decoupling capacitor.
ln parallel with the power supply. Large electrolytic capacitors must be added in parallel with the power supply as shown by Figure 1.
These capacitors store energy and add it to the current supplied by the source when the motor is turned on and draws high currents. Values between 1,000 and 10,000 pF are suitable for common applications. If the motor draws Very high currents on startup, and the Voltage drop m the power supply can,t be avoided, it is recommended that you use a separate battery to power it.
In parallel with the motor. Capacitors in the range between 0.1 and 1 µF (polyester types) are recommended to absorb the spikes generated by the commutation system of the motor. These capacitors will protect the switching devices against high-voltage spikes produced when the motor is running.
