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How Do I Reduce Electrical Noise in My Actuator's Feedback Signal?

DC motors generate significant electrical noise that can corrupt potentiometer or Hall effect signals, causing erratic position readings. This article covers both hardware and software noise reduction techniques.

Where Noise Comes From

Brushed DC motors generate noise through two mechanisms: brush arcing (high-frequency spikes each time a brush segment contacts a commutator bar) and motor inductance switching (voltage spikes from rapidly switching current in motor windings by the H-bridge). Both couple into nearby signal wires through capacitive and inductive coupling.

Hardware Noise Reduction

Technique Component Where to Install Effect
Motor decoupling capacitors 100 nF ceramic capacitor × 2 Across each motor terminal to motor housing (ground) Attenuates brush arc spikes at the source
Signal line filter cap 100 nF ceramic capacitor Between pot signal wire and GND at Arduino pin Filters high-frequency noise before reaching ADC
Shielded cable Shielded 3-conductor signal cable For pot/Hall wires >6" long Blocks capacitively-coupled noise from motor wires
Physical separation Route signal wires away from motor wires Maintain >1" separation; cross at 90° if unavoidable Reduces inductive coupling proportional to distance squared
Motor snubber 100 Ω + 10 nF in series across motor terminals Directly at motor terminals Damps high-frequency ringing from H-bridge switching

Software Noise Reduction

When hardware filtering isn't enough, software averaging further smooths the signal:

Captura de Pantalla 2026-03-10 a la(s) 13.52.03

✅  Recommended combination: 100 nF cap on signal line (hardware) + 8-sample rolling average or EMA (software). This combination reduces typical motor-induced ADC noise from ±15–20 counts to ±2–3 counts on a 10-bit ADC.