If you ever finished a project and wondered what that annoying hum coming from your speaker was, or why your MCU reset every time a high-current motor turned on? Well, you've likely encountered the ground loop. What is a ground loop ? In an ideal setting, ground would be 0V everywhere. In reality, every wire and trace has a tiny bit of resistance and inductance. A ground loop appears when there is more than one path for the current to return back to the power supply. Because none of these paths are the same, they start acting as a antenna of sorts and they start picking up EMI (Electro-Magnetic Interference). This EMI induces a voltage where the voltage should be zero, this turns the reference into a noisy mess. Why it ruins certain projects For us makers, ground loops are most common in Audio projects: it's mostly detectable as the persistent buzz in amplifiers. Digital projects: Ghost triggers and/or "ground bounce" that causes MCU crashes. Power projects: usually manifested by unreliable power delivery and shorter component life. If a high-current return path shares traces with a sensitive sensors ground, the motor will physically shift the ground voltage for the same sensor. How to remove the loop If you've been having issues with ground loops, the good news is that you can fix them during the design phase 😄: Star ground: Instead of daisy chaining ground connections, connect every components ground to a single point on the PCB.This ensures that the return currents don't interfere with each other. Ground planes: Don't use traces for ground, instead use a solid copper plane. It provides the lowest impedance and keeps the areas for loops small. Isolation: You can just break the loop by breaking Opto-isolators or Isolation transformers for audio needs. A clean ground(and therefore a clean signal) is the difference between good products and just a prototype. If you take the time to carefully plan the return paths to your PCB you and your product will thank you later. Quick reference guide Symptom Culprit Fix Speaker Hum Audio ground loop Star Ground or a audio isolation transformer(1:1) i2c errors Hi-current ground bounce Move motor paths away from the MCUs GND pin Video flickering Shielding current Use a Ground loop isolator on the signal cable Random MCU Resets Shared power/ground traces Use separate traces (and a thick ground plane) for power and logic. If you're interested in learning more about ground loops and common areas where it needs to be controlled: Extra 1 Extra 2 (VIDEO) Thank you very much for reading my First ever post on JLCHUB, feel free to ask questions :) -AP #PCBDesign# #ProductDesign##Design#