In the last post we discussed RS485 and its value in industrial settings. The time we see that the concept has a wider application. In the context of IoT communication, a “noisy environment” refers to any physical setting where electrical interference (also called electromagnetic interference or EMI) is likely to occur.
Common Causes of Noise in Communication Lines
- Industrial Machinery: Large motors, generators, and equipment in factories emit electromagnetic fields.
- Power Lines: High-voltage or fluctuating power sources running near the RS485 cables can induce noise.
- Radio Frequency Interference (RFI): Wireless devices, such as cell phones or two-way radios, can emit signals that interfere with wired communication.
- Switching Devices: Devices like relays, switches, and inverters create electrical noise when they turn on and off rapidly.
- Proximity to Other Cables: Signal degradation can occur when RS485 cables are bundled together with power or other signal cables.
Why RS485 Thrives in Noisy Environments
RS485 was designed to overcome these challenges:
- Differential Signaling: It sends data as two complementary signals. Even if noise affects the cables, it typically impacts both signals equally, allowing the system to “cancel out” the interference.
- Twisted Pair Cables: RS485 often uses twisted pair cables, which help further reduce the effect of external electromagnetic interference.
- Long Cable Runs: RS485 can handle distances up to 1,200 meters (4,000 feet), even in noisy conditions, making it ideal for industrial setups.
Real-World Examples of Noisy Environments
- A factory floor with conveyor belts, robotic arms, and welding equipment.
- Power plants where turbines and transformers generate electrical interference.
- Agricultural fields with irrigation pumps and machinery operating nearby.
- Ships or marine environments with powerful motors and radio equipment.
Here are 10 practical tips to reduce noise…
1. Shielding Cables
- What it does: Shielded cables, such as twisted pair or coaxial, reduce electromagnetic interference (EMI) by preventing external noise from penetrating the cable.
- How to implement: Use high-quality cable shielding and ensure proper grounding. Routing cables away from power lines also minimizes interference.
- Source: IEEE guidelines recommend shielded cables for environments with high EMI for better data integrity.
2. Using Differential Signaling (e.g., RS485)
- What it does: Differential signaling transmits the same signal over two wires with opposite polarity. Noise affects both wires equally but cancels out at the receiver.
- How to implement: Deploy RS485 or similar protocols in noisy environments for reliable communication.
- Source: Texas Instruments confirms that RS485’s differential method reduces susceptibility to noise.
3. Isolating Power Supplies
- What it does: Separate power supplies prevent electrical noise from one system affecting another.
- How to implement: Use dedicated circuits for sensitive equipment or employ isolation transformers.
- Source: National Electrical Manufacturers Association (NEMA) suggests isolating power sources in high-noise setups.
4. Grounding and Bonding
- What it does: Proper grounding drains unwanted noise into the earth, preventing interference in equipment and communication lines.
- How to implement: Follow local electrical codes to create a unified grounding system across all industrial devices.
- Source: According to the National Institute of Standards and Technology (NIST), consistent grounding reduces EMI-related issues in industrial setups.
5. Filters and Surge Protectors
- What it does: Filters and surge protectors remove unwanted high-frequency noise from power lines.
- How to implement: Install EMI/RFI filters at key junctions and use surge protectors for critical equipment.
- Source: Schneider Electric advises installing filters to maintain clean power in industrial facilities.
6. Physical Barriers
- What it does: Enclosures or shielding materials block electromagnetic fields from interfering with sensitive devices.
- How to implement: Place noise-generating equipment like motors in shielded compartments.
- Source: EMC Directive compliance documents recommend shielding as a key practice.
7. Optimizing Sensor Placement
- What it does: Strategic placement avoids areas with high electromagnetic or radio frequency activity.
- How to implement: Position sensors away from industrial machinery like motors, welders, or compressors.
- Source: Siemens’ application notes stress sensor placement to avoid interference.
8. Using Noise-Cancelling Software
- What it does: Software algorithms can filter out noise from collected data.
- How to implement: Implement built-in noise filters provided by PLCs (Programmable Logic Controllers) or IoT platforms.
- Source: Rockwell Automation recommends using noise filtering software to clean noisy input signals.
9. Maintaining Equipment
- What it does: Properly maintained equipment generates less noise and interference.
- How to implement: Regularly check and repair damaged cables, worn-out motors, and aging power supplies.
- Source: The Occupational Safety and Health Administration (OSHA) suggests that maintenance reduces both electrical and acoustic noise.
10. Choosing the Right Frequency Bands
- What it does: Selecting less-congested frequency bands minimizes cross-talk and interference.
- How to implement: For wireless IoT systems, consider using frequency bands designed for industrial use, like 868 MHz in Europe or 915 MHz in the US.
- Source: LoRa Alliance points to frequency band optimization as key for reducing interference in industrial IoT.
