Noise control is very important in systems that use control panels, PLCs, HMIs, motors, and drives.
When a motor starts or stops, the noise it creates can affect nearby sensor signals, PLCs, and HMIs. In some cases, the system may behave strangely even though the program itself has no problem.
Of course, there are expensive ways to reduce noise. You could use fiber optic cables, many power filters, UPS units, and other special equipment. But in most real-world systems, that is not practical.
Before spending a lot of money, check the basics first.
- Keep signal wires away from power wires and motor wires. If they must cross, try to make them cross at a right angle.
- Use shielded cables when possible. A shielded cable is only effective when the shield is properly grounded.
- Use ferrite cores on sensor cables and communication cables. They are inexpensive, easy to install, and often very effective.
- Keep cables as short as possible. Long cables can act like antennas and pick up noise from nearby equipment.
- Check the grounding. Poor grounding is a very common cause of noise problems. In some buildings and factories, the ground connection itself may not be properly installed.
- For sensor lines, adding a simple filter between the sensor and the controller can also help reduce noise.
- At the power input, using an isolation transformer and a noise filter can help prevent noise from entering the control system through the power line.
If your system is unstable because of noise or surge problems, go through these items one by one. In many cases, the problem is not caused by one big mistake, but by several small things that were overlooked.