How can I improve EMC in my design?
Submitted By: Craig Steiner FAQ Last Modified: 07/10/06
- Insert a soft ferrite bead like BL02RN2 (Murata) or similar where the +5V enters the board, just between power supply connector and the 470µF power supply decoupling capacitor. This will heavily minimize high frequency currents running in the power supply cable.
- Use common mode filtering on cables leaving or entering the board. Otherwise it will result in heavy noise radiations. Bend each cable arround an individual soft ferrite ring core or feed it through a bigger soft ferrite bead. This will minimize common mode noise on each cable and by this minimize radiation. In any case, keep the cables as short as ever possible.
- Have ferrites at the entry to a steel case with your board for all outside connections. Have all connections to the high amperage opto-isolated in a way that does not allow any noise from the high amperage parts enter your steel box.
- Pay adequate attention to enclosure design. Use Mild Steel around 1mm thick with Zinc coating. Don’t have any unwanted holes or openings in the enclosure. For ventilation some tiny holes 2mm diameter can be introduced but keep the number of holes as small as possible.
- For cables leaving or entering your box tie the shields to the enclosure at the point where these cables enter or exit your box.
- Connect the signal ground at the shield connecting point and also connect the safety ground at the same point.
- It’s better if a ferrite is used to connect signal ground and enclosure ground.
- Noise entering into your box depends on the length of the holes and not on the areas. If at holes are desired make them square or circular but not rectangular.
- If you need to connect devices like keypad or LCD for which a large hole is needed in the box. Use the Clean box dirty box method for incorporating these devices.
Add Information to this FAQ: If you have additional information or alternative solutions to this question, you may add to this FAQ by clicking here.