protection for microcontroller of electromagnetic interference and noise ?

tom66

Joined May 9, 2009
2,595
In some electronics where shielding is necessary for performance or legal reasons, you can use metal cans over the devices.



This is one example. In this example there are two shields and one is being removed (this is from some kind of instruction manual.) The shields are soldered on the board, like through-hole components.

The shields are usually custom designed, but you may be able to get a manufacturer to make some, or make them yourself.
 

Thread Starter

Osama Mostafa

Joined Oct 15, 2010
3
I will design stepper motor drive circuit by PIC microcontroller with current control which has a high frequency so I want to make sheilding for controller to avoid any elctromagnetic interference and any electrical noise from supply
 

thatoneguy

Joined Feb 19, 2009
6,359
I will design stepper motor drive circuit by PIC microcontroller with current control which has a high frequency so I want to make sheilding for controller to avoid any elctromagnetic interference and any electrical noise from supply

This can be reduced quite a bit by good filtering on the power rails. Such as mid value electrolytics, small value ceramic caps, perhaps an inductor depending on frequency of noise. Separate the power for the uC from that of the stepper as much as possible, on the extreme end, use optocouplers to move the signal and feedback liines.

Use a metal grounded case for the uC and components (faraday cage). Keep wire runs and PC Board traces short so they act less like antenna. Ensure you have a good ground plane on the PC Boards and they are well laden with bypass caps to keep the power supply filtered.

Need more specific info on the interference, if it is a known frequency, a filter can be added to notch that particular frequency and most harmonics out.

Same realm as a computer motherboard, or other digital circuits running at high clock frequencies. The design needs to ensure the traces do not turn into accidental radio transmitters. This is why 4 layer boards (sandwich with power and ground planes entirely across circuit) are used, as well as the smallest components for shortest trace lengths.
 
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