Circuit advice

future · Joined: 14 May 2004 Posts: 330

Hi,

What should be a good PI CLC filter for my F452@40mhz working in car?

or, what frequencies should I hunt?

Thank you.

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

I don't quite understand what you want. Are you worried about interference from the car electronics affecting the PIC? Are you worried about the PIC affecting the car? Are you worried about the PIC affecting something else?
Is the PIC under the hood with the ignition wires, or in the passenger compartment with the cell phone, wireless laptop, and static laden plastic surfaces?
More info please.
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future · Joined: 14 May 2004 Posts: 330

hmm yes more info,

The circuit will be under the hood near ignition, in an aluminum case.

I want to make sure that I will not get random resets or errors.

SherpaDoug · Joined: 07 Sep 2003 Posts: 1640 Location: Cape Cod Mass USA

To stop ignition noise look for something called a "hash" choke. It is a deliberately lossy inductor that absorbes high frequency energy. Digi-Key lists about 20 of them. Check the current rating, physical size and price. More inductance is better but 100uH with a pair of 1000pF caps should handle most situations. There are also EMI filters that have a three parts in one package for small signals.

Of course if you are trying to bring a high frequency signal into your box, like a radio signal, then things get complicated.
_________________
The search for better is endless. Instead simply find very good and get the job done.