Help in isolating RF radiation/signal from a 6802 mprocessor

[coolneo]

Hello, can someone please help me in my project which I have a big problem. My project which is an automated vacuum cleaner is run by an RF controller is having problems in the signal of the microprocessor. The microprocessor is having problems on operation due to the RF's signal. Can someone give me tips on how to isolate the microprocessor (mc6802) so that it won't be affected by the signal of the RF? Thanks and more power to this site....

 

[kinjalgp]

Construct a Faraday Cage around your Processor circuit. Faraday cage is a metal box which covers the entire circuit from all the sides and shields it from RF radiation. I hope this will solve your problem.

 

[stevez]

Any wires running thru the sheild can carry RF so it might be helpful to use feedthru capacitors, ferrite beads or other means of preventing RF from entering on line that are not operating at RF.

 

[kinjalgp]

Yes, I forgot to mention that point. Use ferrite beads on the VCC line to isolate RF signals.

 

[Sebi]

I think the application contain a simple supreg-receiver, it can radiate high-level RF. If possible, put the receiver-block nearby the aerial, and feed the digital signal to processor via cable.

 

[coolneo]

Thanks for the tips but how can I make a Faraday cage? What are the materials needed and can I make one out of household items?

 

[kinjalgp]

Faraday Cage is nothing but a box of any metal like aluminium or steel plates. There is no special material required for that. The only requisit is that the box should be closed from all the sides and should not have any electrical connection with the enclosed circuit. Even the aluminium electronics Kit Box serves as good faraday cage.

 

[stevez]

It seems that a lot of radio amateurs who do their own building use single or double foil circuit board material. They solder the seams. The nice thing about the board material is that it is easy to work with.
Metal screen or perforated metal can serve well let allow a little ventilation. I do not know how small the screen or holes have to be in order to be effective in sheilding.

 

[Sebi]

If the diameter of hole smaller as wawelength, is equal to continous shielding.

 

[jacques]

Faraday Cage is nothing but a box of any metal like aluminium or steel plates. There is no special material required for that. The only requisit is that the box should be closed from all the sides and should not have any electrical connection with the enclosed circuit. Even the aluminium electronics Kit Box serves as good faraday cage.

Stop me if I say something stupid:
1-I found sheet steel works better than aluminum kit box for stopping AM. Is it so, and is this because of the unique magnetic properties of iron?

2-I usually connect my faraday cage to the ground of the circuit. Is it right?

thanks
jacques
www.ts808.com

 

[kinjalgp]

No its not a good idea to connect your circuit ground to Faraday cage. This may lead a path for the EM waves to reach your circuit. Regarding metals, it is not necessary to use only aluminium. You can use whatever you desire. Since aluminium is less corroded in air than iron, I suggested that.

 

[jacques]

No its not a good idea to connect your circuit ground to Faraday cage. This may lead a path for the EM waves to reach your circuit. Regarding metals, it is not necessary to use only aluminium. You can use whatever you desire. Since aluminium is less corroded in air than iron, I suggested that.

thank you for your answer.
However, what about the ferromagnetic properties of iron/steel regarding its use in a Faraday cage ?

 

[kinjalgp]

Sinec there is no physical contact between the circuit and cage, it is not going to matter how the metal reacts to EM waves. Even if circulating currents are generated in the iron cage, it won't cause any trouble to the circuit.