My friend and I are working on a Civil War telegraph project, and we incorporated a Pi into the project, for reading and displaying the received code from the key. My friend created a period correct sounder, which relies on an electromagnet. However, the electromagnetic interference from the sounder crashes the file system. Is there any easy way to prevent this interference? Are there any decent Faraday cages for the Pi?
A Faraday cage will provide shielding from electromagnetic radiation, but this is unlikely to be the cause of your problem. I assume you are connecting the Pi to external circuitry (you don't give us much to work on) and this is almost certainly the problem. There are many established methods for protecting these, ranging from ferrite rings for common mode rejection, filter capacitors or complete isolation (using opto isolators). Don't forget the power to the pi, which is also a potential source of problems.
If the power to the RPi is not sufficiently decoupled/filtered, it may be the causing the problem you are seeing. If the RPi isn't on a separate power adaptor, you should try that - just connect the grounds together.
Before you get carried away with fabricating something, you can try just about any metal container you have lying around. Coffee tin/Biscuit tin, etc will do.
Put the Pi in the metal container and bring the wires out of the smallest hole that is practical. If you have some ferrite cores, loop the wires through those as close to the tin as you can.
Any chance of a pic? There may be something else obvious wrong with your layout/setup.
While not meant Exactly for being a Faraday case :
is a billet aluminium case that's super burly. This -grounded out- would Probably do you well, but again if you share Any lines with the other electronics, then who knows where you're getting the interference.. Coupled with a few of these :
(Just search for "ferrite core protection", or "snap on ferrite core") and you MIGHT be on the right track.
Now, having said that, I'm sure that any "Phone Faraday Bag" or case will do the same for a lot less ;) Good Luck!