Faraday Enclosure Assembly Manual
© Alex Asen, Open Source Instruments Inc, 2009
© Kevan Hashemi, Open Source Instruments Inc, 2009
Use Spreadsheet to Determine Materials and Cuts.
- The box is made of right-angled aluminum epoxied together. The mesh is held in place with aluminum foil tape. There are no rivets, bolts, or screws. There is only one hole, and that is for a BNC feed-through in the bottom edge of the enclosure.
- We refer to sections of the enclosure as "bottom", "top", "sides", and "lid". The lid and the top are distinct pieces. The lid sits on the top of the enclosure.
- The FE2A enclosure has six mesh walls and a plexiglass base. The FE2B has three mesh walls: front and two sides. The remaining walls, which are the top, bottom, and back, are all 0.8-mm (1/32") aluminum sheet.
- In this Assembly Manual we assume you are making an FE2B enclosure, with aluminum sheet for the bottom, lid, and back walls.
- The mesh walls are fragile. If you puncture one, you can patch it with the aluminum foil tape we use in construction of the enclosure.
- Download our faraday enclosure materials Spreadsheet. The file is in Microsoft Excel format.
- The best way to determine how much mesh to order is to calculate it by hand on graph paper. The mesh is sold by the foot and is 58" wide.
- Add a 1/2" hole for the BNC Bulkhead in one of the bottom brackets of the enclosure.
If you buy a materials kit from Open Source Instruments, it will include all the components of the enclosure, but not the clamps you need to hold the pieces together while they dry. Nor does the kit include the epoxy dispensing gun that holds the epoxy cartridge.
Assemble the Top
- Right-angled aluminum from McMaster, 88805K66.
- Aluminum foil tape from DigiKey, 3M1120C.
- Steel mesh from Less EMF, Less EMF.
- Epoxy is from McMaster, 3M's DP460, 7467A26.
- BNC feedthrough from Digi-Key, Tyco's 5332215, A33827, or AAA2061 from AAA RF Products.
- Aluminum sheet from McMaster, 1/32" thick, 89015K71.
- Microwave absorber from Emerson and Cuming, AN-77.
|The corner pieces are borrowed from the lid and are there to help square the "top," but do not get epoxied in place.
||Add weights to insure everything is flush.
||The finished top flipped over after it has dried. Notice no corner pieces.
Assemble the Lid.
- Use a uniform film of epoxy. If the film is too thin, the joints will not be strong enough. If the film is too thick, the epoxy will ooze out the seems and causes problems later. If that happens, use tissue and alcohol to wipe off excess epoxy before it sets.
- Square the box carefully. It is easier to square the box if you allow the epoxy to get a little tacky.
- If you assemble many enclosures, we suggest you cut a plywood fixture.
||Use the top as a fixture.
||Use the bottom pieces as spacers
||Epoxy the lid together on top of the fixture.
Add Corners to the Lid.
- Once the top has dried, use it as a fixture for the lid.
- Place the un-epoxied bottom angled aluminum on the top as a spacers. You may want to use tape to hold the pieces in place.
- Epoxy the lid together on top of this fixture. When dry, the lid should be 1/8" (3.2 mm) larger than the top, which is twice the thickness of the aluminum used in the aluminum angles.
|The corner pieces are added.
Assemble the Bottom.
- After the lid has dried and you have tested it fits on the the top, add the corner pieces.
Connect the Bottom and Top with Side Pieces.
- The bottom is identical to the top. We do not assemble them at the same time because we want to use the un-epoxied bottom angled aluminum as spacers for the lid.
||All four sides are glued at once.
||Close up of one corner.
Cut the Steel Mesh.
- The side pieces must be on the inside for the lid to fit on.
- You may want to invest in additional clamps if building more than one enclosure.
|Mesh unrolled on the table.
||Mesh with masking tape, ready to be cut.
Tape the Steel Mesh in Place.
- Draw out the dimensions on your table. Stretch the mesh over the table and your marks will show through easily.
- Use masking tape to transfer the lines from the table to the mesh.
- Use sharp metal scissors to cut along the edge of the masking tape.
|Piece of tape in the corner to hold mesh in place.
||Mesh fully taped.
||Ignore the BNC hole while taping. Later use a razor blade to cut tape and mesh away from the hole.
Tape Aluminum Sheets in Place.
- We tape the mesh on the inside of the enclosure so that the lid does not rub against it.
- First put a small piece of tape in each corner to hold the mesh in place.
Install the BNC Feedthrough Connector.
- Cut the lid wall to size and place it on top of the lid. The sheet edges should be parallel to the edges of the lid, and within 5 mm of the edges.
- Tape the lid wall in place. Half the width of the tape should adhere to the wall. Fold the other half over onto the lid frame. The folded tape covers the 1.6 mm (1/16") gap along two sides of the lid.
- Lower the bottom sheet and back wall sheet into the enclosure frame.
- Tape the aluminum bottom and back wall in place, just as you taped the steel mesh walls.
Attach Absorber to Lid
- Fasten the BNC feedthrough into the hole you have drilled. Tighten the nut upon the locking washer. You must ensure that the nut it tight enough that it will not come loose when BNC connectors are turned by hand on either side of the feedthrough.
- With a liberal quantity of glue, attach the gray side of the 6-cm thick, 61-cm square, AN-77 microwave absorber.
- The absorper should be centered upon the lid area.
- Inspect the steel mesh for holes. Patch any holes with aluminum tape on both sides of the mesh.
- Place the lid upon the enclosure. It will fit only in two orientations. Mark the lid and the enclosure to show which orientations work.
- Apply torque and pressure to corners and sides of enclosure and listen for creaking in the joints. Creaking indicates broken epoxy bonds.