How to Make a Faraday Cage from a Cardboard Box

Materials:

  • Cardboard box (with either flaps or lid)
  • Aluminum foil
  • Adhesive tape (double sided works best but single sided ok)
  • Scissors

Instructions:

(1) Think about what size object(s) you want to measure. For example, pot plant or slime container.

Also where you are going to test and store as difficult to flat pack.

(2) Look out for suitable sized cardboard box. The box could be made of another material (say plastic or wood) which is more durable. Cardboard is usually lightweight & easy to work with.

The box could have either flap(s) or removable lid. In this example, we’ve selected flaps.

(3) Add double sided adhesive tape to edges, as shown below:

Alternatively, use single sided adhesive tape.

(4) Cut piece(s) of aluminum foil large enough to completely warp around the box. Ideally, wrap the whole box in a single piece. If you must use multiple pieces, overlap sections of foil at least 50mm and make sure they make electrical contact (double sided tape is an electrical insulator).

(5) Careful wrap the box and fold the excess foil to the inside, see below.

Take care not to tear the foil when wrapping. Optionally, tape along edges to improve robustness.

Ensure ALL sides (including the rear) are covered with aluminium foil.

(6) Trim the foil to leave a small lip (say 25mm wide ) on the inside. Cover with tape to insulate.

The object(s) being measured need to be electrically insulated from the conductive aluminium foil. Cardboard works well as an insulator. This is why the foil is usually placed on the outside (rather than the inside).

(7) Add some tape to close the flaps (or use lid).


Grounding Faraday Cage

In theory, Faraday Cages should be grounded to properly disperse electrical charges. This can be a wire connecting the aluminium foil to the ground (often the negative) of the measurement instrumentation. The easiest way to make a good electrical connection with the aluminium foil is with a suitably sized crocodile clip, see example below:

The ground wire can be connected to the ground/negative of the Arduino board(s) via DC power supply socket, see green wires in photo below. If you are using multiple PhyLink units they should all be connected to aluminium foil.