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kid with detector Texting Trapper Saved by a Faraday Cage

This is one of my favorite stories of an eleventh-hour save of a Maker Faire project. Makers Sophi Kravitz and Ollie Tanner built an 8′ bar graph that indicates the signal strength of nearby cell phones. It worked great at home, but not so much at the San Mateo Fairground:

Since the idea of the product is to detect transmitted and received signals from a good distance, I made sure that there would not be any cell towers too close to the Maker Faire site ahead of time. It was fun looking at maps of where cell towers are located!
Unfortunately, since cell service where Maker Faire is located (San Mateo fairgrounds) is poor, a temporary tower was brought in, and placed very close to the building we were exhibiting in. After setting up the exhibit, we realized that it was full on all the time, the cell tower was overpowering the exhibit and we weren’t going to be able to show anything except a big, red, bright light.

After a few failed attempts fixing their troubles with antenna design and attenuators, Sophi called in her brother, Lex Kravitz, to build a Faraday cage.

making the cage Texting Trapper Saved by a Faraday Cage

This allowed Sophi to place her cell phone under the cage, and she asked booth visitors to text her phone to see the gigantic signal strength bounce. It worked wonderfully! It was a real treat to see both the original project in action and the ingenious solution to the last-minute problem.

faraday cage Texting Trapper Saved by a Faraday Cage

Texting Trapper at Maker Faire 2012

John Edgar Park

John Edgar Park likes to make things and tell people about it. He works in CG animation at DisneyToon Studios and writes for Make, Boing Boing, and other places online and in print. You can find him at and twitter @johnedgarpark — if you like that sort of thing.

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