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Homemade Photocell

March 6, 2011

I love The Toaster Project, and I really hope that this thesis will soon begin to take on some of its finer qualities. I took out a little time today to try making a homemade photocell.  This is not a photoresistor–it actually demonstrates the photo-electric effect.  When exposed to light, metals give off electrons; a photoresistor changes (lowers) its resistance when exposed to light, but does not produce voltage.  With the excellent tutelage of these two websites, I was able to produce 36-39 mV:

http://www.sparkbangbuzz.com/els/photocell-el.htm

http://www.ehow.com/how_7290427_make-adjustable-homemade-photocell.html

Start with a plate of copper, and cut off a strip.  I tried a couple of 1″ strips of different lengths, but it didn’t seem to affect voltage.

Throw it on the hottest burner on your stove:

Leave it on for a few minutes until it oxidizes:

Mix a tablespoon of salt with a pint of water.  It’ll dissolve more quickly in hot water:

Make two coiled leads, attach them to a multimeter, set it to DC voltage.  Put a few drops of salt water on various parts of the plate, and test the voltage at each location–it will vary:

The leads are knee deep in salt water, and I’ve got a laser pointer aimed at it.  Without the laser pointer, I’m getting 36 mV, and with it, 39 mV.  I’m going to try it again on a sunny day, and will also work tomorrow on sending sound-modulated light.  I’m also wondering if it will make a difference to get the plate hotter, and leave some copper raw.  To try that I’ll need a propane torch.

As always, working first-hand with these phenomena suggests many directions for the finished work.  I was quite taken by the rapid changes in color and texture in the copper, the stark contrast of the laser, the subtle detail of the spiraling wire leads, and the messy potential of the saline solution.

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From → ITP, Thesis

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