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Matt Mets made this “Light Record:”
I am using some photocells to read the intensity of light that shines through a sheet of paper, upon which I have encoded an image using shades of grey. By spinning this paper around and shining a light through it, the image can be viewed on an oscilloscope. The circuit consists of two resistor dividers, one for each channel, made up of a photocell and a fixed resistor. When there is a large amount of light on the photocell, its resistance drops dramatically and the output voltage rises; when there is little light on the photocell, its resistance goes down and the voltage goes down as well. That’s it!
It’s the first of Matt’s ambitious Thing-a-Day efforts. – Link.
Check that thingaday link
How clever! You might experiment with making the data disks with a laser printer on a piece of acetate, or maybe just paper dampened with mineral oil. This device doesn’t seem to focus well, a fact which would allow bars to be used in an FM-like scheme. The CdS sensors are slow and tend to self-excite. Another way to make this would be with an op amp trans-resistance amplifier. This circuit can be speeded-up by using current-source loads rather than resistors.
That music really creeped me out.
I fixed the link, thanks Im!
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Make: School’s Out! Summer Fun Guide
This Summer Fun Guide is brimming with over 50 projects for kids of all ages. You’ll also find inspiring young maker profiles, as well as tool reviews written for and by kids! Plus, it’s our 3D issue, complete with 3D glasses and tons of super-cool 3D photos!
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