So I tried constructing a laser trip wire and I got the design from http://dawes.wordpress.com/2009/12/18/build-a-laser-tripwire/
I am wondering what exactly is the use of the 2n3904 in this circuit, is it necessary to connect one? And how does it drive the NE555.
I am wondering what exactly is the use of the 2n3904 in this circuit, is it necessary to connect one? And how does it drive the NE555.
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