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10. Optocoupler: The optocoupler is part of the VCA circuit that controls the volume of the Noisette.
It consists of a light dependent resistor (LDR) and a light emitting diode (LED), both of which are
sealed inside a length of heat-shrink tubing. In a previous step we set aside the LDR with the
black dot on its backside. We will now use this dotted LDR in building the optocoupler. We will
first construct the optocoupler and then install it on the board.
a. Insert the green 5mm LED into the end of a piece of heat-shrink tubing. Proper placement of
the LED in the tube is important. Slide the LED into the tube until the back of the LED is about
5mm from the end. The LED just needs to be far enough into the tube so the end can be
pinched fully closed around the backside of the LED (38). This will keep as much ambient
light out of the tube as possible.
38
39
