learning the ropes

things I made at ITP and after: sketches, prototypes, and other documentation

Tuesday, April 15, 2008

Pulley Encoder Boards

Today I etched two test boards for the pulley encoders: the RJ-45 breakout board and the emitter/detector pair board. I wanted to make sure that the board design worked correctly before ordering multiple copies of the boards. After soldering the components onto the boards, I connected a CAT-5 cable between the newly fabricated boards and the interface board I made last week. Before plugging anything in, I checked continuity on the various traces to make sure things were wired properly — or so I thought. When I plugged in the unit after testing, I found that it didn’t detect rotation. I inspected the infrared LED on the detector and found that it wasn’t glowing (I used my digital camera to check). I wasn’t completely surprised; when I hacked apart the mouse circuit board, I found that the X- and Y-axis LEDs were wired together. To fix this problem, I soldered the second IR LED onto the bottom of my interface board. Still no luck. Double checking things, I found that copper traces were bridged on one of the the circuit board I etched. After fixing the bridged traces, I found that the circuit still didn’t work. From prior experience, I figured that either the LEDs, the phototransistors, or both were probably blown, so I decided to try again with another mouse.

Pulley Construction 001 Pulley Construction 003 Pulley Construction 004 Pulley Construction 005

posted by Michael at 11:32 pm  

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