Wednesday, January 30, 2008

DIY MPG for Mach3 (Part 1)

After failed attempts using stepper motors as encoder for the Mach3 MPG (details), I decided to find alternative encoder to use and I am still unwilling to spend USD75 for an industrial encoder. While attending a CAD/CAM training, which heavily relied on mouse center scroll function, it hit upon me that cheap optical mouse may offer me a solution. True enough, after a quick scope check, the center encoder do provides quadrature output needed for MPG operations. Resolution is roughly about 20ppr and the circuit is physical contact rather than optical.

The encoder is only 3 pins, i.e., Ground-OutputA-OutputB. Two 10k pullup resistors to the USB +5V are needed to provide suitable signal to the PC parallel port. Quick config update and MPG calibration in Mach3 and I was in business... yahoo....
The photo below show the actual encoder after removal from the PCB. I'm in the process of designing and building a suitable pendant to house the encoder and relevant switches for practical use... next installment though... going vacation this weekend...

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