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Sunday, August 15, 2010

Mouse Movement Emulator - An Automated Test Fixture

A while back, I posted a blog entry detailing a serial relay control fixture for automated testing. That device contained 48 relays that were individually controlled by RS-232 commands. A PC running LabVIEW software issued the control signals in the proper sequence, and collected and logged all data. One of the peripheral devices the serial relay fixture controlled was the mouse movement emulator described herein.

I designed this mouse movement emulator prototype - as seen in the picture - to generate signals for mouse movement, "left button clicks" and "right button clicks" without any human intervention required. The fixture consists of an optical mouse, two "dip" type relays, a vibrator motor to shake the mouse, and a resistor to reduce the current from a 12 volt supply to a safe level for the vibrator motor - which is rated for only 3 Vdc. The relays came from "in-house" parts stock; the vibrator motor, resistor, and aluminum chassis box were all bought from a local electronic supply house. A ceramic disc capacitor, visible in the picture, is connected across the motor's terminals. This capacitor, in conjunction with the current limiting resistor, forms a low-pass filter and helps supress electrical noise from the motor brushes.

The motor and relay control signals are transmitted through a 5-conductor cable which I made from separate pieces of hookup wire twisted together using an electric drill. The mouse signals are transmitted via the original gray colored shielded mouse cable. I threaded these two cables through a length of woven sheathing to keep them neat and tidy. A small section of the sheathed cable is visible in the lower left hand side of the picture. The cable is terminated in a male D-SUB connector which plugs into the serial relay control fixture.

Together with the serial relay control fixture and a PC running LabVIEW software, this device successfully exercises the mouse functions of the units under test (UUTs) WITHOUT a human being present to observe the test and/or operate the mouse.

Benifit for the project I was working on:
This unit made possible FULL automation of engineering design verification tests as well as manufacturing testing.

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