Self-aligning pointing device having ESD protection
A pointing device includes a pointer that is confined to move within a field of motion. A mounting structure is attached to a substrate and positions the field of motion upon the substrate. The pointing device further includes a restoring mechanism that returns the pointer to a predetermined resting position within the field of motion. A sensor determines the position of the pointer with respect to the substrate.
1 . A pointing device, comprising:
a substrate;
a mounting structure attached to the substrate;
a pointer confined to move within a field of motion, wherein the mounting structure positions the field of motion on the substrate;
a restoring mechanism that returns the pointer to a resting position within the field of motion; and
a sensor that determines the position of the pointer with respect to the substrate.
2 . A pointing device as in claim 1 , further comprising:
a housing attached to the mounting structure, wherein the housing defines the boundaries of the pointer field of motion.
3 . A pointing device as in claim 2 , further comprising:
an alignment pattern formed on the substrate, wherein the mounting structure is attached to the alignment pattern.
4 . A pointing device as in claim 3 , wherein the alignment pattern is symmetric about the X-axis and Y-axis.
5 . A pointing device as in claim 4 , further comprising:
a first electrode on the pointer; and
a second electrode on the substrate, wherein the sensor detects a change in capacitance between the first and second electrodes.
6 . A pointing device as in claim 3 , wherein the alignment pattern comprises a conductive footprint on the substrate.
7 . A pointing device as in claim 6 , wherein the housing includes conductive material.
8 . A pointing device as in claim 7 , wherein the conductive footprint is connected to a low impedance.
9 . A pointing device as in claim 8 , wherein the mounting structure is soldered to the alignment pattern.
10 . A pointing device as in claim 9 , wherein the mounting structure and the housing form a shunt for electrostatic discharge.
11 . A pointing device as in claim 8 , wherein the mounting structure is connected to the alignment pattern with non-conducting adhesive.
12 . A pointing device as in claim 8 , further comprising springs that maintain contact between the housing and the mounting structure.
13 . A pointing device as in claim 3 , wherein the alignment pattern is a fiducial mark on the substrate that indicates the attachment point for the mounting structure.
14 . A method for assembling a pointing device, comprising:
providing a substrate with an alignment pattern;
attaching a mounting structure to the alignment pattern;
attaching a pointer sub-assembly to the mounting structure, wherein the pointer sub-assembly includes a pointer confined to move within a field of motion over the substrate; and
determining the position of the pointer with respect to the substrate.
15 . A method as in claim 14 , wherein detecting a value further comprises:
providing a first electrode on the pointer;
providing a second electrode on the substrate; and
detecting a change in capacitance between the first and second electrode.
16 . A method as in claim 15 , wherein attaching a mounting structure to the alignment pattern further comprises:
applying solder to the alignment pattern;
placing the mounting structure onto the solder; and
reflowing the solder.
17 . A method as in claim 16 , wherein attaching a pointer sub-assembly further comprises:
attaching a housing to the mounting structure, wherein the housing defines the pointer field of motion.
18 . A method as in claim 17 , further comprising
connecting the alignment pattern to a low impedance.
19 . A method as in claim 18 , further comprising
shunting an electrostatic discharge through the housing and the mounting structure.