Resistive scanning grid touch panel
View Patent ↗An improved resistive touch panel is disclosed. The improved resistive touch panel includes a first plurality of stripes of a resistive coating on a front sheet running in a first direction and a second plurality of stripes of a resistive coating on a back sheet running in a second direction. The overlapping regions between the first and second plurality of stripes are scanned by a controller circuit to detect voltage drops at these regions. Because the overlapping regions are independent of each other, the controller circuit is able to detect the individual regions involved in the touch area. In this manner, the controller circuit is able to determine between small and large areas of contact by detecting adjacent contact areas.
1. A resistive touch panel, comprising:
a first sheet, comprising a plurality of independent stripes of a first resistive coating, the first sheet being transparent;
a second sheet, comprising a second resistive coating separated from the first sheet by a plurality of insulator dots, wherein a voltage difference exists between the second resistive coating and the plurality of independent stripes, wherein the plurality of independent stripes and the second resistive coating form a plurality of independent overlapping regions; and
a controller, coupled to the first sheet and the second sheet, the controller configured to detect a contact between the first sheet and the second sheet in at least one of the plurality of independent overlapping regions and scans the plurality of independent stripes and the second resistive coating to determine a position of the contact, wherein the scanning includes:
switching between applying a current to each of the plurality of independent stripes and monitoring the second sheet and applying the current to the second sheet and monitoring each of the plurality of independent stripes,
determining the position of the contact in a first direction by measuring a first voltage difference between a first and a second side of each of the plurality of independent stripes, when the current is applied to the first sheet, and
determining the position of the contact in a second direction by measuring a second voltage difference between a first and a second side of the second sheet, when the current is applied to the second sheet.
2. The panel of claim 1 , wherein the second resistive coating comprises a second plurality of independent stripes of the second resistive coating.
3. The panel of claim 2 , wherein the plurality of stripes of the first resistive coating runs in a first orientation, wherein the second independent plurality of independent stripes run in a second orientation different from the first orientation.
4. The panel of claim 3 , wherein the second orientation is approximately perpendicular to the first orientation.
5. The panel of claim 1 , wherein the controller comprises:
a microcontroller; a plurality of analog-to-digital converters coupled to the microcontroller; and
a plurality of multiplexers coupled to the plurality of analog-to-digital converters.