User manual

Hillstar Boards – Hardware Description
 2013 Microchip Technology Inc. DS40001721A-page 25
3.3 HILLSTAR 95x60 mm REFERENCE ELECTRODE
The 95x60 mm Reference Electrode provided with the Hillstar Development Kit
consists of one Tx and a set of five Rx electrodes (north, east, south, west, center),
which are placed in two different layers. An additional ground layer is placed
underneath the Tx electrode and shields the electrode’s back from external influences.
FIGURE 3-3: HILLSTAR PCB ELECTRODE
The PCB is connected to the MGC3130 Unit by the 2 mm 7-pin board-to-board
connector. The interface includes the following signals: GND, Rx4, Rx3, Tx, Rx2, Rx1,
and Rx0.
The dimension of the board is 120 x 85 mm; the sensitive area is 95 x 60 mm.
The five Rx electrodes include four frame electrodes and one center electrode, as
shown in Figure 3-3. The frame electrodes are named according to their cardinal
directions: north, east, south and west. The dimensions of the four Rx frame electrodes
define the maximum sensing area. The center electrode is structured (cross-hatched)
to get a similar input signal level as the four frame electrodes.
The Tx electrode spans over the complete area underneath the Rx electrodes. It is
cross-hatched to reduce the capacitance between Rx and Tx (C
RxTx
). The Tx area
below the center electrode covers 50% of the copper plane, the area around only 20%.
The Rx feeding lines are embedded into the Tx electrode in the third layer (refer to
Figure 3-4 and Figure 3-5). This supports shielding of the feeding lines.
Dimensions are given in Table 3-2.