Payment terminal stylus with touch screen contact detection
In an exemplary embodiment, a stylus operates with a capacitive touch screen only when the stylus tip is in contact with the touch screen. The stylus is used as a sensor to determine the location where a user is touching the surface of a capacitive touch screen, but is not active until the stylus tip is pressed against the touch screen. In an exemplary embodiment, pressing the stylus tip against the touch screen activates the stylus by creating a physical separation in the circuit and disconnecting the stylus tip from ground. When the stylus tip is no longer grounded, it becomes active and is able to operate with a capacitive touch screen. In an exemplary embodiment, signal attenuation may be performed by diverting the sense signal to ground via a capacitor or other electronic component.
1. A stylus comprising:
a stylus tip configured to generate a sense signal using an electromagnetic field of a capacitive screen;
a tip plunger connected to the stylus tip, wherein the tip plunger comprises a grounded state and a conducting state; and
a conductive ring, connected to ground, comprising a grounded state;
a cable shield to connect the conductive ring to a ground connection;
a capacitor in communication with the cable shield;
wherein the tip plunger is configured to operate in the grounded state if in contact with the conductive ring; and
wherein the tip plunger is configured to operate in the conducting state in response to separation from the conductive ring, whereby pressure on the stylus tip creates separation of the tip plunger and the conductive ring and facilitates transmission of the sense signal.
2. The stylus of claim 1 , further comprising a spring configured to maintain a connection between the tip plunger and the conductive ring, wherein the spring compresses to create separation between the tip plunger and the conductive ring in response to pressure on the stylus tip.
3. The stylus of claim 1 , wherein the tip plunger is in contact with the conductive ring if no pressure is applied to the stylus tip.
4. The stylus of claim 1 , wherein a separation between the tip plunger and the conductive ring of about 0.3 millimeters or less facilitates transmission of the sense signal.
5. The stylus of claim 1 , further comprising a wired connection from the stylus to a receiver.
6. The stylus of claim 1 , further comprising a wireless connection between the stylus and a receiver.
7. The stylus of claim 1 , wherein the stylus and the capacitive screen are part of a point-of-sale terminal.
8. A method comprising:
pressing a stylus tip of a stylus against a capacitive screen;
generating a sense signal from an electromagnetic field of the capacitive screen in response to separation of a tip plunger from a conductive ring, whereby pressure on the stylus tip creates separation of the tip plunger and the conductive ring and facilitates transmission of the sense signal, wherein a cable shield connects the conductive ring to a ground connection, wherein a capacitor is in communication with the cable shield; and
transmitting the sense signal to a receiver;
wherein the conductive ring prohibits transmission of the sense signal if in contact with the tip plunger.
9. The method of claim 8 , further comprising compressing a spring in the stylus to facilitate separation of the tip plunger from the conductive ring.
10. The method of claim 9 , further comprising decompressing the spring to cause contact between the tip plunger and the conductive ring.
11. The method of claim 8 , further comprising removing the stylus tip from the capacitive screen to facilitate replacement.