Capacitive touch switch arrangement

• US 4,561,002 A
• Filed: 08/30/1982
• Issued: 12/24/1985
• Est. Priority Date: 08/30/1982
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Chiu, Norman H.
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Heim, Michael F.
• Application Number:
  US06/412,737
• Time in Patent Office: 1,212 Days
• Field of Search: 340/365 C, 340/365 E, 340/365 R, 340/365 S, 340/365 A, 400/479.1, 200/DIG. 1, 200/5 A, 179/90 K, 219/10.77
• US Class Current: 341/26
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2017/9615 using three electrodes per touch switch
• CPC Class Codes: H03K 2217/96077 comprising an electrode which is floating
• CPC Class Codes: H03K 2217/960775 Emitter-receiver or "fringe" type detection, i.e. one or more field emitting electrodes and corresponding one or more receiving electrodes

Abstract

A capacitive attenuator type touch switch cell arrangement employs a touch responsive pad or electrode and a receiver electrode of comparable surface area on opposing surfaces of a dielectric substrate for capacitive coupling therebetween, which capacitive coupling is alterable by the human touching of or proximate to the touch pad. A scan signal is coupled from signal generating circuitry to the touch responsive pad by a separate transmitting capacitor. Signal detection circuitry senses the signal coupled to the receiver electrode to detect attenuation of the coupled signal signifying the touching of the touch pad. The use of a separate capacitor to provide the transmitting capacitance reduces the touch pad area requirement, thereby permitting closer spacing of touch switch cells for greater switch density on a control panel.

Claims

1. A capacitive touch switch arrangement comprising:

means for generating a scan signal;

a substrate of dielectric material having first and second opposed surfaces;

a touch electrode formed on said first surface for human touching;

a receiver electrode formed on said second surface in an area overlying and bounded by the area of said touch electrode;

a capacitive element separate from said touch electrode and said receiver electrode for coupling the scan signal from said signal generating means to said touch electrode;

said touch electrode cooperating with said receiver electrode to capacitively couple said scan signal from said touch electrode to said receiver electrode, said capacitive coupling being alterable by the human touching of said touch electrode, such that the human touching of said touch electrode changes the signal at said receiver electrode; and

signal detection means coupled to said receiver electrode and operative to detect changes in the signal at said receiver electrode caused by human touching of said touch electrode.

2. A capacitive touch switch arrangement comprising:

a scan signal generating means;

a substrate of dielectric material having first and second opposed surfaces;

a first electrode formed on said first surface responsive to human touching proximate thereto;

a second electrode formed on said second surface to enable the capacitive coupling of the signal from said first electrode to said second electrode, said capacitive coupling being altered by human touching proximate said touch electrode;

a capacitive element separate from said first and second electrode for coupling the scan signal from said signal generating means to said first electrode;

a conductive path formed on said first surface for electrically connecting said capacitive element to said first electrode;

input signal detection means coupled to said second electrode and operative to detect the alteration of said capacitive coupling resulting from said proximate human touching.

3. A capacitive touch switch arrangement in accordance with claim 2 further comprising an outer dielectric panel overlying said dielectric substrate having an inner surface facing said first surface and on opposite outer surface;

said panel having defined thereon a touch zone in register with said first electrode such that human touching of said outer surface in said touch zone alters said capacitive coupling.

4. A capacitive touch switch arrangement in accordance with claim 3 wherein said capacitive element comprises a discrete capacitor device having a pair of terminals, one of said terminals being coupled to said scan signal generating means, the other of said terminals being coupled to said conductive path.

5. A capacitive touch switch arrangement comprising:

a substrate of dielectric material having first and second opposed surfaces;

a touch pad formed on said first surface for human touching;

a receiver electrode formed on said second surface in an area overlying and bounded by the area of said touch pad for capacitive coupling through said substrate with said touch pad;

a capacitor separate from said touch pad and said receiver electrode;

a first conductive path formed on said first surface electrically coupling said capacitor to said touch pad;

circuitry for operating said touch pad and said receiver electrode as a capacitive attenuator switch by applying a scan signal to said touch pad via said capacitor and sensing the resultant signal capacitively coupled from said touch pad to said receiver electrode to detect a decrease in the coupled signal when said touch pad is touched.

6. A capacitive touch switch arrangement in accordance with claim 5 further comprising:

a capacitive network comprising a pair of capacitors serially connected between an input terminal and an output terminal;

a second conductive path formed on said first surface of said substrate substantially adjacent to said first conductive path such that human touching of said first path would ordinarily also result in touching the said second path, said second path being electrically coupled at one end thereof to the junction of said pair of capacitors and the other end thereof being unconnected;

said operating circuitry for applying a test signal at said input terminal simultaneously with the application of the scan signal and sensing the signal capacitively coupled to said output terminal to detect a change in said signal when said second conductive path is touched, the simultaneous detection of a decrease in the signal at said receiver electrode and the signal at the output terminal signifying an erroneous input.

7. A touch switch arrangement comprising:

a dielectric substrate having first and second opposed surfaces;

a touch pad formed on said first surface;

a receiver electrode formed on said second surface opposite said touch pad to enable capacitive coupling therebetween, said capacitive coupling being alterable by the presence or absence of the human touching of said touch pad;

a scan signal generator for applying a pulsating scan signal to said touch pad, which signal is capacitively coupled from said touch pad to said receiver electrode thereby providing a first output signal at said receiving electrode;

a transmitting capacitor having an input connected to receive the scan signal from said signal generator and an output connected to capacitively couple the scan signal to said touch pad;

a first conductive path formed on said first surface connecting the output of said transmitter capacitor to said touch pad for coupling said scan signal from said transmitting capacitor to said touch pad;

a second conductive path formed generally adjacent said first path such that the human touching of said first path would ordinarily result in the simultaneous touching of said second path;

a capacitive network having an input and an output, said input being connected to said scan signal generating means said network further comprising circuitry for capacitively coupling the scan signal from said network input to said network output thereby providing a second output signal at said network output;

said second conductive path being coupled to said capacitive network such that said capacitive coupling between said input and output of said capacitive network is alterable by the presence or absence of the human touching of said second conductive path;

signal detection circuitry having a first input connected to receive said first output signal and having a second input connected to receive said second output signal, said signal detection circuitry being operative to detect decreases in said first and second output signals indicative of a human touch and to generate a control signal to initiate a switching action upon detection of a decrease in said first output along and to generate a control signal to inhibit the initiation of a switching action upon detection of a decrease in said second output regardless of the state of said first output whereby initiation of a switching action resulting from the touching of said conductive paths is prevented.

8. A capacitive touch control panel arrangement comprising:

a substrate of dielectric material having first and second opposed surfaces;

a plurality of touch pads fabricated on said first surface;

a plurality of receiver pads fabricated on said second surface, each being arranged for capacitive coupling through said substrate with a corresponding one of said touch pads;

a plurality of transmitting capacitors, each associated with one of said touch pads;

a first plurality of conductive paths formed along said first surface electrically connecting one of said transmitting capacitors to its associated touch pad;

a capacitive network comprising a pair of capacitive elements serially connected between an input terminal and an output terminal;

a plurality of second conductive paths formed on said first surface, each extending closely adjacent an associated one of said first paths such that touching of one of said first conductive paths ordinarily results in the touching of its adjacent second conductive path;

each of said plurality of second paths being commonly connected to the junction of said pair of serially connected capacitive elements; and

circuitry for operating said plurality of touch pads and said plurality of receiver pads together as an array of capacitive attenuator touch switches by applying a scan signal to each of said transmitter capacitors, which signal is coupled by each of said transmitter capacitors to its associated touch pad; and

sensing the resultant signal capacitively coupled to said associated receiver pad to detect a decrease in the coupled signal when said touch pad is touched;

said circuitry further operating to avoid erroneous signal inputs resulting from inadvertent touching of one or more of said first conductive paths by applying said scan signal to the input of said capacitive network and sensing the resultant signal at the output of said capacitive network to detect a decrease in the coupled signal when one of said second conductive paths is touched, detection of a simultaneous decrease in the signal at the capacitor network output and the receiver pad signifying an erroneous input.

9. A capacitive touch control panel arrangement comprising:

a substrate of dielectric material having first and second opposed surfaces;

a plurality of touch pads fabricated on said first surface;

a plurality of receiver pads fabricated on said second surface, each being arranged for capacitive coupling through said substrate with a corresponding one of said touch pads;

transmitting capacitor means for coupling a scan signal to each of said touch pads;

a first plurality of conductive paths formed along said first surface electrically connecting said capacitor means to said touch pads;

a capacitive network comprising a pair of capacitive elements serially connected between an input terminal and an output terminal;

a plurality of second conductive paths formed on said first surface, each extending closely adjacent an associated one of said first paths such that touching of one of said first conductive paths ordinarily results in the touching of its adjacent second conductive path;

each of said plurality of second paths being commonly connected to the junction of said pair of serially connected capacitive elements; and

circuitry for operating said plurality of touch pads and said plurality of receiver pads together as an array of capacitive attenuator touch switches by applying said scan signal to said transmitter capacitor means, which signal is coupled by said transmitter capacitor means to each of said touch pads, and sensing the resultant signal capacitively coupled to said associated receiver pad to detect a decrease in the coupled signal when a touch pad is touched;

said circuitry further operating to avoid erroneous signal inputs resulting from inadvertent touching of one or more of said first conductive paths by applying said scan signal to the input of said capacitive network and sensing the resultant signal at the output of said capacitive network to detect a decrease in the coupled signal when one of said second conductive paths is touched, detection of a simultaneous decrease in the signal at the capacitor network output and the receiver pad signifying an erroneous input.

10. A multiplexed capacitive touch control panel arrangement comprising:

a substrate of dielectric material having first and second opposed surfaces;

a plurality of touch responsive electrodes fabricated along said first surface;

a plurality of receiver electrodes fabricated along said second surface, each being arranged for capacitive coupling through said substrate with a corresponding one of said touch responsive electrodes;

a plurality of discrete transmitting capacitors formed independently of said touch responsive electrodes and said receiver electrodes, each of said transmitting capacitors being associated with one of said touch responsive electrodes;

a first plurality of conductive paths fabricated on said first surface electrically connecting each of said capacitive elements to its associated touch responsive electrode;

an outer dielectric panel overlying said first surface of said substrate having an inner surface facing said substrate and an opposed outer surface, said panel having defined thereon touch zones, each zone being in register with corresponding ones of said touch electrodes such that human touching of one of said touch zones alters the capacitive coupling between the corresponding touch electrode and receiver electrode;

circuitry for operating said plurality of touch zones, touch electrodes and receiver electrodes together as an array of capacitive attenuater touch switches by applying a scan signal to each of said transmitter capacitors and sensing the resultant signal capacitively coupled to its associated receiver electrode to detect a change in the coupled signal when said touch zone is touched.