Control-safe capacitive switch
AssigneePepperl + Fuchs GmbH
InventorsHermann Wieth, Hans-Jurgen Schiefer
Life of this patent
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Abstract
A palm-button control system provides for machinery control with minimized operator hand pressure by use of capacitive switches and reduced susceptibility to radio frequency interference. The system employs first and second capacitive palm-button switches, both of which must be contacted before machinery is activated. Each capacitive palm-button includes a radio frequency sensor which functions to disable machine activation in the presence of a sufficiently strong radio signal. Circuitry for periodically testing the radio frequency sensors provides periodic visual operator feedback indicative of operability of the system. All controls are synchronized or enabled in accordance with a series of digital pulses.
Claims15
A switching system including a first capacitive switch unit, the capacitive switch unit comprising:
- a capacitive sensor terminal;
- a radio frequency sensor terminal disposed proximate to the capacitive sensor terminal;
- sensor means adapted for sensing a first voltage induced within the capacitive sensor terminal by an associated object proximate thereto;
- radio frequency sensor means adapted for sensing a second voltage induced within the radio frequency sensor terminal by a radio frequency;
- and
- a controller including,
- trigger signal generating means for generating a trigger signal in accordance with a sensed first voltage,
- cutoff signal generating means for generating an inhibit signal in accordance with a sensed second voltage, and
- activation means for selectively generating an activate signal in accordance with a trigger signal and a cutoff signal.
In a switching system including a capacitive sensor, a radio frequency sensor, and a controller, a method of selectively enabling an electrically controllable apparatus comprising the steps of:
- (a) generating a first periodic voltage pulse;
- (b) inducing a second periodic voltage pulse into the radio frequency sensor in accordance with the first periodic voltage pulse;
- (c) generating a signal representative of a presence of radio frequency energy;
- (d) sensing a capacitive change in the capacitive sensor terminal by in accordance with an object positioned generally proximate thereto;
- (e) generating a trigger signal in accordance with a sensed capacitive change in the capacitive sensor;
- and
- (f) suppressing the trigger signal in accordance with the signal representative of a presence of radio frequency energy.
A two hand switching mechanism comprising:
- first and second capacitive switching units, each capacitive switching unit including,
- a capacitive sensor terminal;
- a radio frequency sensor terminal disposed proximate to the capacitive sensor terminal;
- sensor means adapted sensing a first voltage induced within the capacitive sensor terminal by an associated object proximate thereto;
- radio frequency sensor means adapted for sensing a second voltage induced within the capacitive sensor terminal by a radio frequency;
- a controller including,
- trigger signal generating means for generating a trigger signal in accordance with a sensed first voltage,
- cutoff signal generating means for generating an inhibit signal in accordance with a sensed second voltage, and
- activation means for selectively generating an activate signal in accordance with a trigger signal and a cutoff signal;
- combining means for combining logically combining activation signals from the first and second capacitive switching units;
- and
- means for generating a system activation signal in accordance with an output of the combining means.
Dependencies are inferred from the claim text.