Abstract:
A high frequency oscillation type proximity switch, comprising: an oscillation circuit having a first resonant frequency; a tank circuit connected in a positive feedback path of the oscillation circuit and including an LC resonant circuit having a second resonant frequency slightly different from the first resonant frequency; and a comparator circuit which discriminates the amplitude of an oscillation output of the oscillating circuit at a predetermined threshold level; the comparator producing a detection output signal when a nonmagnetic metallic object is brought to a certain proximity of a coil included in the LC resonant circuit and a level of the oscillation has thereby changed by a certain amount as a result of a change in the susceptance of the coil. Since the approach of a magnetic object increases the loss of the coil whereas the approach of a nonmagnetic metallic object increases the susceptance of the coil, it is possible to detect magnetic objects alone, nonmagnetic metallic objects alone, or both magnetic objects and nonmagnetic metallic objects alike by appropriately selecting the resonant frequencies of the oscillation circuit, and the tank circuit and the threshold level of the comparator circuit.
Abstract:
Disclosed is a proximity switch which includes an oscillation circuit whose oscillation output is variable depending on the inductance of a coil so that an object in proximity may be detected from the decline in the oscillation output. Further, the oscillation gain of this oscillation circuit is variable according to an input from an external source. Thus, for the purpose of increasing the recovery speed of the oscillation which has dropped as a result of detecting an approaching object, comparison circuits are provided so that upon reduction in the oscillation output of the oscillation circuit a certain signal is applied to the oscillation circuit to increase its oscillation gain. As a result, even when an object in proximity is detected and the oscillation level is maintained at a certain low level so that the oscillation may be resumed quickly when the object has moved away from the proximity switch. By virtue of the increased response speed of the proximity switch, not only its detection capability is improved but also it is usable in an environment where a strong AC magnetic field is present.
Abstract:
Disclosed is a proximity switch which includes a current feedback time oscillator so that an object in proximity may be detected from the decline in the oscillation output. In order to increase the recovery speed of the oscillation which has dropped as a result of detecting an approaching object, in addition to a first comparison circuit for detecting the object from the oscillation output level, a second comparison circuit is provided for varying the feedback current to the oscillation circuit to the end of maintaining the oscillation level at a certain low level even when the object has come sufficiently close to the proximity switch to otherwise completely terminate the oscillation. By virtue of the increased response speed of the proximity switch, it may be used in an environment where a strong AC magnetic field is present.
Abstract:
Disclosed is a power source reset circuit which deactivates a contactless switch for a time interval determined by a delay means so as to prevent any erroneous output from the contactless switch while the output of a power source is unstable immediately after the power source is turned on. The reliability of the delay means is enhanced by the use of a Miller integration circuit which includes a current mirror circuit as a means for amplifying electric current. Furthermore, a switching device may be connected across the capacitor for integration so that the charge in the capacitor may be quickly discharge when the power is turned off, for the purpose of setting the power source reset circuit ready for the subsequent action when the power source is turned on thereafter. This invention is useful in applications where the power source for the contactless switch is frequently turned on and off.
Abstract:
An interrogation responder system composed of a transmitter stationarily mounted in a certain fixed place and a receiver mounted on a mobile object. The receiver on the mobile side starts the operation when a power is supplied to the entire circuit in accordance with a wake-up signal from the transmitter on the fixed side so as to modulate the electromagnetic signal emitted from the transmitter on the fixed side in accordance with a predetermined code and reflect a response. This enables continuing bilateral communication of a command, data and so forth. By starting communication between the transmitter and the receiver by a direct wave of a carrier signal in a microwave band after sensing that the receiver on the mobile side has entered a good communication zone, secure communication is enabled at a sufficient electric field strength.