Boots – shoes – and leggings
Patent
1989-03-20
1991-05-28
Teska, Kevin J.
Boots, shoes, and leggings
307231, 324 76R, 364487, H03K 522, G06F 1520
Patent
active
050199951
DESCRIPTION:
BRIEF SUMMARY
D E S C R I P T I 0 N
1. Technical Field
The present invention relates to an input signal discrimination method for discriminating an AC input signal by a PLC (programmable logic controller) or the like, and more particularly to an input signal discrimination method for discriminating the state of an AC input signal by counting pulses.
2. Background Art
FIG. 4 shows an input circuit conventionally used to discriminate an AC input signal by a PLC or the like. In the FIG., 1 represents an AC input signal, 10 represents an input circuit, and 20 represents a PLC for processing the input signal.
The input circuit 10 includes a rectifier circuit 11 for carrying out a full-wave rectification of the input signal, a resistor R and a capacitor C for smoothing the signal, and a photocoupler 12 to which the smoothed signal is supplied, to thereby separate a DC output from the AC input signal 1. A resistor R1, in cooperation with the resistor R, divides the voltage of the AC input signal 1 to lower the output level. The PLC discriminates the state, and carries out a sequence processing, of the AC input signal 1, based on the signal from the photocoupler 12.
With this circuit configuration, however, the output of the input circuit 10 must be a ripple-free signal, and therefore, the time constant R1.multidot.C of the circuit must be large. As a result, the response time of the input circuit 10 is prolonged and it is difficult to obtain a value shorter than three cycles of the alternating current of the AC input signal.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an input signal discrimination method which solves the above-mentioned problem and in which the state of an AC input signal is discriminated by counting pulses.
To solve the above problem, the present invention provides an input signal discrimination method of discriminating an AC input signal. The method includes a step of carrying out a pulse count in a time for which the AC input signal remains above a predetermined threshold level and a time for which the AC input signal remains below the predetermined threshold level. Another step includes deciding that the AC input signal is on by counting the number of pulses the AC input signal remains above the predetermined threshold level and determines that the number of pulses counted is larger than a previously calculated number of pulses. The method also includes deciding that the AC input signal is off when the number of pulses counted while the AC input signal remains below the predetermined threshold level is larger than the previously calculated number of pulses.
When the AC input signal is on, the signal level remains higher than the threshold level for a predetermined time, and therefore, this high-level time is discriminated by the number of pulses counted to discriminate the signal on state.
Alternatively, when the AC input signal is off, the signal level remains lower than the threshold level for a predetermined time, and therefore, this low-level time is discriminated by the number of pulses counted to discriminate the signal off state.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating an embodiment of the present invention;
FIG. 2 is a timing chart for illustrating the embodiment of the invention;
FIG. 3 is a flowchart illustrating the embodiment of the invention; and
FIG. 4 is a diagram showing an example of conventional prior art input circuit.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating an embodiment of the present invention. In the FIG., 1 denotes an AC input signal, the on or off state of which is determined by the effective value thereof, and 10 represents an input circuit which receives the AC input signal 1 and outputs a DC signal. The input circuit 10 includes resistors R and R1 which carry out a voltage division of the input signal and apply the divided voltage to a photocoupler 13. The photocoupler 13 include
REFERENCES:
patent: 4054834 (1977-10-01), Boirat et al.
patent: 4063121 (1977-12-01), Bartlett
patent: 4208627 (1980-06-01), Ebert, Jr.
patent: 4475086 (1984-10-01), Allen
Saito Yoshiyuki
Sato Jun-ichi
Fanuc Ltd.
Teska Kevin J.
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