JPH0423846B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a separate type non-contact switch in which a transmitter and a receiver are separated and detect passage of an object between them.

Conventional technology and its problems Non-contact switches that detect objects using light or ultrasonic waves include reflection-type or groove-type non-contact switches in which a transmitting part and a receiving part are integrally formed, and contactless switches in which a transmitting part and a receiving part are integrally formed. There is a separation type non-contact switch, such as a transmission type, in which the parts are arranged opposite to each other across the object detection position.
In a non-contact switch with an integrated transmitting and receiving section, the transmitting section is driven in pulses to remove the noise components that are normally superimposed on the received signal, and the receiving section is synchronized with the transmitting section to obtain a signal corresponding to the pulse wave. A synchronization method is used that extracts only the received signal components. However, in a separate type non-contact switch, the transmitting section and the receiving section are placed separately, so if a synchronization method is used, it is necessary to install a synchronization signal cable between the transmitting and receiving sections, making the structure complicated. There is a problem with that. Therefore, in many cases, an asynchronous type is used, but the asynchronous type is easily affected by noise, and countermeasures such as slowing down the response time of the receiving section are taken to eliminate this effect as much as possible. In such cases, there was a problem that the switch could not respond as quickly as an integrated non-contact switch, resulting in a delay in object detection.

Purpose of the Invention The present invention solves the problems of such a separate type non-contact switch, and the purpose of the present invention is to generate a synchronization signal based on a transmitted signal on the receiver side without using a synchronization signal cable, and to perform synchronization. The object of the present invention is to provide a non-contact switch that can be operated as a conventional switch, and in particular, to provide a non-contact switch that can measure the period of a transmitted signal without error when the power is turned on.

Structure and Effects of the Invention The present invention includes a receiving element that receives a pulse-driven signal at a predetermined period, and a period within a predetermined range of the received signal obtained from the receiving element after a predetermined time has elapsed after turning on the power. , a start period measuring means that determines a start measurement period when a signal having substantially the same period as the signal of the period is successively received; and a reception signal obtained from the receiving element at predetermined time intervals after the period is measured by the start period measurement means. an intermittent period measuring means for measuring the period of the period, a synchronizing signal generating means for generating a synchronizing signal having the latest period measured by the starting period measuring means and the intermittent period measuring means, and a synchronizing signal generated by the synchronizing signal generating means. The device is characterized by comprising an output means for detecting the reception output of the element.

According to the present invention having such characteristics, there is provided a non-contact switch that does not require transmitting a synchronization signal from the transmitter to the receiver, and is less susceptible to noise and does not malfunction in the same way as when transmitting a synchronization signal. It is possible to obtain Furthermore, when the power is turned on, a cycle within a predetermined range stored in advance is set as the measurement cycle, and only when a reception signal of substantially the same cycle is subsequently received, the measurement cycle is set as the measurement cycle.
Since the same synchronizing signal is generated thereafter, it is possible to accurately measure the period even when the power is turned on. In addition, the receiving section generates a synchronization signal based on the received signal, but the synchronization signal is updated at predetermined intervals and replaced with the previously measured periodic data, so the transmission pulse may be affected by changes in temperature, etc. It becomes possible to follow fluctuations in the period, and it becomes possible to obtain a stable synchronization signal.

DESCRIPTION OF EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of a non-contact switch according to the present invention. If this embodiment is a transmission type photoelectric switch, the light projecting section is provided with a light projecting element 1 such as a light emitting diode and a light projecting circuit 2 that drives the light projecting element 1 in a pulsed manner. A light receiving section is provided at a predetermined distance from the light projecting section. A light-receiving element 3 such as a phototransistor or a photodiode is provided on the front surface of the light-receiving section and receives light from a light-emitting element and converts it into an electrical signal, and its output is given to a light-receiving circuit 4. The light-receiving circuit 4 amplifies the light-receiving signal obtained by the light-receiving element 3, and its output is given to a comparator 6 via a coupling capacitor 5 that blocks direct current. The comparator 6 discriminates the received light signal using a predetermined threshold level and shapes the received light signal into a square wave signal, and its output is given to the synchronization signal generator 7 and gate circuit 8 according to the present invention. The synchronization signal generation section 7 has a microprocessing unit (hereinafter referred to as MPU) 9 and a memory 10 for storing its arithmetic processing procedures and temporary data. and is given to MPU9. Synchronization signal generator 7
It also has a clock generator 13 for driving the MPU 9, and a counter 14 for counting the clock and measuring the cycle of pulses obtained from the light receiving circuit 4. The synchronization signal generator 7 generates a pseudo synchronization signal by setting the period of the pulse included in the received light signal, as will be described later.
A synchronization signal output generated by the MPU 9 is given to the gate circuit 8 via the I/O port 12. The gate circuit 8 provides the output circuit 15 with the AND of the synchronization signal and the light reception signal provided by the comparator 6. The output circuit 15 outputs an object detection signal only when a predetermined number of output pulses are given from the gate circuit 8.

FIG. 2 is a diagram showing a memory map of the memory 10. In this figure, a fixed storage area such as a read-only memory has a program area that stores the arithmetic processing procedures of the MPU 9, and the period of the signal given from the light emitter varies depending on changes over time, surrounding temperature, voltage, etc. , its minimum value T01, maximum value
Since T02 and the period once measured are thought to gradually fluctuate by a minute amount of time due to temperature changes, etc., it is stored in the storage area of the deviation ΔT corresponding to the fluctuation time. Further, in a rewritable storage area, the time of 1/2 of the signal width of the synchronizing signal generated by the synchronizing signal generating section 7 is stored as ΔT', and the measured period Ti and the range used for measuring the period are determined. An area for storing measurement start time Ts and measurement end time Te, a measurement synchronization signal time TT area for determining synchronization signal time during measurement, and a synchronization signal counter N area are provided.

Next, the operation of this embodiment will be explained with reference to a flowchart and waveform diagram. Numbers indicated using lead lines in the flowchart indicate operational steps or subroutines of the MPU 9. FIG. 3 is a flowchart showing the processing of the MPU 9 after the start of operation, and FIGS. 4 and 5 are waveform diagrams showing waveforms of various parts after power is turned on. In these figures, when the operation starts, the routine 20 is first executed.
In this step, the initial processing of the MPU 9, that is, the definition of input/output of the I/O ports 11 and 12, the setting of the program counter in the MPU 9, the setting of the stack pointer, etc., is performed, and when the reset time for this ends, the process proceeds to step 21. Then, it is checked whether an input signal can be obtained from the comparator 6 via the I/O port 11. As mentioned above, the light emitting circuit 2 drives the light emitting element 1 in a pulsed manner, and when the light emitting element 1 and the light receiving element 3 are installed with their optical axes aligned, there must be an object blocking the gap between them. For example, a light-receiving signal is obtained by the light-receiving element 3, and the light-receiving signal is amplified by the light-receiving circuit 4 and converted into a square wave signal by the comparator 6, as shown in FIGS. 4b and 4c. Therefore, an input signal is given to the MPU 9 based on the light reception signal. As shown in FIG. 4c, after the reset time has elapsed, if there is an input signal at time t1, the process proceeds to step 22 and the counter 14 starts counting the clock signal of the clock generator 13. After the counter 14 starts counting in step 23, it waits for the elapse of the minimum value T01 of the expected period stored in the memory 10, and when the time T01 has elapsed, the comparator 6 further detects the I/O
It is checked whether an input is given through the O port 11 and whether the count value of the counter 14 has reached the maximum value T02 of the expected period (steps 24, 25). If no input is obtained even when the period exceeds the maximum value T02, it is considered that an object has passed between the light emitter element 1 and the light receiver element 3 and is blocking the light, so return to step 21 and repeat the same process. is repeated, and if an input is given from comparator 6 at time t2 before reaching the maximum period value T02, step
24, the process advances to step 26, and the count value T11 of the counter 14 at that time is stored in the memory 1 as the measured period.
Write in measurement period area T of 0. and step
At 27, the counter 14 is reset again to start counting the period, and the memorized measurement period is
The value obtained by subtracting the minute deviation ΔT from T11, and the deviation ΔT
The added values are stored in the memory 10 as the measurement start time Ts and the measurement end time Te of each cycle (steps 28 and 29). Then, the process proceeds to step 30, and it is checked whether the count value of the counter 14 has reached the value of the measurement start time Ts. When the measurement start time Ts has been reached, the process advances to steps 31 and 32 to wait for an input from the comparator 6, and perform cycle measurement again based on the output of the comparator 6. The reason for continuously measuring the period in this way is that if the period measured when the power is turned on is incorrect, an incorrect synchronization signal will be output in all subsequent operations, and normal operation cannot be expected. This is because it is necessary to measure the period. and counter 14
The time it takes for the count value to reach the measurement end time Te
If an input is given to t3 from the comparator 6, the process proceeds to step 33, where the count value T12 at that time is written in the measurement period area T as the period measured after the power is turned on. Then, in step 34, the counter 14 is reset again to start counting, and in step 35,
36, measure the cycle measurement start time Ts and measurement end time Te in the same way. And step 37
The program proceeds to step 1, and sets the synchronizing signal counter N, which is a software counter that determines the pulse interval for measuring the period, to 0. Furthermore, in step 38, it is checked whether the counted value of the counter 14 becomes Ti (T12 in the first loop), and if it becomes Ti, the counter 14 is reset and counting starts again (step 39).
Outputs synchronization pulse. Assuming that the output circuit 15 is triggered by the falling edge of the comparator output 6, the synchronization pulse is made to form an output pulse that includes the falling position, and the pulse is sent to the gate circuit via the I/O port 12. Give to 8. When this synchronizing pulse is generated in step 40, the process proceeds to step 41, where the synchronous signal counting counter N is incremented, and the process proceeds to step 42, where it is checked whether the synchronous signal counting counter N reaches a predetermined value, for example, 7. If this is not the predetermined value, return to step 38 and repeat the same process.
A pseudo synchronization signal is generated from the synchronization signal generator 7. Then, the synchronization signal count counter N is the set value,
For example, if it is 7, the routine goes to routine 43 and the period of the light reception signal obtained from the light projection circuit 2 is measured again.

FIG. 5 is a waveform diagram when noise is superimposed on the received signal at the time of measuring the first period from steps 21 to 36. As shown in c in this figure, after the input is detected in step 21 at time t4, counting is started, and after a period of time has reached the minimum value T01, at time t5 while waiting for the end of the cycle in steps 24 and 25, the light receiving circuit When the comparator 6 outputs an output due to the noise from 4, the count value T13 at that time is written into the measurement period area T as the measurement period (step 26). Then, in steps 28 and 29, the period measurement start time is determined based on this measurement period T13.
Ts and the measurement end time Te are calculated, and when the measurement start time Ts has elapsed, the process proceeds to steps 31 and 32 to check whether the next periodic signal is given by the comparator. However, in this case, the measurement start time Ts and measurement end time Te are calculated based on the incorrect cycle T13 measured due to noise, so the cycle measurement is detected in the loop of steps 31 and 32. It is determined by the comparator 6 that no input is given during the time period. Therefore, in this case, the process returns to step 21 via step 32, and period measurement is restarted from the beginning. If there is an input at time t6, the counter 14 starts counting from that point (step 22), and calculates the minimum expected period.
The period T14 obtained between T01 and the maximum value T02 is written in the measurement period area T. Assuming that the measurement is started by the correct output from the comparator at time t7, the measurement start time Ts and measurement end time Te are calculated in steps 28 and 29 based on the measured period, so Ts , Te, unless the light is blocked by an object, an output is given from the comparator 6. Therefore, in that case, the process advances to step 33 via step 31, and the period measurement value T15 at the time t8 is written in the measurement period area T as the measured period. Similarly, after time t8, a pseudo synchronization signal is generated in the loop of steps 37-43.

By the way, the period measured at power-on will also change slightly over time due to voltage fluctuations and temperature changes in the projector. Therefore, the cycle is remeasured at predetermined time intervals to generate a synchronization signal with the correct cycle.

FIG. 6 is a flowchart showing this period measurement routine 43, and FIG. 7 is a waveform diagram showing waveforms of various parts at that time. In these figures the time
When this routine is started from t10, first in step 50, the sum of the deviation ΔT and the time ΔT' which is 1/2 of the synchronizing signal width when a normal synchronizing signal is generated is calculated and stored as the measuring synchronizing signal time TT. Then, in step 51, the count value of the counter 14 is the measured value T of the period already stored in the memory 10 in advance.
(for example, let this value be To). When this reaches To at time t11, the process proceeds to step 52, where the counter 14 is reset and counting starts again, and at the same time, at step 53, the synchronizing signal output is set to the "H" level. Then, in steps 54 and 55, it is checked whether the output of the comparator 6 falls and whether the count value of the counter 14 reaches the measurement synchronization signal time TT. If an output is obtained from the comparator 6 first, it means that an optical signal has been given from the light emitter during the synchronization signal generation time as shown in FIGS. 7b and 7c. Therefore, the count of the counter 14 at time t12 At the same time as restarting (step 56), after waiting for a predetermined minute time T' in step 57,
As shown in FIG. 7c, the synchronous output is set to L level in step 58, and the process proceeds to step 59, where it is checked whether the counter value is equal to the measurement start time Ts. When this reaches the measurement start time Ts at time t13, the synchronous output is set to "H" (step 60).
Next, the process proceeds to steps 61 and 62, and it is checked whether there is an input from the comparator 6 before the count value of the counter 14 reaches the measurement end time Te. As shown in FIG. 7b, if there is an input from the comparator 6, the count value of the counter 14 at time t14 is stored in the memory 10 as the period measurement value T1, and
The counter 14 is reset and counting starts again (steps 63 and 64). Then, in steps 65 and 66, after a predetermined waiting time T', the synchronization signal output is lowered to the "L" level, new measurement start time Ts and measurement end time Te are determined (steps 67 and 68), and the process proceeds to step 69 where the counter is started. Check whether the value becomes T-ΔT'. This is the end time of the measured period
This is to determine the timing for measuring the cycle of the next period based on t14. and time t15
When this time is reached, the process proceeds to step 70, where the counter 14 is reset and counting is started again, and a synchronizing pulse is output as shown in FIG. 7c, thereby terminating this subroutine. and step
Returning to step 37, the synchronizing signal counter N is set to 0, and the process advances to step 38. Then, as shown in FIG. 7a, the counter value is the period measurement value measured in routine 43.
When T1 is reached, the counter 14 is reset and counting starts again, and at step 40, the counter 14 is counted again.
As shown in Figure c, a synchronizing signal pulse is generated and a period measuring counter N is incremented. Thereafter, in the same manner, the loop of steps 38 to 42 is repeated until the period measurement counter N reaches 7 to generate a pseudo synchronization signal every period T1, and the AND of the synchronization signal shown in FIG. 7c and the output of the comparator 6 is performed. A signal is given to the output circuit 15. and in step 42
When becomes 7, the process proceeds to the period measurement routine 43, which measures the period T2 at the next measurement time as shown in FIG. 6c, and thereafter generates a pseudo synchronization signal using the period T2 let

FIG. 8 is a waveform diagram showing the operation when the light given from the light projecting element 1 is blocked by an object and is no longer received by the light receiving element 3. If the cycle measurement routine shown in FIG. 6 is entered at measurement time t20, then at time t21 when the count value of the counter 14 reaches the previous cycle, for example T1, the counter 14
is reset and counting starts again (step 52). After outputting the synchronization signal in step 53, the output from the comparator is awaited in the loop of steps 54 and 55, but since the light emitting signal is not received and no output is given from the comparator, the count value of the counter 14 is signal time
When TT is reached, the process passes through step 55 and proceeds to step 72. In step 72, the synchronizing signal output is set to the "L" level at time t22, and the process proceeds to step 73, where the measurement periodic signal time TT is reset to a time twice the deviation ΔT. Then, the process returns to step 51 and the same process is repeated. When the counter value reaches the previous cycle T1 in step 51, the process proceeds to step 52, where counting is repeated and a synchronizing signal is output. In this way, the loop of steps 51 to 73 is repeated, and a synchronization signal is output as shown in Figure 8b for each cycle T1 that has already been measured, and during this time, the comparator output to start measurement is confirmed. .

FIG. 9 is a diagram showing the output of the comparator 6 and the waveforms of the synchronization signal when the comparator output is applied only at the start of measurement. In this figure, the measurement time
Assuming that the period measurement routine shown in FIG. 4 is entered at t30, it is checked in step 51 via step 50 whether the period T4 which has already been measured at that time has been reached, and further the synchronization is performed in steps 54 and 55. It is checked whether an output is given from the comparator 6 within the signal time. If there is a comparator output, the synchronization signal at the measurement start point is terminated at time t31 in steps 56 to 60 in the same way as the period measurement start process explained in FIG. Generates the next synchronization signal. And step 61,
At step 62, it is checked whether the comparator output at the end of the cycle measurement is obtained. At this time, if no output is obtained even when the count value reaches the measurement end time Te, the process proceeds to step 74 via step 62 at time t34, and the counter 14 starts counting. Then, in step 75, the synchronization signal output is set to L.
level, the process proceeds to step 76, where the measurement periodic signal time TT is set to twice the deviation ΔT, and in step 77, the count value of the counter 14 is T-
Wait until it reaches 2ΔT. In this case the time
It is necessary to perform the measurement again since no output was given from the comparator 6 between t33 and t34. Therefore, when the value of the counter 14 reaches the predetermined value in step 77, the process returns to step 52 and the process is restarted from the point of time when the measurement was started. In this way, if the comparator output is obtained during the synchronization signal output time of the measurement start and measurement end, the period is measured as a correct measurement period, and in other cases, the same process is repeated until these are confirmed. Once the period has been measured, the period measurement routine 43 is terminated and the process returns to the main routine shown in FIG.

Next, in FIG. 10, stray light is superimposed on the light receiving element 3,
The light receiving circuit 4 is a waveform diagram showing the operation when outputting a light receiving signal containing noise. Figure 10a
If noise is superimposed between times t71 and t81 as shown in FIG. 2, the comparator 6 similarly outputs a shaped signal containing noise. However, the synchronization signal generator 7
Since the synchronizing signal generates a pulse with a time width of 2ΔT' in which the light reception signal should be applied, even if noise is applied at a time other than this time period, the gate circuit 8 will not obtain an AND signal. No output is transmitted to the output circuit 15. Note that if noise is added between the output pulses of the synchronization signal, the period is measured by regarding the noise as the original signal, resulting in a deviation in the period measurement. However, since this deviation is within the range of the predetermined deviation ΔT, even if a synchronization signal is generated based on an incorrectly measured period, it can be processed as a correct synchronization signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a non-contact switch according to the present invention, FIG. 2 is a memory map of the memory 10, FIG. 3 is a flowchart showing synchronization signal generation processing of the non-contact switch according to the present invention, and FIG.
Figure 5 is a waveform diagram showing the waveforms of each part when measuring the cycle at power-on, Figure 6 is a flowchart showing the cycle measurement routine, and Figures 7, 8, and 9 are for measuring the cycle. FIG. 10 is a waveform diagram showing the waveforms of each part when noise is superimposed on the received light signal. 1... Light emitting element, 2... Light emitting circuit, 3... Light receiving element, 4... Light receiving circuit, 6... Comparator, 7
...Synchronization signal generation section, 8...Gate circuit, 9...
MPU, 10...Memory, 14...Counter, 1
5...Output circuit.

Claims (1)

[Claims] 1. A receiving element that receives a pulse-driven signal at a predetermined period; and after a predetermined time elapses after power is turned on, a period within a predetermined range of the received signal obtained from the receiving element is measured; , a start period measuring means that determines a start measurement period when a signal having substantially the same period as the signal of the period is successively received; and after the period is measured by the start period measuring means, the period is obtained from the receiving element at predetermined intervals. intermittent period measuring means for measuring the period of the received signal; synchronizing signal generating means for generating a synchronizing signal having the latest period measured by the starting period measuring means and the intermittent period measuring means; and synchronizing signal generating means generated by the synchronizing signal generating means. A non-contact switch comprising: output means for detecting the reception output of the reception element using a synchronization signal. 2. The non-contact switch according to claim 1, wherein the receiving element is a light receiving element. 3. The non-contact switch according to claim 1, wherein the receiving element is an ultrasonic receiving element.