JPH03242512A - Time sharing driving system for sensor - Google Patents

Abstract

PURPOSE:To obtain a flow pulse only by a gate by adjusting the voltage level at a source terminal of a sensor part corresponding to the output level of the sensor part and driving the sensor part by a sink current or a source current. CONSTITUTION:When a sensor part 1 detects H level, the voltage of an output terminal O of the sensor part 1 becomes H level. At this time, the voltage at a source terminal V<+> is fixed to H level and the voltage at a source terminal V<-> is reduced to L level (GND level) by every short time for every predeter mined cycle, so that the sensor part 1 is driven by the sink current. When the output of the sensor part 1 is turned to L level, the voltage of the source terminal V<-> is fixed to the grounding potential, namely, L level, while the voltage of the source terminal V<+> is increased to H level every short time and every predetermined cycle, so that the sensor part 1 is driven by the source current. As a result, a flow pulse is obtained at the output terminal O.

Description

[Detailed description of the invention] ;Industrial application field] The present invention relates to a time-division driving method for sensors.

: Conventional technology] For example, in a flow meter such as a water meter or gas meter, the rotation of a rotating body that rotates once every time a certain amount of water or gas flows is detected by a sensor such as a magnetic sensor and converted into an electrical signal. By counting the number of electrical signals, the cumulative flow rate (so-called amount of water or gas used) is calculated. A rotating shaft such as an impeller is used as the rotating body, a magnet is attached to this, the magnet is rotated together with the rotating shaft, and a magnetic sensor such as a fixed glue inch or a magnetic resistance element is installed near the rotating magnet. and received an electrical signal.

In this way, when a physical phenomenon such as rotation is converted into an electrical signal by a sensor, the sensor is driven in a time-division manner in order to reduce power consumption of the sensor and prevent exhaustion of the t-source battery.

An example of such time-division driving is shown in FIG.

FIG. 5 shows a reed switch la placed close to a rotating magnet (not shown) and a resistor 1b connected in series to the reed switch la. level, and a driving voltage is applied to the power supply terminal V1 for a short time t every period T, thereby performing so-called time-division driving.

The reed switch 1a is turned on and off during one rotation of the rotating magnet.
Repeat FF twice. Reference numeral 2 denotes a sampling pulse generation circuit which applies an H level drive voltage to the power supply terminal V1 of the sensor unit 1 for a short time t every period T. During other times in the period T, the sampling pulse generation circuit 1
The output of is at L level (GND level) (see FIG. 6C). The short time t is called the pulse width of the sampling pulse. 3 is a latch circuit,
It is composed of a well-known D-FF, and latches the voltage level at the terminal at the rising edge of the sampling pulse applied to the clock terminal CK, and outputs it to the output terminal Q. The voltage level at the terminal is determined by the reed switch 1 as shown in Figure 6C.
When a is ON and a drive voltage is applied to the power supply terminal V+ of the sensor part l, it is at H level, and when the reed switch is OFF or when no drive voltage is applied to power supply terminal V+, it is at L level. be. The 6th diagram is the launch circuit 3
The reed switch 1a is turned ON/OFF by the output of the output terminal Q.
It corresponds to F. By counting the number of output pulses from the output terminal Q, the number of rotations of the rotating magnet can be determined. As mentioned above, the reed switch la repeats ON-OFF twice during one rotation of the rotating magnet, so count the number of times the output of the output terminal Q of the latch circuit 3 is at H level as shown in Figure 6. Then, the count value 〃 becomes the number of revolutions that the rotating magnet rotates. In addition, in FIG. 5, 4 is an inverter.

Further, the waveforms A to D in FIG. 6 are voltage waveforms at points A to D in FIG. 5, respectively.

In the conventional technology shown in FIG.
a, and a sampling output (see Fig. 6C) is generated at the output terminal O in accordance with the rotation of the rotating magnet. sensor 1
It consists of a circuit in which a1, voltage dividing resistors R1 and R2 for generating comparison voltage, and a comparator 1c are connected as shown in the figure.This sensor part 1' is connected in place of the sensor part l in FIG. However, voltage waveforms similar to A to D in FIG. 6 can be obtained.

[Problems to be Solved by the Invention] In the above conventional technology, in order to count the physical phenomena detected by the sensor units 1, 1', for example, the rotation of a rotating magnet, the sampling signal obtained at the output terminal O is first passed through a latch circuit. 3, the pulse is changed to the pulse shown in Figure 6 (this is called a flow rate pulse in a flowmeter), and the flow rate pulse is counted to accumulate the amount of water, gas, etc. used.

Therefore, there is a problem that a latch circuit is required which is more expensive than a gate circuit, and the circuit becomes complicated like a D-FF. Furthermore, when the drive voltage is not applied to the power supply terminal ``'' of the sensor section 11'', if noise enters the clock terminal CK of the latch circuit 3, the current level of the terminal will be increased. There was a problem in that the signal was latched at 3, resulting in a malfunction as shown in Figure 6 (a).
When time-divisionally driving the sensor section 1.1'', t/T is reduced to about 1/200 in order to reduce the average value of drive power, so there is no chance that the latch circuit 83 will be affected by noise. This is extremely high, and the conventional technology has the weakness of being susceptible to noise.This weakness is essentially D-
The reason for this was also due to the use of an FF launch circuit.

In view of the above, the present invention provides an inexpensive, simple, and noise-resistant time-division drive system in which a circuit can be configured to obtain flow rate pulses using only gates without using FFs.

[Means to solve the problem]

In order to achieve the above purpose, in the time division drive method of the present invention, when the sensor section (1, 1') detects the H level, one power terminal of the sensor section (1, 1') ■ By fixing the voltage of "" at H level and lowering the voltage of the other power supply terminal V- to L level for a short period of time every period T, the sensor section is sink-driven, and the sensor section (1, 1' ) output is L
When the level is reached, the voltage of the other power supply terminal V~ of the sensor section (1, P) is fixed at the L level, and the voltage of the one power supply terminal V+ is raised to the H level for a short time every period T. The sensor unit was configured to be source-driven by increasing the power level to .

[Effect]

When the sensor unit detects the H level, in Figure 3,
The voltage at the output terminal ◯ of the sensor section 1 becomes H level, and at this time, the voltage at the power supply terminal V+ is fixed at H level.
Then, the voltage of the power supply terminal ■- is decreased by t for a short time every cycle T.
By lowering the voltage to the ground level (GND level), the sensor section 1 is driven in sync.

During the short period of time between T-t during driving, as indicated by * in the diagram, the voltage at the power supply terminal ■- is at the H level, so during this period the voltages at both power supply terminals ■ and ■ are both H. level, and the voltage at the output terminal O naturally becomes I] level.

When the output of the sensor section changes to L level, it is converted to source drive. In source driving, as shown in FIG. 4, the voltage of the power supply terminal 2 is fixed to the ground (GND) potential. In other words, it is fixed at L level. Then, by raising the voltage of the power supply terminal V+ to the H level G by a short time t every period T, the sensor section 1 is driven as a source. During the driving time t between the TLOs outside the open circuit, the voltage at the power supply terminal V+ is at 1] level, so during this time both power supply terminals V and V+
The voltages at both are at the L level, and the voltage at the output terminal ○ is also at the L level.

As a result, a flow rate pulse is obtained at the output terminal O.

Note that the terms sink drive and source drive are tentative names used in this specification and are not common terms. Further, although the width of the sampling pulse is indicated by the symbol t in FIGS. 3 and 4 for convenience of explanation, the pulse width t does not have to be the same for each sampling pulse.

[Example] In the example shown in Fig. 1, the work is the sensor part, and the reed switch 1
It consists of a series connection of a and a resistor 1b, and power terminals v', v-
and output terminal 0. In addition, lid switch 1a
is placed near a magnet attached to the impeller of a flowmeter (not shown), and is turned ON and OFF twice for each revolution of the impeller. Reference numeral 2 denotes a sampling pulse generating circuit which outputs the sampling pulses Pl+ P2+P3+ . . . shown in FIG. 2A for a short time every period T, as in the case of FIG. 1. Reference numeral 5 denotes an OR gate, 6 an inverter, 7 an inverter, and 8 an AND gate, which are connected as shown in the figure. Therefore, sampling pulse P2
Sink driving is performed until P4 is applied, and source driving is performed until sampling pulse P4 is applied.
A flow pulse is obtained, as shown in the second diagram, 11'. Note that A-D' in Fig. 2 are A-D' in Fig. 1, respectively.
This is the voltage waveform at the point. Note that the sampling pulse p
,, p2. The pulse width t of p, . . . is also l
You don't have to.

In the embodiment shown in FIG. 1, the sensor part shown in FIG. The flow rate pulse shown in ” can be obtained.

5. Effects of the Invention: Since the time-division drive system of the present invention is configured as described above, it is possible to obtain flow rate pulses only by gates using FFs (flip-flops). That is, a flow rate pulse corresponding to ON-OFF of the reed switch 1a can be obtained directly at the output terminal of the sensor section 1 using a gate-only circuit as in the embodiment shown in FIG.

Therefore, it is inexpensive, simple, and has the effect of being resistant to noise because it does not use FF.

[Brief explanation of drawings]

FIG. 1 is an electric circuit according to an embodiment of the present invention, FIG. 2 is a timing chart of FIG. 1, FIGS. 3 and 4 are circuits and drive voltage waveforms explaining sink drive and source drive, respectively, and FIG. 5 6 shows a timing chart of FIG. 5, and FIG. 7 shows an electric circuit of the sensor section. 1.1゛...Sensor part, 2...Sampling pulse generation circuit, 5...OR gate, 6...Hassofa, 7
...Inverter, 8...AND gate

Claims (1)

[Claims] 1. When the sensor section (1, 1') is detecting the H level, fix the voltage of one power supply terminal V^+ of the sensor section (1, 1') to the H level, and turn off the other power supply. The sensor unit is sink-driven by lowering the voltage at the terminal V^- to the L level for a short period of time every cycle T, and when the output of the sensor unit (1, 1') reaches the L level, the sensor unit (1 , 1') by fixing the voltage at the other power supply terminal V^- to the L level and raising the voltage at the one power supply terminal V^+ to the H level for a short time every period T. A time-division drive method for a sensor configured to source-drive the main part.