CN215415624U - Detection circuit of capacitive sensor - Google Patents
Detection circuit of capacitive sensor Download PDFInfo
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- CN215415624U CN215415624U CN202121881499.3U CN202121881499U CN215415624U CN 215415624 U CN215415624 U CN 215415624U CN 202121881499 U CN202121881499 U CN 202121881499U CN 215415624 U CN215415624 U CN 215415624U
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Abstract
The utility model discloses a detection circuit of a capacitive sensor, belonging to the technical field of sensor detection, wherein the detection circuit comprises a power supply cathode GND, a power supply anode VCC, a time base chip LMC555, a resistor R1, a capacitor C1 and a measured capacitor CX; the power supply cathode GND comprises a first power supply cathode GND, a second power supply cathode GND and a third power supply cathode GND. The detection circuit of the utility model is not influenced by the power supply voltage, can keep good precision within a certain voltage range, and is more accurate than the existing capacitance detection circuit.
Description
[ technical field ] A method for producing a semiconductor device
The utility model belongs to the technical field of sensor detection, and relates to a detection circuit of a capacitive sensor.
[ background of the utility model ]
The capacitance type sensor is a sensor which is used more at present, changes of liquid level are described through capacitance continuous change values, the defect that a traditional magnetic turning plate cannot measure continuously can be overcome, and meanwhile, a single chip microcomputer module is required to have the capacity of measuring a tiny capacitance value.
Most of the existing capacitor detection circuits are based on the charge and discharge of capacitors, the voltage for starting the charge, the end voltage and the charge time are collected by an analog-to-digital conversion chip, and the measured capacitor is calculated according to a capacitor charge and discharge formula, which has several defects: (1) ADCs or voltage comparators with high precision are required; (2) in a battery powered scenario, if power supply degradation occurs, the measured value may become larger.
[ Utility model ] content
The utility model provides a detection circuit of a capacitive sensor, which aims to solve the problems that the existing capacitance detection circuit can detect the measured capacitance only by a high-precision ADC or a voltage comparator, so that the reduction is high and the like.
In order to solve the technical problems, the utility model adopts the following technical scheme.
A detection circuit of a capacitive sensor comprises a power supply cathode GND, a power supply anode VCC, a time base chip LMC555, a resistor R1, a capacitor C1 and a measured capacitor CX; the power supply cathode GND comprises a first power supply cathode GND, a second power supply cathode GND and a third power supply cathode GND; the negative pole GND of the first power supply is connected with an eighth pin GND of the time base chip LMC 555; a first pin V + of the time-base chip LMC555 is connected with a power supply anode VCC and one end of a capacitor C1; the other end of the capacitor C1 is connected with the cathode GND of the second power supply; a seventh pin of the time base chip LMC555 is connected with one end of the capacitor CX to be detected; the other end of the capacitor CX to be detected is connected with a third power supply cathode GND; the sixth pin of the time base chip LMC555 is connected with one end of the resistor R1; the other end of the resistor R1 is connected with the capacitor CX to be tested, the third pin of the time base chip LMC555 and the seventh pin of the time base chip LMC 555.
Preferably, the voltage of the power supply cathode GND is 0V.
Preferably, the voltage of the power supply anode VCC is 2.5-5.5V.
Preferably, the time base chip LMC555 comprises 8 pins.
Preferably, the resistor R1 is 10K.
Preferably, the resistor R1 is packaged with 0603.
Preferably, the capacitance C1 is 100 nF.
Preferably, the capacitor C1 is packaged in 0603.
Compared with the existing capacitance detection circuit, the detection circuit of the utility model has the following advantages:
(1) the detection circuit can detect the measured capacitor without a high-precision ADC or a voltage comparator, so that the cost can be greatly reduced;
(2) the detection circuit of the utility model is not influenced by the power supply voltage, can keep good precision within a certain voltage range, and is more accurate than the existing capacitance detection circuit.
[ description of the drawings ]
Fig. 1 is a schematic diagram of a detection circuit of the capacitive sensor according to the present invention.
[ detailed description ] embodiments
The present invention will be described in further detail with reference to the following detailed description and accompanying drawings. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the utility model or its application.
Examples
Referring to fig. 1, the pin numbers, codes and connection relationships of the time-base chip are shown in the following table:
| pin number | | Connection relation | |
| 1 | V+ | Connected with the anode of the input power supply and connected with a |
|
| 2 | DIS | No need of use, no |
|
| 3 | THR | An input holding pin connected to the positive terminal of the capacitor CX to be measured | |
| 4 | CTL | No need of use, no |
|
| 5 | RST | Reset, no |
|
| 6 | OUT | Frequency capture pin, signal output, connecting |
|
| 7 | TRI | A trigger pin connected to the positive end of the capacitor CX to be measured | |
| 8 | GND | Negative pole connected with input power supply |
From FIG. 1, the component numbers, meanings and specifications are as follows:
as shown in fig. 1, a detection circuit of a capacitive sensor includes a power supply cathode GND, a power supply anode VCC, a time base chip LMC555, a resistor R1, a capacitor C1, and a measured capacitor CX; the power supply cathode GND comprises a first power supply cathode GND, a second power supply cathode GND and a third power supply cathode GND; the negative pole GND of the first power supply is connected with an eighth pin GND of the time base chip LMC 555; a first pin V + of the time-base chip LMC555 is connected with a power supply anode VCC and one end of a capacitor C1; the other end of the capacitor C1 is connected with the cathode GND of the second power supply; a seventh pin TRI of the time-base chip LMC555 is a trigger pin and is connected with one end of the capacitor CX to be detected; the other end of the capacitor CX to be detected is connected with a third power supply cathode GND; a sixth pin OUT of the time base chip LMC555 is a frequency capture pin and is connected with one end of a resistor R1; the other end of the resistor R1 is connected with the capacitor CX to be tested, a third pin of the time base chip LMC555 and a seventh pin of the time base chip LMC 555; the third pin of the time base chip LMC555 is an input holding pin; and the seventh pin of the time base chip LMC555 is a trigger pin.
A detection method of a capacitive sensor comprises the following steps:
firstly, a detection circuit of a capacitive sensor is constructed, and a capacitor CX to be detected and a matched resistor R1 are connected to a trigger pin and a holding pin of a time-base chip LMC555 after forming an oscillation circuit;
secondly, after the time base chip LMC555 is powered on, the power is input into a frequency capturing pin of the singlechip;
thirdly, converting the acquired frequency into a capacitance value;
and fourthly, determining the current capacitance value according to the proportional relation between the initial value and the final value of the capacitance value.
The time base chip LMC555 used by the detection method is a time base chip with low price and low power consumption, a square wave pulse is formed on the sixth pin OUT of the time base chip LMC555 by utilizing the matching of the resistor R1 and the capacitor CX to be detected, after power is supplied to the positive pole VCC of the power supply, a pulse port can output a pulse with a fixed duty ratio of 50%, the amplitude is as high as the positive pole VCC of the power supply, and thus the CX 1/(1.4fR) can be detected, wherein f is the frequency of the output pulse, R is R1, and 10K is selected.
The following data were actually measured:
| capacitance value (pF) | Frequency (kHz) | Capacitance value (pF) | Frequency (kHz) |
| 2.0 | 590 | 820 | 7.1 |
| 2.4 | 582 | 1000 | 6.9 |
| 2.7 | 548 | 1200 | 6.2 |
| 3.0 | 540 | 1500 | 6.0 |
Through determination, the capacitance value has obvious resolution within the whole range of 2-1500 pF (see the following table), and the frequency value can be correctly read by using the timer capture function of a common single chip microcomputer, so that the corresponding capacitance value is calculated.
Through tests, the above table shows that the precision can be kept well within the power supply voltage of 2.5-5.5V of the battery, and the influence of the attenuation of a power supply is avoided.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A detection circuit of a capacitive sensor is characterized by comprising a power supply cathode GND, a power supply anode VCC, a time base chip LMC555, a resistor R1, a capacitor C1 and a measured capacitor CX; the power supply cathode GND comprises a first power supply cathode GND, a second power supply cathode GND and a third power supply cathode GND; the negative pole GND of the first power supply is connected with an eighth pin GND of the time base chip LMC 555; a first pin V + of the time-base chip LMC555 is connected with a power supply anode VCC and one end of a capacitor C1; the other end of the capacitor C1 is connected with the cathode GND of the second power supply; a seventh pin of the time base chip LMC555 is connected with one end of the capacitor CX to be detected; the other end of the capacitor CX to be detected is connected with a third power supply cathode GND; the sixth pin of the time base chip LMC555 is connected with one end of the resistor R1; the other end of the resistor R1 is connected with the capacitor CX to be tested, the third pin of the time base chip LMC555 and the seventh pin of the time base chip LMC 555.
2. The detection circuit of the capacitive sensor as claimed in claim 1, wherein the voltage of the power supply cathode GND is 0V.
3. The detection circuit of the capacitive sensor as claimed in claim 1, wherein the voltage of the positive electrode VCC of the power supply is 2.5-5.5V.
4. The detecting circuit of the capacitive sensor as claimed in claim 1, wherein the time base chip LMC555 comprises 8 pins.
5. The detection circuit of a capacitive sensor according to claim 1, wherein the resistance R1 is 10K.
6. The capacitive sensor sensing circuit of claim 5, wherein said resistor R1 is 0603 packaged.
7. The detection circuit of claim 1, wherein said capacitance C1 is 100 nF.
8. The capacitive sensor sensing circuit of claim 7, wherein said capacitor C1 is 0603 packaged.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121881499.3U CN215415624U (en) | 2021-08-12 | 2021-08-12 | Detection circuit of capacitive sensor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121881499.3U CN215415624U (en) | 2021-08-12 | 2021-08-12 | Detection circuit of capacitive sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113532586A (en) * | 2021-08-12 | 2021-10-22 | 矽朋微电子(无锡)有限公司 | Detection method of capacitive sensor |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113532586A (en) * | 2021-08-12 | 2021-10-22 | 矽朋微电子(无锡)有限公司 | Detection method of capacitive sensor |
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