A circuit structure for a calibrable and adjustable reflective sensor

Abstract

This utility model discloses a circuit structure for a calibrable and adjustable reflective sensor. The circuit includes a reflective photoelectric sensor, a DAC, and a controller. The reflective photoelectric sensor includes a light-emitting diode (LED) and a phototransistor. The positive terminal of the LED is connected to a first VCC terminal, and the collector of the phototransistor is connected to a second VCC terminal. The emitter of the phototransistor is grounded or preset to a low level. The controller is connected between the phototransistor and the DAC. The output voltage terminal of the DAC is connected to the negative terminal of the LED. The controller reads the level state of the phototransistor's level signal detection point and accordingly controls the DAC to output an adjusted level to set the LED current. Thus, by adjusting the LED current using the DAC, the phototransistor characteristic curves of each machine are made consistent during production. Furthermore, for machines sold after the factory, the DAC adjustment can restore the machine to its factory-stable performance.

Description

Technical Field

[0001] This utility model relates to the field of reflective sensors, and in particular to a circuit structure for a calibrable and adjustable reflective sensor. Background Technology

[0002] Reflective sensors are widely used in various fields. For example, card printers utilize many sensors, including reflective sensors. Reflective sensors are commonly used for object detection; the object must possess reflective properties for the sensor to detect it. A typical reflective sensor assembly consists of a light-emitting diode (LED) and a phototransistor.

[0003] Traditional card printers use reflective sensors with fixed LED resistors (single current) and fixed phototransistor bias resistors. To achieve consistent sensor response, reflective sensors require rigorous selection of the sensor itself and stringent design requirements for materials and assembly. Even so, achieving stable and consistent card printer performance is still difficult because: 1. Reflective sensors have electrical tolerances (e.g., LEDs have luminous intensity tolerances, phototransistors have sensing capability tolerances), and the components have dimensional and assembly tolerances. This causes the phototransistor characteristic curve and the bias resistor's operating point to differ, resulting in variations in the sensor's sensing voltage during production, leading to reduced machine stability. 2. After prolonged use, aging of the reflective sensor and components can cause the phototransistor characteristic curve and the bias resistor's operating point to shift, resulting in differences in the sensor's sensing voltage compared to its factory settings. This further reduces printer stability and may even necessitate sensor repair or replacement.

[0004] Combination Figures 10 to 14 As shown: Figure 10 This demonstrates that under normal circumstances, the device under test (DUT) and the reflective sensor should be designed to be parallel and at a fixed distance to maintain consistent and optimal detection functionality. However, in reality, material tolerances, assembly errors, and even user behavior may cause the distance between the DUT and the reflective sensor to increase. Figure 11 As shown, this results in a decrease in reflected light, leading to detection anomalies; as Figure 12 As shown, it is also possible that the object under test and the reflective sensor become non-parallel, resulting in less reflected light and causing detection abnormalities; such as Figure 13 As shown, even if the components and assembly are fine, prolonged use of the machine can lead to issues such as aging of the reflective sensor itself or dust and dirt, causing the LED or phototransistor to degrade and resulting in detection abnormalities. For example... Figure 14As shown, when a reflective sensor may come into contact with an external light source, it may misjudge the external light source as the object being measured, leading to detection anomalies.

[0005] Therefore, a new technical solution needs to be researched to address the above problems. Utility Model Content

[0006] In view of this, the present invention addresses the deficiencies of the existing technology and its main purpose is to provide a circuit structure for a calibrable and adjustable reflective sensor. It uses a DAC to adjust the current of the light-emitting diode, so that the phototransistor characteristic curves of each machine are consistent during production. Furthermore, for machines after the sale, the DAC can be used to adjust the machine to return it to its stable performance at the factory setting.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A circuit structure for a calibrable and adjustable reflective sensor includes a reflective photoelectric sensor, a DAC, and a controller.

[0009] The reflective photoelectric sensor includes a light-emitting diode and a phototransistor. The positive terminal of the light-emitting diode is connected to the first VCC terminal, the collector of the phototransistor is connected to the second VCC terminal, and the emitter of the phototransistor is grounded or preset to a low level.

[0010] The controller is connected between the phototransistor and the DAC. The output voltage terminal of the DAC is connected to the negative terminal of the light-emitting diode. The controller reads the level state of the level signal detection point of the phototransistor and controls the DAC to output the adjusted level accordingly, so as to set the current of the light-emitting diode.

[0011] As a preferred embodiment, the DAC is either the DAC of the controller's original core main chip or an external DAC chip connected to the core main chip.

[0012] As a preferred embodiment, the controller has a digital interface and a GPIO port. The level signal detection point is electrically connected to the GPIO port. The controller reads the state of the GPIO port and controls the DAC to output the Vdac level accordingly through the digital interface.

[0013] As a preferred embodiment, a level follower is added after the DAC, and the level follower is connected between the DAC and the negative terminal of the light-emitting diode.

[0014] As a preferred embodiment, the light-emitting diode is connected in series with a current-limiting resistor, and the positive terminal of the light-emitting diode is connected to the first VCC terminal; the collector or emitter of the phototransistor is connected in series with a bias resistor, and the level signal detection point is set between the bias resistor and the corresponding collector or emitter.

[0015] As a preferred embodiment, the current-limiting resistor is connected in series between the positive terminal of the light-emitting diode and the VCC terminal, and the bias resistor is connected in series between the collector of the phototransistor and the second VCC terminal.

[0016] As a preferred embodiment, the current-limiting resistor is connected in series with the negative terminal of the light-emitting diode, and the bias resistor is connected in series between the collector of the phototransistor and the second VCC terminal.

[0017] As a preferred embodiment, the current-limiting resistor is connected in series between the positive terminal of the light-emitting diode and the first VCC terminal, and the bias resistor is connected in series between the emitter of the phototransistor and the ground terminal.

[0018] As a preferred embodiment, the current-limiting resistor is connected in series with the negative terminal of the light-emitting diode, and the bias resistor is connected in series between the emitter of the phototransistor and the ground terminal.

[0019] Compared with the prior art, this utility model has significant advantages and beneficial effects. Specifically, as can be seen from the above technical solution, it mainly achieves the following through the setting of a reflective photoelectric sensor, a DAC, and a controller. The reflective photoelectric sensor includes a light-emitting diode and a phototransistor. The controller is connected between the phototransistor and the DAC. The output voltage terminal of the DAC is connected to the light-emitting diode, thereby achieving: 1. Adjusting the current of the light-emitting diode using the DAC to ensure that the characteristic curve of the phototransistor of each machine is consistent during production, and that the high and low level responses of the reflective photoelectric sensor of each machine are good, thus achieving the purpose of stable and consistent production; 2. Adjusting the current of the light-emitting diode using the DAC means that even if the reflective photoelectric sensor ages or the mechanical materials age, causing the characteristic curve to differ from the factory setting, it is not necessary to return the machine to the factory to replace the reflective photoelectric sensor. The machine can be directly calibrated and adjusted to return to the stable performance at the factory setting, reducing the manpower and material costs caused by maintenance and improving customer satisfaction. Therefore, during production, it can correct the electrical tolerances, mechanical components, and assembly tolerances of reflective photoelectric sensors. After sales, adjustments can reduce cleaning and maintenance caused by component aging or dust contamination.

[0020] To more clearly illustrate the structural features and effects of this utility model, the following detailed description of this utility model is provided in conjunction with the accompanying drawings and specific embodiments. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of a calibrable and adjustable reflective sensor according to an embodiment of the present invention (without a level follower);

[0022] Figure 2 This is the first basic circuit architecture of the reflective sensor according to an embodiment of the present utility model;

[0023] Figure 3 This is the phototransistor characteristic curve and operating point of the reflective sensor according to an embodiment of this utility model;

[0024] Figure 4 This is a comparison diagram of the characteristic curves of the reflective sensor of this utility model during production and assembly and the calibrated phototransistor with the operating point;

[0025] Figure 5 This is a comparison chart of the characteristic curves and operating points of the phototransistor after prolonged use and after calibration of the reflective sensor according to an embodiment of this utility model.

[0026] Figure 6 This is a circuit structure diagram (with level follower) of a calibrable and adjustable reflective sensor according to an embodiment of the present invention;

[0027] Figure 7 This is the second basic circuit architecture of the reflective sensor according to an embodiment of the present utility model;

[0028] Figure 8 This is the third basic circuit architecture of the reflective sensor according to an embodiment of this utility model;

[0029] Figure 9 This is the fourth basic circuit architecture of the reflective sensor according to an embodiment of this utility model;

[0030] Figure 10 This is a schematic diagram of the state of the object under test and the reflective sensor under ideal conditions;

[0031] Figure 11 This is a schematic diagram showing the state after the distance between the object to be measured and the reflective sensor increases;

[0032] Figure 12 This is a schematic diagram showing a state where the distances between the object to be measured and the reflective sensor are not parallel.

[0033] Figure 13 This is a diagram illustrating a state where the abnormality in detection is caused by fogging or dirt on the reflective sensor itself.

[0034] Figure 14 This is a schematic diagram of a state where a reflective sensor misjudges an external light source as the object being measured, leading to a detection anomaly.

[0035] Figure 15 This is a schematic diagram of the theoretical analysis of the selected bias resistor R2 for the phototransistor. Detailed Implementation

[0036] Please refer to Figures 1 to 9 As shown, it illustrates a specific embodiment of the present utility model.

[0037] In the description of this utility model, it should be noted that the terms "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0038] A circuit structure for a calibrable and adjustable reflective sensor includes a reflective photoelectric sensor, a DAC (digital-to-analog converter), and a controller (which may also refer to a processor or control system); wherein the reflective photoelectric sensor includes a light-emitting diode and a phototransistor, the controller is connected between the phototransistor and the DAC, and the output voltage terminal of the DAC is connected to the light-emitting diode.

[0039] Specifically:

[0040] The light-emitting diode (LED) is connected in series with a current-limiting resistor, and its positive terminal is connected to the first VCC terminal. The phototransistor is a light-sensitive semiconductor device with amplifying current capability. Based on the structure of a conventional transistor (with a base, collector, and emitter), its collector is connected to the second VCC terminal, but the base region is designed as a light-receiving window, capable of converting light signals into electrical signals and amplifying them. When light shines on the base region, electron-hole pairs are generated. These charge carriers move under the influence of the electric field between the base and collector, causing a change in the collector current. Due to the current amplification characteristics of the phototransistor, even weak light signals can produce a significant current change at the collector, thereby achieving efficient photoelectric conversion and signal amplification. In this embodiment, an NPN type phototransistor is used. A bias resistor is connected in series with the collector or emitter of the phototransistor, and a level signal detection point is set between the bias resistor and the corresponding collector or emitter.

[0041] The DAC is a device that converts digital signals into analog signals. The output level of the DAC is connected to the negative terminal of the light-emitting diode (LED). The DAC receives digital signals from the controller and converts them into an analog level Vdac, where Vdac is the DAC's output level. It should be noted that the DAC can be the DAC built into the controller's core chip or an external DAC chip connected to the core chip.

[0042] The controller has a digital interface and GPIO ports (i.e., general purpose input / output interfaces). Internally, it is configured for input mode. The level signal detection point is electrically connected to the GPIO port, for example, via a level signal line. The controller reads the status of the GPIO port (also referring to the GPIO pin), that is, it monitors the level status of the level signal detection point in real time, and accordingly controls the DAC output to adjust the appropriate Vdac level through the digital interface. This sets the current of the LED to ensure it has a corresponding luminous intensity (brightness), ensuring a good V (signal) level response, thereby achieving stable and consistent production.

[0043] like Figure 1 As shown, a current-limiting resistor R1 is connected in series between the positive terminal of the light-emitting diode and the VCC terminal, which limits the maximum current of the light-emitting diode. A bias resistor R2 is connected in series between the collector of the phototransistor and the second VCC terminal, which determines the detection sensitivity of the phototransistor.

[0044] like Figure 2 and Figure 3 As shown, when a reflective object is detected, the smaller R1 is, the larger Ib is, the stronger the light, the larger Ic is, and the smaller V(signal) is.

[0045] During production and assembly, when a suitable current-limiting resistor R1 for the LED is selected (below the maximum current specification value of the LED) and a suitable bias resistor R2 for the phototransistor is selected, the value of V(signal) will not change significantly due to external light sources. This is because when the reflective sensor comes into contact with an external light source, the phototransistor on the reflective sensor may be too sensitive or the bias resistor may be too large, causing the reflective sensor to misjudge the external light source as the object under test, resulting in detection abnormalities. Furthermore, when R1 is fixed, if a larger R2 is selected during the design, the high and low levels of V(signal) will perform well under normal conditions. However, when affected by an external light source, even without reflection, V(signal) will still exhibit signal degradation due to light leakage, leading to system misjudgment. With a fixed R1, if a smaller R2 is selected during design, the high and low levels of V(signal) will perform well under normal conditions. However, with material or assembly tolerances, the reflection angle and distance may increase, resulting in less reflected light and a deteriorated V(signal) signal, causing misjudgment. Regarding how to select a suitable bias resistor R2 for the phototransistor, this embodiment provides a practical solution: such as... Figure 15 As shown, the general standard for judging digital logic levels is that a value greater than 0.7Vcc is a high level, less than 0.3Vcc is a low level, and the range between 0.3Vcc and 0.7Vcc is an unstable level. If R2 is too large, V(signal) will deviate to an unstable level due to external interference light sources. In the initial design, a large fixed value is given to R2, and an interference light source (fluorescent lamp, sunlight, or other light source) is manufactured according to the actual design. Then, V(signal value) is measured. If the deviation is large, R2 is reduced until V(signal) is very close to Vcc even when there is external light interference. This R2 is the appropriate value. Usually, DACs have more than 8 bits. If an 8-bit DAC is used, the LED can have up to 256 levels of current adjustment, i.e., [(Vcc-Vled)-Vdac] / R1. Vdac can be any value from 0 to Vdd (Vdd depends on the DAC level). In the case of sensors with electrical specification tolerances and mechanical material and assembly tolerances, if the performance is as follows... Figure 4 As shown, the current of the light-emitting diode can be increased through the DAC, which increases the reflected light and Ic, so that the reflective sensor falls within a stable and good characteristic curve region, thereby achieving the purpose of consistent machine production performance and machine stability.

[0046] After prolonged use since the machine's manufacture, component aging and dust accumulation may cause the LED's intensity or sensitivity to decrease, resulting in a smaller Ic, a worse characteristic curve, and a lower V (signal) level, leading to system misjudgments, such as... Figure 5As shown, at this time, the DAC can be used to increase the current of the light-emitting diode, calibrate the sensor to be equivalent to the factory value, and enable the machine to work stably.

[0047] like Figure 6 As shown, a level follower (also known as a unity-gain amplifier, buffer amplifier, or isolation amplifier) ​​can be added after the DAC. Its output level directly follows the input level, meaning the output level is the same as the input level. The level follower is connected between the DAC and the negative terminal of the LED. Its purpose is to improve the driving current capability. For the original core chip of the controller, the current driving capability of the core chip is generally limited. Adding a level follower can improve the current driving capability. If the reflective sensor used requires relatively high power, adding a level follower can protect the core chip and ensure sufficient current thrust. If the sensor used has very low power, the level follower may not be necessary.

[0048] like Figures 7 to 9 As shown, the basic circuit architecture of a reflective photoelectric sensor is not limited to... Figure 1 The structure shown can also be applied to any of the other three basic circuit architectures for reflective photoelectric sensors.

[0049] exist Figure 7 In this configuration, the current-limiting resistor R3 is connected in series with the negative terminal of the light-emitting diode, and the bias resistor R4 is connected in series between the collector of the phototransistor and the second VCC terminal.

[0050] exist Figure 8 In this configuration, the current-limiting resistor R5 is connected in series between the positive terminal of the light-emitting diode and the first VCC terminal, and the bias resistor R6 is connected in series between the emitter of the phototransistor and the ground terminal.

[0051] exist Figure 9 In this configuration, the current-limiting resistor R7 is connected in series with the negative terminal of the light-emitting diode, and the bias resistor R8 is connected in series between the emitter of the phototransistor and the ground terminal.

[0052] Generally, the basic circuit architecture of a typical reflective sensor mainly consists of the four types mentioned above. When an object approaches the sensor, it reflects light from a light-emitting diode (LED), and a phototransistor receives the reflected light, thus achieving detection. The only difference between these four basic reflective sensor circuit architectures is whether the signal is high or low when an object is detected; this does not affect the judgment. Therefore, a circuit structure for a calibrable reflective sensor can be used in any of the four basic reflective sensor circuit architectures mentioned above.

[0053] The key design feature of this invention lies in its use of a reflective photoelectric sensor, a DAC, and a controller. The reflective photoelectric sensor includes a light-emitting diode (LED) and a phototransistor. The controller is connected between the phototransistor and the DAC. The output voltage terminal of the DAC is connected to the LED. This achieves the following: 1. By adjusting the current of the LED using the DAC, the characteristic curves of the phototransistors on each machine are made consistent during production, ensuring good high and low level responses of the reflective photoelectric sensor on each machine, thus achieving stable and consistent production. 2. By adjusting the current of the LED using the DAC, even if the reflective photoelectric sensor or mechanical materials age, causing the characteristic curve to differ from the factory setting, it is not necessary to return the machine to the factory to replace the reflective photoelectric sensor. Calibration and adjustment can be performed directly on the machine to restore its stable performance from the factory setting, reducing the manpower and material costs associated with maintenance and improving customer satisfaction. Therefore, during production, the electrical tolerances of the reflective photoelectric sensor and the assembly tolerances of mechanical components can be corrected. After sale, adjustments can reduce cleaning and maintenance caused by component aging or dust contamination.

[0054] The above description is merely a preferred embodiment of the present utility model and does not constitute any limitation on the technical scope of the present utility model. Therefore, any minor modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present utility model shall still fall within the scope of the technical solution of the present utility model.

Claims

1. A circuit structure for correctable adjustment of a reflective sensor, characterized by: It includes a reflective photoelectric sensor, a DAC, and a controller; The reflective photoelectric sensor includes a light-emitting diode and a phototransistor. The positive terminal of the light-emitting diode is connected to the first VCC terminal, the collector of the phototransistor is connected to the second VCC terminal, and the emitter of the phototransistor is grounded or preset to a low level. The controller is connected between the phototransistor and the DAC. The output voltage terminal of the DAC is connected to the negative terminal of the light-emitting diode. The controller reads the level state of the level signal detection point of the phototransistor and controls the DAC to output the adjusted level accordingly, so as to set the current of the light-emitting diode.

2. A circuit structure for calibrating a reflective sensor according to claim 1, characterized in that: The DAC is either the DAC of the controller's original core main chip or an external DAC chip connected to the core main chip.

3. The circuit structure for calibrating and adjusting a reflective sensor according to claim 1, wherein: The controller has a digital interface and a GPIO port. The level signal detection point is electrically connected to the GPIO port. The controller reads the state of the GPIO port and controls the DAC to output the Vdac level accordingly through the digital interface.

4. The circuit structure for calibrating and adjusting a reflective sensor according to claim 1, wherein: A level follower is added after the DAC, and the level follower is connected between the DAC and the negative terminal of the light-emitting diode.

5. The circuit structure for calibrating and adjusting a reflective sensor according to claim 1, wherein: The light-emitting diode is connected in series with a current-limiting resistor, and the positive terminal of the light-emitting diode is connected to the first VCC terminal; the collector or emitter of the phototransistor is connected in series with a bias resistor, and the level signal detection point is set between the bias resistor and the corresponding collector or emitter.

6. A circuit structure for calibrating a reflective sensor according to claim 5, characterized in that: The current-limiting resistor is connected in series between the positive terminal of the light-emitting diode and the VCC terminal, and the bias resistor is connected in series between the collector of the phototransistor and the second VCC terminal.

7. A circuit structure for calibrating a reflective sensor according to claim 5, characterized in that: The current-limiting resistor is connected in series with the negative terminal of the light-emitting diode, and the bias resistor is connected in series between the collector of the phototransistor and the second VCC terminal.

8. The circuit structure of claim 5, wherein: The current-limiting resistor is connected in series between the positive terminal of the light-emitting diode and the first VCC terminal, and the bias resistor is connected in series between the emitter of the phototransistor and the ground terminal.

9. The circuit structure of a calibrable and adjustable reflective sensor according to claim 5, characterized in that: The current-limiting resistor is connected in series with the negative terminal of the light-emitting diode, and the bias resistor is connected in series between the emitter of the phototransistor and the ground terminal.

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