Photoelectric switch application and precautions - Solutions - Huaqiang Electronic Network

Photocoupler

1: Input power supply voltage fluctuations to DC input mode, also pay attention to its fluctuation value, usually can allow ± 10%.
2: Wiring should be carried out correctly. It should be noted that in the case of regulations, the cable should be within the specified length, and most of the wiring should be protected against noise. However, for safety reasons, attention should also be paid to the power. Line isolation, high-voltage lines, power lines and photoelectric sensor wiring should not be placed in the same wiring tube or in the cable trough, otherwise it will cause (sometimes) the photoelectric switch malfunction or damage due to induction, so in principle, separate Wiring.
3: Response time Select the photoelectric switch that has the remaining force in response speed according to the size and moving speed of the measured object. In addition, regarding the opposite beam type, since the thickness of the beam has an influence on the detection, it is necessary to pre-calculate the entire beam. time.
4: Sensitivity Regarding the set distance, in the case of a harsh environment, when using the through-beam type, it is necessary to leave room for four times or more, and when using the reflection type, it is necessary to leave room for 1.5-2 times or more.
5: Protection measures Generally, the reverse polarity is provided in the DC-powered photoelectric switch, and the polarity does not need to be protected by polarity.
The output of the DC-powered photoelectric switching transistor has overcurrent and short circuit protection. The protection mode is tempo or self-locking. Each has its own characteristics. The beat type generates beat protection at the output maximum current critical point. When used, the load current needs to be controlled within the rated output current of the photoelectric switch. After the self-locking overload and short circuit, after the protection circuit is started, there is no output, and it needs to be powered off again to return to normal.
The protection of the contactless output pole is usually the collector of the freewheeling protection transistor. If there is a high-power inductive load, it is better to provide protection by externally setting a surge absorbing circuit.
6: Anti-vibration and impact If the vibration is 0-2000 beats/min, and the re-vibration width is about 2 mm, it has no effect on the general photoelectric switch, but the use of incandescent lamps as the light source requires the use of an equipment structure that is not subject to vibration.
7: Interference light Due to the problem of light source and modulation of photoelectric switch, the ability to resist light is also different; usually infrared photoelectric switch is resistant to ambient light incandescent light 3,000 Lux, sunlight 10,000 Lux. If the strong sunlight directly illuminates, since the sunlight contains light in the infrared band, it is not enough to use optical filters to improve the ability to resist light interference. Among the teopto optoelectronic products are products with 100,000 Lux exclusively for intense ambient light. In the direct current mode, it is necessary to avoid direct illumination of ambient light as much as possible. Due to the interference of ambient light, it is necessary to finely adjust the sensitivity to meet the needs of actual use. When the angle between the optical axis of the photoelectric switch (receiver) and the strong light source cannot be changed, a visor or a light-shielding long tube can be added around the photoelectric switch.
8: Preventing mutual interference The most effective way to prevent mutual interference is to cross the transmitter and receiver. When more than 2 groups are used, the group distance is also opened. Of course, you can also choose to use different frequency models. The reflection type needs to be separated by a certain distance, and the adjacent spacing is determined according to the pointing angle of the product parameter and the detection distance.
9: Mirror angle influence When the measured object is shiny or encounters a smooth metal surface, the general reflectivity is very high, and it has a mirror-like effect. At this time, the emitter and the detecting object should be installed at an angle of 10 to 20°. So that its optical axis is not perpendicular to the object being detected, thus preventing malfunction.
10: Excluding background effects When using reflective diffused emitters and receivers, sometimes the photoelectric switch or the background is smooth and other objects with high reflectivity may cause the photoelectric switch to be unstable due to the proximity of the detected object to the background. Detection.
Therefore, it is possible to use a distance-limited transmitter, receiver, or to remove the background object, remove the background, apply the background to matte black, or try to make the background rough, gray, and the like.
11: Self-diagnosis function When installing or using, there may be problems such as slight deviation of the optical axis, lens contamination, dust accumulation, external noise, and ambient temperature out of range due to the influence of the table top or the background and the use of vibration. . These problems may cause the photoelectric switch to deviate from the stable working area. At this time, the self-diagnosis function of the photoelectric switch can be used to notify the user through the STABLITY green stable indicator to remind the user to adjust it in time.
12: Eliminating the influence of the countertop When the transmitter and receiver are mounted close to the table, a partial beam reflected by the tabletop may appear on the receiver and cause unstable operation. In this regard, the transmitter and receiver can be separated from the table by a certain distance and a visor can be added.
13: Mirror surface maintenance regularly cleans the dust on the surface of the mirror or reflector, so that the light quantity of the photoelectric switch is not lost, so that the photoelectric switch works normally. It is strictly forbidden to use chemicals such as thinner to wipe the lens, so as not to damage the plastic mirror and the reflector.
14: Temperature characteristics The general working environment temperature is -20 ° C ~ 55 ° C (not frozen), need to pay attention to the detection under complex environmental conditions, such as the need to take cooling in a higher temperature environment. There are various cooling methods, such as air cooling, water cooling cutting, electric cooling, etc.; if the temperature is lower than the rated value of the product, heat is required to prevent the detection of mirror frost and ice; if these conditions are used, if technical support is required, please Consult with teopto's application engineers for technical advice and select the right product for the project.
15: Optical axis calibration In order to facilitate the calibration of the optical axis, it can effectively prevent the offset, as long as the following points can meet the requirements:
1 When setting the detection distance (sensitivity), leave a lot of room.
2 The optical system of the transmitter and receiver can be expanded.
3 The assembly is orderly and sturdy.
4 For the narrow optical axis form of the micro-fence, the visor or optically adjust the parallel light and set the distance without any room, it should be finely adjusted, and then mechanically firmly fixed after the calibration.
16: The problem of the detected S/N ratio
The S/N ratio is the ratio of signal to noise. This problem is easily overlooked. The photoelectric switch mainly uses the incidence of light and the shading difference for ON-OFF conversion. Therefore, when the light is incident, It is possible to select an angle and a position where the amount of incident light is large; when shading, the amount of incident light is required to approach zero for stable detection.
17: Other problems The following places may generally cause malfunction of the photoelectric switch, and should be avoided as much as possible:
1 places with more dust;
2 places with more corrosive gases;
3 places where water, oil and chemicals may splash directly;
4 Outdoors or sunlight, where there is strong light and no shading measures.
5 places where the ambient temperature changes beyond the scope of the product;
6 Locations where vibration and impact are large and no shock measures are taken.
The above is a general application method, such as the roughness, color, transparency, etc. of the material surface of the sample.