I. What are some common terms used in photoelectric switches?
① Detection distance: refers to the spatial distance from the reference position (sensing surface of the photoelectric switch) to the detection surface when the switch is activated, after the detection object moves in a certain manner. Rated operating distance refers to the nominal value of the proximity switch's operating distance.
② Backlash distance: The absolute value between the action distance and the reset distance.
③ Response frequency: The number of times the photoelectric switch is allowed to cycle within a specified 1-second time interval.
④ Output state: Normally open and normally closed. When no object is detected, the load connected to the normally open photoelectric switch does not work because the output transistor inside the photoelectric switch is cut off. When an object is detected, the transistor turns on, and the load is powered on.
⑤ Detection method: Based on the different paths by which the light emitted by the transmitter is reflected back to the receiver when the photoelectric switch detects an object, it can be divided into diffuse reflection, specular reflection, through-beam, etc.
⑥ Output forms: There are several commonly used output forms, including NPN two-wire, NPN three-wire, NPN four-wire, PNP two-wire, PNP three-wire, PNP four-wire, AC two-wire, AC five-wire (with built-in relay), and DC NPN/PNP/normally open/normally closed multi-function.
⑦ Pointing angle: See the schematic diagram of the pointing angle of the photoelectric switch, as shown in the three small figures at the bottom of Figure 4.
⑧ Surface Reflectivity: The light emitted by a diffuse reflection photoelectric switch needs to pass through the surface of the object being detected before it can be reflected back to the receiver of the diffuse reflection switch. Therefore, the detection distance and the surface reflectivity of the object being detected will determine the intensity of the light received by the receiver. The intensity of the light reflected back from a rough surface will be less than that reflected back from a smooth surface. Moreover, the surface of the object being detected must be perpendicular to the emitted light from the photoelectric switch.
⑨ Environmental Characteristics: The environment in which a photoelectric switch is used also affects its long-term operational reliability. When the photoelectric switch operates at its maximum detection distance, the optical lens may become stuck to contaminants in the environment or even corroded by strong acidic substances, leading to a decrease in its operating parameters and reliability. A simple solution is to determine the optimal operating distance by derating the photoelectric switch based on its maximum detection distance (Sn).
II. How photoelectric switches control intermediate relays
An intermediate relay is a small relay used to control high-power equipment. It can receive input from control signals and convert them into high-power output to drive other devices.
The following are the steps for controlling an intermediate relay using a photoelectric switch:
1. Select appropriate photoelectric switches and intermediate relays: Choose appropriate photoelectric switches and intermediate relays according to application requirements. The photoelectric switch should have an appropriate detection range and sensitivity, while the intermediate relay should have sufficient load capacity.
2. Connect the photoelectric switch and the intermediate relay: Connect the output terminal of the photoelectric switch to the input terminal of the intermediate relay. Typically, the output signal of the photoelectric switch is a switching signal that controls the coil of the intermediate relay.
3. Configure intermediate relays: Configure the normally open or normally closed contacts of the intermediate relays as needed. Normally open contacts are open when the relay is not activated, while normally closed contacts are closed when the relay is not activated.
4. Connect the load device: Connect the load device to the output terminal of the intermediate relay. The load device can be a motor, light, or other equipment that needs to be controlled.
5. Testing System: After connecting all components, test the system to ensure that the photoelectric switch can correctly control the intermediate relay. When an object blocks the light from the photoelectric switch, the intermediate relay should activate and open or close the load device.
6. Adjust sensitivity and response time: Adjust the sensitivity and response time of the photoelectric switch as needed. Sensitivity determines the photoelectric switch's ability to detect objects, while response time determines the speed at which the photoelectric switch outputs a signal.
7. Installation and protection: Install the photoelectric switch and intermediate relay in the appropriate location and ensure that they are protected to prevent damage or interference.
8. Troubleshooting and Maintenance: Regularly inspect the system to ensure that the photoelectric switches and intermediate relays are working properly. If problems occur, troubleshoot and perform necessary maintenance.
In summary, using photoelectric switches to control intermediate relays is a simple and effective method for achieving precise control of high-power equipment. By selecting appropriate components, ensuring correct connection and configuration, and conducting proper testing and maintenance, the system's performance and reliability can be guaranteed.
