What is a photoelectric switch and how to detect it?

Last Update Time: 2018-12-14 14:53:08

1.The photoelectric switch is a component that is packaged together by a light emitting tube and a light receiving tube, and is widely used in various control circuits of computer, audio and video industry .

 

There are two common photoelectric switches, one for transmission and the other for reflection.

 

Compared with the two, the transmission-type photoelectric switch has higher sensitivity, but sometimes it is not as convenient as the reflective switch. Most of the photoelectric switches adopt the structure that the input and the output terminals are mutually isolated, that is, the transmitting tube and the receiving tube are independent from each other, and the electrical insulation is maintained. But there are a few products using non-isolation, that is, the launch tube and the receiving tube for the common ground. 

 

The  common transmission and isolation photoelectric switches which when the voltage is applied to the transmitting tube, the emitter tube emits light, and if at this time, there is no covering between the transmitting tube and the receiving tube, the receiving tube can receive the light, the internal resistance changes, and the cover changes.

 

2.Detection(as an example of transmission and isolation)The detection method of the transmitting tube and the receiving tube is as follows.

(1) Detection of the emission tube. Measuring the positive and negative resistance values of the transmitting tube of the photoelectric switch in the RX10k2 gauge should have a one-way conduction characteristic. With this characteristic, it is easy to separate the input port (transmitter) and output (receiver) of the photoelectric switch.

(2) Detection of receiving tube. In the RX 10k2 block, the red and black pens contact the C and E terminals of the receiving tube respectively. The resistance value measured at this time is the penetration resistance of the receiver. The greater the value, the smaller the penetration current of the receiver is, the better the stability of the pipe. Normally, when the meter is measured with Multimeter RX1kQ, the transmission resistance of the photoelectric switch receiver is infinite.

 

(3) The isolation performance between the transmitting tube and the receiving tube is detected. When the multimeter is in RX1kQ, the insulation resistance between the transmitting tube and the receiving tube should be infinite. Otherwise, if there is a resistance between the transmitting tube and the receiving tube, it is indicated that there is a leakage phenomenon between them. Such a transmission isolation photoelectric switch can not be used.

(4) Detection sensitivity. The positive electrode of the battery is connected to the positive pole of the transmitting tube by a resistor of 2002 or so, and the battery negative pole is connected to the negative pole of the transmitting tube. The multimeter is placed in the RX 10kQ gear, the red pen is connected to the receiving pipe E end, and the black watch pen receives the receiving tube C terminal. A black paper is inserted between the transmitting window and the receiving window of the photoelectric switch to shield the infrared rays emitted from the transmitting tube. When testing, the black paper is moved up and down, and the pointer of the multimeter should be swinging with the moving up and down of the black paper. The greater the amplitude of the swinging, the higher the sensitivity of the photoelectric switch.  Note : in order to prevent the impact of external light on the test, the test operation should be carried out in the dark. During the test, if the multimeter needle does not move up and down with the paper, it shows that the photoelectric switch is damaged.

After the repair of the photoelectric switch is damaged, the transmitting tube can be removed and welded with the same type of launching tube; if the receiver is damaged, replace the new photoelectric switch.

 

This article is from Allicdata Electronics Limited.