As an important component in electronic devices, infrared receivers are widely used in remote controllers, photoelectric switches, infrared sensors, and other electronic devices. Their performance directly affects the stability and reliability of the entire system. Correctly distinguishing the positive and negative poles of an infrared receiver is a crucial step when using it, as it directly affects the correctness of the circuit connection and whether the components can work properly. This article will elaborate on how to accurately determine the positive and negative poles of an infrared receiver tube from the basic principles, appearance characteristics, testing methods, and precautions in practical applications.

1、 Basic principle of infrared receiver tube

Infrared receiver tube, also known as infrared photodiode or infrared photodiode, is a semiconductor device that can convert infrared light signals into electrical signals. It works based on the principle of photoelectric effect, that is, when infrared light shines on the sensitive area of the receiving tube, the photon energy is absorbed by the semiconductor material, causing a change in the electronic state inside the material, thereby generating an electrical signal. This electrical signal can be amplified and processed by subsequent circuits to ultimately achieve detection and control of infrared light signals.

2、 Appearance feature judgment

Although infrared receiver tubes produced by different manufacturers may have differences in appearance, most products follow certain design specifications, including the identification of positive and negative poles. Generally speaking, there are obvious markings on the outer shell of an infrared receiver tube to indicate the positive and negative poles. There are several common ways to do this:

1. Color differentiation: Some infrared receiver tubes have their positive and negative poles distinguished by different colors, such as the positive pole being painted red or black, while the negative pole may remain in its original color or be painted with other colors. But this method is not absolute, as different manufacturers may use different color standards.

2. Marking symbols: A more direct and accurate way is to directly mark the positive and negative symbols on the outer shell of the receiving tube, such as the positive pole marked as "" or "P", and the negative pole marked as "-" or "N". This is an internationally recognized electrical symbol that is easy to identify and remember.

3. Pin length: In some cases, the pin length of the infrared receiver tube may also vary, usually the positive pin is slightly longer than the negative pin. This design facilitates automatic alignment of polarity when inserting the circuit board, reducing human errors.

3、 Test method judgment

If there are no clear positive and negative pole markings on the infrared receiver tube, or the markings are already blurry, then it is necessary to determine its positive and negative poles through testing methods. Common testing methods include multimeter measurement and LED assisted testing.

1. Multimeter measurement method:

Firstly, adjust the multimeter to the diode measurement mode (usually the beep mode or diode symbol mode).

Then, use the red and black probes of the multimeter to touch the two pins of the infrared receiver tube respectively, and observe the reading of the multimeter or the response of the buzzer.

If the multimeter displays a positive conduction voltage (usually ranging from a few hundred millivolts to several volts, depending on the receiver model) and the buzzer sounds, it indicates that the red probe is in contact with the positive terminal and the black probe is in contact with the negative terminal. On the contrary, if the multimeter displays reverse cutoff or extremely low reading, and the buzzer does not respond, it indicates that the pin polarity is opposite.

It should be noted that due to the special internal structure of the infrared receiver tube, its forward conduction voltage may be low. Therefore, the multimeter reading should be carefully observed during testing to avoid misjudgment.

2. LED auxiliary testing method:

Prepare a light emitting diode (LED) with a known polarity, connect its positive pole to the positive pole of the power supply, and temporarily suspend its negative pole.

Connect one pin of the infrared receiver tube to the negative terminal of the LED, and the other pin to the negative terminal of the power supply through a suitable current limiting resistor (such as a few hundred ohms).

Slowly adjust the power supply voltage and observe if the LED lights up. If the LED lights up, it means that the pin of the infrared receiver connected to the negative terminal of the LED is negative, and the other pin is positive. On the contrary, if the LED does not emit light, the polarity of the pins is opposite. This method utilizes the weak conductivity that the infrared receiver tube may exhibit under reverse voltage, and indirectly determines its positive and negative poles through the light emission state of the LED.

4、 Precautions in practical applications

In practical applications, in addition to correctly distinguishing the positive and negative poles of infrared receivers, the following points should also be noted:

Ensure that the working voltage and current of the receiving tube do not exceed their rated values to avoid damaging the components.

Infrared receiver tubes are sensitive to light and should be avoided from direct sunlight or prolonged exposure to high temperatures to avoid affecting their performance.

When designing circuits, reasonable layout should be adopted to reduce the impact of electromagnetic interference on the receiver and ensure the stability and accuracy of the signal.

Regularly check the performance of the receiving tube, and replace it promptly if any abnormalities are found to ensure the normal operation of the entire system.

Through the above methods, we can accurately determine the positive and negative poles of the infrared receiver tube and pay attention to them in practical applications to ensure the stability and reliability of electronic devices.