The main parameters of the photosensitive receiving tube are as follows:
1. The highest working voltage Umax refers to the reverse maximum voltage value when the reverse current of the photosensitive receiving tube does not exceed 0·lμA when no light is irradiated.
2. Photocurrent IL, the current value of the photosensitive receiving tube when it is exposed to a certain light, when a normal reverse operating voltage is applied. The larger the value, the better.
3. Dark current ID, when there is no light, the photosensitive receiver receives the reverse leakage current when the normal working voltage is applied. The smaller the value, the better.
4. Response time Tr, the time required for the photosensitive receiving tube to convert the optical signal into an electrical signal.
5, photoelectric sensitivity, also known as current sensitivity. It indicates the sensitivity of the photosensitive receiving tube to light. It is the amount of photocurrent generated under the energy of each μW of incident light. The unit is μA/μW.
Features and uses
1. The photosensitive receiving tube is a photoelectric conversion device, that is, it can convert the received light into a change in current.
2. The working mode of the photosensitive receiving tube is to add reverse voltage or no voltage. When reverse bias is applied thereto, the reverse current in the tube will change with the change of the light intensity. The greater the illumination intensity, the greater the reverse current.
3. The sensitivity of the photosensitive receiving tube to the illuminating light is different. The light wave in one range has the strongest response, while the other light wave responds poorly. The magnitude of the reverse current is different.
4. The photosensitive receiving tube is mainly used for automatic control. Such as optical coupling, photoelectric reading device, infrared remote control device, infrared anti-theft, automatic control of street lamps, process control, encoder, decoder and so on.
5. The photodiode is packaged in a metal case package with a glass window at the top or a light receiving window on the side. Still other photosensitive receiving tubes are packaged in a black resin.
There are many types of photosensitive receiving tubes: general photosensitive receiving tube, avalanche photosensitive receiving tube, blue light receiving tube, visual sensitive receiving tube, infrared photosensitive receiving tube, laser photosensitive receiving tube, ultraviolet photosensitive receiving tube and plug-in photosensitive receiving tube .
There are many types of photosensitive receiving tubes, and the parameters vary greatly. The selection should be based on the requirements of the circuit. First determine what category to use, and then determine what model, and finally select the photosensitive receiving tube that meets the circuit requirements from the same model.
The most commonly used photosensitive receiving tubes in China are about 2CU type, 2DU type and HPD type. Imported Sharp SPD type, SBC type, BS type, PD type, etc.
How to distinguish between positive and negative
The difference between the pins of the photosensitive receiver tube can be directly distinguished by directly looking at the length of the pin of the photosensitive receiving tube: the length of the lead is positive (P pole), and the short length is negative (N pole).
For a tube with a colored dot or tube key identification, one leg near the mark is positive and the other pin is negative.
The difference between using the multimeter is to place the multimeter in the Rx1k block, block the tube's light receiving window with the baffle, and measure the resistance twice with the red and black test leads. The resistance is larger in one measurement (reverse resistance) The pin connected to the red test pen is the positive pole, and the pin connected to the black test pen is the negative pole.
Difference from phototransistor
The photocurrent of the photosensitive receiving tube is smaller than the photocurrent of the phototransistor; the output characteristic of the photosensitive receiving tube has good linearity, the response time is fast, and the linearity of the output characteristics of the phototransistor is poor; the load resistance of the phototransistor is small, generally the photosensitive receiving tube load 1/10.
To detect the photosensitive receiving tube, use the multimeter Rx1k resistor file. When no light is irradiated on the photosensitive receiving tube, it has a unidirectional conduction effect like a normal diode. The forward resistance is 8-9kΩ and the reverse resistance is greater than 5MΩ. If you do not know the positive and negative poles of the photosensitive receiving tube, you can use the method of measuring the positive and negative poles of the common diode to determine. When measuring the forward resistance, the black meter is connected to the positive pole of the photosensitive receiving tube.
When the photosensitive receiving tube is in the reverse connection, that is, the multimeter red pen is connected to the positive electrode of the photosensitive receiving tube, and the black pen is connected to the negative electrode of the photosensitive receiving tube, and the resistance should be close to infinity (when no light is irradiated), when the light is irradiated to the photosensitive receiving tube When it is on, the multimeter's hands should ask for a sharp deflection. When the light is strong, the hands will hit the 0 mark.