How to judge the quality of a light emitting diode?

It is a short-circuit gauge, a buzzer or diode symbol, it provides a 2V+ signal, and the LED is OK

But of course, only non-high-power LEDs can be measured

First, the multimeter selects the diode gear.

When observing, the long legs are positive. When measuring with a meter, if the watch has a reading, the end measured by the red watch pen is the positive pole of the diode, and the light-emitting diode will emit light;

If there are no readings, the pen is reversed and measured again, and if there is no indication on both measurements, the LED is damaged.

If not, test again. If there is no indication for both measurements, the Zener diode is damaged. If there is a reading, it is normal.

Detect with a multimeter. An analog multimeter with 10k stops can be used to roughly determine whether a light emitting diode is good or bad. Under normal circumstances, the forward resistance of the diode is tens to 200K, and the value of the reverse resistance is .

If the forward resistance value is 0 or , and the reverse resistance value is small or 0, it is susceptible to damage. With this detection method, the light emitting tube cannot be physically seen, because the 10K stop does not provide a large forward current to the LED.

If you use a digital multimeter to detect a light-emitting diode, the gear is set to the diode gear, and the forward measurement shows that the voltage is about and right, and the reverse is infinity.

The operating voltage is very low (some are only a few volts); The working current is very small (some can emit light only a few tenths of a milliampere); Good impact and seismic resistance, high reliability and long life; By modulating the strength of the current passing through, it is possible to talk about the strength of the luminous light in a convenient way.

Because of these characteristics, light-emitting diodes are used as light sources in some optoelectronic control devices and as signal displays in many electronic devices. The core of the tube is made into strips, and 7 strips of light-emitting tubes are used to form a 7-segment semiconductor digital tube, each of which can display 0 9, 10 Arabic numerals and some letters such as a, b, c, d, e, f (must be case-sensitive).

What is the difference between a light-emitting diode, an emitting diode, and a receiving diode? How can I tell the difference?

The light-emitting diode can only emit a variety of light, there are two kinds of emitting diodes, one is the one that emits a laser (that is, the kind of laser whip) and the infrared (that is, the kind of TV remote control) The diode that receives the signal is the kind of TV receiver, the resolution is very good, the shell of the light-emitting diode will be dyed according to the color of the light emitted, the transparent one is generally highlighted, and the shell is plastic. The shell of the emitting diode laser is generally copper, which is very different from the light-emitting diode, and the infrared is similar to the light-emitting diode, but if you look closely, there are no two pieces of the light-emitting diode in the shell, and most of the diodes that receive signals are black.

1. Look at the logo.

Many SMD LEDs will be marked with corresponding logos, generally green, for example, similar to the English letter "T", as shown below

2. Look at the triangle.

If you look at some SMD LEDs, they will be marked with a silk screen similar to the triangle symbol, so the bottom edge of the triangle is close to the positive pole, and the top corner is close to the negative pole.

3. Look at the gap.

Some SMD LEDs will have a gap, for example, for 5050 SMD LED, which is a more commonly used in the LED energy-saving lighting industry, the entire 5050 SMD LED is square, one of the four right angles has a corner with a small missing angle, which is the place where the small red circle is on the way, and the other right angles have no small missing corners, and the end with a small missing angle is the negative pole, and the other end is the positive pole.