How to determine the polarity in LED

Any amateur make anything his own advantage fakes LEDs, for example, to indicate the work of home-made or just for beauty. And to ensure that the LED regularly worked in the scheme, it must be connected correctly. And for that you need to determine where it has a cathode (negative) and an anode (positive). In this article, and we will talk about how to determine the polarity.

Marking Scheme

If we turn to the schematically indicated, you will see the following picture:

Where triangle labeled anode and the vertical bar indicates the cathode, and two parallel arrows indicate that the element emits light. So with a designation in the schemes like everything is simple and clear, let us now look at other ways to determine.

visual determination

Determination of the polarity of the diodes in the DIP package

Let's first look at the most common among the "amateur professionals" LEDs:

So, if you purchased a new LED look carefully at his feet. You will notice that one leg longer than the other. This is not a factory defect, as a design feature.

So, the longer leg is the anode (plus) and short - the cathode (negative).

If you are using b / a diode (which was unsoldered), then pay attention to the plinth itself, where the cut will be a cathode.

And considered the internal structure can be seen extensive detail, which is a drawback and a small "detalyushka" (plus).

We determine the polarity at a SMD diode housing

These diodes are also quite widely used in lamps and LED strips and know where it has such a product cathode and anode will also not be amiss.

Inside this diode will not look within, but producers left a special mark in the form of a bevel angle:

So with the side where the chamfer is a cathode (negative), while the opposite side - the anode (positive).

Determination by means of devices

The next best one for determining the polarity of LEDs is to use a multimeter - multimeter.

For a successful test, attach the ends: black jack with COM, red in VΩmAC, further put the regulator on a dial and touch the ends of the LED display.

And when you touch the red probe anode and black cathode, LED will light, and on the board of the device you will see a drop in the voltage across the LED.

If a special connector to check the PNP and NPN transistors present in your multimeter, then you can check without any probe. For this swap controller in «hFE» position.

And we put our diode ends in slots marked 'E' - the emitter, and "C" - the collector. So as PNP-transistor collector is negatively biased, if you have inserted in the slot cathode, and accordingly in the "C" is inserted into the anode, the LED will light up. This is the fastest and easiest option determine the polarity of the LEDs.

Note. If you want to determine the polarity of the diode without legs, the connectors multimeter you can insert small needles and touch their end of the output of the diode being tested.

Determination of the polarity of the power source

Another embodiment of determining the polarity of LEDs is to use a power supply for 3 - 6 volts. For example, it is quite suitable already podsevshih battery with the computer motherboard CR2032

Thus, by connecting the diode to the battery legs can easily determine the polarity of the diode.

conclusion

These are all methods for determining the polarity of the LEDs, which I wanted to tell you. If the article was useful to you, or are interested in, you will appreciate it Like. Thanks for attention!