The inclusion of a diode in the circuit in the wrong polarity threatens a short circuit or failure of other components. In this case, the rupture of electrolytic capacitors is especially dangerous. In case of any doubts, before soldering the diode, it is necessary to clarify the location of its terminals.
Instructions
Step 1
The simplest case occurs if there is a symbol on the diode body. It consists of an equilateral triangle and a straight line segment, against which this triangle abuts one of its corners. On diodes marked according to the new standard, this designation is additionally, as it were, crossed out - the essence of this does not change. Look at exactly how the designation is oriented relative to the diode terminals: the one that is closer to the triangle corresponds to the anode, and the one that is closer to the line segment corresponds to the cathode.
Step 2
If you know exactly the type of diode, and you have a handbook or datasheet at hand, you can determine the polarity like this. Look at which of the pins a point (or several points) or a circle should be located. Sometimes, by the number or color of dots, it is possible to additionally determine the letter index of the diode within the series, and from it, in turn, the maximum reverse voltage.
Step 3
If the diode does not have any designations at all and all you know about it is forward current and reverse voltage, determine its polarity as follows. Take an ohmmeter (or a multifunctional device that has this function). Determine the polarity of the voltage on its probes in the resistance measurement mode, using another diode as a reference, the pinout of which is known. Then, connecting the probes to the diode under test in different ways, determine the location of its electrodes by analogy.
Step 4
It is very convenient to use a special probe to determine the pinout of diodes. Take two AA batteries, an LED, a 1 kilo-ohm resistor and two probes. Connect all parts in series, and determine the polarity of switching on the diode experimentally, so that when the probes are closed, it glows. Connect the diode under test to the probes first in one polarity, then in the other. When the LED is on, the output of the diode facing the negative side of the power supply is cathode.
