![]() One example for this is the Arduino Uno's barrel jack connector. This circuit is probably the most common reverse polarity protection circuit and used in many products. This simple solution is shown in the circuit diagram below. ![]() A reverse biased diode does not allow a current to flow through it and thus the attached circuit is unpowered if a reverse voltage is applied and won't be damaged. The easiest way to provide a reverse polarity protection to a circuit is by connecting a diode in series. Thus, let's look at some reverse polarity protection circuits. If you replace it with a microcontroller you can be pretty sure that it will be fried when a reverse voltage of 9V is applied. The LED may degrade faster and depending on the age, the construction wise or temperature a breakdown may occur earlier. If we exceed the 5 V, we are operating out of spec. The important point is, that there is no guarantee provided for this. The real breakdown voltage is usually around 30 V and above. In practice a breakdown at 5 V is unlikely. If we connect the battery the wrong way around, the reverse voltage of 9 V could possibly destroy the LED. This essentially translates to: "Never apply a higher reverse voltage to our LEDs". A typical reverse breakdown voltage given in many datasheets is 5 V with an allowable reverse current of only a few microamperes. ![]() However, LEDs are not designed to be used as rectifiers. LEDs are diodes as well and won't conduct current if they are reverse biased. We will use an example circuit with an LED and a 9 V battery. In this tutorial we will look at how to protect a circuit against reverse voltages by using diodes. Devices like the Arduino Uno can be easily destroyed by applying a reverse voltage. Almost all semiconductor components and electrolytic capacitors are sensitive for reverse voltages. Let's look at simple reverse polarity protection circuits using diodes. A reverse voltage can easily damage electronic circuits. ![]()
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