on video How to protect circuits from reversed voltage polarity!

 

The right polarity matters. Almost all semiconductor components and electrolytic capacitors are sensitive for reverse voltages. Devices like the Arduino Uno can be easily destroyed by applying a reverse voltage. In this tutorial we will look at how to protect a circuit against reverse voltages by using diodes.

We will use an example circuit with an LED and a 9V battery. LEDs are diodes as well and won't conduct current if they are reverse biased. However, LEDs are not designed to be used as rectifiers. A typical reverse breakdown voltage given in many datasheets is 5 V with an allowable reverse current of only a few microamperes. This essentially translates to: "Never apply a higher reverse voltage to our LEDs". If we connect the battery the wrong way around, the reverse voltage of 9 V could possibly destroy the LED. In practice a breakdown at 5V is unlikely. The real voltage breakdown is usually around 30 V and above. The important point is, that there is no guarantee provided for this. If we exceed the 5V, we are operating out of spec. The LED may degrade faster and depending on the age, the construction wise or temperature a breakdown may occur earlier. Anyway, the LED is just an example. 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. Thus, let's look at some reverse polarity protection circuits.

 

The right polarity matters. Almost all semiconductor components and electrolytic capacitors are sensitive for reverse voltages. Devices like the Arduino Uno can be easily destroyed by applying a reverse voltage. In this tutorial we will look at how to protect a circuit against reverse voltages by using diodes.

We will use an example circuit with an LED and a 9V battery. LEDs are diodes as well and won't conduct current if they are reverse biased. However, LEDs are not designed to be used as rectifiers. A typical reverse breakdown voltage given in many datasheets is 5 V with an allowable reverse current of only a few microamperes. This essentially translates to: "Never apply a higher reverse voltage to our LEDs". If we connect the battery the wrong way around, the reverse voltage of 9 V could possibly destroy the LED. In practice a breakdown at 5V is unlikely. The real voltage breakdown is usually around 30 V and above. The important point is, that there is no guarantee provided for this. If we exceed the 5V, we are operating out of spec. The LED may degrade faster and depending on the age, the construction wise or temperature a breakdown may occur earlier. Anyway, the LED is just an example. 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. Thus, let's look at some reverse polarity protection circuits.

 

The right polarity matters. Almost all semiconductor components and electrolytic capacitors are sensitive for reverse voltages. Devices like the Arduino Uno can be easily destroyed by applying a reverse voltage. In this tutorial we will look at how to protect a circuit against reverse voltages by using diodes.

We will use an example circuit with an LED and a 9V battery. LEDs are diodes as well and won't conduct current if they are reverse biased. However, LEDs are not designed to be used as rectifiers. A typical reverse breakdown voltage given in many datasheets is 5 V with an allowable reverse current of only a few microamperes. This essentially translates to: "Never apply a higher reverse voltage to our LEDs". If we connect the battery the wrong way around, the reverse voltage of 9 V could possibly destroy the LED. In practice a breakdown at 5V is unlikely. The real voltage breakdown is usually around 30 V and above. The important point is, that there is no guarantee provided for this. If we exceed the 5V, we are operating out of spec. The LED may degrade faster and depending on the age, the construction wise or temperature a breakdown may occur earlier. Anyway, the LED is just an example. 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. Thus, let's look at some reverse polarity protection circuits.

 

The right polarity matters. Almost all semiconductor components and electrolytic capacitors are sensitive for reverse voltages. Devices like the Arduino Uno can be easily destroyed by applying a reverse voltage. In this tutorial we will look at how to protect a circuit against reverse voltages by using diodes.

We will use an example circuit with an LED and a 9V battery. LEDs are diodes as well and won't conduct current if they are reverse biased. However, LEDs are not designed to be used as rectifiers. A typical reverse breakdown voltage given in many datasheets is 5 V with an allowable reverse current of only a few microamperes. This essentially translates to: "Never apply a higher reverse voltage to our LEDs". If we connect the battery the wrong way around, the reverse voltage of 9 V could possibly destroy the LED. In practice a breakdown at 5V is unlikely. The real voltage breakdown is usually around 30 V and above. The important point is, that there is no guarantee provided for this. If we exceed the 5V, we are operating out of spec. The LED may degrade faster and depending on the age, the construction wise or temperature a breakdown may occur earlier. Anyway, the LED is just an example. 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. Thus, let's look at some reverse polarity protection circuits.