Hi,

I have an arduino micro and an Uno.
do I need to add a resistor to my LEDs going to the boards it or is it already imbedded?
The board’s nomenclature was somewhat confusing to me.

thanks

 

The board’s nomenclature was somewhat confusing to me.

Hello there could you clarify?

 

If you are using an led like this. We observe pictures and become comfortable with procedures double checking the polarity before applying power making sure the light emitting diode is going the right way by setting up your power rails correctly.
https://create.arduino.cc/projecthub/karmette/basic-led-setup-for-beginners-0a124a

 

Hello there could you clarify?

Typically a circuit using an LED requires a resistor to control the amount of current going to it..usually around 370 ohms depending on the voltage and what the LED requires. I’ll be setting up several LEDS to flash on and off using an Arduino board. Just wondering if the board already has an internal resistor so I won’t need to add one in series with the LED..

thank you

 

Typically a circuit using an LED requires a resistor to control the amount of current going to it..usually around 370 ohms depending on the voltage and what the LED requires. I’ll be setting up several LEDS to flash on and off using an Arduino board. Just wondering if the board already has an internal resistor so I won’t need to add one in series with the LED..

thank you

There is no internal resistor.

 

https://www.arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf

As noted, the ports are connected directly to the headers with no resistors. You will need one for the LED. 1K would be a safe value to start.

 

Whether you actually need a resistor depends on the internal construction of the microcontroller. I have driven LED's directly from port pins on PIC's, especially when multiplexing, because I have found that the internal FET resistance on that particular PIC has been enough to limit current. BUT...it's always safest to use a resistor.

You can calculate the current through the LED:

( Vdd - Vf ) / R = I

Vdd = power supply
Vf = forward voltage drop of the LED
R = resistance
I = current

With the LED's that I use, a 1K resistor limits current enough and still gives a good brightness. I haven't used 330 or 470 ohms in a long time...modern LED's are way more efficient and need less current.

 

Ok great. Thanks for the info. Much appreciated!

Whether you actually need a resistor depends on the internal construction of the microcontroller. I have driven LED's directly from port pins on PIC's, especially when multiplexing, because I have found that the internal FET resistance on that particular PIC has been enough to limit current. BUT...it's always safest to use a resistor.

You can calculate the current through the LED:

( Vdd - Vf ) / R = I

Vdd = power supply
Vf = forward voltage drop of the LED
R = resistance
I = current

With the LED's that I use, a 1K resistor limits current enough and still gives a good brightness. I haven't used 330 or 470 ohms in a long time...modern LED's are way more efficient and need less current.

 

Thank you very much. My question has been answered.

https://www.arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf

As noted, the ports are connected directly to the headers with no resistors. You will need one for the LED. 1K would be a safe value to start.

 

There is no internal resistor.

Ok. That definitely narrows it down and nails it. Thanks. I’m still a noobie.

 

It's advisable to add a resistor to your LED

 

@navyguy

If you posting and listening to the answers like this
you are not a noobie

well done.