# Max current draw of the Arduino Nano? (64 LEDs, piezo, etc)

After losing my first circuit board when a wire accidentally touched some wrong trace and blew the 5V regulator on the arduino. Next time I am using a socket to connect that nano to my main board. I was unable to desolder the nano off my board. Why did I not use a socket?!?

Anyhow, I am thinking my design may needs to be changed. My project is based on this instructable:

http://www.instructables.com/id/810-LED-Matrix-with-4017/

The 4017 decade counter, 595 shift register, and an 8X8 LED matrix driven by transistors is all powered by the +5V regulated pin on the nano. Now I am thinking that may not be the best idea. Should I have the power come from the VIN instead?

Thanks for the guidance! :)

That many LEDs will easily exceed the current capability of the Nano's voltage regulator. You should have a separate 5V power supply with the ground connected to your Arduino ground.

If you have some other voltage power supply (12V, 9V etc) then that can power Vin on the Arduino as well as the LED array.

Thanks, that makes sense. I will just have the +voltage that leads to the VIN of the nano just continue on to power everything else. So, quick question, the nano is powered at 5V, and the I/O pins lead to a 4017 decade counter and 595 shift register, I trust the nano will still be able to successfully provide high enough signals to trigger the logic chips, etc?

If te Arduino is running on 5V (internally, generated from the Vin) and the logic with e.g. 12V (same voltage as Vin), you're probably calling for trouble, specially if an 12V output is being connected to an input pin on the Arduino.

Not knowing your circuit makes it difficult, but the 4017 datasheet specifies a minimum Vih of 7V (if the 4017 is powered with 10V). So the Arduino will never be able to supply that.

The 5V output of the Arduino might be strong enough to drive your (off-board) logic; feed the leds with 12V.

// Edit Max supply voltage for 74HC595 is 7V, by the way.

I suggest that you consult the datasheets of the components that you use.

I was using my test circuit today. I was testing it with a +6V, 300 mA power supply and then with 4AA batteries. Both seemed fine. Logic inputs of the nano were responding fine to my switch inputs.