what are 5v regulator current limitations on ProMini?

I am driving two ir sensors and two neopixels (low brightness) off of the 5V regulated output pin.

In order to save power during standby mode, I was thinking of swapping them out of the 5v regulator and plugging into digital pins... The idea is that while in standby mode, I can make those pins go low and limit the current draw when the sensors and lights aren't being used...

I found that the IO pins can handle 40ma each, but couldn't find a current rating for the 5v regulator pin...

Does anyone know what that is? Is it also 40ma?


Look at the markings on the regulator. On my 3.3V Pro Mini clone it says “KB33”. A Google search for ‘KB33 regulator’ turned up the Micrel MIC5205 (http://www.micrel.com/_PDF/mic5205.pdf) which has a guaranteed output of 150 mA.

Please clarify what you want to do. A Pro Mini has an 3.3V regulator on board, none for 5V.

Do you want to power multiple Minis from Uno pins? That’s quite impossible, with only 40mA per pin and a total of 150mA.

My Pro Mini 5V has a 5V regulator. :wink:

My Pro Mini 5V has a 5V regulator. :wink:

So does mine. It depends on which type (3.3V or 5V) you buy.

There are indeed two flavors of Pro Mini, 3,3V or 5V. Both with the corresponding regulator.

I have some with the MIC5205 (KB05 marking). They can indeed do 150mA but you have to watch the thermal dissipation. You can only dissipate +-800mW ( (125C - 40C) / 220C/W = +-800mW) in the regulator. So when the input is 12V you are limited at around 110mA

I also have board with the regulator marked L05 which is the 78L05. It's rated at 100mA but has around the same max dissipation.

But driving a neopixel from an IO pin is a bad idea. Each neopixel has 3 led's (red, green, blue) and each has a 18mA driver. So one neopixel is rated at 54mA and that's to much for an IO pin. But I don't know what the standby current is of a Neopixel but it's low. So just turn off the Neopixel and you are fine.

I can't say jack about the sensors because you didn't provide us with info.

The regulator output current can be increased, up to the regulator limits, when a small resistor and big capacitor is added between power supply and RAW input. For an 5V Uno on a 12V supply, and 1W regulator power, a 12 Ohm resistor is optimal.

How do you mean? Cap en resistor in series?

The resistor in series, to consume excess voltage. The capacitor to Gnd should prevent the regulator from oscillating, on certain load conditions (current spikes...).