Basic DC Power Question

[wildfrontier]

A control box I'm using provides +12 vDC output limited to 100 mA or 1.2 watts. I'd like to use this for Vin on my Arduino, thus avoiding having to build a separate power supply.

Am I correct in thinking that once the 12v runs thru my Nano's voltage regulator circuitry (see attached schematic) that I still have 1.2 watts? Or am I limited to 100 mA even at the Arduino's reduced voltages (+5 and +3.3).

Sorry for the newbie question, but I don't want to make any boneheaded assumptions here

[kmin]

@wildfrontier

Or am I limited to 100 mA even at the Arduino's reduced voltages (+5 and +3.3).

Yes, you are limited to 100mA, arduino voltage regulator just waste the conversion in to heat.

[gilshultz]

You can use an appropriate buck converter, and get a little more amperage. The difference coming from the efficiency. Linear regulators control the output by burning the excess voltage as heat. SMPS (Switch Mode Power Supplies) switch on and off and are more efficient.

[jim-p]

That is not the schematic of an Arduino Nano.
A Nano does not have a 3.3V regulator.

What Arduino do you have?

Also, there was no need to start a new topic.

[wildfrontier]

@jim-p

A[n Arduino] Nano does not have a 3.3V regulator.

Correct. I'm actually using the Seeeduino embodiment of the Nano, which does include the 3.3v regulator shown in the above schematic. This is handy for add-ons such as the Adafruit Mini Relay which runs off 3.3v.

[kmin]

@wildfrontier

This is handy for add-ons such as the Adafruit Mini Relay

So be careful, Nano+relay coil+few LEDs makes already 100mA

[jim-p]

Does all this have to do with you other project?

First Time Arduino Feedback Please

Greetings from Wonderful Wyoming. As a newbie I'm hoping a few Obi Wan Arduino types might weigh in on my first-ever Nano project. It gets pretty cold up here, so if the temperature gets below say, 25º F, I want my Generac generator to start automatically, run for a few minutes, then shut off for an hour or so (the generator is factory set to start if wires GENST1 and GENST2 are connected). The idea is to use a Nano with a single switch input to enable the cold weather feature. A dual LED wi…

There seem to be a lot of conflicting information between the two

[wildfrontier]

@jim-p

Does all this have to do with you other project?

Indirectly, yes.

In the future I’d like to power some other projects with this +12V 100 mA 1.2 watt supply, independent of the generator on/off project. A better understanding of 12V to 5V conversion can help me in this regard.

I was hoping the regulator circuit would provide 1.2 watts in the 5V domain as well, giving me a whopping 600 mA to work with, but - as has been pointed out above - it doesn’t really work that way.

Thanks to all for the input.

[kmin]

@wildfrontier

I was hoping the regulator circuit would provide 1.2 watts in the 5V

Consider different regulator like suggested by @gilshultz

[gilshultz]

@jim-p

A Nano does not have a 3.3V regulator.

I disagree, mine has a FT232 which has an internal 3V3 regulator. I also have some china ones that use the 1117 regulator.

[jim-p]

@gilshultz

I disagree,

You obviously did not understand or read my entire post and have taken what I said out of context. It should have been clear that I was referring to the schematic shown by the OP in post #1

[gilshultz]

@jim-p

That is not the schematic of an Arduino Nano.
A Nano does not have a 3.3V regulator.

What Arduino do you have?

I just took it from post 4.

[jim-p]

So I should have said a Nano does not have a 3.3V regulator as you show in your schematic.

Is that OK?

[gilshultz]

No problem! I took it as a literal statement, my mistook.