One power supply and brushless motor

In advance English ain’t my first language so this post might be a little bit hard to read, sorry for that.
Also I am in no way familiar with electronics my major is actually in mechanical engineering and I am just starting.
So let’s get straight in.

In this project I am using:

  • The Arduino Uno (Rev.3)
  • An old 4 wired Dell brushless fan, 12V. Lost the label, so I am not sure if it’s either 0.75 or 2.5 A, though I think it’s 0.75 A since my AC adapter doesn’t have any problems running it
  • An AC adapter, 12V 1A
  • 4 led’s (3 red, 1 blue), a few resistors, a potentiometer, on-off switch…

I have got a little circuit going on to control the speed of my 4 wired, it should work as planned and I have made grate progress by just googling or researching the answers to my questions.

Now I have come upon a little problem that I haven’t found an answer for yet and annoys me a lot.
I have read all over the internet that I have to wire the arduino and the fan to it’s own power circuit with a common ground. This works totally fine but I need to use one power supply for both ther arduino and the fan. I don’t mean to hook the fan directly to the arduino, but just to share the output between the arduino and the fan, as shown in the graphic below.

Maybe I am missing something but it seems like this could be the simple solution.

But fellow potential problems I have found at my researches:

  • too high Ampere draw from the arduino (shouldn’t be the case since the fan isn’t directly hooked to the arduino)
  • higher voltages for the arduino means higher heat distribution (going to solve that by applying a heat sink if necessary)
  • Power supply to weak to mange both, the arduino and the fan
  • electrical noise from the fan

Well those are the few things I have found, but I have no clue if those apply to my scenario and if so how to solve them.
I should mention that I am going too hook up the 3 led’s and the potentiometer to the arduino, if this is a problem.
I also might switch to the arduino nano, if this problem is manageable, since it would fit more into my purpose.

And remember guys I am a total newbie to this stuff, so be patient with me :slight_smile:

Your power supply is 12V, 1A. That would be good enough in case Your fan is the 0.75 Amp version.
As I understand Your power supply does not manage. My first thought is that Your fan is the 2.5 Amp version.
An UNO needs very little current, some 50 - 100 mA maximum. Your UNO is not the current thursty item bringing Your project down!

First of all thanks for your reply.
No I haven’t tried it yet I fear that I would burn out my arduino if I hooked up to the AC adapter

If you use 5V to power Arduino (first picture) the 5V can come through the USB connector or the 5V pin, NOT the VIN pin (needs at least 7V).
If you power the Arduino from 12V motor supply through the VIN pin (second picture), be aware that after dropping 12V to 5V (7V), Arduino's voltage regulator may only be able to supply 100 to 150 mA for the rest of your components, also, you may have a problem with motor noise coming through the VIN pin.
I prefer the first way.
Best way, power only the fan with 12V supply, power Arduino from a 5V plug pack or phone charger and connect 12V - (GND) to Arduino GND (for signal return).

The main problem for an Uno plus some LEDs on 12V is that the regulator may overheat. At best it'll get really hot, possibly hot enough to burn your finger burning off all the excess voltage. That's where the separate 5V supply comes in. For a quick test it most likely works, but you can expect the Arduino to switch off after a few minutes due to overheating (the regulator has an overheat protection which should protect it from permanent damage, but triggering it still means the part is overheated and that's always bad).

If you want to power your Uno off the 12V supply long term you best add a buck converter to produce the 5V you need. They're much more efficient than linear regulators, no issue with overheating.

wvmarle:
The main problem for an Uno plus some LEDs on 12V is that the regulator may overheat. At best it'll get really hot, possibly hot enough to burn your finger burning off all the excess voltage. That's where the separate 5V supply comes in. For a quick test it most likely works, but you can expect the Arduino to switch off after a few minutes due to overheating (the regulator has an overheat protection which should protect it from permanent damage, but triggering it still means the part is overheated and that's always bad).

If you want to power your Uno off the 12V supply long term you best add a buck converter to produce the 5V you need. They're much more efficient than linear regulators, no issue with overheating.

Yeah this seems to be a suitable solution thank you very much.
Other than that there wouldn't be any problems right?
And would it work with the Arduino nano right?
Also do I have to look for something special when hooking up the buck converter, like special wiring or something?
And again thank you very much this seems to be the perfect solution, just ordered some :slight_smile:

No special wires needed, and it'll of course also work fine with a Nano or Pro Mini. Just remember to use the 5V pin, not the VIN or RAW pin as that's going to the built-in regulator.

I'm quite sure you will run into other problems but this should take care of your power supply issues :slight_smile:

wvmarle:
No special wires needed, and it'll of course also work fine with a Nano or Pro Mini. Just remember to use the 5V pin, not the VIN or RAW pin as that's going to the built-in regulator.

I'm quite sure you will run into other problems but this should take care of your power supply issues :slight_smile:

You mean using the 5V pin for output right?

PS:
And yeah you are right I have been stuck on the PWM for weeks haha

If you have any advice on that I would be glad, otherwise I am going to open a new post :smiley:
And yes I have tried different timers, also experimented with analogwrite and OCR2B.

The 5V pin is mostly for powering the Arduino. Not the other way around (other than a few sensors maybe).

Best way to power your Arduino is really by using a regulated 5V supply to the 5V pin.

wvmarle:
The 5V pin is mostly for powering the Arduino. Not the other way around (other than a few sensors maybe).

Best way to power your Arduino is really by using a regulated 5V supply to the 5V pin.

Oh okay that's good to know. Thank's again.