Confusing Schematic - Powering the Whole System from One Input

Projects
1

Hello everyone,

I’m working on a Gas Chromatography project and I’m using a schematic from Marb’s lab as a base:

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I’m a bit confused about the power supply part.
From what I see, a 9–12VDC input (as written on his final PCB) goes into J3, and the output of the LM2596S-ADJ regulator gives VCC, which is then used to power the 12V air pump, pushbuttons, and the MQ-2 gas sensor.

What I don’t get is: on this schematic, everything should run on 5V, except the motor, which clearly needs 12V.
So why not just power the motor directly from the jack (12V), and then use the LM2596S-ADJ to step down the voltage to 5V and feed that into the Vin of the Arduino? That way, everything else could be referenced from that.

In the video, he powers both the Arduino and the PCB.
I’d rather power everything just from the J3 input if possible.

What do you think?

Thanks for your time,
natrist

2

I think this question is outside the scope of this Forum and is not a direct KiCad question . . . why not simply ask the author ?

3

ok that’s what I was wondering, that’s why I posted it on the “Project” sub

1 Like
4

When asking not KiCad related question people are typically send to use other forums with EEVblog as an example.

1 Like
5

I agree with the others, this is not a KiCad related question, and opinions about that here are … divided. :innocent:

Why does your screenshot have these weird dark bars on top and bottom? It does not really help with visibility.

Why? A 12Vdc motor runs perfectly fine from a 5V power supply, it just runs a bit slower, and that is probably the intention. The speed is also more constant then from a “9 to 12V” barrel jack. And what about LA1, a 6V 40mA light bulb that burns on “+1.25V to +2.5V”.
And what’s the difference between “+5V” and “VCC”?

6

I don’t know, youtube add these when I pause a video.

I just got an answer from Marb’s Lab that says. “The power source for the Wheatstone bridge and the pump is not connected to the Arduino, which is powered via USB to avoid interference.”

So there isn’t any 12VDC on the PCB.

Then “+5V” and “VCC” are both +5V power supplies but not from the same source if I guessed right.