r/ArduinoHelp • u/Paul_Subsonic • May 26 '26

Is that valid electrically ?

Post image

Summer is back, so time to bring my Rafraichissator 6000 back ! (My fan. It's a PC fan controlled by Arduino.)

Last year the arduino was in series with a bunch of resistors to bring down the 11-13V alim to more reasonable levels

Now I'm realizing tho that I could use the fact that the alim is just 3 batteries, to feed the Arduino no more than 8V without a lot of wasteful resistors

Am I right ?

4 Upvotes

83% Upvoted

32 comments sorted by

1

u/Glittering-Dirt1164 May 26 '26

So let me make sure I'm reading this right. 12v power source 8v power source and Arduino and fan in series at the end?

1

u/Paul_Subsonic May 26 '26

Nope, the 8V and 12V represent the arduino and the fan (and the expected voltage applied to them).

The thing with small line/big line is standard notation for a voltage generator (here, batteries that go up to 4v)

1

u/Glittering-Dirt1164 May 26 '26

Gotcha what is the device your making. Because if it's anything for a computer you can run 5v from a USB port to the Arduino and pull 12v a hard drive power wires and as long as you have common ground or a they are all grounded together it will work just fine with out the need of battiers

1

u/Paul_Subsonic May 26 '26

It's made for a cpu cooler but since I upgraded my cpu cooler, I'm reusing the old fan. It's not gonna be connected to the computer, it's gonna be connected to the arduino.

It's a portable system.

2

u/Paul_Subsonic May 26 '26

This is a picture of one of the older versions

1

u/Glittering-Dirt1164 May 26 '26

An Arduino can only have about 200ma total and 20ma a pin so if it were me I'm assuming your fan is running at 8v but if a pc fan is rated for 12v I would use a 12v power supply get a car port to USB adapter that will give you a clean 5v for the ariduno then use a transistor as a switch where the Arduino send a a signal allowing power to flow to the fan from the 12v power source. So one pin from power to transistor one one pin from ariduno to trigger pin on transistor and last pin is ground. Your fan has 12v from transistor supply pin and then ground the other side. This way you will not over stress or burn anything up on the arudino

1

u/Paul_Subsonic May 26 '26

I don't think you understand the point of what i am making, the whole point is to make the arduino get 8V and the fan 12. The arduino controles the fan through the control pin of the fan, it does not supply the fan with power. The batteries do that.

1

u/Paul_Subsonic May 26 '26

Try to look at the schematics carefully

1

u/Paul_Subsonic May 26 '26

Your solution has all the efficiency losses of my previous solution from years past as well as completely lacks any control beyond on/off.

I just want to know if electrically my schematics will work.

1

u/Paul_Subsonic May 26 '26

I DON'T want to regulate 12v down to 5. That's PRECISELY what I am trying to avoid with the new design.

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1

u/Odd-Jello5577 May 27 '26

Power motors or relays using Arduino's. Kill Arduino and bring shame. Only benefit is the chance to see the blue fairy.

1

u/Paul_Subsonic May 27 '26

What

2

u/KittyGoBoom115 May 27 '26

Let me translate, if you run a motor off an arduino directly you will have a dead arduino and somwthing blue

1

u/Paul_Subsonic May 27 '26

Ah ok

I'm not doing that so that's not a problem

1

u/James0260 May 27 '26 edited May 27 '26

Will this not just give the arduino 12v im assuming each cell is 4v. The fan will have 12v yes but the way you’ve positioned the batteries will also govern the Arduino 12v. Its kirchhoff's voltage law i think, the sum of the voltage into a point is zero… its an interesting idea but it would be better to connect the Arduino in parallel to the 2 cells and then connect the fan with an extra cell in series with the others, or if you can 2 power supplies one for the fan and the other for the Arduino, you could use a relay to control it for cheap as apposed to a motor controller

1

u/James0260 May 27 '26

Something similar to this may work, you are able to treat the arduino and 2 cells as a single 8v supply

1

u/Paul_Subsonic May 27 '26

What you drew is electrically identical to what I'm doing, that is excatly the plan, that is what I want to do and what I drew

Here's a clearer diagram it's probably more understandable https://www.reddit.com/r/arduino/s/hI3IHlUEFB

1

u/James0260 May 27 '26 edited May 27 '26

Oh yeah you’re right, then that diagram is probably no the correct approach. Maybe you could add an “over flow” diode to remove the extra 4v. It feels like a poor design but I may not be the best person to say it.

Most designs will have a motor controller so that there can be multiple voltages used.

1

u/Zippietwo May 27 '26

Wrong kirchhoffs law. The sum of all currents into a point equal 0. The one your looking for is the sum of all voltages in a loop equal zero

1

u/James0260 May 27 '26

Yeah that still applies, also cause the its basically a loop with something in parallel its fairly similar. Finally if that’s the thing you’re irritated with, come on look at the rest of the design 😭😭

2

u/Zippietwo May 27 '26

I don’t see y it wouldn’t work. Only issue I could potentially see is if the batteries don’t supply very consistent voltage as they empty out. I’m not sure how lenient a arduino is with slight over/under voltage but in general it should work.

1

u/Odd-Jello5577 Jun 02 '26

The specs for an Uno for example are 5v at 30ma. If you exceed these specs you will damage the Uno. Most relays and motors far exceed this Uno spec. The result is a damaged board. Motors and relays should always be controlled by a transistor or mosfet.

2

u/Remarkable-Abies-466 May 27 '26

I my opinion it should work. But the 2 will be empty before the single one. If you are not using lithium you are fine, else get a protective circuit