Step down converter overheating

Hello everyone,

I hope that this is the right place where to post my question, otherwise I’ll be more than glad to close this topic and open it elsewhere!

I’m working on a personal project for a friend’s birthday and I’m programming a bluetooth controlled dispenser, but I’ve found some issues. One of the main focuses of the project has been on having only one power input that would power both the board and the 4 12V peristaltic pumps that I intend to use. I’ve completed the whole wiring of it a couple of days ago and I’ve been roaming the internet in search for the following problem: I’m using a step down converter (NB: it is not a variable one) in order to feed just 9V to the Arduino Uno board instead of plain 12, but it seems that once the 4 pumps are activate all at once, the converter and the board overheat almost immediately. I am well aware that I’m drawing “a lot” of current with the four pumps all active at once, but I would love some insights/advices just in case any of you would have any.

I’m leaving here the fritzing scheme I’ve been working with, which is unfortunately missing the stepdown converter that goes to the board. I’ll be leaving also a picture of the total circuitry that I have at the moment so that may be a little bit clearer (sorry for the mess, I’m still trying to figure it all out).

(Sorry for any uncleareness, first post here)

Actual Dispenser Schematics_bb.pdf (1.06 MB)

but it seems that once the 4 pumps are activate all at once, the converter and the board overheat almost immediately.

No surprise you are vastly overloading that tiny little regulator.

You need numbers,
How much current does each motor draw?
What voltage do they need?
It is best to get a regulator that actually produces the voltage you want. The onboard regulators can barely cope with powering the Arduino and a few LEDs.

I'm leaving here the fritzing scheme I've been working with, which is unfortunately missing the stepdown converter that goes to the board.

At the best of times Fritzing physical layout diagrams are useless, you just made it doubley so.

photo_2020-08-29_17-29-18.jpg

Project01.png
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ignite97:
I'm using a step down converter (NB: it is not a variable one) in order to feed just 9V to the Arduino Uno board instead of plain 12,

Wrong sort.

The Arduino requires 5 V not 9, and other devices you are using also require 5 V - notably that relay bank - so you need a switchmode converter adequately rated to feed 5 V to the Arduino "5V" terminal as well as the other devices. :grinning:

And a UNO is a bad choice for a real project unless there is a shield which fits and performs all the interfacing in one piece. :roll_eyes:

But it gets worse!

There is a 220 Ohm resistor attached to that breadboard doing nothing but the series resistors to the RGB LED are all missing!

And when you take pictures, take it out into actual daylight but not full sun, and with no less than two megapixels of resolution. A photo in a dark room like that is not at all useful.

It is not clear from the diagram how it is all powered, but if the add on regulator gets hot when the four 12v motors are active, then I guess that at least the 4 relay modules are contributing to this. Surely the motors are not powered via the regulator.

You could consider using logic level mosfets instead of relay modules or use relay modules which can be powered directly from the 12 volt supply.

If it is to be battery powered, then low quiescent power consumption becomes important.

Hi,
If the "step down converter" is actually a linear regulator by the looks of it, it should have bypass capacitors around it, positioned at its pins.
Consult the datasheet for details.
What are you using for a 12V power supply?

Your picture doesn't seem to resemble your circuit, the regulator for one and the LED.

Please hand draw your schematic from your project, label the pins and components.
I know doing this is a pain , but it will help you understand your project components and reverse engineering will possibly find any wiring errors.

Do you have a DMM?

Tom... :slight_smile: