28BYJ voltage requirements / faulty power supplies?

[kugerard]

Hello,

A fast question, regardless of the setup I have. I am controlling 2 28BYJ 5v motors with an Arduino clone and L298N drivers. The 2 drivers feed with the 5v that arduino provides through its pin.

Then, when I connect the arduino through the 5V USB connection, using a laptop, which at the end should give 500 mA, everything works as expected.

But if I connect the arduino with a 12V 2A power supply through the arduino jack (no usb connected), then the motors lose a lot of steps and quite often.

I would say this happens when not enough intensity is given. But since it is a 2A power supply, I find it difficult to believe.

Is this common (this is a cheap supply)? Of this has nothing to do with the power and it's something else?

[flashko]

Most likely, you are overloading the built-in voltage stabilizer. At 7 volts difference (12-5), even if you only have 200mA consumption, the stabilizer must dissipate 1.4 watts of heat, and that is too much. Better to use a DC DC step down converter like the mini360 for example and power the Arduino directly through the 5 volt pin.

[Railroader]

That powering is a diaster!
Don't ever power motors from the Arduino 5 volt pin. Just don't do it.
Don't use the tiny built in 5 converter via Vin. It just barely supports the controller from 12 volt at Vin.

[gilshultz]

Rule #1 A power supply the Arduino is NOT! You are lucky the board survived.

[kugerard]

Thanks to all for your time. As far as I understand, I can use the DC to power the arduino through the jack, I guess there's nothing wrong with it, so the problem is using arduino as a power supply for the 28BYJ.

Then, what I've read out there

from How to control "Arduino 5V pin" - #4 by Paul_B

"
The "5V" pin is the pin you use to supply power to the Arduino. If you have the Arduino plugged into a USB power source, you can use the "5V" pin to supply 5 Volts to some other devices such as sensors, up to perhaps 450 mA on the basis that the USB can supply up to 500 mA. The polyfuse (UNO) or diode (Nano) restricts you from passing more current through to the "5V" pin.

The on-board regulator is generally useless if you have anything else connected other than the basic Arduino itself, so do not even consider attempting to use the "Barrel jack" or "Vin".
"

And from power - If the USB gives 5v, how can the Arduino supply 5v to the 5v pin? (And another question) - Arduino Stack Exchange

"
1. USB. The 5V line from USB is (or should be) already regulated, so it's feed directly (in fact it goes through a polyfuse) into the +5V rail of the board. The maximum current draw operating this way is 500 mA, limited by the polyfuse so you don't blow up your PC.
2. Barrel connector (wall adapter). It accepts 7-12V and brings it down to 5V using a linear regulator whose output goes to the +5V rail of the board. The maximum current draw operating this way is 1,000 mA, limited by the regulator capability.
"

Then, the first one warns about using the "barrel jack", but supports using the usb, and the second ones looks like it says both could be used.

So @flashko I understand that perhaps the regulator doesn't provide homogeneous current doe to the difference, and this confuses the rotors, and that I could use a 7-9V to fix this?

@Railroader @gilshultz the two 28BYJ should draw max 480mA, a little bit over what the usb should provide (a little less of 500 mA). but let's say I only have one, why shouldn't I power it from the arduino? Do you have any doc clarifying this? I'm asking because a lot of tutorials saying otherwise, is there a trustable source of information about that?

EDIT: I should have searched this forum, I googled instead. There are some identical questions. I can see @Railroader that you advise that through the barrel jack there'll be only a few milliampers through the 5v pin, and in the same sense of what @flashko says there is Arduino UNO Behaving different on Barrel Jack power vs USB - #2 by sterretje

"
When you power via Vin or the barrel, power goes through a voltage regulator that has virtually no heatsink. The voltage difference (9V -5V) multiplied by the current that the system uses is converted into heat that needs to be dissipated by the voltage regulator and it will battle with that without a heatsink.

Adjust your buck converter to 5V and feed into the 5V pin. Note that if you do so, you are advised not to power the board via USB; you either need to hack a USB cable and cut the Vcc or disconnect the buck converter from the 5V when you have a need for Serial or upload.
"

So what's the problem in using the USB to power the arduino and use the 5v to power out 240 mA? I get that 480 mA is too much, but why less than 300 mA is wrong?

[Railroader]

@kugerard

let's say I only have one, why shouldn't I power it from the arduino?

Because You still need power to the second motor. Get a supply that is enough for 2 steppers, or more.

@kugerard

Do you have any doc clarifying this?

No. This fundamental for anyone having some education in electronic circuitry. That's a bit more than "one document"....

Power the controller from USB or a separate 5 volt power supply.
Power the steppers from a separate power supply having enough of over voltage to compensate for the 2 - 4 volt loss across the L298.

[kugerard]

Thanks @Railroader (needless to say I don't have this basic education).

[gentiamelectronics]

Hi @kugerard,

I know that your main question has already been answered but I figured I'd chime in with some extra resources that our team just published that might be helpful for working with the 28byj-48 stepper motor.

We sorted through all the information we could possibly find on this motor, interpreted it as best we could, and compiled it into a 28byj-48 third-party datasheet.

The datasheet not only includes parameters of the motor but also detailed descriptions of each parameter as well as some guides on common calculations you will need to perform. Hope it helps and good luck with your project!

[kugerard]

Thanks @gentiamelectronics , this paragraph (pg 22) is the perfect response to this question

"It is generally recommended that an external power supply is used to power the 28BYJ-48 motor instead of the Arduino 5V pin. Otherwise, under heavy load, the motor can draw enough current to damage the Arduino UNO. "