L298N and stepper mitsumi M49SP-1

Hello everyone,
I am new to this forum (and new to Arduino), and not an English native speaker… please forgive my mistakes :slight_smile:
Here is my challenge: I am planning to automate a chicken coop door, using Mega 2560, H-bridge L298N… some extra modules for light sensing and door switche, and a second-hand Mitsumi M49SP-1 stepper, taken for a HP Printer I believe.

I found plenty of info about M49SP-2K with Arduino, but none about *-1 version. I And to make it even more confusing, it has 4 wires… but is said in documentation to be a 4 phases bipolar stepper ?!?

Still, I connected it via L298N, and used the OneStep example library, and it indeed works, but it is very weak. The rotor goes both ways, in steps, but I can block the rotor with my finger tip barely touching it.

I tried all possible combinations of the 4 wires (they all 4 are purple in color) , and either nothing happens, or it works, but very weakly. The motor is powered (through the L298N) with the adequate 12v-1.4A.

?? Anyone having any advice, schematic ? I attached the M49SP-1 datasheet.

Four wires is normal for a bipolar stepper motor.

Please measure the resistance (Ohms) of the motor coils with a multimeter and post the results.

What do you mean by "12v-1.4A" - is that the capability of the power supply you are using.

...R
Stepper Motor Basics

I will check the resistance tonight, I am away from home at the moment.
But I have somewhere in my mind that it wa 1.8 Ohm, which indeed what is labeled on the motor.

In which case I may see what's the issue : 12v , 1.8Ohm --> I need more the 6A !!

And the my alim is by far to weak.

There is no obvious relationship between the voltage, the ohms and the current that will fry the motor. Normally when you see a motor datasheet it will tell you the permitted current (amps).

If you don't have the correct datasheet you will have to guess and I would start with 1 amp. How does the resistance of the motor you have compare with the resistance of the motor for which you have the datasheet? And what current is permitted by the datasheet?

The problem with using an L298 rather than (say) a Pololu DRV8825 is that the L298 has no simple way to limit the current to protect the motor. The DRV8825 board has a small potentiometer for that purpose and that allows the use of higher voltages which would otherwise cause too much current to flow.

You can expect a stepper motor to be hot enough to feel uncomfortable to touch with a finger. If it seems too hot you would need to reduce the current. If it remains cool you could try increasing it.

...R

Ok Robin, in fact from the voltage pov, I am powering the Motor with expected voltage. In other words, the M49SP-1 motor is rated 12v, and was powered with 12v in the printer (but that alim is dead) , and basically it is now connected to a 12v source.

Thus in theory I cannot fry the motor. I provide the very expected voltage. But according to the resistance of that motor, it needs some 6A to run correctly... when my actual source can deliver max 1.5A, which may explain that the motor does not run correctly.

And if I am not wrong, I can basically connect the motor to a rated 20A source... the motor will not fry, it will take the 6A it requires, according to the U=R.I rule ?

jmdiels:
And if I am not wrong, I can basically connect the motor to a rated 20A source... the motor will not fry, it will take the 6A it requires, according to the U=R.I rule ?

According to this info....

They reckon it's 30 Ohm per 'phase'. So expecting 400 milliAmp per phase at around 12V DC. They reckon 4 phases. So assuming 1 coil is 1 phase, then expecting about 1.6 Amp needed. But since L298N can only handle a certain amount of power ..... the L298N could be out of normal operation limits. See what happens if you drop the RAW motor supply voltage to some smaller value (less than 12V DC)..... such as 8V DC or maybe 10 V DC.

jmdiels:
Thus in theory I cannot fry the motor. I provide the very expected voltage. But according to the resistance of that motor, it needs some 6A to run correctly... when my actual source can deliver max 1.5A, which may explain that the motor does not run correctly.

And if I am not wrong, I can basically connect the motor to a rated 20A source... the motor will not fry, it will take the 6A it requires, according to the U=R.I rule ?

I would be very surprised if a motor from a printer requires 6 amps. The 400 mA that @Southpark suggested seems more likely. You MUST measure the resistance before going any further.

...R

Hello all, it is now all working :slight_smile:

First issue solved :
Having a 12v source, I was using the L298N to power the Arduino (via the 5v out of L298N) and the Motor. But as you know, L298N can take up to 30v, if you remove a Jumper, and in this case the 5v becomes "in", and L298N must be powered by the Arduino itself. --> I tried that configuration , and bingo, the motor has its full power !
Second problem solved: Any example Stepper library coming with the Arduino does not work properly. I had to look for some "hand made unipolar" library to have it working properly. Now it is all fine.

I guess this is all due to this "special" M49SP-1", which seems to be one of a kind!

Thanks all for your help and support.

jmdiels:
Hello all, it is now all working :slight_smile:

First issue solved :
Having a 12v source, I was using the L298N to power the Arduino (via the 5v out of L298N) and the Motor. But as you know, L298N can take up to 30v, if you remove a Jumper, and in this case the 5v becomes “in”, and L298N must be powered by the Arduino itself.

That’s one of the stupid things about the L298N. Its pin labelling or usage is not really intuitive. I think it catches many users out - not necessarily the fault of the user. It’s really more to do with the lack of really easy to understand information about what we’re supposed to do with the “5V” pin.

Also… a quote from a L298N instructions source says:

Note that the 5V regulated power on pin 5 above is an output when the 5V_EN jumper is in place. Otherwise you must input 5V regulated power at pin 5 so that the circuit can operate properly. Do not enable the onboard 5V regulator if you are supplying more than 16V to motors on the VMS (motor supply) pin, or the regulator will burn out.

The above is semi-clear. But what they really should say is something like:

The “5V” pin can EITHER be an output pin or an input pin - DEPENDING on whether or not the JUMPER (written as “5V_EN” aka ‘5 Volt ENABLE’) is connected or removed. If this jumper is connected, then this will enable an onboard 5V voltage regulator circuit, and the “5V” pin will be an OUTPUT pin having an output voltage of 5V (which could be used to power an arduino). The voltage regulator (when it is enabled ONLY) will also power the L298N logic circuitry. Do not enable the onboard 5V regulator if you are supplying more than 16V to motors on the VMS (motor supply) pin. That is, if supplying more than 16V to the motors, then the 5V_EN jumper needs to be removed, otherwise the regulator can be damaged.

If the 5V_EN jumper is removed, then the onboard voltage regulator becomes disabled, and the L298N logic circuitry will be unpowered. In this case (with jumper disconnected), the “5V” pin becomes an INPUT pin, and an EXTERNAL regulated 5V supply must then be connected to this “5V” pin in order to power the L298N logic circuitry.

Too many manuals, instructions, teaching guides, text books, papers etc out there are too vague. If only they put in that little bit of extra effort to get the message across properly, then everybody would be better off.

Indeed Southpark.
And I can even tell you I have seen a few diagrams with totally wrong connections, that would result in the burning the regulator!

Well, on the other hand, this is to me part of the pleasure of DIY and OpenSourcing: challenge and question what google tells you, and compare several sources and approaches to get the best of it.

Thank you all