[TriEmbed] Stepper motor help

[Craig Cook]

I think we have a winner!
Found a 5V supply that says it has 3.0A. Now the larger stepper does its rotations.
The wiring is:Black A+Green A -Red B+Blue B -
 
Replaced my adifruit stepper, now the rope is pushed with authority.
Next: find out why arduino code has bugs. Simple program uses Stepper.h and tells the stepper to move one revolution, pause 2 secs, continue in same direction.  Sometimes the motor goes backwards though.  What fun.

Thanks
Craig

    On Monday, January 22, 2018, 11:13:07 PM EST, <jonjwolfe at anibit.com> wrote:  
 
 
As soon as I sent that last mail, I thought maybe the supply isn't 
crapped out at all, you're probably just supplying too much voltage to 
the motor, and a PTC fuse in the wall wart is tripping, causing the low 
current reading you are seeing (sometimes they hum or squeal when this 
happens). That PTC might actually be saving you from burning out the 
motor(though PTCs will burn out eventually too if abused, which will 
ruin the power supply).

I would recommend you DO NOT try a different power supply, but first 
make sure you're current limiting to 2 Amps to the motor. The motor when 
it sees 12V is going to try to draw 10.9 amps! That will surely make the 
wall wart freak out, which is probably why the current reading goes so 
low. If you did find a supply that could give you that many amps, then 
your motor would quickly self-destruct.





On 2018-01-22 21:00, jonjwolfe at anibit.com wrote:
> My first suspect would be that your recycled power supply is crapping
> out. Can you test it with a different supply? Those are the same
> motors used on a lot of 3D printers, so they should have a decent
> amount of torque. Is your "capstan" wheel large? If you're shopping
> for steppers, look at the holding torque values when comparing them.
> 
> There is also the possibility that you burned the motor out (though in
> my experience they seem to be able to withstand a fair amount of
> abuse). The current rating is what is important for steppers, so at 2A
> and 1.1 Ohms, the max voltage at hold should be 2.2 Volts. That's
> quite lower than what you're giving it. I would measure the resistance
> across the appropriate leads to make sure you're getting around 1.1
> Ohms. If not, the motor might be fried.
> 
> 
> Also, steppers loose torque dramatically as they speed up, so the
> drivers like the Pololu a4988 and its kin can help by letting you
> safely "overdrive" the stepper by limiting the current, but supplying
> a higher voltage than what the motor is listed for. They will let you
> supply 12V and, at hold, will drop the voltage down to 2.2V. Once the
> motor is moving and providing back emf (or whatever it is called for
> steppers, same principle), the Pololu drivers will allow higher
> voltages to pass through it to keep the current at 2Amps as much as it
> can.  You'll have to browse Pololu's stepper driver offerings to find
> one that can do 2A.
> 
> I'm pretty sure the L298-based drivers are nowhere near that
> sophisticated, but tend to have a better current/price ratio, so if
> they work for your application, they make sense.
> 
> Also, the Pololu drivers do microstepping, which can lower the
> instantaneous torque applied and possibly help you avoid stalling, if
> you "accelerate" the step speed. I know first hand in CNC applications
> steppers can be very sensitive to the acceleration rate.
> 
> 
> 
> On 2018-01-22 19:52, Craig Cook via TriEmbed wrote:
>> I have a project where I need to move a stepper motor, it needs to
>> push a 1/4 inch rope through a roller.
>> 
>> I have one of these working: https://www.adafruit.com/product/324 but
>> it seems to lack pushing power.  If I help pull the the rope it works
>> well.  I think I need a more powerful stepper.
>> 
>> I also have one of these:
>> https://smile.amazon.com/gp/product/B00PNEQI7W/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
>>  (17HS16-2004S1)
>> 
>> I am using this to drive them:
>> https://smile.amazon.com/gp/product/B014KMHSW6/ref=ask_ql_qh_dp_hza
>> 
>> I think it should work. My power supply says it is DC output 12 V,
>> 3.33A Max. (I think it came from an old laptop or printer)
>> 
>> With no pressure on the Adifruit stepper it seems to work. When I try
>> the other stepper, it gets lots of pauses, the power light on the
>> L298N flashes on sometimes and the stepper hums like it is trying to
>> move.
>> 
>> I'm using an Arduino Uno to control everything.
>> 
>> When the larger stepper is trying to run I measure around 3 V at the
>> power terminals on the L298N, around 0.01 mA (using breadboard jumper
>> wires to connect power supply to controller).
>> 
>> Do I need a different motor controller? Should I find a different
>> stepper? Should I buy a bench power supply?
>> 
>> Thanks
>> 
>> Craig
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