i have a nema 17 17HD48002H-22B motor, with 0.59Nm, and i drive it with DRV8825 with a current limit of 1.7A.
when it works, i seem to be able to stop it with my grip easily, at slow speeds and fast speeds.
am i doing something wrong? i thought that this kind of motor will be very powerful.
is there something i can do to increase the torque?
The DRV8825 driver cannot deliver 1.7A continuously without extra cooling.
It may be going into thermal shutdown, so carefully set it to 1.4 or 1.5A and try again.
Post the voltage and current rating of your motor power supply.
the DRV8825 has a heatsink.
the power supply is 9V/1.75A
i've tried working with a 12V/3A power supply but the result is the same
The motor will work better with the higher voltage power supply.
Are you sure you have the current limit set correctly?
Post your program.
I measure the current limit with a multimeter between the trim pot and gnd, i've set it to 0.85v, which by the formula of (Current Limit = VREF × 2) gets me to 1.7A
At the moment the program is just for testing the motor, has it constantly spinning.
const int stepPin = 3;
const int dirPin = 4;
void setup() {
// set the two pins as outputs
pinMode(stepPin,OUTPUT);
pinMode(dirPin,OUTPUT);
}
void loop() {
digitalWrite(stepPin,HIGH);
delayMicroseconds(800);
digitalWrite(stepPin,LOW);
delayMicroseconds(800);
}
What happens if you try a much lower speed?
The net torque of a stepper motor declines with speed. If you need high speed then you need a high voltage supply - perhaps 24v or 36v if the driver can accept that.
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Even when switching the delayMicroseconds() function to the delay() function and using very slow speeds i can stop the motor with my grip.
You need to measure the torque produced by the motor. Maybe your grip is very much stronger than my weak fingers.
There is a simple method for measuring torque in Stepper Motor Basics
Start by measuring the holding torque.
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Well, i just measured the holding torque
It's about 362g per 10cm, which is 3.62 kgm
35.5 Newton meters? How about a picture of that motor, I think you're off by a factor of about 50. :o 
Exactly how did you measure torque? I would expect somewhere in the 2 to 3 range.
gania13:
Well, i just measured the holding torque
It's about 362g per 10cm, which is 3.62 kgm
No, that's wrong, torque is the product of force and distance, not the ratio.
362gf at 0.1m is 36.2 gfm, or in modern units 0.354 Nm (gf = gram-force, to distinquish from grams)
You are right, i didn't calculate it right.
i printed on a 3d printer a 10cm radius wheel with a mounting point on the edge and started testing at which weight will it move, the motor and arduino were powered and in static state.
An unloaded stepper is undamped and will be very susceptible to resonance effects like stalling until is has
a reasonable amount of mechanical damping, or microstepping is used.
what do you mean unloaded?
it's connected to a driver and power supply, and the arduino is loaded with a program that currently holds the motor in place until an optical sensor sends a signal to the board.
gania13:
what do you mean unloaded?
Without any mechanical load on the output shaft
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