Accelstepper doesn't give any step/pul Signal

Projects Programming
1

I'm trying to power a nema 23 with an update of TB6600 and a cheap arduino mega from ebay. When I manually generate the steps everything works fine.
Using the accelstepper library (with the setting for dedicated stepper drivers (AccelStepper stepper(1, 4, 5)) I don't get any Signal on the step/pul pin (the Voltage stays at 0V). I would expect 2.5V at high speeds and a shift from 0-5V for very low speeds.
When I change the driver setting to (AccelStepper stepper(2, 4, 5)) I get a signal (and also a ramping of the speed) but I don't get a useful signal for a dedicated stepper driver since the dir pin receives also an alternating signal.
I've used 10 different codes and tried all possible speeds and accelerations, also tried to use older versions of the library and tried different pins for step and dir.
Here is an example. I would be very glad for any idea.

#include <AccelStepper.h>

AccelStepper stepper(1, 4, 5);

void setup()
{  
    stepper.setMaxSpeed(400000);
    stepper.setAcceleration(1000);
    stepper.moveTo(100000);
}

void loop()
{
    stepper.run();
}
2

I would expect 2.5V at high speeds and a shift from 0-5V for very low speeds.

Why would you expect a pin that can be on r off to be halfway on?

3

It sounds like you have the step and dir pins reversed.

4

Hey, thanks for you answers.
The 2.5V is just because i measure with an analog multi-meter, so I get the average of 0V and 5V. I checked, if i reversed the dir and step pin, but that's not the case (I also tried both ways). The dir pin works fine (+5V or 0V when going in plus or minus direction).
Any other ideas?have

Thanks again

5

I would expect the step pin to produce very narrow pulses - about 10 or 20 microsecs. That is very short compared to the interval between pulses which is probably measured in 10s of millisecs And because of that the duty cycle won't change much even when the interval between pulses changes.

You really need an oscilloscope to examine that sort of stuff.

These are ridiculous numbers

    stepper.setMaxSpeed(400000);
    stepper.setAcceleration(1000);

Try 400 and 40.

...R

6

Hey,

thanks a lot for the hint (I thought the pulswidth would be half of the step Duration which is wrong). The solution is, that my stepper driver can't work with a pulswidth smaller than 30mus. With the function stepper.setMinPulseWidth(30) everything works like a charm.

Thanks a lot again

7

That's interesting. This datasheet says that the minimum pulse width is 2.2 µsecs

There must be some other stuff on the board that is slower to react - maybe an opto-isolator.

...R