I have the Pololu A4988 Stepper Driver and I am trying to understand how to time the pulses and set the current limiter pot.
The way I understand to make the driver step is to:
Send the step pin high
Delay some amount of time to allow the A4988 to see the pulse
Send the step pin low
Delay some amount of time to allow the motor time to actually move
Repeat
How do I detirmine what the amounts of time should be?
Also, how do I know where to position the current limiting pot?
Power Supply Specs:
Adjustable Wall Wart Style Power Supply
1.3 A
10 V (but this can be adjusted)
Page 6 of the A4988 datasheet has timing specifications and diagrams. Beyond that, the motor can also limit your pulse speed. For example, our stepper motors have a torque pullout curve graphs on the product pages that compare torque to pulses per second. Example:
- Ryan
It looks like this char is not part of the data sheet in the link you have here or on the website. I am sure it used to be there but why was it removed?
We replaced that pull-out torque curve with an updated datasheet from the manufacturer, which includes a new pull-out torque curve. The current datasheet is available on the motor’s product page under the “Resources” tab.
Hello,
It seems there is some misinformation here.
We still can’t find any “pullout/pull-out” or “torque” mentioned in the A4988 datasheet, neither the one linked to on the Pololu site (revision 5 May 7, 2014) nor the one presently on Allegro Systems webpage (revision 8 April 5, 2022).
So the the OP’s question still stands unanswered: “How [does one] detirmine what the amounts of time should be?”
The pull-out torque curve is a function of the stepper motor and can be found in the manufacturer datasheets for our stepper motors.
As far as the A4988 driver, the timing requirements of the step pin are detailed in the diagram and chart on page 6 in its datasheet, as mentioned by ryantm. For reference, here’s a screenshot of the relevant information:
So I take it, that for each pulse width, any value works, provided it is ”longer” than one microsecond! I guess that’s a restriction one could learn to live with
Now l only need to determine a reasonable default value (range) in practise.
