Greater than 1000 steps/S?

[Matt Hodder]

Hello All,

I can't seem to get a very hight step/sec count out of my arduino mega 2560 and accelstepper, Im curriouse how fast other people are able to get up to, I see in the design sight that speeds over 1000 are unreliable.

 

My situation is this,

I have built a linear machine that uses a 10mm/turn ball screw, that is paired with a nema 23 hybrid server/stepper with encoder. I have to be able to achieve a speed of 1 in/s travel speed which is about 2540 steps/second.

In the past I have corrected this by using different microstepping on my driver, however this hybrid drive is synced with the encoder and locked in at 1000 steps/rev.

 

I guess what im asking is should I be looking for a mechanical solution to this problem or is there some hope for a software solution.

 

Thanks

 

Matt

[Brian Schmalz]

Matt,

 

Using a chipKIT UNO32 (or any chipKIT compatible board – there are several) allows me to run the Accelstepper library unchanged, and get far faster step rates. I don’t think I’ve measured the maximum I can get reliably, but it will have no problem doing 4Ksteps/s, and I think quite a bit more.

 

*Brian

 

Brian Schmalz  //  Principal Embedded Systems Engineer | product development services

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[Matt Hodder]

Brian,
Thanks for the info, I currently have this project fully wired and
programed on arduino mega. I’m not 100% against changing boards, it’s
just that it’s a little late in the game to do so now.
Currently I am using accelstepper, liquidcrystal, and EEPROM
libraries. From what I can tell the EEPROM library does not work at
all on chipkit. currently I am storing speeds and positions in the
EEPROM so that after a reboot they dont need to be entered again.
I also use about 20 pins as inputs for buttons, it looks like I would
have to add pull-up resistors manually for those.

The concept does look more appeasing that designing a belt drive
system, but it looks like I would have to figure a lot of things out
first.

if you know of any workarounds for the EEPROM issue then id be happy
give it a try.
is there any way to mount an sd card and do reads from that?

Thanks
Matt

[Brian Schmalz]

Matt,

Yup, you can use an SD shield, or use a Fubarino SD board (disclaimer: I designed that one) : http://www.seeedstudio.com/depot/fubarino-sd-p-1265.html?cPath=132_133
Which comes with a microSD connector all ready to use. But the SD library does work properly in the latest MPIDE test build.

The EEPROM library does work, I believe, on the chipKIT boards, as we were doing testing with it early on and I believe all of the problems with it have been resolved.

And many pins do have pull-ups available on them (but not all). All of the CN inputs can have pull-ups turned on inside the PIC32. I think there are, what, maybe 18 of those?

*Brian

-----Original Message-----
From: accels...@googlegroups.com [mailto:accels...@googlegroups.com] On Behalf Of Matt Hodder

[Chris Kelley]

Hi Matt,

I am using this library with a Mega and Rugged Circuits rugged motor shield and the stepper motor is Pololu pn# 1208. Iteratively using various values, I learned that for my stepper to get over 1k rpm (with 12V 1A wall wart), I needed to use the highest power setting (255). If the power isn't enough to make the rpm work, the stepper skips steps, which seems to aggravate the whole situation, as the library somehow knows not to count those missed steps. I played with acceleration values and stopped trying at 15000.

I'm sure there's a lot I don't know, but seems my experiments yesterday might help answer your question.

:) Chris

[Brian Schmalz]

Note that on a faster platform like the chipKIT (Arduino compatible PIC32 @80MHz) you can achieve far more than 1000 steps/second. I reach the limit of my stepper motors before the library poops out. And AccelStepper runs great on chipKIT boards.

 

*Brian

 

From: accels...@googlegroups.com [mailto:accels...@googlegroups.com] On Behalf Of Chris Kelley
Sent: Tuesday, April 2, 2013 6:57 PM
To: accels...@googlegroups.com
Subject: [accelstepper] Re: Greater than 1000 steps/S?

 

Hi Matt,

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[Matt Hodder]

I ended up using an arduino due board, external EEPROM and a logic level converter to achieve over 4000 steps/s. I have since started building version 2 of my project and moved to an automation direct Plc for controls. The arduino platform is great for prototyping, but not robust enough for my needs.