this is what Anaheim Automation uses in their combined stepper
motor/driver models:
https://www.allegromicro.com/en/Products/Motor-Driver-And-Interface-ICs/Bipolar-Stepper-Motor-Drivers/A4975.aspx
http://www.anaheimautomation.com/products/stepper/stepper-integrated-list.php?cID=50
On 3/21/2018 2:03 PM, WAM wrote:
> For my bandsaw feed I used simple timer like IC and driver for the
> stepper:
> http://www.ajawamnet.com/ajawam3/swarf/bandsaw.html
>
> For z axis of the sieg mill I used an arduino with an Anaheim
> automation stepper with integral drive built in:
> http://www.ajawamnet.com/ajawam3/swarf/mill_mods.html
>
> For my CNC I went with Gecko. One of the reasons I went with Gecko is
> that Mariss has dealt with the dynamic of stepper motors for long
> time. One issue that you can run into is resonance. Typically you'll
> never see it - but if you run enough jobs you'll come across it; where
> it just so happens a line of G code will cause one or more of the
> steppers to hit it and stall:
> http://homepage.divms.uiowa.edu/~jones/step/physics.html#resonance
>
> "In practice, this oscillation can cause significant problems when the
> stepping rate is anywhere near a resonant frequency of the system; the
> result frequently appears as random and uncontrollable motion. "
>
> and this
> http://www.haydonkerkpittman.com/learningzone/technicaldocuments/stepper-motor-theory
>
> "Resonance
> Stepper motors have a natural resonant frequency as a result of the
> motor being a spring-mass system. When the step rate equals the
> motor's natural frequency, there may be an audible change in noise
> made by the motor, as well as an increase in vibration. The resonant
> point will vary with the application and load, but typically occurs
> somewhere between 70 and 120 steps per second. In severe cases the
> motor may lose steps at the resonant frequency. Changing the step rate
> is the simplest means of avoiding many problems related to resonance
> in a system. Also, half stepping or micro stepping usually reduces
> resonance problems. When accelerating to speed, the resonance zone
> should be passed through as quickly as possible."
>
>
>
> I talked with Mariss about how he handles this in the older, all
> analog drives as well as the newer ones that use an FPGA. On the older
> 201's he does it using a slick comparator circuit that detects it -
> most probably like Jones mentions:
>
> "Controlling resonance in the low-level drive circuitry
> A resonating motor rotor will induce an alternating current voltage in
> the motor windings. If some motor winding is not currently being
> driven, shorting this winding will impose a drag on the motor rotor
> that is exactly equivalent to using a magnetic eddy current damper.
> If some motor winding is currently being driven, the AC voltage
> induced by the resonance will tend to modulate the current through the
> winding. Clamping the motor current with an external inductor will
> counteract the resonance. Schemes based on this idea are incorporated
> into some of the drive circuits illustrated in later sections of this
> tutorial. "
>
>
>
>
>
> On 3/21/2018 1:44 PM, Chris Albertson albertson.chris@gmail.com
> [7x12minilathe] wrote:
>> Yes, you can make a pulse generator. But when you have a lab bench
>> full
>> of test instruments you tend to use the instruments for testing. The
>> signal generator can do "sweeps". this is where it changes the pulse
>> rate
>> per time. I can sweep the step rate and in that way measure
>> acceleration. I get measurements good to more decimal points than I
>> need
>> and I don't need to build anything.
>>
>> In the end the motor will be controlled by some kind of computer, likely
>> one running Linux and LCNC or MK.
>>
>> I think if I were building a simple power feed I'd want at least a
>> tiny LCD
>> screen that reads out the feed rate in units like mm per second or
>> inches
>> per minute and some stop/start and direction buttons. The 555 timer
>> can't
>> drive the LCD. And you'd want to be able to make it stop EXACTLY at
>> some point (because maybe you are milling an internal pocket.)
>>
>> The hard part of building a pulse generator for a power feed is
>> getting the
>> user interface right. Generating pulses is trivial. But I think the
>> user wants to set the feed rate BEFORE he presses "start". and likely
>> wants to be able to set a limit. I would like to be able toes and
>> verify
>> those numbers before I press "go".
>>
>> Cost for a controller of any kind is very low, so that is not the issue,
>> the hard part is figuring out what it should do.
>>
>> One use case of the CNC mill will be to design parts using Autodesk
>> Fusion
>> 360 then make parts. But this is a long process. For simple things,
>> like boring a hole or pocket or face mining or dozen other easy jobs
>> I'd
>> like to just tell the machine what I want done. Where the current
>> state
>> of the art needs to be "pushed" is right there -- how to tell a machine
>> what you want. Current methods are primitive and limited
>>
>> On Wed, Mar 21, 2018 at 9:52 AM, mark.kimball2@frontier.com
>> [7x12minilathe]
>> <7x12minilathe@yahoogroups.com> wrote:
>>
>>>
>>> RE: pulser for simple stepper control. I made one for zero dollars
>>> -- I
>>> already had a 555 timer chip, and my electronics scrap box had the perf
>>> board, resistors and capacitors I needed to make a simple clock
>>> generator..
>>> A slide switch allows me to select the direction, and I can adjust the
>>> clock rate with a pot.
>>>
>>> I used the thing to run a stepper as a low-speed diamond grinder for
>>> shaping and sharpening carbide scrapers. I bought a set of 6" diamond
>>> lapping disks from a lapidary supply outfit, 150 grit up to 3,000.
>>> The low
>>> speed keeps everything cool (particularly since I run the bottom
>>> portion of
>>> the disk through a pool of water). It does a good job for me. I
>>> made a
>>> simple arbor to mount the disks using my lathe.
>>>
>>> The ebay pulse generator looks like a good value if you're not able or
>>> willing to DIY one.
>>>
>>> Mark
>>>
>>>
>>
>>
>
Posted by: WAM <ajawam2@comcast.net>
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