Low cost, public domain, stepper analyzer - season 2.
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The analyzer now can measure and show fractions of a full step in 1/100th of a step resolution.
The Allegro Microsystems datasheet such as this one (starting at page 16) https://www.allegromicro.com/-/media/files/datasheets/a5985-datasheet.ashx provide useful information about the relation between the current and the sub-step position.
The current patters are divided into electric cycles or 'electric rotations', each representing 4 full steps and the position of the stepper within that electric rotation can be done by feeding the two coil currents into the standard trigonometric function atan2(current1, current2). It ended up simpler than I expected.
I also updated the firmware and 4 steps diagram to reflect the new understanding that the centers of the full steps at the points where both coils have the exact same current (regardless of polarity, this happens at ~70% of peak current which is also the RMS current) and not when one is at its peak and the other at zero as I thought before.
I tested it with a Pololu stepper driver, incrementing a 1/8 of a step every 2 seconds and watching the display. Works like a charm.
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I am really interested in buying some when it is available. As a mounting kit or fully assembled. Any price is cheap just by saving time with this amazing idea.
I'll keep an eye around here.
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I am experimenting now with a new screen whose purpose is to evaluate the signal and phase cleanness. It takes the signals from the two coils and draw them as https://en.wikipedia.org/wiki/Lissajous_curve .
Here what you get from a well fed stepper with good microsteps interpolation, a balanced, large and smooth circle.
And this is what you see in a system where the supply is insufficient to drive the current at high movement speeds. Skinny and distored.
BTW, each rotation along the circle is equivalent to 4 full steps that make up a single 'electronic rotation'.
These patters are shown in real time while the printers operates. This screen is experimental, need to clean it up and include in the official release.
EDIT: here is an interesting animation from Wikipedia that shows how it works:
https://en.wikipedia.org/wiki/Lissajous_curve#/media/File:Circular_Lissajous.gif
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PCBs are here,
i can supply the pcb, the two sensors and the eprom.
due too some family buisness i do not know if i can solder them in the next weeks. So selling the parts only would be the best for me. Best -
No problem to sold them myself.
How do we proceed to pay you? -
Contact me via PM
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So for the price.
5 € the pcb
2,5€ for the sensors and eprom
1€ for 40 pin connector
1€ for resistorsdue to a mistake at digikey the capacitors are to small.. So these have to be self sourced ( easy)
shipping with tracking 8€ without 4€ in europe
germany 3 € shipping -
@PCR said in Low cost, public domain, stepper analyzer - season 2.:
So for the price.
5 € the pcb
2,5€ for the sensors and eprom
1€ for 40 pin connector
1€ for resistorsdue to a mistake at digikey the capacitors are to small.. So these have to be self sourced ( easy)
shipping with tracking 8€ without 4€ in europe
germany 3 € shippingDo you have any for sale?
Can you ship to the US?
Thanks.
Frederick
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I have about 20pcbs and for 10 pieces parts
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I sent you a message in the private chat; did you get it?
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This post is deleted! -
Hi @PCR, did you manage to get it working? Any problems with the design?
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where are you purchasing acs70331 ?! comet don't hold them, jlc don't have them, mouser offer only dev boards, digikey nothing on stock for ages and min order q is 6000 .. I was looking to get them for another project but ..
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@arhi orderd them at digikey.
Best
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@arhi , this is the digikey part I used https://www.digikey.com/en/products/detail/allegro-microsystems/ACS70331EESATR-2P5B3/8120682
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@PCR do you still have spare boards and parts?
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@zapta I really love your project! Just what I was looking for!
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@PCR what part? QFN also or?
@zapta that's QFN
I need soic and taht's 2.5A I need 5A ..I'll probably go then with 5A regular HAL ACS712 .. it's not fancy GMR but regular HAL but at least I can get it easily .... I hoped I can easily get GMR version in soic8 package but..
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@zapta I'd like to get one of your boards, if you still have one. I sent a private chat message.
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@tenaja, don't have spare boards left but I can make a few for shipping in the US if there is a demand. It will be at cost, and you will need to order the TFT display from buydisplay.com yourself.
