Choosing stepper motors page
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How accurate/up-to-date is this wiki page: https://duet3d.com/wiki/Choosing_stepper_motors ?
This question is mainly directed at @dc42 because as I understand it, he tested the values there. What I found out from the formulas there, is that the formula for back EMF inductance doesn't make any sense. The values @dc42 got are wrong due to rounding (I guess? What else could it be). What I got was completely different, and basically after applying this formula I got the supply voltage back. Always. Changing inductance, current etc. had no effect on this, meaning you could never have a high enough supply voltage. I've prepared an example spreadsheet with the values from that wiki page: https://docs.google.com/spreadsheets/d/1OVMbsiDDr5Fs4YFG2YvgqywIt_NdG0XkNiIsKGuiXL8/edit?usp=sharing
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In cell C10 you calculate the revs/second as (2C3)/(C4PI()C5C7)*1000 where C3 is the supply voltage. That isn't right, you should have the target belt speed there instead. I haven't checked the rest of the calculations.
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That's the exact formula from the linked wiki page: revs_per_second = (2 * supply_voltage)/(steps_per_rev * pi * inductance * current). It's the max revolutions per second of the motor itself, why would a target belt speed be in there?
