Hi All,
Having just got my hands on a couple of cheap Nema 17 stepper motors and done a bit of testing.
I feel another robot coming on, one that can draw perhaps!! I can drive the motors OK, no problems YET!!
Wanting to work out things like, distance per wheel REV, steps to turn, etc.
I came up with the following Excel work sheet, the maths seem simple, but have I over looked anything?
Here's a shot of it and the full job is uploaded (I hope) would be good if some of you could take a look, at it could even prove to be useful to others.
Your PNG is not exactly the same as your spreadsheet and I think the spreadsheet is correct.
Rather than use floats you could use integers representing 0.1mm so the distance per step would be 14 rather than 1.41.
Another option, if your stepper can do 1/8th steps is to do your calcs in units of 0.125mm - so 1.41 becomes 11
You get a bit more precision and it is easy to revert to "real" measurements.
But, then, by using integers rather than floats maybe you will accumulate errors. Maybe it is better to use floats and just convert to integer steps for motor control. And don't ever convert the integer steps back to floats.
And another thought, if you plan to control the device from your PC you can do all the calculation in high precision and just send the actual numbers of steps to the Arduino. That is what I do to drive a small lathe.
Hi Robin,
Thanks for your reply. I am using a couple of cheap controller PCB's with the A3967 on-board and this will let my do 1/8th micro-stepping! In fact it's wired that way by default, which confused me when I ask it do do a 200 count spin and it only moved about 45 Deg. It seems micro-stepping gives me very smooth movement and also quite movement. As for the maths! think I might carry on as now, until I get something that moves, this buggy I hope will be able to draw...
Here's a couple of images the PCB and an updated excel page, 1600 steps per REV??
