RE: [CAD_CAM_EDM_DRO] stepper issues

Update -

Thank you all for your input - it was useful and quick.

This student is a "winner" in my eye for just taking this on and allowing me
to blindly "lead". I just didn't lead fast enough.

We tried several of your suggestions, but I'm now thinking that we just
don't have a big enough stepper and/or have too much noise in our circuit.

Temp of 5804 rises only about 10 deg F, fr 75 F to 85 F.
Temp of motor doesn't rise appreciably.
We slowed motor substantially and still get resonance. May bave too much
hysterisis in the mechanical drive - but the motor has some trouble without
trying to drive the cart.
Sometimes now the motor just doesn't start out correctly - leading me to
believe the error might be inherent to the circuit/motor, rather than an
accumulation.
As I read the 5804 datasheet, we can only run 7V Vcc to it, and we are
thinking that the motors are only 5-6V, so we removed LM7805 and made whole
circuit Vcc and Vm run at 7.2 V.
I think we have diodes placed correctly - we used 4001's I think, but we
shall draw this circuit soon, which has really been "compiled" from 4
circuits and may have messed it up somewhere along the way.
We'll try the half stepping today - we had hardwired those, so it'll take a
little bit to change, vs having installed a switch to begin with.

And as for Phil's comment about the R/C tolerances - a question - so are the
errors in R and C repeatable? That is, if a C is rated 10 uF and 20%, is it
always 8 or 9 or 10 or 11 or 12, or is it 8 sometimes and 12 at other
times?? If it is repeatable, we can calibrate it out, but if not, well I
sure get your point.

So, what are we going to do? Well, we've learned a lot, but not fast
enough, so I think today we will drop a VEX motor, encoder and switch to the
cart, toss about 10 lines of EasyC code at it probably have a cool unit. I
had actually hoped to get to this point after having successfully
accomplished a timing/counting stepper circuit, so he could more fully
appreciate today's technology vs that of some years ago, but we leave for
the competition today and it goes off tomorrow. Will be a limited swimming
time at motel for him tonight :o))

We have a couple 2 phase motors - might they work better? We chose motors
we could drive with a unipolar driver, since it all looked easier, but we
have a couple 2 phase motors and I'd like us to build the drivers.

Thanks again!! Will pick this up after Thanksgiving - and hopefully get a
stepper circuit to work - I still want to build a CNC router with the kids
and saw this as a good first step.


Chuck

<http://www.srvscience.org> www.srvscience.org
Lemelson-MIT Inventeams - http://web.mit.edu/invent/n-main.html
US FIRST Robotics - http://www.usfirst.org/




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