Re: stepper issues

Precision of the R/C components is relative to the stated values, but there
is also some variation due to temprerature and other factors. You could
calibrate a timer specific to the components you use, but for long R/C
constants, temprerature and other factors come into play much more. I
believe this is explained somewhere in the 555 timer documentation.
--
Phil Mattison
http://www.ohmikron.com/
Motors::Drivers::Controllers::Software

----- Original Message -----
From: Chuck Merja <chuckm@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Cc: <sqone@...>
Sent: Monday, November 19, 2007 6:24 AM
Subject: 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/
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
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