Re: Hey Tim!

> From: "Tim Goldstein" <timg@...>
>
> Matt,
>
> I didn't have this, but I do now!! Ask and you shall receive.
>
> Go to http://www.ktmarketing.com/CNC.html and it is the link labeled
> "Calculate Steps/In for setting up your stepper software" which you'll find
> as the last entry in the upper block of links.

I would swear I saw this somewhere on your site, or maybe you have some other
calculator type page? Anyway, Thanks!

> Let me know if it causes any problems.

Actually, I got a question via e-mail about what value to use if you have 5mm
pitch leadscrews like some of the Asian machines have and I wasn't sure what
value was wanted (steps/inch), or even whether it went in INPUT_SCALE, or
OUTPUT_SCALE. Your calculator accepted 5.08 TPI with no problem.

> Does this mean that you just about have a stepper setup running on EMC????

I'm slowly getting my Bridgeport BOSS4 conversion done. I assembled the
Camtronics 5A stepper driver board and hooked it up to the original BP motors
and they work! It's a little hard to keep the acceleration rate slow enough
using the onboard pulse generator to avoid phasing out the motor. I will say
that raising the power supply voltage increases the maximum acceleration rate
considerably. There seem to be certain RPM ranges where the motors are more
sensitive to the pulse rate change. I am doing this on the bench at the
moment, so there aren't any mechanical loads on the motors and I'm hoping
that once the motors are loaded that the added inertia of the system will
help reduce this effect. Another possible problem in that I rigged up a power
supply using a variac, bridge, and a smaller than recommended filter
capacitor. I think it may be possible that excessive power supply impedance
may be the cause of some of this effect as well. When I bought the kit I also
added an additional 6 .1 ohm resistors in parallel with the existing sense
resistors which increases the range of current adjustment to about 10 amps
max. I haven't gone past 5 amp so far, but I may have to in order to get
these large motors to work without losing steps. So far cooling hasn't been a
problem, but I'm not taking any chances until I can get everything mounted in
its permanent place with a fan and the final version of the power supply. I'm
using a couple 120V/12V 35A transformers with their primaries and secondaries
in series and the ubiquitous bridge and a filter cap I salvaged from the old
electronics, 16000uF@50V. I had it all hooked up and I put 240 across the
input with nothing other than the bridge and cap attached to the secondaries.
It worked really good, putting out 38-1/2 volts for about 2 minutes and then
the primary of one of the transformers went up in smoke :(. I moped around
all day after that happened! I think I need to tie the center tap of the two
primary windings (created by my connecting them in series) to neutral to
ensure that each primary gets only 120V across it. I had left the center tap
floating and perhaps there was some difference between the impedance of the
two primary windings that caused the problem. Or maybe the transformer was
just bad. I like that explanation better myself. Another thing I learned was
to always fuse the primary circuit of transformers! I ordered 3 more
transformers (you can never have too many), and eagerly await their arrival
along with the PC, etc.

I'll be done, uh, _Any Day Now_,

Matt