Camtronics and Sanyo-Denki Review

I've recently tested the new 2amp Camtronics (
http://www.seanet.com/~dmauch/ ) controller and am quite happy with
it. I've also tested two different Sanyo-Denki stepper motors
from Mendonet ( http://www.mendonet.com/steppers/nema23.htm ).

Assembly of the controller is straightforward if you have some experience
with such things. My only suggestion is that Dan include more
documentation on the jumpers and connectors. There is no pinout of the
parallel connector and no schematic is supplied forcing me to trace the key
pins on the PCB and use the L297 data sheet to get my software configured
for the board. The pinout is somewhat non-standard but all the software
I'm aware of is easy to configure to work with the controller.

The PC board is high quality as are most of the components. The only place
he's skimped a bit is with the heatsinks. There has been some discussion
on this forum about running the board on higher than the rated 18
volts. If you plan to run more than 1 amp of current to your motors,
and/or more than 12 volts, bigger heatsinks are a very good idea (if not
essential) on the L298 chips.

Dan suggests the heatsinks need airflow from a fan for currents greater
than 1 amp. I'd very much agree. In fact, I'd say 12 volts (not 18) is
the maximum I'd go at 2 amps even with a good fan. I added an extruded
finned heatsink that runs the whole width of the PCB and probably has at
least ten times the surface area of the 3 small stamped heatsinks
supplied. Even with this relatively massive heatsink, running 2 amps at 24
volts, a fan is a good idea.

Dan has also mentioned the 5 volt regulator running too hot on higher
voltages. This is also true. The 5 volt current draw is about .25 amps
and it gets quite hot at 12 volts. With a 24 volt supply, the regulator is
putting off (24-5)*.25 or 4.75 watts which would require a much bigger
heatsink than the one supplied. A better idea is to run about 9 volts or
so into the board power connector. A cheap "wall wart" DC transformer
could probably be used.

The current reduction is independent for each axis and seems to work quite
well. The running and idle currents are independently adjustable for each
axis. I do wonder if it might drop a step or two under some circumstances
as the current is ramped up? So far I haven't caught it doing anything
bad. It also seems to be quite noise immune.

The Sanyo-Denki motors from Mendonet were promptly shipped and well
packed. They are the lowest inductance 2 amp motors I could find (and
hence should be faster than most). They also run quieter than other
similar sized steppers I've used. I did encounter a specific resonance
problem at 3300 steps/sec even with half stepping but I can't blame the
motors or controller. In practice, there are a few sustained feed rates you
might want to avoid or you could stall the motors. Only a microstepping
Gecko drive or physical damping is likely to get around this.

At 12 volts, the 232-117 motor (2 amp, 1.6 volt, 117oz) runs 1900
steps/second without ramping and 3500 steps/second with ramping on my MaxNC
mini-mill with the gibs fairly snug and zero backlash 20 pitch BSA
screws. Using half stepping, that works out to 14.5 in/min (285rpm) and 26
in/min (525rpm). Running 24 volts bumps the non-ramped maximum to 2100
steps/sec and a much improved 6000 steps/sec ramped. That works out to 45
in/min (900 rpm). Not bad for a stepper system!

The triple stack 232-180 motor (2amps, 2.1 volts, 180oz) is slightly slower
as you'd expect from it's higher inductance. On 24 volts, it runs 1800
steps/sec unramped and 4500 steps/sec ramped (34 in/min). It's a good
choice for the Z axis but even the smaller motors seem to have plenty of
torque. Both motors are available with single or double shafts. These
values are about 15% below the observed maximums before the motors stalled
or were noticeably dropping steps. You may want to be more conservative in
practice with your maximum settings.

Overall, for under $500 and a little effort, you have a CNC mini-mill
hardware solution that outperforms setups costing several times as
much. It's vastly superior to the 7 in/min and 70oz of torque you get from
the basic MaxNC system. It's also superior to their upgraded 12 in/min
145oz system. With a 24 volt power supply, it rivals their servo system in
speed.