3/20/2017, last updated
As discussed in the overview, the old controller went up
in smoke last fall, RIP. I couldn't get
the interest up over the winter to rebuild it.
Last fall I saw the controller that Laura and
Dominik of Integral Circuits made for the
small Critter Locomotives Dick McCloy
and Mike Price were making. It left
a good impression, especially the physical
packaging. I looked up the specs on
their website (www.integralcircuits.com
-the specific controller is Model CC 50A).
It does 50 amps continuous for 1080 watts at
24 volts and my motors are 500 watts each.
Called Laura and she said she could send me
one in a week and it arrived in a week.
Rather than describing the system I just
copied stuff from their website:
There is a neat wiring diagram on the
Integral Circuits website (link
to diagram) that shows all the
connections including the optional
accessories. To simplify this
removed all the wiring for the accessories
in the drawing above and kept only what is necessary to get it up
and running. I used a 90 amp 28 volt
breaker instead of the main fuse. I
used a 70 amp 28 volt breaker in the
positive lead to both motors instead of the
individual 30 amp fuses.
The main breaker is also the main power
switch. The motor breaker is normally
left on but is useful to disconnect the
motors when towing.
|The controller arrived before I
finished making a number of repairs
and the drive unit was still off the
frame. Great, I could
install the speed sensor as
described on page 26 of the manual
and repeated on the right. The
sensor is a magnetic reed switch that is
encapsulated in a ~3/8" diameter
plastic bolt and held in position by
a pair of plastic nuts.
The magnet is 5/16" diameter and
about 3/16" thick and really strong.
The end of the sensor is positioned
about 1/8" from the magnet.
I would have preferred to mount the
sensor above the motor mount
platform but there is no room so I
had to put it underneath as shown in
photo. A concern
was that I'd wipe off the sensor the
first time I derailed so I made the
pictured mount from a piece of easy
strut and 1/2" angle.
The wire feeds up through a hole in
the mount platform and is bundled
with the motor wires to get to the
controller was later set up for the
correct wheel size.
This shows the controller installed on the
plastic drive cover. The
controller is attached to a 1/2" aluminum
angle with Nylock nuts on two of the studs
the case. The 24 volt
power enters via the terminal block on the left.
The motor and speed sensor wires come up
through the channel behind the mount cover.
The motor wires connect to the terminal
block on the right and the speed sensor
cable plugs into the controller (small red &
white wires). That is the motor
circuit breaker mounted on the back of the
drive cover. The heavy (I used 12 gauge
stranded) wires connect to the controller
via provided barrel connectors soldered to
the ends of the wire. These connectors
are really neat. I questioned
the reliability but was assured that they
are reliable --- and quite expensive.
After everything was connected I found the
motors ran backward so I reversed the
motor wires in a couple seconds.
That brass hex rod sticking up is a really
tall head for one of the two 6-32 screws that
secure the drive cover. The cover must be
removed to reinstall and/or adjust the chain
so quick and easy removal is a must.
This is looking down on the
controller after the body was
installed. Laura suggested the neat
fuse block available from MCM Electronics
The power connection to the block is via a
bare stud and bar. I covered the stud
with heat shrink and the bar with silicone
caulk. I don't find low voltages
such as 24 volts intimidating.
However, I am intimidated by the high
current capability of the batteries that can
instantly turn a dropped tool into a welder.
Hence, I try to keep all exposed terminals
That is the radio unit
setting on the controller. It comes
with ~3' cable that is probably useful if
the controller is buried in the bowels of a
steel bodied locomotive. The railbus
body and roof is mostly wood so that is a
good place to put it. There are
no attachment tabs so Duct Tape will be
used. (Every project needs Duct Tape
So --- how did it run.
Ran great in the shop --- once I released
the brakes. Once the wheel size was
entered via the setup menu the top speed
registered at just less than 10 mph matching
the calculations in the Drive section.
It was off to the Mill Creek Central
track for a real test. Dick McCloy
jointed me for a really real test (it
only groaned a little). Ran
perfectly. Did a lot of testing
of the throttle controlled slow down on
the steep grades and it worked as advertised
and far better than I expected. The
E-STOP feature brought the locomotive
to a nearly complete stop in 20 or 30 feet.
This is as fast as I could stop by locking
up the brakes since I have to reach for the
brake handle which eats up 10 or 20 feet ---
if I find it quickly.
lot of observing of the battery voltage to
see if it appeared charge was going back
into the battery when going down grade -- and
it appeared to be working. Need
to install an ammeter to get a better
As expected I confirmed
that I need to keep the air brakes for at
least the park brake function.
Going to consider using one of
Integral Circuit's Brake Controllers.
I did about ten miles total on the first run
and then got bored. Brought it home to
finish dealing with the accessories and
install an ammeter.
At this point
the controller is exceeding expectations.
Will update this after I get some current
readings. The accessories are
described in the accessories section.
More Data (4/22/2017):
Today I did another test run at
Mill Creek Central. The addition
of brakes, light and horn via the handset
are great! These features
are discussed in the
Accessories Page. The big deal at this point is
The analog ammeter is
zero center and plus minus 100 amps full
scale. A momentary switch
changes the scale to plus & minus 20 amps full
I did some runs at half
power and the speed was just around 4.8 mph on
a flat track. On a 3 % up grade
grade the speed dropped to about 4 mph and
it went up to about 6 mph on a 3% down
grade. These are approximate. I
was alone on the railbus.
readings were very interesting. On the
level track at half throttle the
current was about 10 amps and dropped to
near zero on a slight down grade. The
current went up
significantly for steeper grades reaching 30 to
40 amps on a 3% grade. At
one point on the 6% grade of the logging
line it went to current limit of ~ 70 amps
but kept pulling.
On the steeper down grades
significant current went back in the
batteries from the regenerative process.
This was as high as 5 to 10 amps
on the 2%-3% down grades to 20 amps on the 6%
down grade on the logging line.
The regenerative action did limit the
increase in speed to maybe 25%-30%.
(I'm now a believer.)
One thing I
observed was that the current didn't change
much as the throttle was increased (there
was a spike initially but then it settled
down to about the same current).
This makes sense --- current is
proportional to the required torque and
torque is a function of the
load. Speed is related to the
voltage. As the voltage increases the
speed increases. Power is speed
X torque and voltage X current. Makes
The bus seemed to run much
smoother at the higher power settings.
I also verified that the top speed of nearly 10
mph is really too fast. It
looks like I can replace the 60 tooth axel
sprocket with a 70 tooth sprocket.
That would reduce the top speed 16% and also
increase the torque 16%.
That is worth doing!
More Data (5/27/17):
drive is now equipped with a 70 tooth
sprocket. Bench testing in the shop showed
the no load top speed at 8 mph, about as
expected. The no load current for both
motors in parallel is about 6 amps. That is
the no-load starting current listed on the
motor performance graph for one motor. These motors
should be a bit worn and loose.
at the track showed the anticipated
increased in torque/reduced current.
The key performance indicator was that the
wheels slipped before the controller went to
current limit. That was with one
rider. The controller seems to
be a really good match to the motors.
At this point the controller exceeds all