DCC Decoders and Coreless Motors
Ian BARNETT
of use to you.
Date:
Thu, 4 Mar 1999 17:44:28 -0800
From:
"Paul Claffey" <cla...@ix.netcom.com> (by way of
s...@railway-eng.com)
Recently we had a discussion on what type of DCC decoder to use with a
coreless motor. I found they are used in the WSL Shays (not #12),
Heislers
and all Geese (Faulhaber motors). I did not check with Backwoods
Miniatures
nor Bill Meredith (Finescale..). They may also have been used in BLW
engines? Here is a summary of what I found in the past week.
The decoder provides a pulse width modulated (PWM) current to the motor.
These are full voltage spikes of varying widths. The motor turns a
little
bit with each spike. The coreless motor is so efficient, that it offers
little resistance to the full voltage spike of the decoder and a large
current spike is produced. This makes the motor surge and can be
observed
as a vibration and heard as a hum. Operation of the loco will not be as
smooth as with a pure DC throttle. This will also occur with
non-coreless
can motors or open frame motors, but these motors are not as efficient
and
the problem is less pronounced.
I conversed with two manufactures (Soundtraxx and North Coast
Engineering),
two large DCC dealers and some of you. The recommendations are as
follows:
1. Always use a load compensated decoder (Lenz 130 series or the new
Zemo)
2. With a regular decoder, add a 47 ohms resistor in series and 47mf
bipolar capacitor in parallel with the motor leads. Alternately, place
a
3-6 volt ballast lamp in series with the motor. This added circuit
smoothes out the pulses.
3. Try a regular decoder and if not satisfied with operation, go back to
solution 1 or 2.
Soundtraxx (not load compensated), in particular, said the individual
motor
response determines if the additional circuits are necessary. Some of
their
customers have not had to use these circuits. Also, the characteristics
of
the motor may require different values of the resistor and/or capacitor.
I
reason that a particular motor may even require the use of a load
compensated decoder to work smoothly. If I find this to be the case, I
would use the new Soundtraxx DSX 'sound only' decoder together with a
load
compensated decoder for the motor and lights in that loco. Both decoders
would be programmed to the same address so the pair would work as one.
This is the way I plan to do a Heisler as it also solves the space
problem
in that loco.
I hope this was helpful. I apologize if you considered it a waste of
bandwith. I felt I owed it to the group since I raised the question.
BTW I
get to hear Soundtraxx this weekend and if it sounds as good as
expected,
I'm a convert. I decided on North Coast Engineering's Powerhouse Pro
unit
as the system. Any questions or comments would be welcome.
Paul Claffey
Mission Viejo, CA
--
Ian Barnett
"It is often wiser to remain silent and be thought a fool
than to speak up and remove all doubt." Mark Twain
"You can get much further with a kind word and a gun
than you can with a kind word alone." -- Al Capone
e-mail ian.b...@cern.ch
Phone 0041 22 767 6958 (a.m only)
Fax 0041 22 767 5300
Mobile 0041 79 580 3963
Home phone 0033 450 405 105
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Dick Ganderton
powered by Portescap RG4 motor/gearbox units. The motors are coreless
and are widely used by serious modellers in the UK.
I fitted the locos with low cost decoders as there is no need for
functions and lights on British outline steam locos! The decoders were
Digitrax DH121 and Lenz LE103. One of the locos was run continuously for
over 24 hours with no observable ill effects. Various "experts" had
predicted motor failure after short periods of running varying from
fractions of a second to a few minutes. The decoder was wired directly
to the motor brush terminals with no extra components.
One of the locos has been fitted since with one of the Lenz "Silent'
decoders.
snip