Radio Control Electrics - 2004/02

February 2004 129
THIS COLUMN SHARES an issue of
concern, reviews the “Dump’r” feature, and
shares some related reader comments and
questions.
There’s no question in my mind that
electric power is directly responsible for
many new aeromodelers entering the hobby.
The specific driver is the park flyer—a
concept popularized, if not directly created,
by quiet, capable electric power within the
last few years.
Simultaneous with this is the explosion
in available Radio Control flying sites: parks
and the like that were not previously
available as flying sites because of noise.
Parks and the quiet electric-powered park
flyer are a perfectly wonderful
aeromodeling pair—good for all of
aeromodeldom!
However, there is an issue that may
warrant concern: the disturbing, intruding
thought of glow-powered park flyers that
would be unwelcome in some, or maybe
even in most, park sites. The associated
noise could easily be so unwanted that I can
imagine “No Model Flying” signs popping
up at these now-quiet spots.
We need to demonstrate responsibility
and restraint here. And in case anyone is
interpreting this as my glow/gas/electric
issue, it’s not. I used to fly, and I still have
many friends who fly, wet power, and I
know that this mode continues to be
dominant within aeromodeling.
My point is that we need to fly whatever
we fly in the appropriate location. Losing a
park site because of noise is a grossly
disturbing thought! Hobbywise, could there
be a more awful prospect than that?
Two decades ago a friend lightheartedly
quipped that the difference between a glow
flier and an electric flier is that the latter can
take a shower before flying, and the former
has to shower afterward! I can add to that
distinction; an electric flier can fly
everywhere flying is allowed, but a wet flier
cannot!
Please exercise great care and good
judgment in this matter, everyone.
Reader response to “Dump’r” has been
heavy! The simple battery discharger for
four- to 18-cell packs was presented as a
feature in the October 2003 MA. Reader
reaction was quick and gracious.
It seemed as though the 10/03 issue had
barely hit the street when calls and letters
came rolling in. I can’t believe how fast this
happened! The earliest inputs were a mix of
“Thanks” and “Did you know … ?”
The latter had to do with errors in writing
that crept into parts of the article. Many
readers quickly identified them, and after
roughly two weeks of this I was able to
compile a summary of these issues. This led
to an advisory in the “Letters to the Editor”
Bob Kopski, 25 West End Dr., Lansdale PA 19446
RADIO CONTROL ELECTRICS
Bill Jones’ (Plains PA) nearly finished blue-foam C5A Galaxifoamie will have four EDS
35 fans on two 10-cell packs, two ESCs, and weigh roughly 94 ounces.
Kevin Murray (Madisonville KY) uses Tupperware plastic bread box with fan installed in
normally closed end as battery-pack cooler. It’s clean and easy!
02sig5.QXD 11/25/03 9:50 am Page 129
130 MODEL AVIATION
section of the December 2003 MA.
If you have an interest in Dump’r, please
check out this reference. These mistakes
would disallow proper operation. If you do
not have this issue available, write to me
and I’ll send you the information; you need
it! Especially since most seem to be
building more than one Dump’r!
These were not errors in design but
errors in presentation. (Basically I can’t
read my own writing, it seems!) Dump’r
works exactly as described—not because I
say so but because many readers have said
so. To me, this is the “acid test”; i.e., others
have duplicated and substantiated the
design.
Although many readers quickly
identified some of these writing glitches, no
one picked ’em all out. Eventually it
seemed as though all were made known,
and I hope that’s that. If you have any
problems with or questions about Dump’r
(or any of my electronic construction
features throughout the years), please write
and we’ll work it out. If that approach fails,
I will fix the problem for free, except for
postage.
One reader constructed three Dump’rs.
He was the first reader to inquire about
some writing errors, so he had the corrected
info early. He built accordingly, completing
one Dump’r ahead of the other two. It did
not work properly, and he caught up with
me at the NEAT (Northeast Electric Aircraft
Technology) Fair to say so. I brought his
Dump’r home from that meet and checked it
This is three of the seven mass-launched electric-powered ornithopters at the 2003
NEAT Fair. All seemed to work well and were fun to fly and watch.
resistors all around it so that most of the
switch lugs have two resistor leads in them.
In this case the soldering caught one of the
leads but not the other in some terminals.
The bottommost lead—the one that is more
difficult to see—was not soldered in three
lug locations, and that was the problem.
Make sure of your soldering, not just on the
switch parts but throughout. Also, one part
of that article’s checkout procedure should
have caught this switch problem.
Despite the errors in presentation and
associated confusion and disappointment,
every inquiry was polite. Readers ranged
from first-time builders to those of
considerable skill and experience. The
former are the most adversely affected in
matters such as this. To the best of my
knowledge, everyone who inquired got
Dump’r working. If anyone’s doesn’t work,
I will make it work if you give me the
chance.
Reader input also highlighted one matter
of which I was unaware. In the article where
I listed the majority of parts and supplies
with Mouser (a parts supplier) catalog
numbers, I included the Web-site address
and the company telephone number, either
of which could be used to order the parts.
Those who called in orders received
assistance from the salesperson with some
troublesome catalog numbers, so some (but
not all) issues were fixed on the spot. This
service was unavailable on the Web site.
Other comments included how nice it was to
do business with Mouser. Yup!
Several readers were confused about the
use of Dump’r with all batteries and with
what seemed to be conflicts in advice. Since
so many asked, I’ll expand on this issue. It’s
common for variances in opinion and
preference to appear throughout a
population. That is why there are so many
competing products on the market—
appliances, cars, toothbrushes, motors,
batteries, etc. Similarly, there are differences
and preferences in approach and technique,
almost no matter the topic.
Some readers pointed out that I expressed
out. He was right; it did not work properly.
His Dump’r was beautifully built and the
problem was not obvious, so I immediately
had a sinking feeling that there was still
some yet-uncovered problem. After a more
complete disassembly and inspection with a
lens, I found the problem: three missed
solder joints on the rotary switch. Once I
touched these up, this reader’s Dump’r
worked perfectly. There may be more out
there since this can happen to anyone, so I’ll
explain further.
The rotary switch has a series string of
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February 2004 131
a preference for emptying motor packs that
are not going to be used for a while (hence
Dump’r), and others have written to store
motor packs in a charged condition. There
was also the matter of “flight packs” and
“motor packs.”
I cannot claim that there is anything
absolutely right or wrong about storing
motor packs empty or charged. I think most
will agree that storing them in an inbetween
state is not good at all.
However, having flown Electrics for
more than 30 years (longer than nearly
everyone), I’ve developed the practice of
and preference for only storing packs
“empty”; i.e., ready for fast charge next
time out. Dump’r was designed to aid with
this, as explained in the article.
So would you ever catch me storing
motor packs in a charged condition? No,
unless I make a mistake or someone can
show me, with convincing data, the error of
my ways! Please feel free to comment.
Another point of confusion had to do
with receiver and transmitter batteries. In
this case I always keep ’em in charged
condition, and I’m not advocating routinely
“dumping” these. Some modelers
occasionally cycle these packs to ascertain
their status and performance quality, but
this is a matter distinct from motor packs.
The former are usually slow charged and
the latter are usually fast charged. The latter
process demands beginning with an empty
pack for best battery life and charge
effectiveness, hence Dump’r.
The next question was about discharging
to Dump’r’s design value of 0.9 volt per
cell compared with 1.1 volts per cell. The
former is a common number used for motor
packs, and the latter is the typical criteria in
cycling receiver and transmitter packs. This
distinction has to do with the application.
There is nothing wrong with discharging
receiver and transmitter packs to the 0.9
volt per cell (as with Dump’r); it’s just not
the standard we’ve become used to.
However, the 0.9 volt per cell for motor
packs makes more sense because in-flight
high motor current drains can drag
“normal” cell voltage down to
approximately 1.1 volts per cell anyway.
Another technical issue emerged from
all of this reader communication, but I’ll
cover it in detail next month. It has to do
with the operation and use of ohmmeters,
such as during the checkout procedure in
the Dump’r article (and all of my
electronics articles).
For now, just know that it is possible for
some (not most) ohmmeters to render
readings outside the limits given in the
article and still have a good assembly. This
can be an ohmmeter operational issue and
not necessarily a circuit-assembly problem.
If you are experiencing this, write to me.
Readers have also reacted to my
suggestion for a “needed product” in the
October 2003 column. I suggested that the
world of Electrics was much in need of
speed controls that incorporate a Battery
Eliminator Circuit (BEC) function which is
capable of working with all applicable cell
counts—not just up to approximately 10
cells.
I offered that smaller (lower-cell-count)
systems had all of the advantages that BEC
offers, but that higher cell counts, which
make “Electronic Speed Control + BEC”
impossible, could be designed to offer
these advantages as well. I proposed that
switch-mode regulators—built in as part of
the speed control—would provide this.
Several readers wrote to point out that
this function already exists in the Universal
Battery Eliminator Circuit, or UBEC—a
nifty product that is used separate from any
ESC to derive receiver-system power from
the motor battery. (You can buy UBEC in
two sizes from New Creations R/C, Hobby
Lobby, and other places.)
Basically, UBEC is a switch-mode
regulator that is wired into the motorbattery
path and efficiently provides a solid
5-volt supply for the radio stuff to work on.
It is installed in a fashion similar to, but in
addition to, the normal speed control.
These readers meant well, but this is not
what I meant in the column. UBEC, which
does work well for some modelers, I know,
is still a separate item to install and wire.
Instead I was suggesting that an ESC itself
could be designed and marketed that would
incorporate such a function. This ESC
installation would then be as simple for
larger systems as is the case for smaller
systems now.
In the meantime, if you have a highercell-
count system that requires the use of a
conventional receiver battery and you’d
like to eliminate that, check out UBEC.
You do need to wire it up, but you won’t
have any more receiver pack to charge—a
distinct advantage exclusive to electric
power that our wet-flying friends cannot
enjoy!
A reader from Singapore pointed out
two other motor-battery-to-receiver powersupply
products of which I was unaware.
He suggested referring to www.smartfly.
com/page5.html and
www.acteurope.de.
The first reference is for a product that
is similar to the UBEC in function but is a
linear regulator instead. The second site
may require language translation. As best I
can tell, neither are what I suggested;
namely, a high-capability BEC included as
an integral part and function of an ESC. In
principle, it would be easier, smaller, and
lighter to install but one such system
component.
So ends another column. Please include a
self-addressed, stamped envelope with any
correspondence for which you’d like a
reply. Everyone so doing does get one.
Many happy wintertime and anytime Elandings,
everyone! MA
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