Note: Descriptions are shown in the official language in which they were submitted.
33
i'~ETHOD AND APPARATUS FOR
A ERAT ION OF ST ORE D G RA I N
BACKGROUND OF THE INVENTION
1. Field of the Invention
rrhis invention relates to a method and apparatus
for the controlled aeration of ~tored grain. More
particularly, the invention relates to a method and
apparat~s for sensing ambient temperature and relative
humidity condi~ions and selectively aerating yrain when
suitable or bes~-available ambient temperature and
relative humidity cond itions are present.
2, Descr:iption of Prior Art
Mold is the major cause of spoilage in St~red
grain. Mold growth occurs when a mois~ure and temperature
environmerlt suitable for mold is present around the stored
kernelsO ~oreign matter, along with higher temperatures
and higher humidities, provide the mcst favorable
enviro~ment for mold gr~wth. Clean grain can be stored
indefinitely in a skorage bin i.f its moisture and
temperature are kept within acceptable limits.
~ Moisture can be introduced in~o ~he air spaces
around stored grain by condensation or by the natural
resp;ration ~>f the grain. Condensation ~an occur when
relatively warm, moist air is introduced into the bin and
comes into contact with grain that is colder than the
air~ Condensati~n mo;e frequently occurs as a result of
moistllre migration7 which happens when natural convection
currents within the bin bring warm air from one region of
the bin into contact with cooler grain in another region.
Crusting an~ spo.iling can result~ It is known that the
3~
~6~33
1 efects of condensation can be minimized by keeping the
tempe~ature of the grain at or near the average ambient
air temperature.
M~isture introduced into stored grain fro~ the
natural respiration of the grain i5 a functi~n of the
temperature and relative humidity of the air surrounding
the grain. Por a specified temperature and relative
humidity combination of the surrounding air, there is a
corresponding equilibrium moisture content for the grain;
that is, if the air surrounding t~ie grain is kept constant
at the specified conditions, the grai.n will eventually
reach the equilibrium moisture content. Moisture will be
given of:E by the grain kernels when the moisture content
of the grain exceeds the equilibrium moisture content
supported by the surrounding air conditions; conversely,
moisture content will increase when surrounding air
conditions will lead to an equilibrium moisture content
higher than that present in the grain kernels. In this
regard, it should be noted tlat mold attacks a grain
kernel from the outside in; it is the presence of
excessive moi~re on the out~ide of ~he kernel that is to
be avoided.
Mold growth on stored grain, then, can be
restricted by controlling the moisture content and
temperature of the grain~ The grain temperature and
moisture content determine the allowable storage time that
the ~rain can be kept before .i~ spoils. For that reason
~and others) 7 grain prices are ad justed for the moisture
content o~ the grain. Grain which has an excessive
moistur~ content must either be dried, or used ~uic~ly,
and is there~ore of less value than grain m~rketed at
standard moisture content levels~
33
1 The effects of condensation can be controlled b~
maintaining the stored grain at a temperature equal to the
temperature of the surrounding air. The effects of
moisture release due to respiration could be avoided by
excessively drying the grain. Excessive drying of grain,
however, is undesirable for several reasons. First, grain
that is at or below its equilibrium moisture content for
the ambient air conditionsl will not spontaneously give
off moisture. It requires energy to remove each
additional increment of moisture from a kernel as the
kernel dries, and overdrying of the grain below its
desired market moisture cGntent consumes energy at an
increasingly faster rate as the drying progresses~
Secondly, overdrying of grain creates internal stresses
within the individual grain ker:nel~, causing cracks and
~ines, thus lowering the qual ity of the grain and its
market value. Finallyl gxain is marketed by weight.
Overdrying of ~rain removes more water than is necessary,
thereby reducing its total wei~ht. To maximize price, as
much moisture should be retained in the kernels as
possible~ keeping in mind the upper allowable moisture
content for safe storage and marketing standards~
Proper storage of grain~ then~ involves two
primary considerations. First, the temperature of the
grain should be as close as possible to ~he temperature of
the air surrounding the ~rain, to avoid moisture migration
and conden~ation. Secondly, the moisture content of the
grain should be kept at a predetermined moisture content
level that maximizes the weight of the grain ~t market
time~ yet is low enough to restr ict respiration. A
secondary, econvmic consideration is that aeration used to
--3--
3~
1 ~aintain temperature and humidity should not be performe~
more than necessary, as extensive aeration fan operation
can lead to high energy costs.
U.S. Patent No. 3,563,460 to Nine discloses a
means for controlling the aeration of stored grain. The
Nine device incorporates a plurality of temperature
sensors located within ~he grain, and a comparison device
for comparing the monitored temperature to a manually set
temperature level. An aeration fan is activa~ed when the
grain temperature exceeds the set level. The Nine device,
however, requires a continual manual adjustment o-f the set
temperature level in order to maintain the grain
temperature reasonably near the actual or average ambient
temperature. Moreover; the Nine device does not include
any mechani~m; manual or automatic, to control aeration of
the grai~ as a function of the relative humidity of the
ambient air.
U.S. Patent No. 49045,878 to Steffen discloses a
method for aerating stor ed grai.n wherein the stored grain
is exposed to a throughput of atmospheric air if the
current a~mospheric conditions are opl:imal, in that they
are at or near predetermined historical mDnthly average
a~nospheric conditions. Although the method disclosed in
the Steffen pate~t~ at least in theory~ takes into
consideration both temperature and relative humi~ity,
application of the method has several drawbacks~ First of
all, continuous operator monitorîng o~ ambient air
conditions is required~ Secondly, aeration of grain is
premised on historical monthly temperature averages, and
not on the actual current average temperature, which can
vary considerably frorn historical seasonal averagesO
~2~69C~31 3
1 Finally, lonq y~riods of time may elapse without any
aera~ion of the grain at all if the predetermined optimal
air conditions are not met.
A method for aeration of stored grain that is
responsive to th~ actual (as opposed to historical)
average te~perature, which provides f~r controlled
aeration of the stored grain even when long periods of
less than optimum conditions have elapsed, and that can be
implemented by an automated apparatus, would be a decided
advantage.
SltMMARY OF TEIE INVENTION
The problems outlined above are in large measure
solved by the method and apparatus for controlled ~eration
of stored grain ln accordance with the present invention.
That is to say, the inve~tion hereof provides for the
controlled aeration of stored grain to reduce undesired
moisture accumulation around the graill kernels due to the
effects o condensation and reC;piration~ The method
hereof is responsive to ambienl: temperature and relative
humidity conditions, ta~es into account the actual average
temperature o~er a specified period, and provide~ ~or
aeration of the stored grain under ~next besta criteria
when optimal atmospheric conditions are not met over a
given period of time. The apparatus disclosed herein
provides for continuous monitoring of ambient atmospheric
conditions, and initiates aeration of stored grain
autornatically, withou~ continuous operator involvement.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 :is a schematic sectional di.agram of a
grain storage bin with an aeration fan controlled by the
pr esen t inv en tion .
~2~iQ13~
Figure 2 is an electrical schematic of an
apparatus embodying the present invention.
DEI~AI LED DESCRI PT ION
Referring to Figure 1, an apparatus 10 for the
controlled aeration oE stored grain in accordance w.ith the
present invention is depicted in conjunction with a grain
storage bin 12.
The stor3ge bin 12 includes an upright
cylindrical side wall 14 and an apertured, frustoconi~al
roof 16. ~he bin 12 also includes a raised, perforated
floor 18 beneath which is an air-conducting plenum 20. At
the uppermost point is a vent 24. ~n aeration fan 26 is
received within conduit 28~ Conduit 28 is connected to
plenum 20 in air commurlicating relationship. A ~uantity
of grain 30 is depicted as bein~ stored in the bin 12.
The control apparatus 10 broadly includes ~
cvntrol box 32 attached to the external face of side wall
14, ambient air temperature sensing device 34, ambient
relative humidity sensin~ device 36, and grain temperature
sensing probe 38, all connected to control box 32 by
respective leads 407 42, 44. Control lead 46 extends from
the control box 32 to the fan ~6 for selective operation
of the fan 26.
Control box 32 includes a visual display 48, and
input controls 50, S2, 54 Eor operator input of grain
type, desired grain moisture level, and the desired time
of daily fan operation, respectively. In addition,
control box 32 contains a microprocessor and other
circuitry for performing the information processing
required by the control system.
~2~ 33
- The method for controllin~ the aeration of grain
in a~cordance wi~h the present invention will now be
described.
The primary input data for the present metho3 are
ambient temperature, ambient relative humidity, grain
type, desired grain moisture content and desired time of
daily fan operation. For a given type of gr~in, the
ambient temperature and relative humidity determine an
eq~ilibrium moisture content ~or E~C). The EMC for a
particular type of grain a~ specified ~mbient conditions
can be determined either from a table of known values, or
from a mathematical formulation which approximates the
data in such a table. An example of a table appears at
page 6 of ~Low Te~perature ~ Solar Grain Drying aandbook"
published by Midwest Plan Service, Copyright 1980. An
exarnple of a mathematical formula useful in determining
EMC is the Chung-Pfost equation explained in ASAE paper
76 -3 52 0 O
Once the EMC at ambient temperature and humidity
( in the following all references to humidity shall mean
relative humidity unless otherwise stated) conditions is
knownr thi~ value can be compared to a preselected desired
leYel of moisture content for a guantity of stored grain.
The aeration fan oE the grain storage bin can be
~electively actuated if the EMC i5 equal to tor close to)
the desired moisture content of the stored grain.
Actuation of the Ean will expose the grain to a throughput
of air at ambient temperature and humidity cond:itivns,
thereby causing the grain to move toward a moisture
content equal to the EMC determined by ~nbient conditions.
33
1 ~eration of the stored 9 r ain when the ambient
conditions support an EMC within predetermined limits of
the desired moisture content of the grain will minimize
the accumulation of moisture d~e to respiration of the
grain kernels. As described above, however, moisture also
accumulates within a quanti~y of stored grain due to the
effects of condensation when the grain is exposed to moist
air having a warmer temperature than the grain itself.
The effects of such condensation are best limited by
keeping the temperature of the stored grain at the
temperature of the ~mbient air. ~nfortunately, this
fre~uently cannot be done with precisionl be~ause the air
temperature changes far more quickly than the temperature
of a large mass of stored grain~ MoreoYer, if aerat;on
were initiated whenever grain temperature and ambient
temperature differed, significant amounts of energy would
~e consumed by the aeration fan.
A pos~;ble solution is to make use of historical
data on average monthly or seasonal temperatures, on the
~ tbeory that if the grain can be maintained at the average
monthly or seasonal temperature, this will avoid wide
differences between the temperature of the stored grain
and the actual ambient temperature. With this approach,
aeration would be used whenever grain temperature and the
historical average monthly or seasonal temperature
differ. Actual temperatures on a daily, monthly or
seasonal basis, however, can vary by large amount~ from
historical averages. Moreover, historical temperatures
~ary by geographical region and different data would be
required by each region.
1 The present invention rejects both the continuous
attempt to track ambien~ temperature and reliance on
historical monthly or seasonal averages. Instead~ it has
been determined that an actual average temperature
computed o~ er a specified averaging period (three weeks in
the preferred e~bodimen~, but periods of one week to six
weeks might be used) produces excellent results in
controlling moisture accumulation within stored grain,
when used as the cen~er point of a temperature range with
which the control system causes grain to be aerated, In
particular, a three week running average is maintained by
determining the ambient temperature every Eif~een minutes
in a given twenty-four hour period and averaging the
ninety-six temperature readings obtained within the
twenty~four hour period to determine a daîly average
temperature; ~ running average based on the most recent
twenty-one daily averages is u~ed to determine the three
week average temperature. In the preferred embodiment the
running average is not a true average of twenty-one
individual days. ~o simplify cal~ulation a single average
tempera~ure value i~ kept and ls considered to be the
temperature ~or twenty consecutive days, while the current
daily average is calculated in as the twenty-first day.
(A time average could also be used by storing twenty-one
daily averages and dividing their sum by twenty-one. The
running average would then be calculated by dropping the
oldest daily average and including the newest.)
From the foregoing it can be seen that the basic
aeration control philosophy of the present invention is to
permit aeration only when (a) ~mbient temperature and
humidity conditions determine sn EMC which is at or near
1 the desired grain moisture content, and tb) the ambient
temperature is at or near the running average ambient
temperature, It is recognized~ however, in the present
.invention ~hat precisely optimum air temperature and
humidity conditions may not occur for lon~ periods and may
not persist when they do occur. It is desirable,
therefore, to effect aerat;on of stored grain when the
ambient temperature and humidity are within certain
predetermined ranges of the optimum conditions~ The limit
values selected to define these predetermined ranges in
the preferred embodiment are described in greater detail
below. At this point it suffices to say that the range
around the running average temperature could be as lar~e
as plus or minus 50F, while the range around the desired.
grain moisture con~ent could he as large as plus Gr minus
10 moisture percentage points around the desired grain
moisture contentO
The fundamental steps for the method of
controlled aeration of stored glrain in accordance with the
present invention, then, can be ~ummar~zed as follows.
Firsty the desired moisture content of the particular type
of stored 9rain is sele~ted~ Sesondly, the actual ambient
temperature and h~idity conditions are measured an~ the
ambient equilibrium molsture content (EMC) is determined
therefrom. Thirdly, a running average temperature is
calculated. Fourthly, the ambient EMC is compared to the
de~ired moisture content of the stored grain, and the
actual temperature is compared to the running average
temperature. Finally, ~he grain is aerated by actuation
of the grain storage bin aeration fan only if the ambient
EMC is within a predetermined range of the desired grain
~1 O--
1 moisture content, an~ the actual ai~ temperature is wi~hin
a predetermir~ed range of the running average ambient
temperature.
Grain within a s~orage bin will maintain i~s
~oisture content an~ temperature over a period of time due
to the semi~isolated environment of the storage bin, and
the inherent insulative property of the grain mass. There
is no need to continuously aerate the grain, even if
optimum atmospheric conditions persist. Moreover7 ener~
consumption by an aeration fan can be a significant
consideration, and it is desirable to operate the fan no
more than is necessary. Accordingly, the method and
apparatus of the present invention provides for operator
selection of the deslred run time of the aeration fa~
during any twenty-four hour period. The operator ~elects
the desired run time of the aeration fan based on the size
of the fan and its corresponding air moving capacity and
energy consumption rate.
While various time choice options might be used,
in the preferred embodiment the operator chooses fan
operation tim~ in fifteen minul:e segments, selecting zero,
one, two, four, eight, sixteen or thirty-two such segments
for a twenty-~our hour period, (The operator may al50
override all control and turn the fan on and off manually
for as long as desired.) Thus, the operator may specify
desired fan operation times of zero, 15 minutes, 30
minutes, 1 hour, ~ hours, 4 hours or 8 hours. As will be
seen below, the desired fan operation time parameter
affects several aspects of the present method. For
convenience the n~mber of fifteen minute se~ments selected
as desired fan operation time will be referred to as O~SEG~
--11--
33
1 In the preferred embodiment OP5EG is used to
define the initial predetermined range around the running
average ambient temperature within which aeration may
occur~ In particular, when the actual, ambient
temperature is within X degrees of the running average
amhient temperature, where X ~ OPSEG)/2, rounded down
to the nearest integer, the ~emperature condition for
aeration is satisfied. The other necessary condition for
aeration is sa~isfied, in the preferred embodiment, when
the ambient air and humidity cGnditions ~ogether determine
an EMC within 0.5 percent of the desired grain moisture
contentO Actual ambient temperature and humidity are
sampled every fif~een minutes and if the dual conditions
are satisfied, fan operation is initiated for ~ifteen
minutes if the available fan operation time has not been
used up.
~t is also possible with tight control over the
predetermined, acceptable temperature and ~MC ranges that
conditions for aeration of grain may not be met for a long
period of time or, if met briefly, will not persist. In
that event, the aeration fan will not be actuated or will
not be actuated i~or long enoush E~er iods, an~ the g~ain
will not be sufficiently aerated. ~he temperature and
moist~re content of the grain, when the fan is not
2S activated, will in large mea~ure be maintained by the
semi-isolated environment of the storage bin. On the
other hand, it will be appreciA~ed that respira~ion of
grain kernels and moisture migration may continue, and,
without proper aeration, there will be an accumulation of
moi~ture within the stored grain, and a possible change in
grain moisture content. Moreover, due to heat released by
grain respiration, the grain will not maintain its
1 temperature in~einitely in ~he absence of aeration. The
drift of the grain from optimum moisture content and
temperature levels may become larger as the period of
ins~fficient aeration increases. It will also be
appreciated that, as the drift from optimum grain moisture
content and ~emperature levels increases, the amount of
aeration to restore the grain to optimum conditions
correspondingly increases. In order to accom ~ ate such
circumstances, the present invention adaptively adjusts
its control parameters~ In particular, it selects a
continually widening range of "next best~, acceptable
ambient temperature and humidity conditions so that, even
when conditions within predetermined optimum ranges are
not met, the grain within the storage bin will receive
some aeration. Also, it adapts by preparing to aerate for
longer-than normal periods when acceptable conditiolls are
finally encountered.
! As set forth abover the desired run time of the
aeration fan ~uring any given l:wenty--~our hour period is
selected by the grain bin operator. If the ambient
temperature and humidity ~actui311yl the corre6ponding EMC~
do not fall within the predetermined ranges and available
aeratiDn time is not fully used, then the amount of
selected run time left unused at ~he end of a twenty-four
hour period will be "banked" or stored. For example, if
no time has previously been ~banked" and acceptable
conditions are not met at ~11 for two days, but are met on
the third day, the run time available for the aeration fan
on the third day will be three times the desired run time
limit selected by the operator for a twenty~four hour
period~ The ~bankin~l of unused run time automatically
-13-
~6~33
1 acco~nts for the facts ~hat the grain may drift further
from desire~ temperature and moisture content levels as
the time between aeration increases, and that more run
time is required tc bring the grain back to acceptable
levels as the margin of drift from optimum levels
increases.
It will be appreciated that, as more time is
"hanked"; and the ranges of acceptable temperature and EMC
levels are accordingly increased r it becomes more and more
likely that the aeration fan will be actuated. The time
"banked" will be decreased, time segment for time segment,
once the fan is actually operatedO As the "banked" time
decreases~ the ranges of acceptable temper~ture and EMC
levels will accor~ingly be narrowed, in reverse ~equense
from the range widening progression~
The method of grain aeration in accordance with
the present invention provides for the progressive
expansion of acceptable ambient air temperature and EMC
levels to ensure that long periods without aeration do not
occur. In particular, the range of acceptable temperature
and EMC level s is increased as a step function of
accumulated or ~banked" aeration time. In the preferred
emb~diment/ the range of acceptable temperatures is
expanZed by plus or minus 1 degree, at each step. The
range of acceptable EMC (as determined by ambient
c~nditions) is expanded by plus or minus .2 percent at the
first step and by .3 percent at each following step~ The
first such expansion step occurs when "banked" aeration
time equals or exceeds nine fifteen-minute segments~ The
second such expansion step occurs when "banked" aeration
~ime equals or exceeds thirteen such segments. The third,
fourth~ fifth and sixth expansion steps occur when the
3~
1 "banked" aeration time eq~als or exceeds 20~ 32, 6~ and 96
such segments, respectively. E`urther expansions may occur
in similar fashion as additional aeration time is
accumulated. (It has been fo~nd useful to initialize the
"banked" fan operation ~ime to 20 segments at system
start-up, so that the control system will tend to per~orm
aeration during i~s initial days of operation in case
existing grain condi~ions at start up require aeration and
less than optimum ~nbient temperature and humidity
conditions persist during the ;nitial days of operation.)
In the preferred embodLment, in order to avoid
excessive cooling or heating of the stored grain~ the
running average temperature around which the range of
acceptable ambient temperature i5 defined .is never ~llowed
to go below 20F or above 65~F~ These upper and lower
1 imit.~ may be var ied for installations in different
g eo~ raphic areas .
As explained above, maintaining stored grain at a
desired moisture content, and at a temperature clo~e to
the running average air temperature, are the primary
fac~org to be considered ln pr~per storage o the grain.
It will be appreciated, howe~er, that excessively high or
low grain temperatures indicate collditions which threa~en
grain and are to be avoided. Moreover, to reduce moisture
migration ~nd condensation within the grain, it is
essential th~t grain temperatures be uniform throughout
the storage bin. The method in accordance with the
present invention, therefore, provides for sever~l
automatic "override" conditions that take precedence over
aeration controlled solely as a function o~ ambient
temperature and EMC in the manner described above~ so as
-15-
1 to avoid extreme, or nonuniform grain temperatures. (The
manual override effected by operator selection of manual
control of fan operation has been previously men~ioned.)
The first override ~eature takes into
c~nsideration that molds are particularly active in grain
above 65F, and that grain which is cooled to below 20F
during the winter takes an excessively long time to warm
up to ambient temperatures in the springtime. For this
reason a truncated xunning average temperature may be used
for comparison purposes rather than the normal running
average. The truncated running average is calculated by
considering all average temperatures below 20F to be 20JF
and all temperatures in excess of 65F to be 65F.
Moreover, when a top grain temperature probe is installed,
the top grain temperature can be compared to the truncated
average. When top grain temperat~re data is available,
aeratis:>n will be initiated, reslardless of other
conditions~ when ~a~ the top grain temperature exceeds the
truncated running average temperature by 30~F and (b~ the
actual ambient temperature is at least 15CF cooler than
the ~op grain temperature~
The second overr ide feature takes into
consideration that the top grain temperature should never
exceed the running averag~ ambient temperature by a large
marg in. The method of grain aeration in accordance with
the present invention, therefore, call~ for the aeration
of the grain regardless of other conditions when (a) the
top grain temperatllre exceeds the running average ambient
temperature by at least 10F; and (b~ the actual ambient
air te~perature is at least 5~F cooler than the top grain
33
1 te~ip~rature, and tc) the actual ambient humidity is not
greater than 90 percent.
The third override feature is coordinated with
the basic temperature and EMC criteria for aeration
described above, but is intended to make aeration more
available by widening the ranges around the temperature
and E~C criteria faster than normal. According to this
override, the control system enters ~'reverse highlighting"
mode ~so-called because of a change in the display 48)
when the top grain temperature is not within 8F of the
truncated eunning average temperature. In this mode, the
desired aeration fan operation ~ime as set by the operator
is considered to be doubled for purposes of running the
aeration fans and/or "banking" unused aeration timeO
Thus, more aeration time becomes available andg if
available aeration time ls not used, aeration becomes more
likely to occur due to the increase in banked aeration
time and the resul ting acceptable temperature and EMC
ranges. This override remains in effect until the top
grain temperature is again within 5~ of the truncated
running average temperature. In ~he preferred embodiment,
the ~runcated running average used in the third override
feature is ca:lculated as described above, except that only
the higher ~greater than 65F) temperatures are truncated;
the third override is primarily concerned with cooling hot
graln .
Referring now to Fig. 2, the electronic circuitry
of the apparatus in accordance with the present inv~ntion
will be described, Numerals in the figures appearing on
the integrated circuit chips indicate actual pin numbers
for the indicated types of integrated circuit chips~
~2~
1 ~ference numbers on electrical lines interconneeting the
various integrated circuit chips will assume reference to
the drawings for the proper pin connections.
The apparatus 10 for controlling the storage of
grain broadly includes a p~wer s~pply 56, a processing
unit 58, a display module 60 (associated with visual
display 48), a data inpu~ multiplexer circuit 62 for the
processing unit 580 a driver unit 64 interfacing between
the display module 60 and data input multiplexer circuit
62, grain type and desired time of daily fan operation
selection switch 66t solid state fan actuating relay 68~
and air temperature, air humidity, top grain temperature,
and desired grain moisture level input modules 70, 72, 74,
76, r espec tively .
The power supply 56 receives standard line AC
voltage, and provides DC output voltage levels of 5 volts
(VCC~ and 2.4 volts, and sixty cycle 5 volts ~VCL), for
proper operation of the circuit.D
The processing unit 5B includes a microprocessor
(CPU) 78, memory unit 80, and latch 82~ The
microprocessor is advantageously a type 8031 unit
manufactured by Intel Corporation of Santa Clar~, -
Cal if orn~a. The memory unit 80 is advantageo~sly a type
2764 eraseable pro~rammable read only memory (EPROM)
manufactured by Intel Corporation. The latch 8~ is
advantageously a type B28~ chip manufactured by Intel
Corporation.
Lines 83 ~ 84, 86, 88 and 90, compr ise addressing
lines interconnecting the CPU 78 with EPROM B0. Lines 92,
9~ 96, 98, 100, 102, 104, 106 comprise multiplexed
address/data 1 ines interconnecting the CPU 78, the EP~OM
-lB-
80, and the latch 82. Lines 108, 110, 112, 114, 116, 118,
120, 122 comprise data lines extending between EPROM 80
and latch 82 for carrying the data back to the CPU 7e on
the aforementioned lines 92, 94, 96~ 100, 102, 104, 106.
Line 124 is a progra~ send enable 1 ine interconnecting CP~
78 and EP~OM 80. Line 126 is an outp~t enable line
interconnecting CP~ 78 and latch 82.
Clock circuitry 1~8 provides a time reference ~or
~peration of the CPU 7~. S~pply voltage (VCC3 at 5 volts,
is provid~d to the CPU 78 via line 132. Capacitor 133 and
resistor 134 provide a power-up reset pulse to CPU 78 via
line 135. VCL is applied to the CPU 78 via line 13û as a
time reference for cc)mputing time intervals. CPU 78 is
cc3nnected to ground via line 136 and 137.
The E~OM 80 i~ c~nnected to VCC using filtering
capacitor 138 and line 140~ and to VCC via pull up
resistor 142 and line 144. The EPROM 80 is connected to
ground via lines 146~ 148.
Latch 82 is connected to VCC via line 150, and to
ground via 1 ine 152.
Display module 60 includes three seven-segmerlt
displays 154, 156, 158, and six light emitting diodes 160,
162, 164, 166, 16B, 170~ The seven segment displays may
advantageously be LED-type displays ~Part No. E~PSD 3730 )
manufactured by the Hewlett-Packard Company of Palo Alto,
Cali.fornia. Seven segment display 154 indicates the most
s i g n i f i c an t digit in a thr ee d ig i t number ; d i spl ay 1 5 6
indicates the middle digit, and display 158 the least
significant di.git. The particular value displayed on the
three seven~segment: displays 154, 156, 158 is indicated by
activation of one of the s;x LED's. In partic:ular,
- 1 9 -
33
1 a ~ivation of LED 160 indicates ambient air temperature,
LED 162 indicates relative humidity~ LED 164 indicates the
running average air ~emperature, LED 166 indicates top
grain temperature, LED 168 indicates e~ilibrium moisture
content, and LED 170 indicates ho~rs of fan operation
during the last fourteen days. In addition, deactivation
of all LE~'s simultaneously indicates display of the
accumulated hours of unused fan operation time.
The driver unit 64 comprises three serially
connected driver chips 172, 174, 176, which are
advantageously type MM5484 chips manufactured by the
National Semiconductor Company of Santa Clara, Califoenia.
Driver chip 172 is connected to LED' s 160, 16~,
164, 166, 168, 170 via lines 178, 180, 182, 184, 186, 188
respectively. The dr iver chip 172 is also connected to
the seven-seyment display 154 via lines 190, 192, 194,
196, 198, ~00, 202. Dr iver chip 172 is interconnected
with ~river 174 via 1 ine 202, alnd is connected to VCC and
ground via 1 ines 204, 206 respectiYely.
2Q Driver chip 174 is connected to the seven-segment
display 155 via 1 ines 20û, 210, 212, 21~, 218, 220, 221
and to the seven-segment display 158, via lines 222, 2~4,
226~ 22B, 230, 240, 242. Lines ~44 and 246 each connect
driver chip 174 with both ~he middle digit and the least
signific3nt digit seven segment displays, 156, 158. Lines
248, 250 connect driver chip 174 with VCC and ground
respectively. The seven segment displays 154, 1~6, 153
~re each connected to the 2.4 volt supply voltage via
1 ine~ 252, 254, ~56 respectively.
Enable line 258 and clock :line 260 each
interconnect the CE'U 78 with each of the driver chips 172,
--20--
~6~33
174, 176. Data line 262 in~erconnects the CP~ 78 s7ith
~river chip 172. Data line 264 interconnects driver chips
172 and 174. Data 1 ine 266 interconnects dr iver chip 174
and 17 6 .
Solid state relay 68 is connec~ed to driver chip
176 via actuating lines 268, 270. The solid state relay
68 may include a plurality of switches 68'/ 68'' :Eor
actuation of a plurality of fans 26, 26'.
Driver chip 175 is connected to switch ~6 by
enable 1 ines 272, 274. Enable 1 ine 275 extends to a
heating coil and coil driver circuit 276, The co:il
circuit 276 is used for purging of the h~nidity ~ensor
36. Lines 27B, 280, 28~, and 284 comprise top probe
temperature~ desired grain moisture, air temperature, and
humidity input enable lines, respect;vely, connecting the
driver 176 with the input multiplexer 62. Lines 286, 288
connect the driver chip 176 with VCC and ground,
respectively O
Multiplexer circuitry 62 comprises a type 7403
quad tw~input NAND gate 289 manufactured by the National
Semiconductor Company. Frequency~ encoded input signals
from top grain temperature input module 74, air
temperature input m~ule 70, humidity input module 72, and
desired grain moisture content input module 76 are
received by multiplexer 62 via lines 290, 292, 294, ~96
resE~ectively. The outputs of each ind ividual NAND gate
within the ~ad two inp~3t NAND gate chip 289 are tied
together by 1 ine 298 and input to the CPU 78 via the same
l ine 298 . The NAND gate chip 289 is connected t~ 6upply
voltage VCC and to ground via lines 300, 302 respectively~
-21 -
g33
1 The grain type and desired time of daily fan
operation selection switch 66 comprises a multiplexed
deccder for conversion of the grain type selection, as
indicated by the position of.control dial 50, and the
desired time of daily fan operation selection, as
indicated by the position of control dial 54, into
three-bit binary coded signals. (Each dial has a maximum
of eight selections.~ Enable lines 272, 274 alternately
actuate swîtch 66 for encoding of the grain type and fan
operation time selections. The binary coded signals are
transferred from the switch 66 to the ~U via lines 304,
306, 308.
The air temperature, humidity, top gra;n
tempe{ature and desired grain moisture content input
modules 7fl, 72, 74, 76 provide interfaces between the
various sensors of the control apparatus 10 and the CPU
78~ In particular, the temperature input module 70 is
connected to air temperature sensing device 34 via 1 ine
40, the humidity input module 72 is connected tc> the
humidity s:ensing device 36 via channel ~;2,, and the top
grain tempera'cure input module 74 i~s connec~ed to the top
probe 3B via line 44~ The desired grain moisture content
inp~t module 76 is connected to the desired grain moisture
sel ec t ion swi tch 5~ v i a 1 ine 310 ~
Each of the inpu'c modules 70, 72, 74, 76 provide
for frequency coding o their respective data inputs. For
example, the desired grain moisture level input module 76
includes a type 556 dual timer integrated circuit chip
manufactured by National Semiconductor Company configured
to provide a frequency encoded signal to multiplexer 6~
via line 296 for multiplexed transmission of the signal to
--~2--
16~33
1 CP~ 78 via line 298. ~esired grain moisture selection
switch 52 includes a variable resistor 312, which in
c~mbination with adjusting resistor 314, dropping resistor
316 and capacitor 318 provides an inp~t having a variable
~^ time constant to the timer chip. The timer chip is
connected to supply voltage VCC via line 320 and filtering
capacitors 322, 3~ Timer chip 311 is also connected to
VCC via line 326, and ~o ground via line 328 and via line
330 in conjunction with capaci~or 332. Each of the other
input modules 70~ 72, 74 utlilizes a conventional variable
resistance type temperature or humidity sensor in a
similar ~C circuit to product a frequency encoded signal
corresponding to the sensed temperature or humidityO
Manually actuated switches 334, 336, 338, provide
1~ for operator control of variouc; unctions of the CPU 78.
In particular, switch 334 prov:ides for the enable/disable
of a four-second delay between turn-on of multiple ans,
to avoid large current surges associated with startup of
the fans. Switch 336 allows t!he operator to indicate to
the CPU 78 ~hether or nDt a top grain temperature probe 38
i~ installed in grain bi~ 12. Switch 338 a:l~ows the
opera~or to freeze ~he display of display panel 48, which,
under normal conditiorls, changes its read out every four
second s,
Attached hereto is the assembly langua~e source
code contained within ~PROM 80 for proper operation of CPU
78. This source code also specifies the computational
details for the met:hod of the present inventionO
While the preferred embodiment of the invention
has been illustrated and descr ibed, it is to be understood
tha'c the invention is not 1 imited to the prec ise methsd
--~3--
~;~0~033
1 an~ apparatus herein disclosedl, and the right is reserved
to all variati~ns coming within the scope of the appended
claims. For example, it will be clear that the inventi~n
will work in storage bins with a variety of shapes and
will work as well with duct-type fan arrangements or with
fan arran~ements that pull air down thro~gh the grain
rather than by pushing it up from a plenum. Likewise it
is clear that the method could be performed by other
comparable circuitry or information processing means. It
will further be clear that the invention could be
implemented by substituting a desired ox target humidity
value for the desired grain moisture content and using a
range around the desired humidity value, determined and
adapted in a similar manner as the range around desired or
target grain moisture content. (This is because
equil ibrium moisture content is determined by a
temperature and humîdity value.)
-2~-
