Automatic pump control system with variable test cycle initiation frequency

A pump control system for adjusting the frequency of operation of a pump motor in accordance with the demand on the pump includes means for periodically actuating the pump motor to initiate operation of the pump at periodic intervals; sensor means for sensing the condition of the operating pump motor; and means responsive to the sensor means for adjusting the periodic interval to conform the operation of the pump motor to demand on the pump.

FIELD OF INVENTION 
This invention relates to a pump control system for adjusting the frequency 
of initiation of the test cycle of a pump motor in accordance with the 
demand on the pump. 
BACKGROUND OF INVENTION 
Bilge pumps, sump pumps and similar DC or AC electrical powered pumps used 
to pump out accumulated water traditionally use a float switch for the 
pump power circuit in which the water level raises and lowers the float 
sufficiently to close and open the associated switch. Such float switch 
devices require a number of moving parts which wear or bind and eventually 
fail; and the wearing and binding is often accelerated by the damp, 
corrosive and dirty environment in which these float switches are used. 
Failure of the switch can have catastrophic effects since when the pump 
does not operate the water accumulates and can flood the area. In the case 
of bilge pumps, the flooding can sink the vessel. 
One attempt to eliminate the need for such float switches includes means to 
periodically, automatically, e.g., every five minutes, turn on the pump 
whether or not there is water or liquid buildup. The pump current is then 
monitored, and, if it is low, a no-load condition is detected and the pump 
is shut off. If the current is normal, a load condition is detected and 
the pump is permitted to keep pumping until the water is drained and the 
low current condition reoccurs. See U.S. Pat. No. 5,076,763, "Pump Control 
Responsive to Timer, Delay Circuit and Motor Current", assigned to the 
same assignee. 
While this solves the float switch problems, it adds another. Namely, in 
some installations the noise of the pump turning on every five minutes or 
for a similar time interval annoys owners, passengers and crew. For, even 
if no water is present the pump still relentlessly makes noise every five 
minutes. One attempt to overcome this problem as set forth in copending 
PCT application, International Application No. PCT/US93/09415, "Soft-Start 
Pump Control System", filed Oct. 1, 1993, by Anastos et al., assigned to 
the same assignee and incorporated herein by reference, uses a pump 
control system for periodically yet quietly operating a pump. The system 
automatically energizes the pump motor at regular fixed test intervals but 
at reduced power by reducing the power of the test cycle while sensing the 
motor current and then stepping up the power if the motor current 
amplitude indicates that there is liquid to be pumped. That approach can 
be effectively applied to AC motor applications. In the same manner as DC 
motors, AC motors also exhibit higher levels of current draw when pumping 
liquids. 
However, a problem still exists in that the pump may be coming on at fixed 
intervals too infrequently to properly drain the liquid when a serious 
flooding problem is occurring or is coming on much too often when there is 
little or no liquid present. 
SUMMARY OF INVENTION 
It is therefore an object of this invention to provide an improved pump 
control system for adjusting the frequency of initiation of the test cycle 
of a pump motor in accordance with the demand on the pump. 
It is a further object of this invention to provide such a pump control 
system which requires less power, reduces noise and prolongs pump and 
battery life by pumping less frequently when water is absent. 
It is a further object of this invention to provide such a pump control 
system which responds to hazardous conditions by pumping more frequently 
when water is present. 
The invention results from the realization that a truly safe yet efficient 
pump control system can be effected by providing means for periodically 
actuating the pump motor to initiate operation of the pump at periodic 
intervals, sensor means for sensing the condition of the operating pump 
motor, and means, responsive to the sensor means, for adjusting the 
periodic interval to conform the operation of the pump motor to demand on 
the pump. 
This invention features a pump control system for adjusting the frequency 
of operation of a pump motor in accordance with the demand on the pump. 
There are means for periodically actuating the pump motor to initiate 
operation of the pump at periodic intervals and there are sensor means for 
sensing the condition of the operating pump motor. There are also means, 
responsive to the sensor means, for adjusting the periodic interval to 
conform the operation of the pump motor to the demand on the pump. 
In a preferred embodiment the means for periodically actuating the pump 
motor may be a periodic test cycle generator. The condition sensed by the 
sensor means may be current drawn by the pump motor. The means for 
adjusting may count the number of times that liquid is present and the 
number of times that the liquid is absent and the periodic interval may be 
shortened when the number of times that liquid is present exceeds a 
predetermined number and it may be lengthened when the number of times 
that liquid is absent exceeds a predefined number. The predetermined 
number and the predefined number may be three. 
This invention also features a pump control system for adjusting the 
frequency of initiation of the test cycle of a pump motor in accordance 
with demand on the pump. There are switching means for supplying power to 
the pump motor. There is also a periodic test cycle generator for 
periodically actuating the switching means to initiate operation of the 
pump motor at periodic intervals. There are sensor means for sensing the 
current drawn by the pump motor and a reference circuit. There are also 
liquid detector means responsive to the reference circuit and the sensor 
means for detecting whether liquid is present or absent. There are 
monitoring means responsive to the liquid detector means for adjusting the 
periodic interval to conform the operation of the pump motor to the demand 
on the pump. 
In a preferred embodiment the monitoring means may count the number of 
times in sequence that liquid is present and the number of times in 
sequence that liquid is absent. The periodic test cycle generator may be 
responsive to the monitoring means for shortening the periodic interval 
when the number of times that liquid is present exceeds a predetermined 
number and for lengthening the periodic interval when the number of times 
that liquid is absent exceeds a predefined number. The monitoring means 
may include means for counting the number of times in sequence that liquid 
is present and the number of times in sequence that liquid is absent. The 
predetermined number and the predefined number may be the same and the 
predetermined number and the predefined number may be three. The liquid 
detector means may continue operation of the pump when the pump motor 
current exceeds a reference level provided by the reference circuit and 
deenergize the pump when the pump motor current is below the reference 
level indicating that no liquid is present. The liquid detector means may 
include means for overriding the periodic test cycle generator and 
continuing operation of the pump motor as long as there is liquid present. 
The sensor means may provide a signal proportional to the current drawn by 
the pump motor to the liquid detector means. There may further be included 
filter means for filtering the signal to prevent the generation of a false 
overload current caused by the initiation of the pump motor.

The pump control system of this invention may be utilized to adjust the 
frequency of initiation of the test cycle of a pump motor depending on the 
demand on the pump. The pump controller of this invention may utilize a 
soft-start pump control system, as discussed above, disclosed in copending 
PCT patent application, International Application No. PCT/US93/09415, 
wherein a pump is periodically, at regular fixed intervals, automatically 
energized by a reduced power test cycle. Or, the pump motor may simply be 
energized by a full power test cycle. The motor current is then sensed. If 
the current amplitude indicates that there is liquid to be pumped the 
periodic test cycle generator that initiated the test cycle is overridden 
and the pump motor is energized until the sensed motor current amplitude 
indicates that there is no more liquid to be pumped. The pump motor is 
then shut off until the end of the next periodic interval when another 
test cycle is generated by the periodic test cycle generator and the 
process begins again. If when the pump motor is energized by the periodic 
test cycle, the current sensed initially has an amplitude that indicates 
there is no liquid to be pumped, the pump motor is deenergized and will 
not be reenergized until the next test cycle is generated at the end of 
the next fixed interval. The problem with this pump operation is that if 
there is a serious flooding problem the pump will still continue to only 
pump after each regular fixed interval and this may not be sufficient to 
properly pump the incoming water out. Or, if there is little or no liquid 
present over a period of time the motor will continue to cycle on at the 
end of each interval when the test cycle generator generates its test 
cycle signal and it will then shut off after sensing no water present. As 
discussed above, this can become quite annoying. 
Thus, the primary object of the present invention is to increase the 
frequency of initiation of the pump test cycle when liquid is present 
(i.e., decrease the periodic time interval between test cycles) and reduce 
the frequency of initiation of the pump test cycle when liquid is absent 
(i.e., increase the periodic time interval between test cycles). 
There is shown in FIG. 1 a pump control system 10 for adjusting the 
frequency of initiation of the test cycle of a pump motor 12 in accordance 
with the demand on the pump 14. There is a periodic test cycle generator 
16 which generates a test cycle supplied on line 17 to switching circuit 
18. The periodic test cycle generator 16 actuates the switching circuit 18 
periodically, for example, every five minutes. Actually, any desired 
period may be selected: less than one minute, one minute, two minutes; 
often a range of one to three minutes is satisfactory. The test cycle 
generator 16 delivers a signal on line 17 to operate switching circuit 18 
to allow pump motor 12 to be energized by power source 13. The signal may 
be a full power test cycle signal or a reduced power test cycle signal as 
disclosed in co-pending PCT Patent Application No. PCT/US93/09415. This 
causes the pump motor 12 to operate which in turn actuates pump 14. 
Current sensor 20 senses the motor current drawn by pump motor 12 and 
provides to filter circuit 27 on line 21 a signal proportional to the 
current sensed. Filter circuit 27 filters out motor noise from the signal. 
The filtered signal 21' is provided to liquid detector 22. Reference 
circuit 24 provides a liquid reference signal proportional to the current 
the motor 12 will draw when pumping liquid on line 25 to liquid detector 
22. Liquid detector 22 compares the filtered motor current signal provided 
from filter circuit 27 to the liquid reference signal provided by 
reference circuit 24. If the motor current signal exceeds the liquid 
reference signal, this indicates that there is sufficient water or other 
liquid to be pumped, thus necessitating the operation of pump motor 12. 
Accordingly, a signal is provided from liquid detector 22 on line 26 to 
override the periodic test cycle signal provided on line 17 causing 
switching circuit 18 to provide power to pump motor 12 at the full 
available power until the water or liquid is fully pumped. 
If the signal provided by filter circuit 27 on line 21' is less than the 
liquid reference signal provided by reference 24 on line 25, this 
indicates that there is little or no water or other liquid accumulated and 
ready to be pumped. Thus, liquid detector 22 provides a signal on line 26 
to switching circuit 18 to deenergize pump motor 12 and deactivate pump 14 
until the next periodic test cycle signal is generated. If water or liquid 
was initially detected and the periodic test cycle generator is 
overridden, the system continues to pump until the motor current sensed by 
current sensor 20 falls below the liquid reference signal from reference 
circuit 24. At this time the pump motor 12 is deenergized and pumping 
ceases until the next periodic test cycle signal is generated. 
Every signal provided by liquid detector 22 on line 26 is also provided to 
counter timer 28 on line 29. Counter timer 28 counts the number of times 
that liquid detector 22 detects the presence of liquid and the number of 
times liquid detector 22 detects that there was little or no liquid 
present. Counter timer 28 operates as follows. Each time periodic test 
cycle generator 16 initiates a test cycle signal counter timer 28 is 
enabled. It then counts up if water is present and counts down if no water 
or negligible water is present. If counter timer 28 reaches a 
predetermined count (3,5,10,20) in either the up or down direction 
indicating that there has been an uninterrupted series of indications of 
water or no water present, respectively, then generator 16 is directed to 
decrease or increase the frequency of initiation of the test cycle. 
For example, if the initial periodic test cycle interval between 
initiations of the pump motor 12 is set for two minutes, the pump will 
turn on every two minutes to test for water. If after three test cycles 
(six minutes), water has not been detected, the periodic test cycle 
generator 16 may be adjusted so that the test cycle interval is now 
changed to three minutes and the system will test for water every three 
minutes. If water is still not detected after three three-minute cycles, 
the cycle test time may again be increased. The test cycle time may be 
increased in this manner until some maximum cycle time is reached. 
When water is not detected, the number of times the pump turns on and off 
would be reduced when it is not needed. In the same regard, if after three 
test cycles, for example, water is detected each time, the test cycle time 
can be decreased to a test cycle time less than the original setting. And, 
if after three cycles, for example, at the decreased time, water or liquid 
is detected each time, the test cycle time can again be decreased until 
some practical minimum cycle time is reached. This is a very beneficial 
feature when there are more serious flooding conditions. The numbers given 
in these examples are only for illustration, and any test cycle time and 
cycle time adjustment may be utilized. 
Counter timer 28, FIG. 2, includes control logic 32 and counter 34. 
Periodic test cycle generator 16 generates a test cycle at periodic 
intervals for energizing the pump motor 12, and liquid detector 22 
provides a signal on line 26 indicative of whether liquid to be pumped is 
present or not. This signal is provided on line 29 to control logic 32. 
Periodic test cycle generator 16 provides control logic 32 with the 
corresponding test cycle signal on line 31. Control logic 32 then provides 
counter 34 with an increment signal on line 35 if liquid is detected or a 
decrement signal on line 36 if no liquid is detected. That is, for the 
first test cycle that is generated, counter 34, which can count the number 
of liquid detections as well as the number of times liquid is absent, is 
incremented or decremented. If, for example, after three periodic test 
cycles liquid was detected three times, counter 34 would provide periodic 
test cycle generator 16 with a signal on line 30 to decrease the interval 
between initiation of test cycles. Similarly, if for example after three 
test cycles liquid was not detected three times, counter 34 would be 
decremented three times and it would provide a signal on line 30 to 
periodic test cycle generator 16 to increase the time interval between 
initiation of test cycles. 
Using three (3) consecutive times liquid is detected or liquid was found to 
be absent in the above example for either shortening or lengthening the 
interval between initiation of periodic test cycles is merely for 
illustration purpose. Any predetermined number of sequential signals from 
liquid detector 22 indicating that liquid is present could be used to 
shorten the interval. Similarly, any predefined number of sequential 
liquid detector signals indicating that no liquid is present could be used 
to lengthen the time interval between periodic test cycles. 
There are various ways in which the counter timer 28 can be used to 
lengthen or shorten the time interval between initiation of the periodic 
test cycle generator. If, for example, there is a signal provided to 
control logic 32 on line 29 indicating that no liquid is present, and 
previous to this signal a number of liquid present signals, not exceeding 
the predetermined number, have been received by the counter 34, control 
logic 32 may send a reset signal to counter 34 on line 37 to reset the 
liquid present counter to zero. Under the same circumstances, control 
logic 32 may send a decrement signal on line 36 to counter 34 to merely 
decrement the number of liquid present signals that have been counted by 
counter 34. Similarly, if a number of liquid absent signals have been 
received not exceeding the predefined number and a liquid present signal 
was received, control logic 32 could send an increment signal on line 35 
to counter 34 to increment the count signal or reset the counter to zero. 
In another construction pump control system 10a, FIG. 3, includes pump 
motor 12a and pump 14a. Pump motor 12a includes positive and negative 
terminals 38 and 39, respectively. Pump motor 12a may be energized by 
power source 13a. Power source 13a includes battery 40 with positive and 
negative terminals 41 and 42, respectively. Power source 13a also includes 
a filter 44 that includes capacitor 45, metal oxide varistor (MOV) 46 and 
reverse polarity protection diode 47. The negative terminal 42 of battery 
40 is connected to ground and the positive terminal 41 is connected to the 
filter circuit 44 and positive terminal 38 of pump motor 12a. The negative 
terminal 39 of pump motor 12a is connected to switching circuit 18a on 
line 48. Switching circuit 18a includes a MOSFET transistor switch 49 for 
switching on and off the power supplied to pump motor 12a from power 
source 13a. Switch 49 is controlled by a signal provided from pin 13 of 
microprocessor 52 on line 50. Microprocessor 52, which may be a Zylog 
Z86C08, receives its five-volt power supply from power source 58, which 
power source includes resistor 59 and Zener diode 60. 
The on signal provided to transistor 49 from microprocessor 52 is generated 
periodically. The interval between periodic test cycles is software 
controlled. Microprocessor 52 in order to operate requires oscillator 
circuit 54 which is connected to pins 6 and 7 of microprocessor 52 and 
which provides it with a clock signal. Clock oscillator circuit 54 
includes capacitors 55, 56 and inductor 57. 
Transistor 49 of switching circuit 18a is switched on in response to a 
signal from microprocessor 52 generated on line 50 at the proper time for 
generation of the periodic test cycle. When switch 49 is turned on the 
circuit is completed between power source 13a and pump motor 12a and 
current is drawn by pump motor 12a, thereby causing pump 14a to rotate. 
Current sensor 20a, which includes resistor 61, monitors the current drawn 
by pump motor 12a and provides a motor current signal proportional to the 
current drawn to filter circuit 27a, which includes resistor 63 and 
capacitor 65. The filtered signal is provided to pin 10 of microprocessor 
52 on line 21a'. Microprocessor 52, at pin 9, also receives a liquid 
reference signal on line 25a from reference circuit 24a which includes 
resistors 62 and 63. Microprocessor 52 then determines if the filtered 
motor current signal on line 21a' exceeds the liquid reference signal on 
line 25a, and if it does this indicates that the pump motor 12a is under a 
load condition and liquid, such as water, is present and therefore pumping 
is required. In this case, microprocessor 52 provides a signal on line 50 
to transistor 49 of switching circuit 18a to override the periodic test 
cycle signal and maintain the pumping operation. If, on the other hand, 
microprocessor 52 determines that the liquid reference signal from 
reference circuit 24a supplied to microprocessor 52 on line 25a does not 
exceed the filtered motor current signal provided on line 21a', this 
indicates that the pump motor is operating in a no-load condition and 
there is little or no liquid or water to be pumped. Thus, microprocessor 
52 provides a signal to transistor 49 switch of switching circuit 18a on 
line 50 to turn off the transistor switch 49, thereby deenergizing the 
pump motor 12a and ceasing operation of pump 14a. 
The counter timer function, discussed above with regard to FIGS. 1 and 2, 
is effected in the circuit of FIG. 3 by microprocessor 52. That is, 
microprocessor 52 counts the successive number of times that it is 
determined that liquid is present to be pumped or no liquid is present to 
be pumped, and increases or decreases the frequency of initiation of 
periodic test cycle generation according to the demand on the pump 14a. 
FIG. 4 is a flow chart of the software that may be used to operate 
microprocessor 52 to implement the pump control system of the subject 
invention for adjusting the frequency of initiation of the test cycle of a 
pump motor in accordance with demand on the pump. 
The pump motor is started at step 64 and at step 66 it is checked if liquid 
or water is present to be pumped. If no liquid or water is present to be 
pumped the system proceeds to step 68, where the count is decremented and 
the increment count is reset. After the count is decremented the system 
proceeds to step 70 where it is determined if the decremented count 
exceeds a predefined number. As discussed above, after a predefined number 
of cycles where liquid or water is not detected, the time interval between 
periodic test cycle generation is lengthened. If the number of successive 
decremental counts does not exceed a predefined number the pump is simply 
turned off at step 72 and after the next time interval determined by delay 
74 the motor is again started at step 64. If at step 70 it is determined 
that the number of successive decremental counts has exceeded a 
predetermined number the system proceeds to step 76 where the delay 
between periodic test cycle generations is increased and the system then 
proceeds to turn off the pump at step 72. After adjusting the delay 
generated at step 74 the motor is again started at step 64. 
If at step 66 liquid or water is present, the system proceeds to step 78 
where the count is incremented and the decrement count is reset. At step 
80 it is again determined if liquid or water is present: if liquid or 
water is present the system proceeds to step 82 and pumping is continued. 
The system continues to loop through steps 80 and 82 until all the liquid 
or water is pumped. When no liquid or water is detected the system 
proceeds to step 84. If at this step it is determined that the incremental 
count does not exceed a predetermined number the system proceeds to turn 
off the pump at 72 and start the motor after the delay at step 74. If it 
is determined at step 84 that the incremental count does exceed the 
predetermined number the system proceeds to step 76 where the delay is 
adjusted by shortening the interval between periodic test cycle generation 
in order to start the motor more frequently due to the recurrent detection 
of liquid or water. 
Although specific features of this invention are shown in some drawings and 
not others, this is for convenience only as each feature may be combined 
with any or all of the other features in accordance with the invention. 
Other embodiments will occur to those skilled in the art and are within the 
following claims: