Note: Descriptions are shown in the official language in which they were submitted.
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PULSE ~IDTH MODULATION DC ~OTOR SPEED CO~TROL
BACKGROUND OF THE INVENTION
Elect.ric outboard motors have a dc
motor driving the proeeller. The ~otor speed is
controlled by placing ~ore or les~ re~istance in
~eries wi~h the ~o~or. The ene~gy di~ipated in the
resistance is a los~. It is known that dc motor
speed can be controlled by variatio~ o~ the "on" ti~e
of the motor. This can be done by placing a
~witching device in the motor power ~upply to ~witch
the power on and o~f. The motor ~till receives its
rated voltage but for less time. This conce~t has
been u~ed in controlling the motor Epeed in vehicles
and the control circuits are quite elabolate and a~e
: 15 not cost effective for outboard ~otor co~trols. And
the control circuits require too much power for
outboard motor use.
; At~ention is directed to the ~ollowing
U.S. patents directed to motor controls:
20 Pa~entee Patent No. Issued Date
: Ninebrener 3,686,549 Aug. 22, 1972
Henry 3,694,721 Sept. 26, 1972
~: Mc~enna 3,617,845 Nov. 2. 1971
Salamon et al. 3,708,765 Jan. 2, 1972
25 Miller 3~7l9~a76 March 5, 1973
V08tee~ ~, 803,470 Apr. 9, 1974
Pr~ce et al. 3,803,471 Apr. 9, 197~
Ibamoto st al. 3.903,465 Sept. 2, 1975
: Milligan 3.906,31g Sep~. 16, 1975
30 Grace 3,~82,161 Sept. 21, 1976
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~ttention is also directed to Canadian
Patent 1,211,657 issued September 23, 1986.
SUMMARY OF THE INVENTION
~ The invention provides an electric
: 5 outboard motor including a mounting bracket, a dc
motor supported by the mounting bracket, a propeller
driven by the motor, battery terminal means adapted
for connection to a battery, a MOSFET connected to
the motor to control operation of the motor and
including a gate, a manually operable potentiometer
~; connected to the terminal means, and integrated
~ circuit means including a control input connected to
: the potentiometer to vary the voltage applied to the
input, and an output connected to the gate oE the
M~SFET, which integrated circuit means is operative
to produce a pulse train which is applied to the gate
: through the output, and to vary the pulse width of
~- the pulse train as the voltage applied to the inpu~
is varied whereby the pulse width of the pulse train
~ 20 at the output and the duty cycle of the MOSFET are
:~ varied in accordance with the setting of the
:~ potentiometer and the speed of the motor is varied
accordingly.
The invention also provides an electric
outboard motor including a mounting bracket, a dc
motor supported by the mounting bracket, a propeller
~;~; driven by the motor, battery terminal means adapted
~:~ for connection to a battery, a MOSFET connected to
:~ the motor to control operation of the motor and
including a gate, control means connected to the
terminal means, and integrated circuit means
including a control input connected to the control
means to vary the voltage applied to the input, and
an output connected to the gate of the MOSFET, which
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integrated circuit is operative to produce a pulse
train which is appl~ied to the ~ate through the
output, and to vary the pulse width oE the pulse
train as the voltage applied to the input is varied
whereby the dut~ cycle of the pulse train at the
output and the pulse width of the MOSFET are varied
in accordance with the voltage applied to the input
and the speed of the motor is varied accordingly~
The invention also provides an electric
outboard motor including a mounting bracket, a dc
motor supported by the mounting bracket, a propeller
driven by the motor, battery terminal means adapted
for connection to a battery, switching means
connected to the motor to control operation of the
motor and being conductive when a control voltage
applied to the switching means exceeds a
predetermined value, control means connected to the
terminal means, and integrated circuit means
including a control input connected to the control
means to vary the voltage applied to the inpu~, and
an output connected to the switching means to apply a
control voltage thereto, which integrated circui~
means is operative to produce at the output a pulse
train at a voltage in excess of the predetermined
value, and to vary the pulse width of the pulse
train as the voltage applied to the input 1~ varied
whereby the duty cycle of the pulse train at the
output and the pulse width of the switching means are
varied in accordance with the voltage applied to the
input and the speed of the motor is varied
accordingly.
The invention also provides an electric
outboard motor including a mounting bracket, a DC
~: motor supported by the mounting bracket~ a propeller
driven by the motor, terminal means adapted for
connection to a battery, integrated circuit means
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having an input and an output and operative to
produce at the output a variable width pulse train
which varies in accordance with variations in voltage
applied to the input, a manually operable control
potentiometer connected to the terminal means and the
input to vary the vcltage applied to the input, a
MOSFET serially connected between the motor and the
battery and having a gate connected to the output so
that the duty cycle o~ the MOSFET is varied solely
with variation in the voltage applied to the input by
~; the potentiometer whereby the speed of the motor is
varied accordingly.
~-~ BRIEF DESCRIPTION OF THE-DRAWINGS
Fig. 1 is a simplified representation
of an electric outboard motor.
Fig. 2 is a simplified showing, partly
in section, of the head of the outboard motor shown
in Fig. 1 to illustrate the manner in which a
potentiometer may be mounted for actuation by
twisting movement of the tiller or handle.
Fig 3 is a circuit diagram.
DETAILED DESCRIPTION OF THE DRAWINGS
In the drawings and the following
description, various components are identiied by
manufacturer's desi~nation or by value. This,
coupled with the wiring diagram, will obviate the
need for a detailed description of the particular
wiring arrangement and components associated with the
circuitO The circuit largely will speak for itself
with the following description adding such details as
necessary to understand the invention.
The electric outboard motor 10 shown in
Fig. 1 is typical of the electric outboard motors
used Eor trolling. The motor 10 includes a mounting
bracket 11 which is connected to a boat and which
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supports for rotation a vertical shaft 13, a tiller
16 connected to the upper end of the shaft 13 and a
lower housing 12 connected to the lower end of the
shaft 13. The motor 10 is very quite and simple to
operate. The motor 10 also includes a dc motor which
is conveniently mounted in the lower housing 120 The
motor is identified by the reference 12 in the
circuit diagram of Fig. 3. The motor turns a
propeller 14. The motor speed is dependent upon the
current applied to the motor.
In the past a stepping resistor has
been incorporated in a speed control provided for the
motor. If no resistance was placed in the circui~
the motor received full current from the bank of
batteries carried on the boat. If resistance was put
in a series with the motor the motor received less
current and the speed was reduced. Energy, however,
was dissipated in the resistance. This represents an
undesirable loss and efEectively reduces the
available running time of the motor.
Electric outboard motors are usually
mounted on the bow or stern of a boat. ~hey either
pull or push the boat. Steering is effected by
moving the tiller 16 which can also be rotated about
its own axis to rotate the shaft of a potentiometer
18, as shown in Fig. 2. The potentlometer 18 forms a
part of a speed control 19 for the motor 10.
The potentiometer shaft is rotatable
relative to the potentiometer housing which is fixed
to prevent rotation but which can move axially back
and forth in the motor head for purposes not relevant
to the present description. This general type of
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construction is shown in Canadian Patent 1,211,657
issued Septemb~r 23, 1986. Axial movement of the
rotary switch can be used to actuate a switch (not
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shown) to control forward and reverse operation of
the motor.
The motor speed control 19 includes the
potentiometer 18, as previously described, an
integrated circuit or chip A which generates a pulse
train, timing integrated circuit or chip B which
modulates the pulse train, various resistors,
capacitors and diodes, as illustrated in Fig. 3, and
a switching device 23 in the form of an N-channel
enhanced mode Metal Oxide Silicon Field Effect
Transistor or MOSFET. In Fig. 3 the potentiometer 18
controls the amount of voltage applied to an input 7
of integrated Circuit B. Integrated Circuit B and
Integrated Circuit A are identical except for the
manner in which they are hooked up.
Both integrated circuits are generally
regarded as timer circuits but are wired differently
in this use. Integrated circuit A is wired to
operate as an oscillator operating with a 59
microsecond "on1' time and a 1 microsecond "off" time
to provide essentially a 20 KHz pulse train at output
3 which is connected to input 2 of the integrated
~; circuit B. Integrated circuit A is powered by a 12
volt supply from battery terminal 20 adapted to be
connected to the boat batter~. This terminal 20
provides a 12 volt supply to the potentiometer 18
and, depending upon the setting of the potentiometer,
the full 12 volts can be applied to control input 7
of chip B or a lesser voltage can be applied by
dropping some of the voltage in the potentiometer.
Chip or integrated circuit B is wired
to operate as a variable delay monostable
~- oscillator. The output 3 from chip B provides a
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pul~e width modulated 20 KHz pulse train which is
applied through resistor 22 and diode 24 to the ga~ce
G of the MOSFET 23. The source S of the MOSFE:T i8
connected to ground, and the drain D is connected to
5 the motor lead 26. The other motor lead 2~ is
connected to battery terminal 20.
The duty cycle or pulse width of the
modulated pulse train present at outpu~ 3 o~
integrated circuit B is variable between 30% and 98
depending upon the set~ing oP the potentiome~er 18.
The voltage applied tc the gate of the ~IOSFE:T 23 is
enough to cau e full conduction for the duration of
the pulse. By modulating the pulse width the average
output of the MOSFET i8 varied to vary the speed.
Full 12 volt supply and no added resi6tance effective
at the potentiometer applied to the control input 7
will give full (actually about 9~%) speed and thrust
o~ motor 12. The amount of power dis~ipated in the
potentiometer is negligable ~o the batt~ry current
20 drain is reduced ~ubstantially while the control
: gives a very unifor~ speed change over the ~ull
eange. This is contradi~tinction to the stepping
type resis~or having the usual four -speed step~.
Due to the nature of an outboard motor
; 25 and the rela~io~hip between motor speed and
propeller thru~t (and boat speed) the motor is
a~ ably suited to this very cimpls control. There
i8 no need for sen6in~ the motor s~eed or vehicle
speed or the like. The control is very reliable and
afford~ smoother and more economical ~otor operation
: than with pa6t control
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