DC motor speed control system
First Claim
1. A control system for controlling an electric motor in lawn or garden equipment, said electric motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, comprising:
- means for generating a frequency signal at a predetermined frequency;
means for generating a supply feedback signal functionally related to said supply signal;
means for sensing the current being drawn by said motor;
means for generating a load feedback signal functionally related to the magnitude of said sensed motor current;
pulse width modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal at said predetermined frequency whose pulse width is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current;
switch means for switching current to said motor in response to said switch control signal; and
means for increasing the power to said motor when the sensed motor current is greater than a predetermined level.
1 Assignment
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Accused Products
Abstract
A speed controller for a DC motor minimizes speed droop and load droop through pulse width or frequency modulation. The controller provides an extra power increase upon engine starting or whenever a heavier load is temporarily encountered. The control circuit also has a current limiter, overload indicators, and a battery recharger. The controller is very inexpensive, primarily because all of the timing components are contained on a single integrated circuit timer chip such as a 556 timer. The controller contains other features, including a circuit for limiting the pulse width of the control signal from the pulse width modulator.
120 Citations
50 Claims
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1. A control system for controlling an electric motor in lawn or garden equipment, said electric motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, comprising:
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means for generating a frequency signal at a predetermined frequency; means for generating a supply feedback signal functionally related to said supply signal; means for sensing the current being drawn by said motor; means for generating a load feedback signal functionally related to the magnitude of said sensed motor current; pulse width modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal at said predetermined frequency whose pulse width is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current; switch means for switching current to said motor in response to said switch control signal; and means for increasing the power to said motor when the sensed motor current is greater than a predetermined level. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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5. A control system for controlling an electric motor in lawn or garden equipment, said electric motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, said control system comprising:
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means for generating a frequency signal; means for generating a supply feedback signal functionally related to said supply signal; means for sensing the current being drawn by said motor; means for generating a load feedback signal functionally related to the magnitude of said sensed motor current; frequency modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal having a set pulse width whose frequency is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current; switch means for switching current to said motor in response to said switch control signal; and means for increasing the power to said motor when the sensed motor current is greater than a predetermined level.
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27. A control system for controlling an electric motor in lawn or garden equipment, said motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, said control system comprising:
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means for generating a supply feedback signal functionally related to said supply signal; means for sensing the current being drawn by said motor; means for generating a load feedback signal functionally related to the magnitude of said sensed motor current; a timer means, including; means for generating a frequency signal at a predetermined frequency; pulse width modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal at said predetermined frequency whose pulse width is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current; and switch means for switching current to said motor in response to said switch control signal. - View Dependent Claims (28, 29, 30, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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31. A control system for controlling an electric motor in lawn or garden equipment, said motor being interconnected with a load, said motor drawing current from and being powered by a battery that outputs a supply signal, said supply signal continuously decreasing as said battery discharges, said control system comprising:
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means for generating a supply feedback signal functionally related to said supply signal; means for sensing the current being drawn by said motor; means for generating a load feedback signal functionally related to the magnitude of said sensed motor current; a timer means, including; means for generating a frequency signal; frequency modulation means for receiving said frequency signal, said supply feedback signal, and said load feedback signal, and for outputting a switch control signal having a set pulse width whose frequency is both inversely proportional to said supply signal and directly proportional to the magnitude of said sensed motor current; and switch means for switching current to said motor in response to said switch control signal.
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Specification