Motor speed control with photoresistive element

Claim 2

A motor control circuit including a source of power; a motor to be controlled; a photocell; at least one silicon controlled rectifier wherein control is achieved by varying the length of time that the silicon controlled rectifier anode electrode voltage is positive with respect to its cathode electrode voltage and having its anode electrode connected to one side of the source of power, its cathode electrode connected to the motor armature of said motor, and its gate electrode connected between one end of the photocell and the source of power intermediate said source of power and the anode electrode of the silicon controlled rectifier; a capacitor connected at one of its ends between the gate electrode of the silicon controlled rectifier and the photocell and at its other end between the cathode electrode of the silicon controlled rectifier and the motor armature; a light source connected at one of its ends intermediate the source of power and the anode electrode of the silicon controlled rectifier and at its other end between the motor armature and the motor field windings of said motor; an adjustable aperture for controlling the amount of light allowed to shine on the photocell from the light source wherein the impedance of the photocell is varied by varying the amount of light allowed to reach the photocell with the impedance of the photocell determining the length of time that the silicon controlled rectifier anode electrode voltage is positive with respect to its cathode electrode voltage; the other end of the photocell being connected to the other side of the source of power so that when line voltage from the source of power is applied to the light source, the light source emits light, and as the amount of light reaching the photocell changes the impedance of the photocell changes causing the time for charging said capacitor to change resulting in a change in conduction time of said silicon controlled rectifier whereby the speed of said motor is varied; a diode and a resistor connected in series with the photocell between its points of connection with the gate electrode of the silicon controlled rectifier and the source of power and with the photocell comprising a half-wave voltage divider across the source of power; a second diode connected in parallel with said capacitor and a second resistor connected to the gate electrode of the silicon controlled rectifier intermediate the photocell and the capacitor with said second resistor and said capacitor constituting and RC time delay that provides an exponential ramp voltage at the gate electrode of the silicon controlled rectifier; and feedback means to maintain constant speed with varying loads and including a second capacitor connected in parallel with the photocell, a third resistor connected at one of its ends to the second capacitor and at its other end between the light source and the motor field windings and a fourth resistor connected between the third resistor and the second capacitor, the third and fourth resistors constituting a voltage divider and the second capacitor acting to maintain the voltage constant between the fourth resistor and the photocell.

Claim 3

A motor control circuit including a source of power; a motor to be controlled; a photocell; at least one silicon controlled rectifier wherein control is achieved by varying the length of time that the silicon controlled rectifier anode electrode voltage is positive with respect to its cathode electrode voltage and having its anode electrode connected to one side of the source of power, its cathode electrode connected to the motor armature of said motor, and its gate electrode connected between one end of the photocell and the source of power intermediate said source of power and the anode electrode of the silicon controlled rectifier; a capacitor connected at one of its ends between the gate electrode of the silicon controlled rectifier and the photocell and at its other end between the cathode elEctrode of the silicon controlled rectifier and the motor armature; a light source connected at one of its ends intermediate the source of power and the anode electrode of the silicon controlled rectifier and at its other end between the motor armature and the motor field windings of said motor; an adjustable aperture for controlling the amount of light allowed to shine on the photocell from the light source wherein the impedance of the photocell is varied by varying the amount of light allowed to reach the photocell with the impedance of the photocell determining the length of time that the silicon controlled rectifier anode electrode voltage is positive with respect to its cathode electrode voltage; the other end of the photocell being connected to the other side of the source of power so that when line voltage from the source of power is applied to the light source, the light source emits light, and as the amount of light reaching the photocell changes the impedance of the photocell changes causing the time for charging said capacitor to change resulting in a change in conduction time of said silicon controlled rectifier whereby the speed of said motor is varied; a resistor connected between the photocell and the other side of the source of power with said resistor being also connected, at its end remote from the photocell, between the light source and motor armature; a diode connected in series with the photocell between its points of connection with the gate electrode of the silicon controlled rectifier and the source of power and a second resistor connected in parallel with the photocell and between the diode and the photocell; a a second diode connected in parallel with the capacitor and a third resistor connected to the gate electrode of the silicon controlled rectifier intermediate the photocell and the capacitor with said third resistor and the capacitor constituting an RC time delay that provides an exponential ramp voltage at the gate electrode of the silicon controlled rectifier; and feedback means to maintain constant speed with varying loads and including a second capacitor connected in parallel with the first resistor and in series with the second resistor, a fourth resistor connected at one of its ends to the second capacitor and at its other end between the motor armature and the motor field windings and a fifth resistor connected between the fourth resistor and the second capacitor, the fourth and fifth resistors constituting a voltage divider and the second capacitor acting to maintain the voltage constant between the fifth resistor and the photocell.

Claim 4

A motor control circuit including a source of power; a motor to be controlled; a photocell; at least one silicon controlled rectifier wherein control is achieved by varying the length of time that the silicon controlled rectifier anode electrode voltage is positive with respect to its cathode electrode voltage and having its anode electrode connected to one side of the source of power, its cathode electrode connected to the motor armature of said motor, and its gate electrode connected between one end of the photocell and the source of power intermediate said source of power and the anode electrode of the silicon controlled rectifier; a capacitor connected at one of its ends between the gate electrode of the silicon controlled rectifier and the photocell and at its other end between the cathode elEctrode of the silicon controlled rectifier and the motor armature; a light source connected at one of its ends intermediate the source of power and the anode electrode of the silicon controlled rectifier and at its other end between the motor armature and the motor field windings of said motor; an adjustable aperture for controlling the amount of light allowed to shine on the photocell from the light source wherein the impedance of the photocell is varied by varying the amount of light allowed to reach the photocell with the impedance of the photocell determining the length of time that the silicon controlled rectifier anode electrode voltage is positive with respect to its cathode electrode voltage; the other end of the photocell being connected to the other side of the source of power so that when line voltage from the source of power is applied to the light source, the light source emits light, and as the amount of light reaching the photocell changes the impedance of the photocell changes causing the time for charging said capacitor to change resulting in a change in conduction time of said silicon controlled rectifier whereby the speed of said motor is varied; a resistor connected between the photocell and the other side of the source of power with said resistor being also connected, at its end remote from the photocell, between the light source and motor armature; a diode connected in series with the photocell between its points of connection with the gate electrode of the silicon controlled rectifier and the source of power and a second resistor connected in parallel with the photocell and between the diode and the photocell; a a second diode connected in parallel with the capacitor and a third resistor connected to the gate electrode of the silicon controlled rectifier intermediate the photocell and the capacitor with said third resistor and the capacitor constituting an RC time delay that provides an exponential ramp voltage at the gate electrode of the silicon controlled rectifier; and feedback means to maintain constant speed with varying loads and including a second capacitor connected in parallel with the first resistor and in series with the second resistor, a fourth resistor connected at one of its ends to the second capacitor and at its other end between the motor armature and the motor field windings and a fifth resistor connected between the fourth resistor and the second capacitor, the fourth and fifth resistors constituting a voltage divider and the second capacitor acting to maintain the voltage constant between the fifth resistor and the photocell.

Claim 5

A motor control circuit as described in claim 1 including a fifth resistor in series with the light source to limit the current through the light source.

Claim 6

A motor control circuit as described in claim 1 including a potentiometer in series with the third resistor to adjust the speed of said motor.

Claim 7

A motor control circuit as described in claim 1 including a thermistor in parallel with the third resistor for temperature compensation.

Claim 8

A motor control circuit as described in claim 2 including a fifth resistor in series with the light source to limit the current through the light source.