Abstract The invention relates to a control circuit for a servomotor of the type having a piston displaceable to selectable positions in one direction by an expansible substance heatable by an electric heating element and in the other direction by a return spring. The circuit includes a pulsating power supply and a control switch and a thermostatic unit for generating a temperature responsive control voltage. A potentiometer for generating voltages corresponding to different positions of the piston is operably connected to the piston. A comparator for comparing the control voltage with the potentiometer voltage generates a go-no go signal which is relayed to the heating element control switch. Upper and lower limit switches are associated with the selectable positions of the piston. The limit switches selectively override the potentiometer to effect operation of the heating element control switch. Light emitting diodes are provided which give visual indications of the heating and cooling cycles.
A control circuit for a servomotor of the type having a piston displaceable to selectable positions in one heating element and in the other direction by a return spring, said circuit comprising a heating element, a power supply circuit for said heating element including a control switch, first means for generating temperature responsive variable control voltage, second means for generating variable position voltages corresponding to different positions of said piston which means includes a potentiometer with a movable tap and means connecting said piston to said tap, means including comparator means for comparing said control voltage and said piston position voltage and operating said control switch when one of said voltages is larger than the other one.
Claim 2
Dependent Claim
117 words
A control circuit for a servomotor of the type having a piston displaceable to selectable positions in one heating element and in the other direction by a return spring, said circuit comprising a heating element, a power supply circuit for said heating element including a control switch, first means for generating temperature responsive variable control voltage, second means for generating variable position voltages corresponding to different positions of said piston which means includes a potentiometer with a movable tap and means connecting said piston to said tap, means including comparator means for comparing said control voltage and said piston position voltage and operating said control switch when one of said voltages is larger than the other one.
Claim 3
Dependent Claim
26 words
A control circuit according to claim 1 wherein said first voltage generating means generates D.C. voltage and said second voltage generating means generates an A.C. voltage.
Claim 4
Dependent Claim
51 words
A control circuit according to claim 1 wherein upper and lower limit switches are associated with said selectable positions for said piston, said limit switches being respectively effective to overide said potentiometer to effect operation of said control switch to either block or direct energy from or to said heating element.
Claim 5
Dependent Claim
14 words
A control circuit according to claim 1 wherein said control switch is a thyristor.
Claim 6
Dependent Claim
40 words
A control circuit according to claim 1 including first and second light emitting diodes, said diodes being alternately on and off when said control switch is correspondingly opened or closed to give visual indications of the heating and cooling cycles.