| 摘要 |
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.
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