Speed control circuit for an electric motor
US4774444A · kind A · utility
Inventor
Key dates
| Filing date | Apr 24, 1987 |
| Grant date | Sep 27, 1988 |
| Priority date | — |
| Expiry date | Apr 24, 2007 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S388/93
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A speed motor control circuit for an electric motor of the type which drives a louvered sign assembly between predetermined rotational positions. The speed control includes a silicon controlled rectifier which is connected in series between the motor and the power supply. A unijunction transistor has one of its bases connected to the gate of the silicon controlled rectifier to switch on, or activate, the silicon controlled rectifier whenever the unijunction transistor becomes conductive. A variable resistor controls the bias to the emitter for the unijunction transistor in order to vary the time period or duty cycle that the unijunction transistor conducts and thus the time period or duty cycle that the silicon controlled rectifier is in its conductive state. A switch assembly and timing module are also employed to activate the motor at predetermined time intervals and for a predetermined angular rotation of the motor shaft.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.