Photoelectric controlling
US3996475A · kind A · utility
Inventor
Key dates
| Filing date | Jul 28, 1975 |
| Grant date | Dec 7, 1976 |
| Priority date | — |
| Expiry date | Jul 28, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K17/79
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A light source, such as a light emitting diode (LED), illuminates a cadmium sulfide or cadmium selenide photocell to lower its resistance and thereby initiate conduction in a solid-state device, such as a silicon controlled rectifier (SCR), to deliver current to a load that is interrupted by removing the light energy and restoring the photocell to its unilluminated high resistance state. A feature of the invention resides in limiting the optical energy incident upon the photocell so that its resistance remains well above the lowest resistance it can attain while still dropping to a resistance value considerably below its maximum resistance when unilluminated so that within the total resistance changes of the photocell, the small percentage resistance charge required for proper activation of the solid-state device, may be effected relatively rapidly both for turn on and turn off.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.