Reduced wattage PLC interface
US5444309A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 14, 1993 |
| Grant date | Aug 22, 1995 |
| Priority date | — |
| Expiry date | May 14, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K2217/0036
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A controller such as a programmable logic controller (PLC) is coupled to a load such as a contactor or motor starter through an interface that operates over a range of DC or AC voltage and couples a Start output of the controller to the load through a low current switch such as an opto-relay. The interface has a charging circuit coupled to the controller output, with a switching transistor, a load resistor and a capacitor in series. The low current switch is operated from accumulated charge in the capacitor and couples power to the load device. Charging of the capacitor to a threshold switches off of the transistor for an interval timed by a one-shot, during which the low current switch remains activated due to current draining from the capacitor. In an AC embodiment with a triac controller output, the capacitor continues to power the low current switch for the remainder of the positive AC half cycle, regardless of the triac, which may cease conduction due to lack of sufficient loading. The circuit substantially reduces the current dissipation of an interface between a PLC and a motor starter or contactor. The interface can include optically isolated signalling in both directions, …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.