Patent GB-1420074-A (GB)
Title: Timing attachment for a relay
IPC: H03K17/292
Filed: 1972-03-21
Abstract: 1420074 Photo-electric relay SQUARE D CO 21 March 1973 [21 March 1972] 13107/72 Heading G1A [Also in Divisions H1 and H3] In a timing attachment for a relay including a housing 12, Fig. 3, an apertured control member 42, Fig. 5 adapted to be mounted on a movable contact carrier of the relay so as to be movable in the housing, a source of electromagnetic radiation 54, LED 1 Fig. 11 and a detector 56, 1PT so arranged in the housing that the detector can detect radiation transmitted from the source and transmission of the radiation is influenced by movement of the control member 42 a control circuit Fig. 11 located in the housing 12 and an output switching device 16, 1TR connected for operation by the control circuit, the detector 56, 1PT is connected to the control circuit for effecting operation of the output switching device 16, 1TR and the housing is mountable on the relay in selected positions to provide for delayed operation of the switching device 16, 1TR after energization or de-energization of the relay. In Figs. 3 and 5 the base 34 of the housing has a pair of mounting lugs 30 for connection to the relay contact blocks. A vane 42 is fastened by leg portions 44 to the top of a moving contact carrier (not shown) of the relay so as to slide in a slot 40 as the relay is energized or de-energized. The vane 42 has two diagonally spaced apertures 52, Fig. 5 and Figs. 6a-6d, (not shown) which when one of these apertures is aligned with apertures 58 in the base 34 allows light to pass from an infrared light emitting diode 54, LED to energize a photo-transistor 56, 1PT. The solid state circuit shown in Fig. 11 is provided on printed circuit boards 20, 22 mounted within the housing and an output device in the form of a triac 1TR is provided in a block 16 which is disclosed in detail Figs. 10a-10c, (not shown) or (60), Figs. 7-9 (not shown). The output device may be a transistor. For time delay after energization, normally open, timed close operation, the NOTC-NCTC link is connected. The relay is de-energized and allows light to pass from the light emitting diode LED1 via the aperture 52 in the vane 42 to the phototransistor 1PT which conducts as do transistors STI, 6TI, 1TI and 3TI. Transistor 3TI holds the emitter of a uni-junction transistor 1 UJT below a peak point voltage so that the triac 1 TR is off as is a transistor 2TI. A timing capacitor C4 charges via 6TI. When the relay is energized the vane 42 blocks the light between LED1 and 1PT which becomes cut off as do the transistors STI, 6TI. Now the capacitor C4 discharges and after a delay time determined by P1 transistor 1TI cuts off and transistor 2TI conducts to cut off 4TI and 3TI which then allows the emitter voltage of the unijunction transistor 1UJT to rise and fire the triac 1TR. A plug (78), Fig. 1, (not shown) provided at the top of the housing enables the initial state of the triac 1TR to be changed so that by altering the connection NOTC-NCTC to NCTO-NOTO time delay after energization, normally closed timed open operation, of the triac 1TR is provided. Time delay after de-energization, normally closed, timed close operation, is possible by removing the timing attachment from the relay, turning it through 180 degrees and refitting it to the relay. This changes the relative positions of the aperture 42 and the timing attachment so that when the relay is deenergized the vane 42 blocks light from 1PT so that the triac 1TR conducts. Energization of the relay allows illumination of the photo-transistor 1PT so that the triac 1TR turns off. Then on deenergizing the relay after the delay time provided by the capacitor C4 the triac 1TR is again fired. Time delay after de-energization, normally open timed open operation, is possible by changing the plug (78) from NOTC-NCTC to NCTO-NOTO position. A temperature compensation circuit including resistors R15, R13 and negative temperature coefficient thermistors TH1, TH2 and a diode D6 stabilize the delay time with temperature changes. A diode D5 protects the light emitting diode LED 1 from reverse voltage.