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Browse Prior Art Database

Time Shared Constant Brilliance Indicator Circuit

IP.com Disclosure Number: IPCOM000074463D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 3 page(s) / 56K

Publishing Venue

IBM

Related People

Dickerson, JA: AUTHOR [+3]

Abstract

In the larger data processors having an operators console, the indicator lights of the console are usually a varying but substantial distance from the control circuits. This requires a large number of cabled connections and the voltage drops combined with the normal variations of a voltage supply line also cause varying brightness of the indicators. The circuit diagrammed substantially eliminates the variable brightness and reduces the cabling requirements.

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Time Shared Constant Brilliance Indicator Circuit

In the larger data processors having an operators console, the indicator lights of the console are usually a varying but substantial distance from the control circuits. This requires a large number of cabled connections and the voltage drops combined with the normal variations of a voltage supply line also cause varying brightness of the indicators. The circuit diagrammed substantially eliminates the variable brightness and reduces the cabling requirements.

In the drawing, a plurality of indicator lights 1, divided into an upper and a lower group, are powered by a transformer 2. The transformer 2 has its primary 3 driven directly by the power line and has a center tapped secondary 4 to power the lights. One end of the secondary 4 is connected through individual diodes 6 to each of the lamps 1 of the upper group and the lower end of the secondary 4 is similarly connected through individual diodes 8 to the lower group of lamps. The center tap of the secondary 4 is connected to a common return lead 9. Thus, each lamp will be powered only on the positive half-cycle of voltage from secondary 4 and the groups will be alternately powered on the respective half- cycles.

The lights 1 are selectively connected to the return lead 9 through SCR switches 10 to provide individual control over the lamps. One lamp from the upper group and one from the lower group have their other ends connected together and to the anode of an SCR switch 10 whose emitter end is connected to common lead 9. When an SCR switch 10 has its gate lead 11 energized, it will pass current from the lead of secondary 4 which is positive through one of the associated lights 1 to light only that lamp and will cease conduction as the voltage output of secondary 4 passes through zero.

The SCR gates 11 are selectively energized to control the phase of secondary 4 on which the SCR's conduct to select either or both of the upper group or lower group light and to select the phase angle over which they conduct to control the brilliance of the light. A reference secondary 12 on transformer 2 has its output full-wave rectified by diodes 13 to provide on line 14, a pulsating DC voltage, as at 14 on the graph with respect to common lead 9. This voltage is clipped by a resistor 15 and zener diode 16 to provide a voltage at point 17 as at 17 of the graph. The voltage at point 17 passes through a resistor 18 to charge a capacitor 19 to a voltage as indicated at 20 on the graph. Capacitor 20 is discharged by a programmable unijunction transistor (PUT) 21 which will conduct when its anode voltage at point 20 is equal to or greater than its gate voltage which...