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US 4,289,999 AGranted
Digital variable voltage level control circuit with automatic return to neutral
AssigneeAmpex Corporation
InventorRobert P. Harshberger, Jr.
Life of this patent
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AssigneeAmpex Corporation
InventorRobert P. Harshberger, Jr.
Estimating the term…
A control circuit generates a variable analog output voltage in response to momentary closure of touch control means by an operator. The control level selected via the touch control means is sampled, digitized, digitally stored and reconverted to the analog output voltage for driving a motor at a commensurate speed. Selection of a different control level generates a correspondingly different digital value and thus a different analog output voltage. The selected control level and the corresponding analog output voltage may be maintained for an extended period of time until a new selection is made, or a different operating mode is entered. A mode change causes an automatic reset to a neutral operating condition (e.g., zero analog output voltage).
A control circuit for generating a readily varied analog output voltage signal for controlling the speed of a tape transport in a selected mode of operation, and including an operator generated control command commensurate with the desired speed from zero to maximum, comprising the combination of;
Dependencies are inferred from the claim text.
Drawings are temporarily unavailable. Open the PDF at USPTO
Driving; Starting; Stopping; Arrangements for control or regulation thereof: speed-changing arrangements; Reversing arrangements; Drive transfer…
Where the program is defined in the fixed connection of electrical elements, e.g. potentiometers, counters or transistors: for delivering a step…
Specific control circuit element or device: pulse or frequency counter
Specific control circuit element or device: sawtooth or ramp waveform generator
Term ended 14 May 1999 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
1. Field
The invention relates to a voltage level control circuit and, in particular, to an operator interface control circuit for digitally providing variable shuttle speed control of a tape transport.
2. Prior Art
The single FIG. 1 is a schematic diagram exemplifying implementation of the invention combination as used in an audio tape transport to provide variable shuttle speeds.
Referring to the FIGURE, a touch control means 10 is shown schematically, and includes a resistive element 12 formed of a large number of serial resistors, and a touch responsive wiper element 14. One end of the resistive element 12 is grounded via a resistor 13, and the other end is coupled to a +15 volt supply via a further resistor 15. The wiper base of the wiper element 14 is coupled to the +15 volt supply via a resistor 16, and also to a positive input of a comparator 18 via an amplifier transistor 19 and a control line 21. When the wiper element 14 is not touched, the touch control means 10 delivers +15 volts to the comparator 18 via the resistor 16. When the wiper element 14 is touched, the means 10 delivers a control signal voltage via line 21 which is greater than zero and less than +15 volts, depending upon where the means 10 is touched.
The comparator 18 is coupled at its negative input to a ramp generator 20 formed of a transistor 22, whose emitter is coupled to a +15 volt supply via a resistor, and whose collector is coupled to ground via a capacitor 24. The base thereof is coupled to a variable tap of a potentiometer 26, which is coupled between the +15 volt supply, and ground via a resistor. The ramp generator 20 provides a sawtooth waveform by charging and discharging the capacitor 24 as described below.
The comparator 18 is coupled to means for analog-to-digital conversion, generally indicated at 28, and particularly to a +5 volt supply via a resistor, and to one input of a NOR gate 30. The latter's output is coupled to the clock input of a (6-bit) digital latch 32, whose data inputs are coupled to the Q outputs of a (6-bit, divide-by 64) counter 34, formed herein by a 2-bit counter 38 and a 4-bit counter 39.