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US 3,946,273 AGranted
Split cross fader for the control of theatre lighting
OwnerRobert M. Goddardinventor
Life of this patent
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Abstract
A split cross fader for the control of theatre lighting in which functions previously found only in separate master control units and cross fader units are combined into a single device which permits operation as a scene master, as a cross fader and also permits pile-on operation with smooth fading between each scene condition commanded.
Claims24
A method of developing voltage control signals to be provided to a control unit which is to be controlled in response to either of two control inputs with fading between inputs possible, comprising:
- a. developing a first pulse train with pulses thereon having a duty cycle of between zero and one hundred percent which is directly proportional to a desired value of P.sub.X corresponding to a first fader control position which may also vary between 0 and 100 percent;
- b. developing a second pulse train having a duty cycle varying between zero and one hundred percent, the duty cycle being directly proportional to the desired value of P.sub.Y corresponding to a second fader control position which also varies between zero and one hundred percent, the timing of said first and second pulse trains being such so that when the sum of the duty cycles of the pulses on said first and second pulse trains is less than one hundred percent, the pulses do not overlap in the time domain;
- c. multiplying said first pulse train by a value C.sub.1X corresponding to a first input preset to develop a first modulated pulse train;
- d. multiplying modulating said second pulse train by a quantity C.sub.1Y corresponding to a second input preset to develop a second modulated pulse train;
- e. combining said first and second modulated pulse trains to provide an output which has a magnitude equal to the largest magnitude of either pulse train present at a given time, said output signal being the signal provided to drive said control unit.
2 more elements
Apparatus for developing voltage control signals to be provided to a control unit which is to be controlled in response to either of two control inputs with fading between inputs possible, comprising:
- a. means for generating a periodic waveform voltage having an upper peak reference and lower peak reference value;
- b. means for generating a first analog voltage proportional to a value P.sub.X corresponding to a first fader control position;
- c. means for generating a second analog voltage inversely proportional to a value P.sub.Y corresponding to a second fader control position;
- d. first means for comparing said periodic waveform with said first analog voltage and for providing an output at one level when said first analog voltage is greater than the voltage of said waveform and at another level when said waveform voltage is greater than said first analog voltage to thereby develop a first pulse train having a duty cycle variable between 0 and 100 percent;
- e. second means for comparing said periodic voltage with said second analog voltage and for providing an output at said one level when said waveform voltage is greater than said second analog voltage and at said other level when said waveform voltage is less than said second analog voltage to provide a second pulse train, the timing of said first and second pulse trains being such so that when the sum of the duty cycles of the pulses on said first and second pulse trains is less than 100 percent, the pulses do not overlap in the time domain;
- f. first storage means for storing a value C.sub.1X proportional to a first preset, said first storage means having said first pulse train as an input and responsive to provide pulses having the same duty cycle as said input pulse train and having an amplitude proportional to said value C.sub.1X ;
- g. second storage means for storing a value C.sub.1Y proportional to a second output preset, said second voltage storage means having said second pulse train as an input and responsive to provide output pulses having the same duty cycle and having an amplitude proportional to said value C.sub.1Y ;
- and
- h. means for combining the outputs of said first and second storage means so as to provide an output equal to the greater instantaneous value of said two inputs, said output being the control voltage of said circuit.
6 more elements
Dependencies are inferred from the claim text.