Color-emitting DC level indicator

A DC level indicator wherein a sensed DC level is indicated by the apparent color of light comprising

• DC input means receiving said DC level within a range having a plurality of overlapping subranges;
• color light generating means formed of first, second, and third light-emitting elements of respective first, second, and third primary colors, and positioned together so that the resulting emitted light appears as a blend of the respective primary colors;
• and
• drive means coupled to said DC input means for supplying current to each of said light-emitting elements of said color light generating means, and operative to vary said current in response to the received DC level so that each said light emitting element radiates its respective color light when said DC level is in a respective subrange, but substantially ceases to radiate when said DC level is outside said respective subrange, including a first, a second, and a third switching circuit to switch said first, second, and third light-emitting elements on when said DC level is within said first, said second, and said third subrange, respectively, and to switch the respective elements off otherwise, two of said elements being switched on by their respective switching circuits in an overlapping portion of their respective subranges.

A DC level indicator wherein a sensed DC level is indicated by the apparent color of light comprising

• DC input means receiving said DC level within a range having a plurality of subranges;
• color light generating means including a pair of back-to-back, oppositely-polarized LED's emitting different respective primary colors, and positioned together so that when more than one such LED emits light the resulting emitted light appears as a blend of the respective colors;
• and
• drive means coupled to said DC input means for supplying current to said LED's as a function of the received DC level so that each said LED radiates its respective color light when said DC level is within a respective subrange but substantially ceases to radiates when said DC level is outside said respective subrange, and including mixing means for superimposing an AC signal on a DC signal corresponding to said DC level, to provide a resulting mixed signal to one end of said pair of LED's, and bias means coupled to the other end of said pair of LED's so that one only of said pair emits light of its color when said DC level is below a first voltage, the other only of said pair emits light of its color when said DC level is above a second voltage, and both LED's of said pair emit light of their respective colors when said DC level is between said first and second voltages.

A DC level indicator circuit to which a "tricolor" LED device, formed of back-to-back parallel LED's of different colors of visible light, is to be connected, the device having a pair of terminals to which electrodes of said device are to be coupled;

• comprising
• means generating an AC signal;
• means receiving an input DC voltage;
• and
• drive means having an input coupled to said generating means and another input coupled to said receiving means for providing across said pair of terminals said AC signal with a DC component thereof governed in accordance with the received input DC voltage, such that the apparent color of light emanating from said LED device is substantially of one said color when said input DC voltage is below a first level, is substantially of the other, different color when said input DC voltage is above a second level, but when said input DC voltage is between said first and said second levels, said AC signal alternately switches said LED's of said device on, so that the apparent color of light emanating therefrom is a blend of said colors.

A DC level indicator wherein a sensed DC level of a particular polarity is indicated by the apparent color of light comprising DC input means receiving said DC level within a range having a plurality of subranges;

• color light generating means including a pair of back-to-back, oppositely polarized LED's emitting different respective primary colors, and positioned together so that when more than one such LED emits light the resulting emitted light appears as a blend of the respective colors;
• and drive means coupled to said DC input means and powered by voltage of said particular polarity for supplying current to said LED's as a function of the received DC level so that each said LED radiates its respective color light when said DC level is within a respective subrange but substantially ceases to radiate when said DC level is outside its respective subrange, and including mixing means for superimposing an alternating signal on a DC signal corresponding to said DC level, to provide a resulting mixed signal to one end of said pair of LED's, and bias means coupled to the other end of said pair of LED's so that one only of said pair emits light of its color when said DC level is below a first voltage, the other only of said pair emits light of its color when said DC level is above a second voltage, and both LED's of said pair emit light of their respective colors when said DC level is between said first and second voltages.