Abstract A liquid crystal indicator has a drive circuit wherein a DC drive voltage is converted to an AC signal for the indicator. The drive circuit includes a capacitor connected in series with the DC drive voltage and the liquid crystal indicator and a transistor paralleled with the capacitor. The bias circuit for the transistor includes a resistor and a diode connected in series and an oscillator is connected to the junction between the resistor and the diode of the bias circuit by a second diode which is poled to bleed bias current from the transistor upon negative excursions of the oscillations to turn the transistor off and on. A third diode connected to the common junction of the other diodes is also poled to bleed the bias current of the transistor to override the control signal from the oscillator and prevent a change in the conductive state of the transistor. A number of drive circuits each connected to an output of a decoder control the visualization of the several segments of the liquid crystal indicator to visualize different alphanumerical characters in accordance with the coded binary input to the decoder.
A liquid crystal indicator having at least one symbol capable of visualization by a series of pulses of short duration and a drive circuit therefor, said drive circuit comprising: a pulse former, a counter responsive to said pulse former to generate a coded binary output signal, a source of DC triggering pulses, a drive circuit responsive to said triggering pulses to actuate said display device, and electric circuit means responsive to said counter to selectively override said triggering pulses to change the visualization of said symbol, said drive circuit comprising: a capacitor connected in series with said liquid crystal indicator, a source of DC drive voltage for charging said capacitor through a resistor, a transistor connected in parallel with said serially connected capacitor and liquid crystal indicator to provide a discharge path for said capacitor, a bias circuit for said transistor to provide a flow of current through a base emitter junction of said transistor sufficient to drive the transistor to saturation, and a diode poled to bleed bias current from said transistor connected to said source of triggering pulses to reduce the level of bias current below the saturation level of said transistor upon a reduction in the level of said triggering pulses.
Claim 2
Dependent Claim
204 words
A liquid crystal indicator having at least one symbol capable of visualization by a series of pulses of short duration and a drive circuit therefor, said drive circuit comprising: a pulse former, a counter responsive to said pulse former to generate a coded binary output signal, a source of DC triggering pulses, a drive circuit responsive to said triggering pulses to actuate said display device, and electric circuit means responsive to said counter to selectively override said triggering pulses to change the visualization of said symbol, said drive circuit comprising: a capacitor connected in series with said liquid crystal indicator, a source of DC drive voltage for charging said capacitor through a resistor, a transistor connected in parallel with said serially connected capacitor and liquid crystal indicator to provide a discharge path for said capacitor, a bias circuit for said transistor to provide a flow of current through a base emitter junction of said transistor sufficient to drive the transistor to saturation, and a diode poled to bleed bias current from said transistor connected to said source of triggering pulses to reduce the level of bias current below the saturation level of said transistor upon a reduction in the level of said triggering pulses.
Claim 3
Dependent Claim
41 words
The device of claim 1 wherein said liquid crystal indicator has a plurality of symbols each connected to the output of a drive circuit responsive to said coded binary output signal to selectively visualize said symbols to display different alphanumerical characters.
Claim 4
Dependent Claim
42 words
The device of claim 1 wherein said bias circuit includes a resistor and second diode connected in series with said DC voltage and the base of said transistor to establish a maximum level of current flow through the base of said transistor.
Claim 5
Dependent Claim
58 words
The device of claim 3 wherein said counter is connected to said drive circuit through a third diode poled to bleed bias current from said transistor to reduce the level of bias current below the saturation level of said transistor thereby to selectively override said triggering pulses and prevent a shift in the conducting status of said transistor.