I have bought a cheap radio controlled clock, and I want to make a hack that replaces the existing LCD display with 7-segment LED's.
With my voltmeter in AC mode, I can measure voltages(with respect to battery minus) on the connectors to the LCD of 0.4V(presumably off) 1.4-1.6V(presumably on). I do not know the waveform or frequency of this voltage, but I suppose I can measure it, if I find an oscilloscope somewhere.
How do I convert this AC to a logic signal, that can be used to drive the 7-segment?
Is there any standard regarding LCD drive voltages?
Does there exist a single drive chip for this purpose?
Do I need transistors, op-amps or a chip to make enough current?
There is absolutely no logic in the display itself – it is just a glass plate(with liquid crystal). I can even make the display turn on shortly with dc. All the connector seen on the picture drives the display directly.
(Wikipedia LCD) says:
Both the liquid crystal material and the alignment layer material
contain ionic compounds. If an electric field of one particular
polarity is applied for a long period of time, this ionic material is
attracted to the surfaces and degrades the device performance. This is
avoided either by applying an alternating current or by reversing the
polarity of the electric field as the device is addressed (the
response of the liquid crystal layer is identical, regardless of the
polarity of the applied field). Displays for a small number of
individual digits and/or fixed symbols (as in digital watches and
pocket calculators) can be implemented with independent electrodes for