LCD displays are driven by AC waveforms. I've seen many references referring to permanently damaging them with DC current. When exposed to DC, LCD's fail and conduct excessive current. My question is: what exactly changes physically? Does a contact become "plated" with liquid crystal molecules preventing current flow? Do electrons permanently migrate? Are molecules broken down?
Electronic – How exactly is an LCD damaged by DC current
damagelcd
Related Solutions
In my experience, the best way to check if a battery is damaged is to hook it up to a multimeter and check the output voltage (if it's fully charged). It should be safe to charge and test unless it is leaking fluid. It's always a good idea to keep an eye on them while they are charging, especially if you think they may be damaged.
It looks like you're resetting your microcontroller, but the display is not resetting (when you press the button the display does not turn off/reset). Note that without a reset, you are starting in 4-bit mode, to send 8-bit commands you need to switch back to that mode.
In this case, the first thing your init should to is reset the display to a known state. Alternatively, you can just wire the display to reset with the same signal as the microcontroller reset.
For proper initialization look at the datasheet. Notice the initialization diagram in the datasheet starts with "Power On". You're not starting there, you're skipping the first couple steps. According to the datasheet,
If the power supply conditions for correctly operating the internal reset circuit are not met, initialization by instructions becomes necessary.
This is the 4-bit initialization by instruction diagram.
Best Answer
A LCD segment consists of a cell filled with liquid with very thin transparent electrodes on either side.
If a DC voltage is applied to this metal is transferred from the anode to the cathode resulting in the anode getting thinner. Eventually the anode will fail or its resistance will increase reducing its effectiveness.
Excessive current will be caused by metallic whiskers growing between the electrodes by the same mechanism effectively shorting the electrodes. Imagine that you have a high point on one surface the electric field is stronger at the high point so it attracts more metal ions making it higher making the field stronger......