LCD goes blank - backlite stays on

[mjfergus]

Using the T100MD888+ to monitor analog and digital inputs along with digital output controls.  A 4x20 LCD is also in use to display menus and data.

After running without issue for 6 months, the LCD now appears to turn off on occassion.  After cycling power, the LCD functions normally.  The LCD backlite stays on with the power.  Connections have been tested, a second LCD was tested with the same results.  The problem appears to be on the PLC board and not with the LCD (the 2nd LCD unit has only a few hours of run time).

Why does the LCD appear to turn off?
Is there any method other than power off/on to reset the LCD connection?
Has this problem been noted?
Is there any solution?

The LCD data may be monitored from a computer connected via XServer and the data programmed to the screen is updating.

Thank you,

Michael

[support]

Dear Sir,

If the LCD display is showing random characters every now and
then or clear screen and hang, it means that there are electrical noise that is coupled onto the ribbon cable connecting between the PLC and the LCD.

1) Did you use the standard 2 ft cable supplied? It is not
recommended to lengthen the ribbon cable to beyond 3 ft as it
become more sensitive to noise.

2) Please ensure that the ribbon cable is not bundled with any
high voltage high current power cable (especially those VFD or
inverter which is extremely noisy). If noise become a problem,
then wrap the ribbon cable in aluminium foil and ground one
side of the foil to the panel chasis to protect against noise
intrusion.

3) Make sure that if you are switching inductive load, use
flyback diode for DC load or varistor for AC load to reduce
the switching noise resulting from turning off an inductive
load.

4) The IC 74HC595 near to the LCD port is the main driver IC for the LCD display. If there is any damage to this IC (such as the LCD being plugged/unplugged accidentally with the power ON) it may give you intermittent display problem. You can try to replace this IC to see if the problem go away.

[FQ-ONG]

I also face to this problem right now. I already try to replace with another 2 pcs of 74HC595 IC and it was tested with the same results.

[support]

This customer reported that by using ferrite cores surrounding the LCD ribbon cable he is able to eliminate the problem of random characters caused by electrical noise.