1. LCD-216 & LCD-420 Wiring Instructions 1 TRi currently supplies two models of back-lit LCD display modules for use with the FMD, F_series and T100MD+ PLC. Each model is supplied with a 0.5m long 14-pin ribbon cable for connection to the PLC’s LCD port. To use the LCD, simply plug the 14-pin plug on to the LCD port header, making sure that pin #1 (the colored wire) of the ribbon cable a ligns with pin #1 of the port header. (Pin 1 is the pin with a square solder pad and the pin number is also printed on the PCB.) Wiring of the backlight differs slightly for th e two models as shown below. It is assumed that the unit will be connected to the 24V power supply of the PLC. If you are using other voltages, then compute the va lues of the current limiting resistors to obtain the same backlight current. 2 lines x 16 chars. MD-LCD216. A K 220 Ω 5W 24V Power Supply + - Current = 90m A Pin 1 16 4 lines x 20 chars. MD-LCD420 150 Ω 5W 24V Power Supply + - Current = 130m A Pin 1 15 IMPORTANT! Please ensure that t he current limiting resistor is in place and functioning properly before turning on the power supply. Connecting the LED backlight to the 24V power supply without the current limiting resi stor will definitely destroy the backlight unit. Also, please ensure that the polarity is connected correctly, because reverse connection is likely to damage the backlight unit as well. For MD-LCD420, the backlight is brought to a screw terminal via a small PCB. Use a multi-meter to check which terminal is connected to pin 15 (Anode) and 16 (Cathode-) if you are unsure of the polarity.