lcd programing

hadiahmadi5 said:

i want to connect a lcd to my plc to show the errors there are in my system. i dont khnow how to program it and how to connect the lcd to the plc. please help me ineed your help so much. iwant to write text that must be shown inthe lcd but idont know how to do that and how to write the program.my plc is siemense and the software ia s7.

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Glad to see you got off of the PM kick and started a thread.

Details of the LCD might help (Manufacturer, model, interface etc.)

what do you mean?

i dont know the model correctly.

in my program i have some inputs when the inputs has failed the lcd must show an error abouth the input. i dont know how to write my program and how to connect the lcd please help me.

how should i write the text for exaple if i had an error in my input i0.0 i wan to show (loom stop open)in my lcd .idont know how to write and use the text in my program and load it.

I think the questioner has no choice in mind for the display. I take it the minimum would be that the display would connect to the PLC somehow, presumably through a communication port, but for this application it could be a display with preset text messages triggered by multiple digital inputs.

hadiahmadi5 - you must be able to write the ladder logic to detect when an input has failed. This method would vary greatly from system to system and indeed from input to input. In the end though you must set a location within your PLC to indicate which input has failed as determined by logic.

Some displays can read a word and interpret it to select a pre-programmed text message to display. Some can use either the least significant bit of the word set to trigger the message or the actual value of the word. No bits set / a value of zero usually indicates no faults detected.

Other very low cost displays can be triggered by wired digital inputs (outputs from your PLC) to show pre-programmed messages. Others can only display messages your PLC specifically formulates and transmits to it.

The selection of displays is so varied that it is difficult to give a more specific answer to your question.

ok.thanks for your help. but how can write the words iwant the lcd to show in my program.

Read Bernie's lips, 'it depends on the display'.

Most cheap displays you would write the words in the display itself, with a text editor supplied by the display manufacturer, for example

Text 1 : Loom Stop Open

This is written and stored in the display. The PLC may have 8 outputs wired to the display to give a binary signal between 0 and 255 (256 messages).

You would program the PLC to SET output bit 0 and RESET output bits 1 to 7, therefore giving a binary 1, which = message 1 = as above 'Loom Stop Open'.

Just an example very much depends on the display bought though.

you mean that i must only set and reset the output bits and program the cd that for example when out put 1 is set and other outputs are reset show the alarm for example (loom stop open)and so.