PLC as a Datalogger

[vbarkley]

Hi,

I have a T100MD888+ PLC. I would like to use it as a datalogger. I don't know how to do this.

I have 2 signals of 0-5vdc and a pulse frequency of 0-4200 Hz that I want to record.

How many readings will the PLC's memory store?

Thank you,
Vincent

[support]

Are these digital signals (On/OFF only)? What are you capturing (pulse frequency or analog values)?

The PLC's digital input accept NPN type inputs, not 5V. So if your digital signals are 5V type then you need to convert them into 24V NPN input. A ULN2003A can do the conversion easily.

If you are capturing analog data at 4KHz then it is too fast for the PLC to capture them. The PLC only have limited data memory (4000 words) and EEPROM memory (1700 words) so it is not suitable for capturing high speed digitized data of analog signal.  You need a DSP based processor with large bank of memory for such apps.

[vbarkley]

Thank you for your reply. Here is my plan so far.

I have 2 analog levels (0-5vdc) that I want to record.
I also have 1 digital pulse stream (0-4200 Hz) that I want to count.
Each interval I will sample these 3 values.
I will compute the difference in the count value from the last count value.
This delta count and the two analog levels I will store.
I will save these three values in data memory (DM[1]..DM[4000]).
I will automatically stop taking data when the data memory is full.
I will write this data in a comma-delimited format to the computer.

I don't know how to write this file to the computer.
Can I increase the data memory in the PLC?

Thank you

[support]

T100MD888+ PLC should be able to do the job. The data can be saved onto a PC running the TLServer using the "File Service" capability of TLServer.

To send a comma delimted or tab-delimited file, you simply format the stream of data to be written to the file by using the PRINT statement. E.g.
FOR I = I to 4000 STEP 5
   PRINT #1  STR$(DM)+","+STR$(DM[I+2])+",";
   PRINT #1  STR$(DM[I+3])+","+STR$(DM[I+4])+","+STR$(DM[I+5])
NEXT