How many inputs can a plc card take?

Hello

I am new to plcs. I am just wondering how many inputs can plc take. Today i was noticing the input of plc and it had numbers like 00,01,02 till 07 and then it started from 10,11,12 till 17 .What does this mean.where did 08 and 09 go. Also,in rslogix500 there is some input out table which showed many inputs.

The inputs are set up as bytes. There are 8 bits to a byte (0-7) there is no 8 or 9. The first byte is byte 0 (0.0, 0.1, 0.2 etc). The second byte is byte 1 ( 1.0, 1.1, 1.2 etc) The actual number of inputs is going to be limited by the type of PLC.

Brodin said:

The inputs are set up as bytes. There are 8 bits to a byte (0-7) there is no 8 or 9. The first byte is byte 0 (0.0, 0.1, 0.2 etc). The second byte is byte 1 ( 1.0, 1.1, 1.2 etc)

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This is actually NOT correct. Yes, they are numbered 0-7 and then 10-17, but the 10 is not "1.0" as in the "second" byte. He is probably looking at a PLC5 style card. The outputs/inputs are numbered in Octal numbering, not decimal. So 10 is not meant to be "1.0", the Octal number 10 is 8 when converted to decimal. Octal number 11 is 9 when converted to decimal, and so on. In decimal, the inputs he's looking at are actually numbered 0-15 like a SLC 500 card would be, but the old school stuff often used Octal numbering instead of decimal.

Although, I guess looking at it in the 1.0, 1.1 way does make it a little easier for someone who doesn't know Octal numbering to understand.

bornwild said:

Hello

I am new to plcs. I am just wondering how many inputs can plc take. Today i was noticing the input of plc and it had numbers like 00,01,02 till 07 and then it started from 10,11,12 till 17 .What does this mean.where did 08 and 09 go. Also,in rslogix500 there is some input out table which showed many inputs.

Click to expand...

That sounds more like an Allen Bradley PLC5 using 1771 I/O. It was Octal, so the biggest number was 7 before you move to the next column (0-7 Actually). Then the next Inputs are 10 to 17. If you count them up, that is 16 Inputs. How you set up the Addressing on an AB PLC5 affects this. If it was a PLC5, you should be using RSLogix 5. The SLC500 family uses Decimal Addressing, 0-15 for a 16 Point Input or Output. The answer to your question depends on what PLC Manufacturer and Model you are talking about.

Stu.....

typing mistake. I am using rslogix5. So how do i look in the input take in rslogix 5. It had columns and rows like I:000/01(in rows) and number from 01 to 17 in columns

RTFM!

bornwild said:

typing mistake. I am using rslogix5. So how do i look in the input take in rslogix 5. It had columns and rows like I:000/01(in rows) and number from 01 to 17 in columns

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In the File Tree on the left side, you will see all the file types, including Inputs, Outputs, and Status Files among others. You can look at there state, usage, and review the forced status or force an Input or Output if you so wish.

There are lots of good resources on the Allen Bradley Web Site, as well as the Internet. Google is your friend.

http://literature.rockwellautomation.com/idc/groups/public/documents/webassets/browse_category.hcst


Stu......

thanks