Inputs

[Guest trn_psycho]

What's the best way to code (Micrologix and/or SLC) four inputs to be read as a decimal number? AKA: I have inputs 8, 9, 10, and 11 wired into a plug. If the inputs see voltage on 10 and 11 then the program needs to see this as a value of 4. Make sense?

[Sergei Troizky 26]

Just copy the inputs to the corresponding bits of the destination word.

[Guest trn_psycho]

So you'd have to use four copy statements? AKA COP (source: I:0/8, dest: N7:1/0), COP (source: I:0/9, dest: N7:1/1), etc....

[Guest]

if I understand your problem, then this should be an example of your first rung ... you'll need three more similar to this ... if this isn't what you need, then you should post again with more details ... best regards, Ron

[b_carlton 61]

Just wondering what coding has 1100 = 4? Or was your example just mistaken? or just follow Ron's lead and ignore this comment. Edited 24 Feb 2005 by b_carlton

[Guest trn_psycho]

Ron, using that wouldn't I have to build a ladder stucture for every possible number in the binary ####. (16 of them).

[Guest trn_psycho]

Oops... Bad math, that would be 3 not four... Edited 24 Feb 2005 by trn_psycho

[Sergei Troizky 26]

By copying I did not mean the COP instruction. Activate the destination coils by the input contacts, that's it. XIC X:0/8 OTE N:0/0 XIC X:0/9 OTE N:0/1 XIC X:0/10 OTE N:0/2 XIX X:0/11 OTE N:0/3 But some combination of the inputs will produce values >9. Edited 24 Feb 2005 by Sergei Troizky

[Ken Moore 23]

I like Sergei's solution best, only takes four lines of ladder, and the destination word will always have the decimal value. Here's an example, you can use as many compares as you need:

[b_carlton 61]

He said that if 10 and 11 were on that would be equal to 4 (later changed to 3). It would seem that they would need to be copied in inverse order. A general note - when a set of inputs are to represent a number it is easiest if the least significant bit is wired to the lowest numbered input (in this case I:0/8). But, if the wiring is now in stone, it can be taken care of in the PLC ladder.

[Guest]

oops! ... I hate it when I do that ... (got the wrong bits on and the wrong bits off) ... this is what I meant to post earlier ... it satisfies the only specific requirements which were given in the original post ... I’m not sure ... just how many possible numbers does your application require? ... please give us all of the details ... we can handle anything - once we know exactly what we’re shooting for ... best regards, Ron Edited 24 Feb 2005 by Ron Beaufort

[mjrx 1]

How about a Bitwise AND with a mask value of 3840 decimal (0F00h) and a SWAP of the high and low bytes to get the bits to the LSB? What this code will do is read the status of bits 8 - 11 and show any combination of these 4 bits as a 0 - 15 decimal value in integer N7:0. Edited 25 Feb 2005 by mjrx

[Guest trn_psycho]

Thanks everyone... What Sergei Troizky said was actually what I was looking for. Sorry if my post was not informative enough Ron. I meant no disrespect. I actually had coded it like you suggested before and was looking for a way to reduce the number of ladders in the program. Dropping from 16 to 4 was a nice change. The whole point of the ? was this: I wanted a better way (AKA: shorter) to identify a program number that is wired into a plug. Four inputs allowed me to get an integer value up to 15 (16 including 0) using a swappable plug. (The value that is connected to this plug determines what program to run...) I'm pretty new to programming in PLC, but have a LOT of C++, C#, VB, Perl experience. So I knew that there must be a more efficient way to capture this data. But Hey! Thanks to y'all, I'll make this transition more quickly! PS: b_carlton, Thanks for advise about lower numbered inputs... That's actually how I set it up. For some reason, when I was asking the ?, I just used the numbers I had written on the right (AKA: Left 8, 9, 10, 11 Right). I guess I just transposed strait down... Edited 25 Feb 2005 by trn_psycho

[Guest trn_psycho]

mjrx, That one gets me... Can you explain (in stupid terms) what the 3840 mask value is?

[Ken Moore 23]

He is doing a bitwise AND the hex value of 3840 is 0F00, so, you get 0110 1110 1110 1110 (input word) 0000 1111 0000 0000 (3840 in binary) 0000 1110 0000 0000 (result of AND) 0000 0000 0000 1110 (after swapping high and low bytes) Edited 25 Feb 2005 by Ken Moore