Delta Bit in Automation Direct Do-More Designer

Hello all.

I've been working with Do-More designer for the past two years. I used to work with AB before then, but since the company I work with doesn't use AB, I probably have got rusty with them.

Curious question.

In Do-More designer there is a really handy bit instruction called the delta bit. It creates a one shot signal when a value changes so that you don't have to use two registers and a compare, with a load new value right after. I was wondering if Studio5k or TIA Portal had a similar instruction like this.

The Delta contact mimics the behavior of a momentary, normally open relay as follows:
- When the state (if a bit location is used) or value (if a numeric location is used) of the assigned element is NOT equal to the state (or value) of that element from the previous scan the contact is Closed, allowing power flow.
- When the state (if a bit location is used) or value (if a numeric location is used) of the assigned element is equal to the state (or value) of that element from the previous scan the contact is Open, interrupting power flow.

In order to mimic this instruction an OSR instruction is required on the leading edge and trailing edge of the logic. (RS5000)
http://www.plctalk.net/qanda/showthread.php?t=35790

http://www.plctalk.net/qanda/showthread.php?t=103082

Regards,

The PLC-5 has a DTR (Data TRansition) instruction that does the same thing and includes a mask word so you can select bits within a word to compare and ignore those you don't care about. That instruction is rarely used in my experience. The DTR is included in Studio 5000 (for Controllogix and Compactlogix) but not in the SLC/Micrologix instruction set.

OkiePC said:

The PLC-5 has a DTR (Data TRansition) instruction that does the same thing and includes a mask word so you can select bits within a word to compare and ignore those you don't care about. That instruction is rarely used in my experience. The DTR is included in Studio 5000 (for Controllogix and Compactlogix) but not in the SLC/Micrologix instruction set.

Click to expand...

With Do-More I've used it for quite a few things such as summing the total accumulated hours for each pump on a pump station then using the delta bit to rearrange the sequence upon request. I've also used to for one shot calculations upon a change in time of day. Without being able to use any other language than ladder, it's actually proved really handy for things that I would use ST for.

TL140 said:

With Do-More I've used it for quite a few things such as summing the total accumulated hours for each pump on a pump station then using the delta bit to rearrange the sequence upon request. I've also used to for one shot calculations upon a change in time of day. Without being able to use any other language than ladder, it's actually proved really handy for things that I would use ST for.

Click to expand...

I think the reason we rarely saw it used in the PLC-5 is because few folks knew about it, plus the fact that it was an "input instruction" with destructive capability which can throw you for a loop. (the DTR instruction overwrites the compare word with the contents of the source when true).

It is less confusing in that platform to just do a NEQ or MEQ, followed by a MOV instruction and any other logic you need to perform. Any PLC guy or gal will recognize and follow that without much effort.

I have been wanting to give the DoMore PLC a try...when the right project comes up, or if A/B scraps the Micrologix I am sure to do it.

OkiePC said:

I have been wanting to give the DoMore PLC a try...when the right project comes up, or if A/B scraps the Micrologix I am sure to do it.

Click to expand...

Software is free and comes with a pretty good built in simulator with full capability. I’d say try it out.