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sutton
July 7th, 2004, 04:32 AM
hi all,

I used mitsubishi plc for one year before. now im using omron and not quite familiar with it.

can anyone tell me how to apply Mitsubishi's 'alternate function ALT' as in Omron software? i look into the manual book but couldn't find this function.

please help. thank you.

Jay Anthony
July 7th, 2004, 10:47 AM
I have looked through several Mitsuibishi programming manuals for "ALT". I cannot find any mention of this instruction. Which model PLC uses this function? Can you describe it's operation?

panic mode
July 7th, 2004, 12:17 PM
ALT instruction is used only in small PLCs (FX) and it
toggles the output bit every time condition is true.
I think the closest Omron equivalent would be KEEP instruction (http://forum.mrplc.com/index.php?act=Downloads&CODE=02&id=160) .

Jay Anthony
July 7th, 2004, 12:49 PM
Thank you, panic mode:

LD 0.00
DIFU 200.00

LD 200.00
AND NOT 10.00
LD 200.00
AND 10.00
KEEP 10.00

Should also work in Mitsuibishi.

sutton
July 11th, 2004, 08:20 PM
HI Jay Anthony,

thanks again. well, there is no KEEP function in Mitsubishi PLC. And there is also no ALT function in the bigger PLC series. How should I work out this Alternate function in it?

thank you for your help. cheers,

sutton

Goody
July 12th, 2004, 04:30 AM
Search this site for 'flip flop'

ALT is a self contained flip-flop instruction

Jay Anthony
July 12th, 2004, 08:34 AM
LD 0.00
DIFU 200.00

LD 200.00
AND NOT 10.00
SET 10.00
LD 200.00
AND 10.00
RESET 10.00

I'm having a hard time believing that there is no latching function in a Mitsuibishi instruction set.

chavak
July 12th, 2004, 08:53 AM
Hi Jay,

There is also Set/Rset function in Mitsubishi, apart from that there is an Alt function there - my experience is limited to FX series (of course in old Medoc days, never used GPP)

I guess the developers gave an Alt function to create easier flip-flop deployment.

Never seen this function in Omron or AB

Tom Jenkins
July 12th, 2004, 09:32 AM
I personally hate "Set" and "Reset" functions because they can cause debugging difficulties. At 11:59 PM it can become very difficult to remember why that particular contact is "On". I try to use the flip flop or holding contacts or anything else where the action is self evident while I'm debugging. I use set/reset, but only if there isn't any other reasonable way.

Jay Anthony
July 12th, 2004, 11:18 AM
but only if there isn't any other reasonable way.

Thus the suggestion for SET/RSET... ;)

OK, Suggestion #3....

LD 0.00
DIFU 200.00

LD 200.00
AND NOT 10.00
LD 200.00
AND 10.00
OR LD
OUT 10.00

sutton
July 12th, 2004, 07:49 PM
Thanks everyone,

Jay, i did tried out that ladder logic earlier on using SET/ RESET. I run the simulation mode but it will not work. In this ladder logic, it will always be a RESET state instead of flip flop 10.00.
Is there any other idea? How to create a flip-flop state in Mitsubitshi? thank you.

LD 0.00
DIFU 200.00

LD 200.00
AND NOT 10.00
SET 10.00
LD 200.00
AND 10.00
RESET 10.00

Jay Anthony
July 12th, 2004, 10:07 PM
I used mitsubishi plc for one year before. now im using omron and not quite familiar with it.
Is there any other idea? How to create a flip-flop state in Mitsubitshi? thank you.
Make up your mind on whether you need Mitsubishi help or Omron help. I'm sure panic mode can help you out on Mitsubishi.

My feeling is that you did not use the differentiated form of 200.00 or you have a coil of either 200.00 or 10.00 somewhere else in your program.
Can you post a screenshot of your ladder?

sutton
July 12th, 2004, 11:20 PM
Jay,

Well, I am sorry to confuse you. I was actually looking for Flip-flop function help in Omron, which you already solved for me. I was only curious when you say this.

Should also work in Mitsuibishi.

So I tried out the ladder in Mitsubishi PLC software but it wont work. I did use ALT function in the smaller PLC - FX series. but I just wonder how to do the similiar keep function in other Mitsubishi PLC series.

If im not wrong, there is no DIFU function in Mitsubishi. So i use Pulse Up function. Then i used SET and RESET as a latching function.

Here, I had attached a ladder diagram. I found that Y001 is always ON everytime you switch X000 On and Off.

Thank you for your help. cheers.

sutton
July 12th, 2004, 11:25 PM
Oops, here is the screenshot of ladder diagram.

Thanks.

Jay Anthony
July 13th, 2004, 06:46 AM
You are right. I concede. It wouldn't have worked in Omron either. You need a KEEP instruction.

Norbert J. Gallagher
July 13th, 2004, 10:48 AM
Hi Sutton,

I was able to create the equivelent of an ALT function in an A1S processor using four lines of logic. I do not remember exactly. It seems like in rung 3, Y0 should replace M10.

This is a really neat circuit if you are using one push button to turn something off and on, such as a lamp.

I hope this information is helpful.

panic mode
July 13th, 2004, 02:12 PM
I don't think so...

The logic as posted by Sutton doesn't work because M10 would never stay on. Even when set by the SET instruction, following rung would reset it.

panic mode
July 13th, 2004, 08:25 PM
Ok, since nobody replied, I'll post something for people
who might use it. There are number of ways to achive
"toggle effect" but the following two sets of rungs
should be fix that's close enough to earlier post.
One shot used in second set of rungs will not work on
all (older) Mitsubishi CPUs so I've left the example with
PLS instruction.
Also in case you are short with memory and you don't want to
use alterantive toggle logic you might want to use same bit
as temporary storage (M201 in this example).
It might not be the best way to save memory but it might do
here or there...
It works because write instruction for this bit is coil
which updates both "high" and "low" state - and this is done
right before changing state of the bit so there is no danger
of false triggering.

Jay Anthony
July 13th, 2004, 08:30 PM
There must be fifty ways to leave your lover.. Good work!

sutton
July 13th, 2004, 09:08 PM
Hi panic mode, thank you for posting the ladder diagram. I will try to simulate it later. At least everyone learn new things here. cheers mate.

Thomas Sullens
July 13th, 2004, 09:17 PM
I`ve seen about the same thing in AB, DirectSoft, & Idec.
Works BUT could be dangerous on a Motor circuit. Would
make a good alternator.
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