Micrologix 1100 - How to mplement this PLC-5 rung?

skyfox

Lifetime Supporting Member
Join Date
Nov 2006
Location
CA
Posts
276
Not Sure why I can't implement this piece of PLC-5 logic in a Micrologix 1100 !!!!!!

1Sec_Pulse.JPG



In Micrologix 1100, S:42 = RTC Seconds Register.
I want to use S:42/0 to toggle a bit so I can have a pretty accurate 1sec timing Pulse.

Is it not possible to address the Real time clock Seconds register in Micrologix 1100 to bit level?

Also, RSlogix 500 does not like the two one-shots with a single output. Say's each one-shot must have an output attached to it. My Rslogix 500 Version = 7.00.00. Any ideas why? A work around perhaps?


-Thanks
 
Last edited:
Hi Alaric,

Thanks for the help. Nice idea. Unfortunately ML 1100 RTC seconds bits only toggle once every two seconds. This is true for both RTC:0.SEC/XX and S:42/XX bits. Any other suggestions how to get a one second pulse from this PLC?

Thanks
 
How accurate does it have to be? See PDF below for free running clock bits. You could use a one second timer and its done bit.
 
Maybe not quite so elegant but I often use a timer with a .01 sec base and a 200 preset that resets itself (basically a 2 second timer).

Say it's timer t4:0. Then use:


T4:0/DN +--[TON]-----+
-----]\[--------------+ T4:0 |
|Base 0.01 |
|Pre 200 |
|Acc 0 |
+------------+

Flash
--+-[LES]-----+-------------( )--
| T4:0.ACC| B3:100/0
| 100 |
+-----------+

 
skyfox said:
Hi Alaric,

Thanks for the help. Nice idea. Unfortunately ML 1100 RTC seconds bits only toggle once every two seconds. This is true for both RTC:0.SEC/XX and S:42/XX bits. Any other suggestions how to get a one second pulse from this PLC?

Thanks

I doubt that skyfox - that would mean the RTC seconds register counts up 0, 2, 4, 6 etc.

Surely bit 0 of the RTC seconds register is ON for one second, and OFF for one second, (as it counts 0, 1, 2, 3, etc., going alternately ODD then EVEN, so the OSR and OSF solution posted should produce an output pulse at each change of state, namely every second.

Have you tried Alaric's solution ?
 
Hi Daba,

I tried it before I replied to Alaric. Nothing hppens with Either of thouse two bits (Bit 0). I even tied them to a up counter as an additional test.
 
I'm pretty sure that the ML1100 RTC doesn't count by twos. But if you are looking at only the rising edge of the RTC:0.SEC/0 bit then you will get a rising edge pulse once every two seconds. Look at the binary value for the seconds.
0000 = 0
0001 = 1 ^
0010 = 2
0011 = 3 ^
0100 = 4
0101 = 5 ^
0110 = 6
0111 = 7 ^
1000 = 8
Notice that you get rising edge pulses at the instant t = 1, 3, 5, 7, etc, or one every two seconds. But you also get a falling edge pulse at 2, 4, 6, 8. Thats why I used both OSR and OSF instructions triggered by RTC:0.sec/0

If you don't want to use RTC:0.Sec/0 then program a timer with a one second timebase and have it self reset once every 30000 seconds, and trigger off from the ACC/0 bit. But the ACC/0 bit will exhibit the same behavior I described above, that is it has a two second duty cycle but it changes state once every second.

It may be worth noting that the displayed value of the S:42 register (seconds) does not update on your computer display while viewing online in Logix500. You have to look at the RTC in the function file to see the value change.

edit: I checked the manual, it doesn't say anything that I can see about not counting every second, and it lists the range of RTC:0.SEC as 0 - 59, even and odd, so I see no reason to think that it should count by anything other than ones - but I'm at home right now and can't check it on an actual ML1100, so if anyone confirms otherwise I'll be glad to know it.
 
Last edited:
Hi all,

Thanks for the replies. It's not working. RTC Bit 0 does not toggle at all. Even the RTC register value updates in 2sec increments. Confused!!!!!

Micrologix_RTC.JPG
 
disclaimer: I haven't been following this thread so I might be sending you on a wild goose chase - but put a temporary "scan counter" rung right under all of that other stuff ...

scancounter.JPG


does the number change? ...
 
Ken Moore said:
Try this, by changing the timer base, you can change the pulse length, should be on for one timer base unit. Shown for one second.

PULSE.png

Clever. Building on that, this will produce a one shot pulse without using one-shot instructions and without accumulating scan time error.

A062308MLSECONDPULSE.JPG
 
Last edited:
Skyfox - why is your counter DN bit on when the ACC is less than the PRE ?

Is this logic being scanned ? I'm thinking along the same train as Ron....
 
Last edited:

Similar Topics

I am currently backing a Micro Logix 1100 and no-one seems to have the file for me to upload from. Is there a way for me to upload the project off...
Replies
15
Views
394
I am trying to set up a read message in a MicroLogix1100 to read the value of a DINT in a ControlLogix5561. I have successfully set up a message...
Replies
2
Views
166
Hello, I have an existing application that has a Powerflex 700 with a 20-COMM-E adapter controlled by a Micrologix 1100 via Ethernet. The setup...
Replies
6
Views
1,156
I have a MicroLogix 1100 and it's capable of ac or dc output voltages. What I don't know is how I'm supposed to tell the 1100 to use dc for the...
Replies
13
Views
1,357
I’m new to plc programming and very new to HMIs. So this is what I have done so far: I bought a micrologix 1100, I used bootP to set the up...
Replies
17
Views
1,630
Back
Top Bottom