Power up s:1/15

roxusa

Lifetime Supporting Member
R
Join Date
Nov 2008
Location
NJ
Posts
992
If I want the first pass bit to enable on a power up do I need a memory module and have to set it to boot from memory on power up or is there another method, using a ML1400 and would like to set a bit if power was off and back on.
Thanks
 
S:1/15 is always on only on first scan, so you can move RTC data to a register in order to know if your power was off and back on. You can also move old data to another register and then you can compare the last two times when plc was turned on.
 
widelto said:
S:1/15 is always on only on first scan, so you can move RTC data to a register in order to know if your power was off and back on. You can also move old data to another register and then you can compare the last two times when plc was turned on.
Click to expand...

Just to clarify, S:1/15 is only on during the first scan after the PLC returns to run mode. It goes off after the first scan. This can mean the PLC was powered off and back on, or was placed in program mode and then back into run mode.

If you XIC S:1/15 ---> CPW Source: RTC:0.YR Destination: N10:0 Length: 6, you will get the real time clock year, month, day, hour, minute, and second stored in registers N10:0 through N10:5. This assumes that you have initialized the RTC (by setting the time from RSLogix 500), otherwise you will get all zeros.
 
I have S:1/15 Latch a bit that displays on HMI and HMI has unlatch button, I noticed if I unplug PLC then power up it doesn't latch my bit. If I upload program and go to run it will.
Instructions on the TON say

If power is lost while a TON is timing but has not reached its preset value, the EN, and TT bits remain set , and the accumulated value (ACCUM) remains the same. This is also true if the processor changes from the REM Run or REM Test mode to the REM Program mode.

But doesn't mention what happens if power is lost and it has reached ACC
 
If power is lost while a TON is timing but has not reached its preset value, the EN, and TT bits remain set , and the accumulated value (ACCUM) remains the same. This is also true if the processor changes from the REM Run or REM Test mode to the REM Program mode.
Click to expand...

where did you read that? ... it's TECHNICALLY correct – but it's leaving out the "rest of the story" ...

when the processor is put back into the Run mode, then the ACC – and the EN bit – and the TT bit – and the DN bit – will all be "reset" back to ZERO values ...

TIP: if you want to "start back up from where you left off" then you PROBABLY need an RTO timer instruction ...

going further:

when you say:

I have S:1/15 Latch a bit that displays on HMI and HMI has unlatch button,
Click to expand...

are you really using an honest-to-goodness "Latch" instruction (OTL) – or are you referring to a "seal-in" rung? (which uses an OTE) ... some people think that these are the same things – but they are NOT ...

tell us a little more detail about your code – and we'll see if we can help you out with that piece of the puzzle ...
 
Last edited:
I was using the S:1/15 XIC -(L)

I read about the TON under RS Instruction help TON
 
What I usually do is have the first pass bit enable a timer with a preset of 0.5 sec just in case it doesn't trigger, but that's usually in front of logic that's a little more involved. Just ensures that the following logic sees the first pass bit go true.
 
I didn't get a chance to change my logic to a TON
I did test again with the first pass bit to set a latch, when powered down I wait a few minutes and make sure the 24 vdc power supply drains (1766-L32bxb) when its powered back up I don't get the latch, I will add the counter (add 1) to verify if I'm getting first pass. But as I said before if I do an upload it works.
 

Similar Topics

S
Modbus TCP connection between my plc and a power meter on TIA Portal
Hello gentlemen, Im working on a small project on TIA Portal, about establishing a Modbus TCP connection between my ET200SP plc and a socomec...
Replies
11
Views
242
saad94
S
T
Power Supply Protection
I have the power supply in the link below. If we want a breaker to isolate and protect the input side how would I size that correctly being 120...
Replies
8
Views
191
JesperMP
JesperMP
S
Power Flex 527 , safety inhibitor fault
Power flex 527 Network based safety drive had faulty and alarm pop up SOS Code internal fault Unable to set or clear the fault manually or...
Replies
5
Views
107
arpus4KM
A
N
24VDC Class 2 Power Supplies
We normally ground the -24VDC side of a control systems power supply. What are you folks thoughts about grounding the -24VDC side of a class 2...
Replies
1
Views
106
OkiePC
OkiePC
M
Honeywell / EnergyICT EIM Flex Power Meter
Hi all. Would anyone happen to have the Modbus register datasheet for the Honeywell/EnergyICT EIMFlex Modular Meter v1.11 We've 40 of these that...
Replies
0
Views
60
muzanz
M
Back
Top Bottom