I am using a DL350 cpu on a project. This cpu has no non-volatile memory. I need for the cpu to remember the last action or input it recieved before a power loss. This machine moves people up down back forth ect. It gets lost when there is a power failure. I have no spare I/O points right now. With no non-volatile memory to speak of how would you make the machine "remember" where it is? If you need anymore information ask away.
DL350 Help
- Thread starter BDL273
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bernie_carlton
Lifetime Supporting Member + Moderator
I don't understand your 'no non-volatile memory'. The CPU has a supercap for short term retention and battery backup for long term retention. Also, as explained in Appendix G of the 350 manual, there is a small amount of EEPROM memory which can can be used for infrequent writes of critical information.
cjh
Member
The 350 has battery backed RAM.
All you need to do is ensure that you have a good battery installed, connect with DirectSoft, go to PLC>Setup>Retentive Ranges and be sure to include the memory locations that you wish to preserve through a power cycle and press the icon with the arrow pointing to the PLC.
You will need to periodically change out the battery thereafter.
All you need to do is ensure that you have a good battery installed, connect with DirectSoft, go to PLC>Setup>Retentive Ranges and be sure to include the memory locations that you wish to preserve through a power cycle and press the icon with the arrow pointing to the PLC.
You will need to periodically change out the battery thereafter.
You probably already have the manual but if not here is the link:
http://www.automationdirect.com/static/manuals/d3350/d3350.html
See page 3-10 for setting retentive ranges and other info.
http://www.automationdirect.com/static/manuals/d3350/d3350.html
See page 3-10 for setting retentive ranges and other info.
bernie_carlton
Lifetime Supporting Member + Moderator
And if necessay, zip and post your program.
OkiePC
Lifetime Supporting Member
I am not an AD guy, but wouldn't you need to use latching instructions in order to retain "coil" states during the re-start of the PLC?
I know that with A/B PLCs, there is a prescan, which occurs before first scan, which will "turn off" any OTE (output coil) instructions.
I know that with A/B PLCs, there is a prescan, which occurs before first scan, which will "turn off" any OTE (output coil) instructions.
Last edited:
bernie_carlton
Lifetime Supporting Member + Moderator
I think of 'internal coils' as 'C' bits. You have 'OUT' instructions and 'JMP' instructions in Stage 2.
Remember that on power cycle your initial stage (ISG) will turn on. Have you calculated the result of that?
Make sure to have the stages you wish preserved noted in the retentive ranges. But if you include the ISG in this range it will take the state at power down instead of turning on.
Remember that on power cycle your initial stage (ISG) will turn on. Have you calculated the result of that?
Make sure to have the stages you wish preserved noted in the retentive ranges. But if you include the ISG in this range it will take the state at power down instead of turning on.
Just to throw another thought in the mix, I have had issues with the PLC's power down sequence as well. When you shut off power to a machine controlled by a PLC that is connected to limit switches, proxes, etc. the inputs go away immediately (assuming 120V AC inputs, 24VDC might be different). However, the power supply in the PLC usually has enough reserve capacity for the PLC to get another couple of program scans in. The problem becomes that to the PLC, all the inputs have been de-energized or off.
You might check to see if this is what is causing your machine to forget where it was. It might be that it isn't so much forgetting as it is reacting to all the inputs going away on power down.
Brian
You might check to see if this is what is causing your machine to forget where it was. It might be that it isn't so much forgetting as it is reacting to all the inputs going away on power down.
Brian
bernie_carlton
Lifetime Supporting Member + Moderator
Good advice Brian
I do like what Brian said it makes sense. I have been thinking this though for a while and for the machine to remember where it is or know what was last energized I was thinking about adding a 2nd limit switch so I would have one for forward and one for reverse. On the other hand I would like to take care of it with some programming. I will check and make sure the pdf file I attached is of the lastest program. In the last version I wrote I used internal coils (c) with sets and resets and change the retentive ranges to match my program. Thanks for all the replies.
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