5/20/2014 9:28 PM | |
Posts: 5225 Rating: (1192) |
Hi franciscorivas, There is no need to connect all the pins of every instruction block. The pin will not all of the sudden decide to go high. You are right. The instruction blocks do not have the properties of discrete electronic ICs. You can think of the "empty" pins already pulled to an approriate voltage level. There is no documentation I can think of that supports me. I do however have years of experience with using LOGOs. Be careful when setting the "retentive" memory on the blocks. The function works.. but the power outage should not be to long. Also caution the use of some of the memory markers. M8 as an example will turn on at the first scan, regardless on what the logic state is that came before it. Before I make more guesses.. is there any reason for this question? w |
This contribution was helpful to1 thankful Users |
5/20/2014 10:39 PM | |
Posts: 5225 Rating: (1192) |
That is indeed a tough one. Quoting me will not help your cause - I'm not a published expert. It would be better is you give in to what the professor said. Some people do not like getting opposition and hold it against you. It it for regaining exam points.. then that is different. I have looked quickly in the system manual and not find anything useful For now I offer official Siemens samples. By random I took "Intelligent foot switch". Even in the sample you'll see that not all pins are connected. examples Let us hope a Forum expert can help us with published documents. Good luck! w |
This contribution was helpful to2 thankful Users |
5/21/2014 8:37 AM | |
Posts: 2930 Rating: (432)
|
Hi, the rule is simple to understand: The inputs of a FB on the left hand side must not be connected to any signal. Expect your application need it. Example: Place a U/D-Counter and do not connect the left pins to a signal, connect the output on the right hand side to an LOGO! output. Now press F2 and check what is written in the status window. Why you have to connect signals on the FB inputs at the left side: 1. You need to "execute" the FB. Most of the FB requires a enable signal. 2. Activity for the FB depending on your requirements. Means when you want to count, then you have to connect the signal to the right FB input. But basically all FB pint on the left hand side do not need to be connected to a signal. But this this is theory only. To get better familiar with LOGO! programming you can go through the LOGO! WBT: https://sitrain.automation.siemens.com/sitrain/open_wbt/logo/index.html I hope this helps. Regards Helmut |
This contribution was helpful to2 thankful Users |
5/21/2014 11:36 AM | |
Joined: 4/22/2010 Last visit: 5/3/2024 Posts: 5697 Rating: (715)
|
Hello, Unused logical inputs of special functions are default to logical "0", so why connect them to 0 twice? You can read this and the states of unused inputs of other functions in the Logo System Manual Chapter 4 Logo! Functions Regards, Marcjan AttachmentDesignation of the inputs.pdf (341 Downloads) |
Last edited by: Marcjan at: 5/21/2014 11:42 AMProblem solved? |
|
This contribution was helpful to2 thankful Users |
5/21/2014 12:00 PM | |
Posts: 5225 Rating: (1192) |
Marcjan, Thank you. That quote resolves the issue. - This is what I was looking for and I missed it. It is worth mentioning that the "default to zero" only applies to the "special functions". In the case of "basic functions" such as "AND" the input pins default to ON. In the same system manual in chapter 4.2.1 (description of the "AND" block): "At an unused block input (x): x = 1." For sure this will do the trick. Thank you. @franciscorivas: Happy now? Let us know if this worked for you. w |
This contribution was helpful to1 thankful Users |
Follow us on