Siemens 1200 and time...?

[Mario Gonzalez 0]

Hello all, First of all I would like to introduce myself, I'm a Mechatronics Engineer student from Mexico (currently in my last semester), I have some knowledge in PLC systems and networks primarily and are still a newbie in certain subjects pertaining the PLC world. The question that I bring to you guys is the following: I currently have a PLC 1200 (CPU 1214) from Siemens and my current project is the control of a water tank through this system, controlling primarily the temperature and lighting of it (it's an algae reactor) The issue that I have is simple i think, other than controlling the temperature of this tank with a thermocouple conected to one of the PLC analog inputs I also requiere to control lighting in this tank depending on the time of the day. As far as my knowledge goes this PLC (and all of them I think) do not have an internal "real" clock. What I need to do is for example turn light A on at 9 am of every day, and turning light B on at 11, and then turning light A off at 8pm, and light B at 9 pm, I do have an idea on how the programing would be done (with timers pretty much) my doubt is how can I "tell" the PLC that it's 9 already so it can start a cycle. The only idea I have is with some kind of circuit which gives me an analog output at time (being 00:00 a signal of 0 volts and 11:59 being 10 volts) but I do not know it there is such a thing. Any ideas on what I can do/use? Thank you all for your time!

[Moggie 17]

The S7 1200 PLC's do have a Real Time Clock. Within TIA Click on the PLC, then look in the "Proporties" section for "Time of Day". Click there, and you can set up the real time clock. Within your program Look at RD_SYS_T in the extended functions tab - this reads the system Time. This will read out the system date & time into 12 Bytes (Type DTL) (Into Year/Month/Day/Day of Week/Hour/Minute/Seconds/Nano Seconds) plc.bmp Edited 1 Dec 2011 by Moggie

[Mario Gonzalez 0]

Great! I guess I still have a lot of things to learn about PLCs. Sorry, just one more doubt, how do I "separate" the DTL to have for example hour in one variable, and minutes in another? Thank you!

[Moggie 17]

Look at the attachments - DB.bmp Cmp.bmp