I am new to plc programing and I want to run a 7 day timer to control 2 pumps, first 1 pump for 7 days then switch to the other pump for 7 days and so on. Can anybody help
Search for "FLIP FLOP" in this forum and the archives, and you'll find some code that will get you started. Just change "PB" for a seven-day timer, and you're in business.
You might want to add logic that checks that the lead pump has not failed to start, and to start the lag pump if it has.
I have done a 7day timer before using PLC but it does not give a accurate 7 day. For Example I want to turn ON the pump at exactly 7 am every monday. The result is there is a delay in turn ON the pump and the delay become longer every time that the pump turn ON. What I did Is used solid state timer with 1 day duration and input this to the PLC. I used counter in my program to come up with 7 days time.
Sounds like a simple control scheme, I wouldn't use a programmable controller for this. Theben http://www.theben.de.com makes a 2 output 7 day programmable timer for about $200.00 (CDN) and it's very easy to program and change your times. I think Luminite Control is the distributor in the US
Most PLCs that have a real time clock have a day of the week register you can access. For the A-B SLC-500 and MicroLogix, for example it is S:53. Check your documentation.
Why not use a Siemens LOGO? It was designed for exactly what you are asking. For a few hundred bucks, you get the display and multiple cams and multiple clocks. It's modular and uses add-on I/O and standard programming. It can have analog I/O also. Any Siemens Automation distributor can help.