Dann
Member
Hello All. New guy here. Good to meet you.
I am working on retofitting an existing system that uses multiple Logo modules to control 15 relay outputs from 14 24 VAC inputs. The system needs to be expanded to 30 stations, which would require more Logo modules than any one human should have to deal with.
I can't convert to straight 24 VDC because of the 3 wire configuration of the stations and the 24 VAC valves being controlled. I'd also like to avoid having to put in 30 interposing relays.
Consequently, I'm looking at an S7-200 system with 24 VDC inputs and relay outputs. This is convenient because I'm familiar with the interface and have all the required programming tools.
Here is the question: Can I simply half-wave rectify the AC input from the PB with a diode into the 24 VDC input and then use a positive-transition one-shot in the logic?
I am working on retofitting an existing system that uses multiple Logo modules to control 15 relay outputs from 14 24 VAC inputs. The system needs to be expanded to 30 stations, which would require more Logo modules than any one human should have to deal with.
I can't convert to straight 24 VDC because of the 3 wire configuration of the stations and the 24 VAC valves being controlled. I'd also like to avoid having to put in 30 interposing relays.
Consequently, I'm looking at an S7-200 system with 24 VDC inputs and relay outputs. This is convenient because I'm familiar with the interface and have all the required programming tools.
Here is the question: Can I simply half-wave rectify the AC input from the PB with a diode into the 24 VDC input and then use a positive-transition one-shot in the logic?