rQx
Lifetime Supporting Member
The Siemend LOGO is a small simple logic module you could use. 24 DI 20DO 8AI 8AO. You can also network them to gain more I/O and it talks modbus tcp. It has a little display on it so you can change parametets without an HMI. We use these alot. The programming tool is good and in FBD but is has some limitations and is not as powerfull as a PLC programming tool. It is not scalable to the TIA portal and the s7-1200. If it's mainly yo replace relays it's perfect.