New Micro PLCs Go In Different Directions
It’s interesting to compare and contrast new micro PLCs from Siemens (S7-1200) and Panasonic (FP0-R).Â Both are compelling upgrades from the previous series (Siemens S7-200, Panasonic FP0), but while Siemens adds Ethernet connectivity, Panasonic adds a USB port.
The FP0-R series looks like a direct replacement for the FP0, but with more: more memory, faster instructions, faster counters, and faster pulse outputs.Â The biggest upgrade is a USB port, which is very nice: no custom programming cable required!Â Or save some money: I like to use PLCs with two comm ports, one for communicating with the PC, and one for debug.Â With the added USB port, I can use a PLC with one serial port, saving about $30, and use the USB port for debug.
I hope Panasonic has improved the USB port speed; I’ve heard that the FPX series uses an internal serial/USB bridge, so the USB port is limited to a wimpy 115,200 bps.
The FP0-R still isn’t as capable as the FPG (FP Sigma) series, but since it’s the same price as the FP0, I’m already looking at changing over from the FP0 to the FP0-R.
The Siemens S7-1200 models appear similar to the previous S7-200 models, but with more: more memory, more analog (even the base models have analog inputs), faster instructions, faster counters, more expansion (using signal boards) and faster pulse outputs.
What’s wonderful?Â Siemens added an Ethernet port with Profinet and standard TCP/IP capabilities.Â Networked devices are so much more convenient and useful than PC-connected USB devices.Â For example, Profinet should make it simple and inexpensive to create a peer to peer PLC network, in addition to high speed communications to HMIs.Â You have to add expensive networking modules to create a Panasonic PLC network.
The S7-1200 CPUs include other goodies, such as room for extra boards on the base CPU (for extra comm ports or wimpy (2DI/2DO or 1AO) I/O boards), 1M flash memory for extra (non-program) storage, and a proprietary memory slot.
Unfortunately, Siemen’s STEP7 Basic software currently only includes Relay Ladder Logic and Function Block programming; Panasonic’s FPWinPro supports all five IEC61131 languages, including my favorite: Structured Text.
Like the previous S7-200 series, base models have limited expansion: no signal modules for the 1211, 2 for the 1212, and 7 for the 1214.
The Panasonic FP0-R PLCs are much smaller; the transistor output models use high density box header connectors , while Siemens provides screw terminals.Â I much prefer the box headers, since I can easily make a cable to a custom PCB breakout board.Â It’s hard to wire directly with screw terminals without additional terminal blocks (for extra power and ground, etc).
The Panasonic FPX series are more like the S7-1200, since they also use screw terminals and provide room for plug in modules.
Excluding communications (USB vs Ethernet), the S7-1200, FP0-R, and FP-X are all similar in capabilities and price (IIRC, S7-1214 DC/DC/DC, FP0R-C32CT, and FPX-C30TD are all about $280, while the FP0R-C32T is about $245).
Which will I use?Â I’d love to try out the S7-1200, but for my current projects the FP0-R and FPG are a better fit, since they support Structured Text and use box header connectors.
The S7-1200 is pretty close to a no-brainer if you need Ethernet:Â Panasonic’s Ethernet module (FPWeb2; ~$430) alone costs more than a S7-1214 CPU; Automation Direct’s Ethernet modules start at $175, and you still have to add the PLC CPU.
I plan to write about this in more detail: I think micro PLCs are a great alternative to PC I/O options such as PCI boards from Advantech or USB modules from Measurement Computing.Â The PLC’s cost the same or less for 24V I/Os, and have the advantage of being programmable — it’s nice to have the PLC handle some I/O, while the PC handles the rest via serial, USB, or Ethernet communications to the PLC.
- Panasonic has gone backwards by not listing prices and requiring registration to download PDFs.
- If you’re interested in the S7-1200, talk to your local distributor to see if they have a package deal.Â For example, in Silicon Valley, E&M periodically offers 1 day introductions with a nice deal on the S7-1211.