PLC and SCADA
PLC channels
A PLC is a device with channels: digital inputs (DI), digital outputs (DQ), analog inputs (AI) and outputs (AO). There are two ways to draw them.
- A PLC part (from an EDZ package or your own part with PLC data): its channels wait in the Devices tab under the PLC. Drag them onto the pages one by one, where the circuit needs them.
- Channel symbols of the PLC group in the Symbols tab, for a PLC without a part: each is one channel of the device whose tag it has (
-A1), with its designation (DI0).
An input takes its wire from above, an output gives it below. The address and the tag name are written in the box of the channel.
Channel data
Select a channel; the Properties panel and the PLC I/O tab at the bottom show:
| Field | Example | For |
|---|---|---|
| Tag name | Pump1_Running | the SCADA; Latin letters, digits and _ |
| Address | 10001 | the register in the PLC |
| Data type | Bool, Int, Float… | |
| Access | ReadOnly, ReadWrite | |
| Precision | 1 | decimals of an analog value |
| Alarm, alarm text | the SCADA shows an alarm | |
| Comment | Pump 1 running |
In the PLC I/O table you can type the data of many channels in a row, and right-click for Assign addresses (the next free ones by kind) and PLC settings of -A1….
SCADA
PLC settings of a PLC: its device id for the SCADA, protocol (e.g. Modbus TCP), host, port, rack, slot and update interval.
- Export tags CSV… writes the named channels in the format of the SCADA's Import tags.
- Export SCADA devices JSON… writes the PLCs with their settings.
Before writing, the program checks the tags: a name used twice, a name with other characters, a tag without an address, a PLC without a device id. With such problems nothing is written; they are listed in the Messages tab.
The PLC I/O list report has one table per PLC.