redPlc Software-PLC

redPlc Node-Red nodes for the realization of Software-PLC with Ladder-Logic according to IEC 61131-3.

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• Download little tutorial using redPlc: automation_using_nodered.pdf

• Install redPlc Nodes:<br> @redplc/node-red-redplc

• Install Module Nodes.<br> Module Nodes exchange data with hardware or communication<br> and updates the redPlc variables.<br> Module Nodes also creates the I, Q, IA and QA variables.<br>

Module Nodes not hardware based

|Module-Node|Function| |---|---| |@redplc/node-red-time| Get System-Time or NTP-Time|

Module Nodes for Raspberry Pi

|Module-Node|Function| |---|---| |@redplc/node-red-gpio|GPIO digital input/output using linux V2 character device interface| |@redplc/node-red-rpi-ads1115|ads1115 16bit analog to digital converter| |@redplc/node-red-rpi-ds18b20 |ds18b20 temperature sensor|

Example

In this example a tank is being filled or emptied.<br> The process is started with the START switch<br> and stopped with the STOP switch.<br> The filling level of the tank is determined using the LOW SWITCH and HIGH SWITCH.<br> When the IN VALVE is activated, the tank is filled.<br> When the OUT VALVE is activated, the tank is emptied.<br> The control automatically fills and empties the tank.<br>

This is the original Ladder Logic:

https://www.sanfoundry.com/plc-program-control-level-single-tank/

Ladder Logic with Raspberry Pi

Node-Red flow file is in examples folder: Tank_Control_RaspberryPi.json<br>

This is the pin assignment for Raspberry Pi:<br> |GPIO Pin|Set|Variable|Function| |:--|:--|:--|:--| |GPIO21|Input/Pullup|I0.21|START| |GPIO20|Input/Pullup|I0.20|STOP| |GPIO16|Input/Pullup|I0.16|LOW SWITCH| |GPIO12|Input/Pullup|I0.12|HIGH SWITCH| |GPIO23|Output|Q0.23|OUT VALVE| |GPIO24|Output|Q0.24|IN VALVE| |||M0.0|MASTER|

Note: All Raspberry Pi inputs are set to Pullup.<br> That's why the switches have to switch to ground.<br>