The Industrial Raspberry Pi Forum

Hello everyone,

I’m looking to set up a Revolution Pi next to a PLC to capture signals from the PLC cables. My goal is to use the digital I/O capabilities of the RevPi DIO module to monitor when relays for ejecting parts are ON or OFF, which will help us count the number of parts produced and track the effective cycle time.

Additionally, I want to capture other signals, such as those indicating the status of the machine (running, alarm, or stopped mode) through wires that trigger status lights on the cabinet. The idea is to achieve this in a completely non-intrusive manner, ensuring that the PLC remains unaware of our data acquisition method by using signal derivation (either T-connectors, wagos, or wire clamps that pierce a bit the isolant).

Has anyone attempted a similar setup with Revolution Pi? I’d appreciate any insights or experiences you might have regarding this approach. I'd also appreciate if you would have any red flags in mind.

Thanks in advance for your help!

Hi ulrich06,

Your setup sounds very feasible and aligns well with the capabilities of the Revolution Pi products. Using signal derivation methods like T-connectors or clamps is a good strategy for non-intrusive monitoring, but it's important to ensure electrical safety, maintain signal integrity, and avoid interfering with the PLC’s normal operation.

The RevPi DIO module will be key in monitoring the ON/OFF states of the relays and other digital signals from the PLC. Since you are using it to track things like part ejection and machine status, you’ll need to wire the output signals (e.g., for ejector relays or status lights) from the PLC to the DIO module inputs.

You can easily configure the digital inputs of the RevPi DIO to monitor when the relays are energized or de-energized. This will help you count parts produced by monitoring the ejection process.
Status signals (e.g., for running, alarm, or stopped modes) can also be wired to the DIO module. These signals are typically discrete, so you can map the machine's states to specific digital inputs.

Software Configuration:
You can set up Python scripts by using the RevPomodio2 library or use existing software like Node-RED on the RevPi to process the input signals, count events (like parts ejected), and log the data.

Good luck with your setup, and I hope others in the community can share their experiences with similar configurations!

Relevant link:
revpimodio
node-red example


Best Regards

Ulrich Kouatang Biakoup | field application engineer