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Building an Industrial Control System with Rock and RS PRO Part 2: Panel Build

3-phase power monitoring and switching with a Rock 4 C+ and RS PRO

3-phase power monitoring and switching with a Rock 4 C+ and RS PRO.

In Part 1 of this series, we introduced the project and took a look at the theory of operation, plus the key components which would be used. In Part 2 we now move on to selecting a suitable steel wall enclosure and the remainder of the components for our industrial control system.

Sizing up

sizing up - components laid out on table

Having taken delivery of the main components, we laid these out on the bench and arranged them such that the industrial power sockets would be correctly oriented, there would be optimal — or at least close to — wiring between components, and sufficient space to run cables. This usually involves an element of trial and error and it is best to leave a reasonable amount of space, based on the assumption that some additional components may need to be added sooner or later.

We came to the conclusion that an enclosure 1,000mm wide, 600mm tall and at least 20mm deep should suffice, but it wouldn’t hurt to be a little wider.

Bill of materials

RS Pro Enclosure

An RS PRO 1200 mm x 600 mm x 250mm steel wall box was selected and this can be seen pictured above. This model features two doors, plus a removable chassis plate and two cable gland plates.

The components which will be used in the build are listed below.

  • Rock 4 Model C+ SBC (249-3158)
  • USB to RS485 converter cable (687-7834)
  • Italtronic ABS Case for use with Raspberry Pi 4 in Grey (211-0349)
  • RS PRO Logic Module, 12 → 24 V dc Supply (917-6370)
  • RS PRO 3 Phase LCD Backlit Energy Meter (236-9296)
  • RS PRO Steel Wall Box, IP66, 1200 mm x 600 mm x 250mm (842-8465)
  • RS PRO Grey Slotted Panel Trunking - Open Slot, W50 mm x D50mm (233-9177)
  • Phoenix Contact Perforated DIN Rail (248-2162)
  • RS PRO Switch Mode DIN Rail Power Supply, 230V ac, 24V dc (136-8319)
  • RS PRO Switch Mode DIN Rail Power Supply, 230V ac, 5V dc (136-8304)
  • Schneider Electric LC1D Series Contactor, 24 V dc Coil, 4-Pole (744-7550)
  • ABB ESB Series Contactor, 24 V Coil, 2-Pole (211-1566)
  • RS PRO MCB, 3P, 16A Curve C (265-0206)
  • RS PRO MCB, 3P, 32A Curve C (265-0208)
  • RS PRO MCB, 1P, 16A Curve C (265-0197)
  • Contactum RCBO, 16A Current Rating, 1P Poles (240-6397)
  • Contactum RCBO, 6A Current Rating, 1P Poles (240-6391)
  • RS PRO IP67 Red Panel Mount 3P + N + E Angled Industrial Power Socket (214-4223)
  • RS PRO IP67 Blue Panel Mount 2P + E Angled Industrial Power Socket (214-4207)
  • Neutrik Mains Plug, 20A (246-8313)
  • Binder Circular Connector, 5 Contacts (046-9014)
  • Binder Circular Connector, 8 Contacts (046-9020)
  • RS PRO 3 Position Selector Switch Head, 22mm Cutout, Red (188-1166)
  • RS PRO 3 Position Selector Switch Head, 22mm Cutout, Green Handle (188-1162)
  • RS PRO Contact Block for Use with RS PRO Modular Plastic Push Button (188-1168)
  • RS PRO Light Block - Red, 24 V ac/dc (188-1179)
  • RS PRO Light Block - Green, 24 V ac/dc (188-1184)
  • Schneider Electric, Harmony XB5, Panel Mount Red/Green/Yellow LED (125-4411)
  • Phoenix Contact E/NS 35 N Series End Stop (803-9481)
  • Phoenix Contact PT 2.5/S-QUATTRO-PE Series Earth Terminal Block (123-7997)
  • Phoenix Contact UT 16-PE Series Green/Yellow Earth Terminal Block (624-6987)
  • Phoenix Contact D-UT 16 Series End Cover (624-6943)
  • Phoenix Contact UT 16 BU Series Blue Feed Through Terminal Block (624-6959)
  • Phoenix Contact UT 16 Series Grey Feed Through Terminal Block (624-6909)
  • Phoenix Contact FBI 10-12 Series Fixed Bridge (648-7419)
  • Phoenix Contact Plug-in bridge - FBS 2-12 (815-8895)
  • Phoenix Contact PT 2.5-TWIN RD Series Red (858-0100)
  • Phoenix Contact PT 2.5-TWIN BK Series Black (858-0096)
  • Phoenix Contact PT 2.5-TWIN OG Series Orange (225-2889)
  • Phoenix Contact PT 2.5-TWIN Series Grey (687-9420)
  • Phoenix Contact PT 2.5-TWIN BU Series Blue (687-9423)
  • Phoenix Contact PTU 2.5-TWIN-PE Series Green/Yellow (687-9427)
  • Phoenix Contact FBS 2-5 Series Jumper Bar (687-9792)
  • Phoenix Contact D-ST Series End Cover (687-9782)
  • Phoenix Contact, ZB Marker Strip (290-1438) #
  • Phoenix Contact PT 4-QUATTRO BU Series Blue (708-1665)
  • Phoenix Contact 4-Way PT 4-QUATTRO-PE Earth Terminal Block (708-1674)
  • Phoenix Contact PT 4-QUATTRO Series Grey Feed Through Terminal Block (708-1668)
  • Phoenix Contact D-PT 4-QUATTRO Series End Cover (708-1630)

As can be seen, this is a pretty sizeable list, but a lot of the items are DIN rail terminals of different sizes and colours, plus DIN rail accessories, such as end covers and jumper bars. It all starts to quickly add up once you have terminals for different wire gauges and purposes. It’s possible there may still be the odd missing item — most likely DIN rail terminal related! — and if so these will be ordered at a later stage. Note that hook up wire and ferrules are absent from the above.

Rock DIN rail mounting

DIN rail mounting ABS case

A DIN rail mounting ABS case originally designed for use with a Raspberry Pi was selected to mount the Rock 4 Model C+.

Aperture in enclosure increased

This just needed the aperture by the Micro SD card enlarging slightly in order to provide access to the Rock’s power button. The area was first marked out with a red pencil.

area removed using needle file

Then the area was removed using a needle file.

Fully assembled case

Fully assembled the case provided a neat DIN rail mounting solution.

Panel switches

Panel switches

The fully assembled control panel will feature four rotary switches, which can be used to switch mains outputs between override on/off and automatic (under Rock SBC control).

switch assemblies are modular

The switch assemblies are modular and each made up of a three-position selector switch head, plus two contact blocks and an LED light block. Above we can see a a light block in the middle, sandwiched by two contact blocks. With this arrangement, we have a switch which is centre off, with a single SPST NO contact block which is on if the handle is turned left or right.


Steel enclosure

A steel enclosure of this size is quite heavy and so the first task was to remove the doors, which was achieved by removing a few circlips and then four hinge pins. Following which the chassis plate was removed so that it could be worked on.

Chassis plate with components laid out

The components were laid out again and this time there were a few more DIN rail terminals, plus also lengths of slotted trunking to help keep the cabling tidy.

Positions marked on chassis

Positions were marked, components cleared, the exact hole positions for securing DIN rail and trunking marked and centred punched, and then holes drilled.

DIN rail fitted to chassis

Lengths of DIN rail were cut and de-burred, then bolted to the chassis plate.

Two sections of trunking were fastened in place

Two sections of trunking were fastened in place.

gland plates had also been removed

The two gland plates had also been removed, marked and centre punched. A smaller hole was cut using a punch, after drilling a pilot hole.

Holde cut in plate for gland

These produce a very neat result and it is quite a satisfying process.

large holes cut and de-burred

The larger holes were cut with hole saws and then de-burred.

Sockets fitted

Sockets could then be fitted, and holes for fixing screws marked and drilled, before final assembly of the gland plates.

Next steps

Next, it will be necessary to compile a wiring spreadsheet with details for mains, DC power and control cabling. Following which the panel will be wired, connected to a single-phase mains supply and testing carried out to confirm that we can indeed control contactors via the PLC and read the energy meter.


This series of articles describes the construction of a simple proof of concept only. No warranties, express or implied, of fitness for a particular purpose are made. It is wholly the responsibility of those implementing solutions to ensure that they meet all applicable regulations and standards.

  — Andrew Back

Open source (hardware and software!) advocate, Treasurer and Director of the Free and Open Source Silicon Foundation, organiser of Wuthering Bytes technology festival and founder of the Open Source Hardware User Group.