Closer Look: Schmersal HDS Modular Switch

Closer Look: Schmersal HDS Modular Switch

Schmersal Group has introduced the new HDS switchgear series for the heavy mining industry with shut-off up to Performance Level PL e and IECEx certification. The fourth generation sets to unite a range of functions into a single platform for the first time to make it easier to select, install and retrofit. The series boasts high-level communications with Dupline, and a kit of various actuating elements available for conveyor belt, positioning, level and pull wire emergency stop control.

  First impressions

The first thing you will notice about the HDS series is its rugged build quality. The base switch unit is available in both thermosetting resin or cast-iron body and offers two alternate choices allowing for installation into any environmental conditions. For instance; the resin version is resistant to aggressive media and provides superior life over the metal version for the agricultural industry in the processing of fertilisers, minerals, phosphates and port logistics applications of loading and unloading operations.

  Setting up

Building your desired switch is a modular approach. First, you’ll need to select the base material and function, the switch elements, contact material, communications, indication lamp and then finally the actuating levers. It’s a lot simpler than it sounds. Schmersal have thought about the different types of applications this product could be used for, and there could be many. Think emergency stop deactivation, belt misalignment monitoring for bulk material transport, end position monitoring in steel making or even level monitoring in material silos.

Because its movement is symmetrical, levers can be installed at any angle in 360 degrees at 10-degree increments. In total, there are six different lever types which can be used for various applications that simply push straight onto the centralised keyed shaft.


For those of you who work alongside conveyors and machinery, the emergency-stop attachment would be a good choice. It can be used as a pull-wire emergency stop including an auto shut-off feature to Performance Level PL e, plus wire breakage detection on material handling plants up to 100 metres in both directions. It really does prove to be extremely versatile… If actuated, the two-sided pull-wire emergency stop switches latch in the emergency-stop position, and unlock when the release button is actuated. Electrically, the connectivity options allow for a combination of two or three open or closed contacts for both actuation directions providing a total of up to 6 contacts. If desired, a high-level communication bus such as Dupline or AS-I-Safety-at-work for quick and easy networking, series switching and transfer of diagnostics data.

What's inside

By simply removing four screws from its yellow lid will allow access to its inner workings. You’ll see that it’s a well-protected device, with all HDS products featuring a closed cover over the switching shafts, cams and switch contacts to prevent contamination from dust and dirt when installed in extreme conditions. Wiring in the switch elements are routed to a central ‘Cage Clamp’ connecting terminal for easy and quick installation.

The relay contacts are either selectable as slow or snap action, which means pull-wire emergency stop switches or belt alignment switches (amongst others) can be easily and efficiently connected, that includes an indicator lamp (if required).

You can choose safe or standard two-wire bus systems such as Dupline that also can be used for signal evaluation as an option. In our testing, only the input and output signal wires needed to be connected, which we found to save a lot of time in both assembly and connection.

Perhaps the most important point to note here, is that users are able to adjust the pre-set contact switching points of the basic switches between 10º and 35º at 1 degree increments. This is extremely easy to do, by simply positioning the dial on the switching element into the desired end position.

  Final Verdict

Schmersal have designed an all-in-one switch solution for many applications. It’s easy to customise with simple swap and connect levers, it’s easy to install, and it’s more versatile than others in the market. They have really thought about how people will use this product. For manual users, the lever positioning configuration makes the HDS design flexible enough to customise the switch or any given machinery scenario. It can be used in hazardous type environments with IP66 and IP67 protection ratings and a range of international approvals including CE, UL, CCC, EAC, Ex, IECEx and INMETRO which really solidifies its robust build and reliability Schmersal is known for.