Why use interference suppressions?
In the case that you use relays to switch loads, depending on the type used, they can cause an EMI (Electro Magnetic Interference). This may interfere with the proper operation of neighboring PLCs, gateways, or other devices. For example, this EMI can become problematically large when switching multiple relays to distribute multiple heaters over different phases of the power grid, or when switching heavy 380V contactors. But caution is also advised with lighter applications!
Often this malfunction is not always noticeable, or always present to the same extent, so determining the cause is not always easy. Indeed, a determining factor is the nature and condition of the load, as well as the timing of the switching of the relays (in the case of switching the 50Hz power supply).
You may have this problem when you notice unexplained device failures, such as (but not limited to):
Failing USB connections between computer and peripherals.
Short-faltering HDMI connections.
Audible interference on audio equipment.
Malfunctions in the operation of PLCs.
Erratically restarting or reconnecting Calculus gateways.
How to prevent EMI?
This interference can be prevented by opting for a relay with a built-in varistor or other interference suppression on DC low voltage systems of 12-24V. You can also buy a robust, prepared interference suppression from us. Ask your representative about this. This must then be placed over the solenoid of the relays (usually the A1 and A2 terminals of the relays). And this as close as possible to the solenoid of the relays in order to work effectively.
In Calculus products such as the smart site shed, this is provided as standard as an add-on to the relays.
Attention!
However, will our application switch on its own relay again? Don't forget to provide it with its own interference suppression. We are happy to provide you with these as well.
You can also buy a varistor yourself. A suitable suppression for low voltage is the ERZV10D101 of the Panasonic brand. This is for sale via this link: https://be.farnell.com/panasonic/erzv10d101/varistor-10mm-disc-100v/dp/1845438
Ask your representative about our offer for AC mains voltages of 230V. We offer a robust prepared module that ensures adequate interference suppression in most cases. This should also be placed as close as possible to and over the solenoid of the relays to be disconnected.
Don't have our article at hand? Then you can, for example, order Vishay VY2103M63Y5UG6TV7 from Farnell (https://be.farnell.com/vishay/vy2103m63y5ug6tv7/cap-0-01-f-20/dp/2860170) or another supplier. This is a Ceramic Disc Capacitor of 10nF with a suppression class of X1/Y2 and a voltage rating of at least 300V.
Tip!
Both solutions (just like the relays themselves) are limited in lifespan and can best be replaced together in case of failure of the relays.
Grounding the 12-24V power supply
In some cases, it is also advisable to connect the GND or V- of the 12-24 Volt power supply used to the earth. This allows you to reduce the effect of interference that travels via conductors. In our product the smart modular unit, an earthing terminal block is specially provided for this purpose.
Attention!
In the case of temporary installations with sometimes questionable earthing connections, this network can cause an increase in malfunctions or even defects. Therefore, proceed thoughtfully when grounding isolated power supplies.
Basic rules when using a Calculus gateway
To prevent interference on our gateways, we observe the following basic rules apart from the above (strongly recommended) interference suppression:
Never run USB or other data cables near a relay or control box.
Keep a distance of at least 10cm between Calculus gateways and relays.
Tip!
Always place the power supply for a Calculus gateway and other connections from each device separately and directly to the power supply via separate conductors. Examples of other connections are: output voltages, relay voltages and other devices connected to the same power supply.