Connection of motorized curtains, blinds, and shades

As it is known, loads can be categorized as active and reactive. Reactive loads can further be divided into inductive and capacitive loads. It is important to pay attention to inductive loads in a Smart Home system. These loads include devices with electric motors (such as fans or pumps) and devices with transformer power supplies (such as power stabilizers). Motorized curtains, blinds, and shades also belong to inductive loads.
One of the disadvantages of inductive loads is the creation of obstacles and disturbances during their switching off due to high-voltage voltage spikes that occur at that moment. During these spikes, the voltage values can reach 2-3 times higher than the supply voltage and cause arcing between the contacts of the output relays of control devices (controllers) when switching off the loads.


The controllers by i3 Engineering implement protection against the occurrence of arcing between the contacts of the output relays by installing appropriate varistors (or suppressors) in parallel to the contacts of these relays. They limit the maximum voltage on the relay contacts and accordingly reduce the level of switching disturbances and increase the relay's service life.
Another feature is the increased starting current of motor consumption by 2-5 times when they are switched on. Therefore, this current should not exceed the nominal current of the contact group of the relay.


Special attention should be paid to the switching of reversible motors used in curtains and blinds, where they operate in forward and reverse modes. They have 2 windings wound on a single core, which are switched according to the direction of movement. At the same time, a voltage is induced in the other winding, which is added to the contacts of the relay that switches it, which can damage the protective elements of the device.

Important! To switch motors of this type, it is necessary to use additional intermediate relays or contactors of suitable power for all our controllers, as the standard voltage protection used in them will be damaged. And to reduce disturbances and protect the contacts of these additional relays or contactors, it is recommended to use additional RC snubbers in parallel with the motor terminals.


Thus, the peculiarities of loads when connecting them to Smart Home controllers should always be taken into account to ensure the reliable operation of the system. More detailed information on connecting inductive loads can be found in the article. Information regarding the connection of other types of loads can be found in the article.

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