Pulse relays
Pulse relays, also known as bistable, holding or latching relays, belong
to the group of electromagnetic relays widely used in the power
industry. Of course, apart from this type of device, there are also
other types of relays on the market, such as electronic static relays or
digital devices (e.g. transmission gates).
How does a pulse relay work?
A pulse relay is used for the same purposes as other relays, ie to
change the state of the output circuit or circuits under certain input
conditions.
In an electromagnetic pulse relay, the first pulse applied to the coil
switches the device on, and the second one disconnects it. In the event
of a power failure, the device retains the last setting and does not
return to the original setting - this is what the bistability of the
relay is all about. The apparatus is stable in both short-circuited and
open working (secondary) circuits. Thanks to this property, the relay
consumes energy only temporarily, at the time needed for switching,
which significantly reduces the current consumption. It is not necessary
to maintain the potential difference at the ends of the control circuit
while the relay is on. It is worth knowing that there are also impulse
relays on the market that use a permanent magnet instead of an
electromagnet in their design - however, they are less common than
devices based on an electromagnet, although they fulfill the same
function.
Timed, group and sequence relays
The impulse relays are divided into 4 groups due to the differences in
the implementation of circuit control. Although the differences in the
design of the devices are not significant, they allow the use of various
control mechanisms of the input circuit (control). So we distinguish
between relays:
- on-off : impulse on-off relays are designed to control a single
circuit to which usually only one electric receiver is connected.
The control system then consists of a relay which controls the
operation of the secondary circuit. The design is simple, and at the
same time allows you to manage electricity consumption.
- with timer : relays equipped with time switches allow not only
to switch the circuit on or off with a button, but also to switch
off (or switch on) the receivers by default after a specified, set
time. Built-in timer relay, it will open or close the controlled
secondary circuit automatically. It allows for some automation of
the process of switching off or switching on of receivers controlled
by a relay.
- group : these are complex multi-relay circuits that allow the
control of working circuits in several ways - for example, as is the
case with on-off devices, but in a specific area. Let us consider
the example of staircase lighting in a multi-family building. The
relay located on the 3rd floor will allow the lighting of the 3rd
floor corridor to be turned on, while all other corridors will
remain unlit. Similarly, the relay from the lower floor will
activate the lighting of the corridor on the second floor. At the
same time, the master set of relays will turn on / off the switch
(turning off the lighting in corridors 2 and 3) or will centrally
close all circuits controlled by local relays.
- sequential : these kinds of relays control two or more circuits
with the push of a button. However, unlike group relays, sequence
devices do not have central control and all operations are performed
from a local relay.
How to choose the right impulse relay?
Regardless of the purpose of the bistable relay, when choosing a device
appropriate to our needs, we should take into account the following
parameters:
- contact currents,
- mounting method (rail or box),
- control method,
- manufacturer and price.
Pulse relays are relatively expensive devices, therefore the option to
buy a relay of an unknown brand seems tempting. However, it is not worth
being deluded - only high-quality products from proven producers
guarantee durability and impeccable operation of the cameras.