LAMPS CONTROLLED FROM FOUR OR MORE LOCATIONS: THE INTERMEDIATE SWITCH (THEORY)
—
Welcome to the home’s electrical systems course by NPR Online Technologies!
Buy our book here:
Before starting this lesson, we recommend that you subscribe to our youtube channel and visit all our lessons on our website.
In this theoretical lesson we will see how to control a group of lamps from four or more different locations. To this end, we will analyze a circuit diagram based on the use of two or more intermediate switches.
We have seen in the previous lessons, that in the case of a lamp to be controlled from more than two locations, we must resort to the use of intermediate or crossover switches.
With reference to the case of three control points, we have considered the following wiring diagram
that allows to change the state of the lamp by operating one of the three switches.
We remind you that the central switch must be an intermediate switch, while the other two switches must be single-pole double-throw switches.
—
We can generalize the circuit just analyzed by observing that it is possible to control a group of lamps from more than two points by adding an appropriate number of intermediate (or crossover) switches in addition to the two SPDT switches.
Therefore, if we want to control the group of lamps from three points, we will use two SPDT switches and an intermediate switch.
If, on the other hand, we want to control the same group of lamps from four points, we will use two SPDT switches and two intermediate switches.
Following this methodology, if we want to control the same group of lamps from five points, we will use two SPDT switches and three intermediate switches, and so on for a higher number of control points.
The scheme to be adopted is based on the insertion of the intermediate switches between the two SPDT switches.
We have already analyzed the connection for the insertion of a single intermediate switch, so we will examine here how to connect two intermediate switches with two SPDT switches in order to control the lamp from four different points.
As already mentioned, it can be observed that both intermediate switches are inserted between the two SPDT switches, and, if you want to add other intermediate switches, simply repeat the connections illustrated here.
Buy our book here:
Let’s run a short simulation to verify that by operating the switches, we are always able to change the status of the lamp: from on to off and vice versa.
For example, we can see that by flipping the first SPDT switch, the hot wire is connected to the lamp, and the lamp turns on.
If we flip now the first intermediate switch,
we observe that this connection breaks the hot wire connection to the lamp, and the lamp will be turned off.
By flipping the second intermediate switch,
we observe that the hot wire connection is re-established and the lamp will turn on.
Finally, by flipping the second SPDT switch,
the connection is interrupted again and the lamp will be turned off.
—
It is noted that the use of SPDT and intermediate switches requires the use of a pair of wires that are necessary to connect them together. In some cases, this can be quite expensive and for this reason this approach is generally adopted in cases where up to three or at most four control points are required. On the other hand, when more than two or three control points are required, relays are used because they allow a more elegant and more compact and in some cases even safer installation. Concerning the safety, in fact, we can say that by using a relay the operating point which, as we will see, is the button, can work at low voltage and consequently accidental contacts with the connections would not involve any risk for the person.
Well, we have come to the end of this lesson. We have analyzed the circuit diagrams that allow to control a group of lamps from four or more different locations by using a combination of single-pole double-throw and intermediate switches.
We suggest you immediately consolidate the concepts you have just learned by carefully reviewing this lesson and above all by going through all videos of our course, by accessing our playlists.
We remind you that our website is active with numerous insights on these issues.
We also suggest some useful actions that will undoubtedly contribute to the growth of this channel: in particular, we invite you to send us your comments, to like our videos and share them with your friends.
Finally, don’t forget to subscribe to our youtube channel to stay up to date on all our activities.
Thanks for your attention and … see you next time!
GO TO THE MAIN PAGE OF THE COURSE (FULL LIST OF LESSONS)…
Buy our book:
