How does a relay sort backfeed
- Thread starter barnies
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A relay can keep circuits seperate and switch using another seperate circuit. The individual circuits can also be over ridden without switching the other circuits.
Example:-
You have two outside lights A + B that are switched by a single timeclock. The timeclock switches on a relay which in turn switches two outputs to each outside light. Say, for instance, whenever the timeclock is off you want the ability to switch on only one of the lights you can by taking a switch wire to the output to the required light on the relay.
If the lights were both connected to the timeclock it would be impossible to switch one without the other (unless it was a two channel timeclock !)
Example:-
You have two outside lights A + B that are switched by a single timeclock. The timeclock switches on a relay which in turn switches two outputs to each outside light. Say, for instance, whenever the timeclock is off you want the ability to switch on only one of the lights you can by taking a switch wire to the output to the required light on the relay.
If the lights were both connected to the timeclock it would be impossible to switch one without the other (unless it was a two channel timeclock !)
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I would consider back feed to be where you have multi ways to control one item some which also control other items as well.
So porch light needs to work independent and when hall light is used for example.
Since the switches are single pole one would work a relay with hall light which would in turn work the porch light, so switching on porch light would not auto switch on hall light.
With DC diodes can do same job.
So porch light needs to work independent and when hall light is used for example.
Since the switches are single pole one would work a relay with hall light which would in turn work the porch light, so switching on porch light would not auto switch on hall light.
With DC diodes can do same job.
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Yes use double pole switches. But make sure double pole not change over (intermediate). There are even three pole switches however often pictures of a fan on them.
It would help if you explained your query more!
In what sense do you mean backfeed?
A relay is a magnetic mechanical switch which is basically a coil operating dry contacts. There is no electrical connection between coil and switch(es) hence you get electrical isolation between the two.
In another sense, to eliminate back emf in a DC circuit to avoild damaging semiconductor controls you can place a reverse biased diode across the relay coil.
In what sense do you mean backfeed?
A relay is a magnetic mechanical switch which is basically a coil operating dry contacts. There is no electrical connection between coil and switch(es) hence you get electrical isolation between the two.
In another sense, to eliminate back emf in a DC circuit to avoild damaging semiconductor controls you can place a reverse biased diode across the relay coil.
P
Paul_C
No. You use each pole of the switch to control one of the lights or other devices.
A hastily sketched diagram illustrating how you could do it for the hall & porch lights example outlined above:
Hands up all those who have found no other way when wiring a house than to use relays.
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