What is the purpose of a relay switch?

[u587162]

Could someone help me with what the purpose of a relay switch is in respect of home automation? I see the LightwaveRF and Fibaro offer this, and whilst I think I know what it is, it would be great to get a qualified answer from someone who understands it better.

Please give a few examples of where it can be used and for what purpose, and some extreme fancy scenarios of where it can be used for security detection, namely for external lighting or PIR sensor activation.

many thanks.

 

[sparkymarka]

To switch a greater load or different voltage ....

 

[lloyda]

In this context, for switching things on/off using remote switches - eg lights that you don't want on a dimmer, a motor etc. I use them for switching the led and CFL lights in my bathroom, and a timer relay for the mirror demisters (stops them being left on)

 

[u587162]

In this context, for switching things on/off using remote switches - eg lights that you don't want on a dimmer, a motor etc. I use them for switching the led and CFL lights in my bathroom, and a timer relay for the mirror demisters (stops them being left on)

I thought it's for variable control of something like a blind rather than a binary on or off command?

 

[lloyda]

No. Very much on or off. Blind motor on / blind motor off.

 

[u587162]

But then what's the difference between having that and having one of those home automation devices which can activate a switch without a relay?

 

[lloyda]

I'm not sure what device you mean?

 

[u587162]

Something like this
http://www.maplin.co.uk/p/lightwaverf-in-line-relay-n64ll

 

[bernardgreen]

http://www.maplin.co.uk/p/lightwaverf-in-line-relay-n64ll

That is a lot more than just a relay.

It might not even have a relay in it.

It is a remote controlled switch.

It has a switch (which might be a relay) together with a wireless receiver and some electronic "intelligence" that can understand messages received on the wireless and if necessary operate the switch.

A basic relay is a coil and one or more sets of contacts. When the coil is energised ( current flowing through it ) it creates a magnetic field which causes a mechancal action to occur which changes the state on the contact set(s). When the coil is de-energised the contact set(s) return to their normal state.

 

[Sam Gangee]

Download and read the FREE eBook "Beginners Guide to Electronics":
http://www.The-Cool-Book-shop.co.uk/begin.htm