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[on:]

hello Everyone,
                       Could anyone tell me what should be the Relay i should be using to switch on/off the electrical appliances. i think 12volt DC will do! what you think and Next how i can power it as Arduino gives 5VDC can you suggest a circuit that can power the relay externally or in any other way you think would go nice.

[Reply #1 on:]

A/C for relays generally have a seperate rating. Check that rating before running anything into mains. Serious injury is a risk when playing with mains power always, and don't do anything that you're not 100% sure what you're doing.

And make sure that you never exceed current limits.

[Reply #2 on:]

Your message is a little confusing.
Did you mean something like this? http://www.glacialwanderer.com/hobbyrobotics/?p=9
or this? http://www.instructables.com/id/Connecting-a-12V-Relay-to-Arduino/
or this? http://blog.makezine.com/archive/2009/02/connecting_a_relay_to_arduino.html
or this? http://www.arduino.cc/playground/Learning/SolenoidTutorial

Korman

[Reply #3 on:]

I will make it more clear i want my arduino to control a relay that can switch on/off an 250 A/c power electrical appliance.

[Reply #4 on:]

Then you should find all necessary information in the 4 links provided above. If those mention 110V, you just need to get the 220V relays.

Korman

[Reply #5 on:]

i think 12volt DC will do!

The coil rating has nothing to do with it, so the 12V is irrelevant. What you need to know is the ratings of the relay contacts. This should be at least twice the amount of current you are planning to switch.

[Reply #6 on:]

Thank You! ALL ,One more thing i will be controlling more than 1 relays so for example there would be 2 relays activated at the same time so it will suck out all the battery , so i'm thinking to use some capacitor to directly power it through wall, wht you suggest?

[Reply #7 on:]

so i'm thinking to use some capacitor to directly power it through wall, wht you suggest?

I suggest you don't go off playing with 220V lines if you don't know what you're doing - as you've just shown in above statement. Get a regular power supply (aka Wallwart) for your Arduino instead and plug it into the socket.

Korman

[Reply #8 on:]

Alternatively, instead of relays, an opto-isolator triac arrangement (designed with the current consumption of the appliance in mind) with sufficient heatsinking and isolation may be a good direction to go in, per multiple switching channels.

Disclaimer: don't use it in the bath.

[Reply #9 on:]

You may want to consider adapting relay boards like below for use with your aeduino.

http://www.electronickits.com/kit/complete/elec/ck1601.htm
http://www.electronics123.com/s.nl/it.A/id.1712/.f