I am on the final stage of my course and we are about to create our proposed projects. what we decided to build was a wireless controlled on/off switching on home appliances. yes it was featured at the google I/O conference last may, 2011. and what we did was something similar to that, but we dont want to put wifi devices on appliances. instead, we wanted to connect all the appliances to just one circuit breaker living the appliances turned on then integrate a wifi device on the breaker. i was really confused on what components to start with. what was i thinking was to integrate relay switches and wifi connectivity to arduino. the only problem we have is that how we can make all 20 switches(because we are required to control 20 appliances) returns signal to arduino giving a turned-ON state. controling relay switches using arduino is not that hard to create. my concern is how it will return a Turned-ON state to the arduino, realizing the fact that we are turning 220v of appliances on/off and i think arduino can only receive 5v of input signal. I really need some advice. the GUI for the Android phone is ready. i have no clue where to start for the hardware. i appreciate the all the HELP i can get. thanks... more power..

 

Welcome to the forums.

realizing the fact that we are turning 220v of appliances on/off and i think arduino can only receive 5v of input signal

That's the whole point of the relays... you just need a relay whose contacts can handle 220vac.

Anyway... your explanation is somewhat confusing... maybe you can narrow it down to a specific question or two? You should have a basic system idea... break it down to bite sized chunks and go from there.

 

thank you very much for the reply guitarguy12387. i really appreciate it a lot.
- attach with this reply is an image of what my project would be. i did this to further elaborate my concern with regards to my project.
- i know this project is silly but i need to finish it in order for me to graduate next year. and i really need the help of all the knowledgeable people in this tiny earth.
thank you so much in advance.

if the image cant be loaded on this site just try to click this link below:
http://www.flickr.com/photos/9613793@N04/5987633480/

thank you very much.

 

Relays have 2 things a coil and contacts.. The coil is typically driven with a lower voltage (like 5, 12,24, or 48VDC). When the coil is energized it causes the contacts to switch. Then you typically switch a higher voltage with the contact side of the relay. Relays feature full isolation between the coil and the contacts so your arduino won't see 220V ever.

Now an arduino pin can only provide 20mA (maybe 40ma I forget) of current to drive something.. A relay typically requires more so you must switch on/off a transistor which will then switch on/off the relay as shown below (option 1)

Now you have 2 choices
Option 1-drive the relays with a transistor as shown here http://www.arduino.cc/playground/uploads/Learning/relays.pdf (to avoid confusion K1 is the relay (pins 1 and 16) Relay power V+ and GND are where you attach a power supply (or use the arduinos pass through 5V with a 5V relay)
Option 2-Instead of a relay use a solid state relay (SSR) this is essentially a relay with a built in optocoupler. You can drive that directly from the arduino pin

 

thank you very much mcgyvr.. about the SSR, is it expensive? i think it would be great if i use that, but if it cost that much, it would be impractical for me to purchase it since i will definitely need 20 pcs of those. now for the transistors, is there an IC that can replace at least 20 transistors? im really looking on either possibilities for this project to be successful. again... thank you very much...