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Show idea/question: cheap wireless light and fan switch

Former Member

I have an idea I would love to see done on the show. I want to be able to control all the lights and ceiling fans in my home from my computer. Since I'm going to need about 15 of these units I'm trying to keep the cost down as much as possible. My thought was I would buy the parts for a JeeNode and add a couple of relays to create a module that would fit in a standard light switch receptical replacing the switch. My question is what is the best/cheapest way to take the main voltage and turn it into something the arduino can use and what would be the best relays to use? I thought about modifying a wall wart but at 7-10 bucks a pop they are a little on the expensive side.

  • 0

    Wall warts can be had for cheaper than that

    http://www.sparkfun.com/products/10214

    and probably even cheaper bulk on eBay.  You aren't going to get much cheaper, the cheapest way you could go, is to use a diode as a half bridge, a dropping resistor and a zener diode and cap, but its probably better to use a wall wart that has an offline switcher such as the one above.

     

    As for relays, it all depends on the load.  Check out the wattage of the device you are controlling to figure out the current and size your relays accordingly.  Keep in mind that relays have a lower breaking or switching current than what their max capicity is.  That is because breaking a circuit that has a large current going through is more difficult and will cause some arcs etc.  Also, remember your protection diodes on the relays!

     

    For a non wireless method that sends signals through your homes' power system, look at x10 home automation.

  • 0 in reply to colecago

    Sorry if this is a silly question but this is the first time I have made an Arduino do more than blink an LED. Can I drive the Arduino directly off the 5v wall wart linked to or do I still need a voltage regulator? The voltage regulator I had picked out requires a minimum of 7.5v which really drove up the cost of the wall wart.

     

    As for the relays the fan + lights are going to draw 2-3A

     

    I looked at x10 and was concerned about the reliability. I looked at other home automation systems and they were way more than I wanted to spend. If I can make that wall wart work I should be able to get the per unit cost to around $20.

  • 0 in reply to Former Member

    If you trust the voltage source and it is at your same level, you don't really need a regulator.  All a regulator does is keep the voltage at a specific level.  Now, its probably a good idea to use a regulator, meaning you would need a larger voltage because of the dropout voltage of the regulator, but Sparkfun insists that that charger can be used to power an Arduino through the USB port (meaning the Arduino would not regulate the voltage either).