Wireless/RF controlled light switches

Wireless & IoT
1

Hi, I am totally new to all of this kind of thing but am taking a great interest in it. I come from a software dev background and would like to learn my way around some PIC controlled hardware.

I am looking to create some kind of home automation, firstly by creating wireless/rf enabled light switches in my house.

I am awaiting delivery of an arduino uno kit which I plan on playing around with and learning the basics for now.

Can anyone explain what kind of work would be involved in achieving what I am trying to do.

My thoughts are to have a board placed behind the light switch on the wall, either powered by tapping into the power to the light switch or by its own battery. I would ideally want it to connect to my PC where I would then control its state (being on or off) through a web interface (an application will suffice for now if easier)

I understand this might be a lot to ask but hopefully you guys could at least point me in the right direction as I’m very keen to learn and would appreciate any help.

Thanks.

2

Ok, this one would actually be a bit more complex then I am sure you are thinking if you are a beginner.

First off, having a board behind the switch would be ideal. You would need to replace the switch with a 3 way switch so that when the board turns it off, the switch could again then turn it back on.

For power control you would need a relay to take the low input signal from the Arduino, and switch a high voltage AC current. I would recommend a Solid State Relay, such as this (http://www.parallax.com/Store/Component … fault.aspx)

If you are using an Arduino you will require some wireless interfacing devices to be able to send data back and fourth, If you use X-Bee radio modems, you can eliminate the use of the Arduino all together, as they have IO ports built in, that can be triggered from the other end, however, these will not give you the option to go to a web interface later on. If you want to start off with a web interface, i would recommend something like the WiFly Wireless Device (http://www.sparkfun.com/products/10050).

You would need to use the Arduino in this case to host a web page at the spot, in which other computers would be able to connect to, or even, computers around the world (i would use some sort of password xD).

For powering the device, you will need a few things. First off, the Arduno operates on (5-12VDC? Not sure-i use Propeller Chips by Parallax) - I started typing it out, but found this which explains it much better then i could have (http://activesharepoint.blogspot.com/20 … upply.html)

And finally, the application / web controlling it. You will need to at some point build a web page to be hosted on the Arduino for it to be all self sustained, but if you would just like an application to control it for you, just have a button that will toggle the relay, sending RS232 commands, wither directly to the arduino, or into an XBee connected to the computer, sending the same string to the Arduino itself.

I know i can be a bit confusing, but if you have any questions feel free to ask and i will try my best to clarify.

~Matt

3

First off thanks for the reply. Really appreciate it.

Im happy to go with the most simple solution but I am not willing to compromise my goal of having the web interface to control it.

You said the Wifly could be used, but these are approx £44? I am looking to keep the cost as low as possible as I am planning on having each light switch in my house (or at least the main ones for now) hooked up to a central location for control.

I had contemplated a wired route, whereby I could use the ring in which the light is connected to pass data through (like a ethernet home plug). This would then be hooked up to a switch and each given its own IP address to identify itself on the network (possibly a standalone, redundant network to avoid conflict and security concerns). I have seen that you can get ethernet shields for the arduino but I think that this route would be pushing the cost and possibly the complexity up again.

FYI, I don’t want to be limited to an arduino if a more robust or simple solution is possible. I’ve seen the xbee boards and have considered these but do they require additional components to run?

If you could think of any other possible ways I could achieve this as well I would like to hear them.

Thanks.

4

Not to bash Sparfun, or Arduinos or anything, but i Prefer the Parallax Propeller Microcontroller offered by parallax. It takes a bit more work to get set up and running but in the end is a lot cheaper if you need to run multiple, (costs only about $10 per setup as opposed to the $$ per Arduino) (http://www.parallax.com/StoreSearchResu … fault.aspx).

I highly debut it, but if you happen to have one centralized location where you could tap into all of your connections, Parallax makes a neat Relay board for this type or work (http://www.parallax.com/StoreSearchResu … fault.aspx).

If not…

One of these (http://www.parallax.com/StoreSearchResu … fault.aspx) in correlation with a Propeller chip should do the trick if you would like to go wired. However you would need a big ethernet switch, as you can not simply just daisy chain network devices.

If you still want to go wireless, (http://www.parallax.com/tabid/829/Default.aspx) use that to pick out an XBee modem. They range from $20 to $33 depending on the output power.

You will need one of these for each switch, as well as one that you would like as a master controller - Computer. These are Mesh devices, so one sends a signal, and they all pick up that signal, meaning each light switch would have its own address.

(Another suggestion, have one RJ45(Ethernet) and one XBee on one switch, so that will be your main controller eliminating the need for a computer. It will host the web interface, as well as send cotrol information to all of the other switches in the house.)

5

I doubt you could fit a dc power supply, solid state relay and rf receiver behind a wall outlet in a gang box. that leaves 2 options:

-buy one from x-10

-make box big enough to add all that stuff together and plug it into an ac outlet

kind of like the setup in the attached picture, but different. Hot side goes thru the relay, neutral and ground bypass it. This set up (in the picture) doesn’t use RF but a temperature controller not shown. I don’t know if a uController has the current to drive the SSR directly. You may have to whip up a little fet high side switch between the uC and the SSR.

6

Could rip apart something like a cell phone charger… All the components required in a small light weight package. And he could do a 2gang box, or… Take a solid face plate, drill a little hole in it, and do a tittle puch button switch controlled through an IC and the relay. Take the ac switch right out of it.

I got your PM and I will reply to it later in the day. Quite tired and going to sleep.

7

A few issues:

  • Here in the US, there’s a chance that you won’t have a neutral in the switch box, only a hot and switched hot. I’m not sure if that’s the case where the OP lives (UK?). That would make it trickier to get power. You can not safely or legally use hot and ground.

  • Depending on the load, you may need to switch your relay so it closes at zero-crossing to save the contacts. Alternatively, as mentioned, you can use a solid-state relay with proper heat sinking

  • Anything exposed and either conductive or with insulation rated at less than your line voltage must be isolated and grounded for safety

  • AC mains-powered projects are a poor choice to for a first hardware project. There are too many safety, insurance, and liability issues involved. Remember, there’s enough power there to kill you or burn down your house.

  • Do you want smart switches or smart loads? A smart load could tell you if it is really on or if the bulb has burned out…

Can this be done? Sure. Just be careful out there.

/mike