Controlling lights with TI ez430 chronos, home easy, arduino and processing
Now that the protocol for basic communication with the TI chronos ez430 has been worked out (see previous posts) I needed to work on something useful. So I set out to try and control my wireless light switch with the watch. Sadly the RF receiver supplied with the chronos does not use a protocol which is likely to ever be compatible with the arduino so this example requires a computer.
The Hardware
Recently I’ve acquired a Home Easy HE217 remote light switch which consists of a unit placed between the light bulb and ceiling rose and a wireless switch to switch the light on and off from anywhere within about 10m. I purchased this with some form of hackery in mind but this is the first real attempt to do anything useful outside of the functionality of the supplied package. The system uses RF at 433MHz and a simple authentication protocol, which is conveniently documented at the Home Easy Hacking Wiki.
433MHz is a common frequency used by radio controlled devices such as remote switches, garage doors and car remote controls and transmitters and receivers are readily available for very little money (around $5). These can be used for many uses especially in combination with an arduino, following on from the work documented on the Home Easy Hacking Wiki an arduino library has been produced (available here). This allows the arduino to control the light switch in the same way as the provided Home Easy light switch.
The RF transmitter was then simply connected to the arduino to allow the light switch to be controlled using the arduino.
The software
The software aspect of this project consists of my previous processing sketch which receives button presses from the chronos watch, to this I added functionality so that every time a button press is received a serial character is sent to the arduino in this case H for on and L for off.
On the arduino a sketch is used that reads the serial input and when H or L is received it send an on or off message using the home easy arduino library thus switching the light. The observant among you will have noticed that this is based on the arduino physical pixel example!
The system works even if the watch is taken out of transmit mode and then restarted.
The code can be viewed below.
In action
The code
The processing sketch chronoslight.pde
The arduino sketch: chronosHE.pde
very cool setup. when i first heard of this watch, controlling lights was one of the first things i thought of. is there any way something like this could just be implemented in the circuitry of a light switch? i.e. a receiver that tells the switch to be either on or off…
also, could this be implemented so that the light turns on whenever the watch is within a certain range? that way the light could be on when you are in the room and it would turn off when you leave. seems like it would be another cool/energy-saving application of your setup.
Yes, I’m sure I could implement it so that when the watch went out of range the light would turn off as pings can be used. However the range of the watch is much bigger than my room, so it wouldn’t be as easy as that.
Re all the circuitry in the light, this is also possible but the 868MHz makes it a little harder and would require a different receiver or some fancy coding that I don’t know of. I’ve mentioned this in my newest post here
very interesting. sounds like the new version of the watch is worth waiting for, but i’m very intrigued by the ability to automate the house using the watch. perhaps some system could be created that would ensure lights are turned off when the watch is out of the house rather than out of the room…the same could go for computer monitors and printers, etc. i’ve always thought it wouldn’t be too hard to build a little adapter which devices can plug into that sits between the plug and the wall socket that could then be turned off wirelessly or with some controller. this watch seems like a good way to incorporate location-based setups.
thanks for the info!
can the ti3z430 chronos watch work with any 433Mhz receiver ? (provided its on the same freq and its modulation method is the same, ASK, FSK , PSK etc…)
The chronos is not communicating with the pictured 433Mhz transmitter, the watch is supplied with a usb transceiver which uses 868MHz which is used here, the 433Mhz device is used to communicate with the lights.
The future 433MHz version of the watch is more likely to be able to use the pictured (and similar) devices for communication.
I think i just figured the answer to my question…
you have a tranceiver(not shown in the pics) – the one for the chronos watch, which probably plugs into your usb.
Chronos -rf-> PC –> arduino -rf->lights
Is that correct ?
LOL…i didnt see your post before…but ya..essentially the same thing
Don’t worry, it’s not necessarily obvious if you’re not familiar with the products.
I’m almost certain (because ive asked this question before…though I cant really remember from whom..I think I asked TI directly), but you cannot use a basic 433Mhz tx/rx such as the ones from sparkfun or seedstudios. It HAS to be a specific or specific series of RF IC’s from TI. So even getting the 433Mhz watch and trying to get the lights to operate without that intermediate RF component, will be hard/impossible to do.
Check with TI or some other place before you really try out various RF Tx/Rx.
I’m about 85% sure that it wont work.
Good luck !
TBH I probably wouldn’t attempt that anyway, my intention was to communicate between the watch and an AVR MCU using the generic 433MHz things, not directly with the light and watch, that should surely be possible? Just might require a little reverse engineering of the protocol?
If what you said turns out to be true then I shall not waste my money on the 433MHz version
This is pretty cool! Are you going to post a link on the chronos wiki?
The RF on the chronos isn’t necessarily limited to communicating with only other TI RF chips, but the frequency, modulation scheme, and protocol stack all have to be compatible. It would take some experimentation to see what else it could talk to.
There’s a big advantage in routing all commands to a PC first because it can control more devices remotely and apply some logic instead of a single point point to point link between the watch and a light.
The watch is using a fairly new Dash7 protocol:
http://en.wikipedia.org/wiki/DASH7
Which in the case of this watch, talks to a TI microcontroller which is combined with the RF hardware. It’s a pretty slick system-on-a-chip.
So in theory it should work with any DASH7 chipset, like a CC430 not in a watch… though they are just now coming on the market.
You should be able to go straight from the watch to an other CC430 system-on-a-chip connected to a relay that can handle the amps of your lights, or whatever you want to turn on and off… and for only about $15 or so
No Arduino, no PC, no Processing… (But some coding of the TI microcontroller which I’m hoping is not too gnarly.)
Thanks for the blog post!
Hey sweet blog, could you tell me what spam plugin you use for comments because i get a bunch on my blog.
I use the integrated akismet that comes with wordpress
Hey there, just looking around some of your work and its all good stuff dude! i wanted to know if you think its possible to use the watch as a ‘key’ with the home easy door lock (he-106) if you can that’d be ace! hope to hear from you soon
I would imagine not, a radio door lock should use an encrypted signal, not a generic one…but never say never.
You could build a system where the watch transmitted to a computer and then computer triggered the door lock via an arduino connected to the original door remote.
right i understand ya! also (i know this sounds cheeky) what programme do you use to programme the watch? im tryin my hardest and seem to failing (badly…. im new to this)
Really nice work, if you have an android device take look on this
http://arduino.cc/blog/2010/09/16/mobile-home-automation-via-android/
That is pretty cool, I would probably use MQTT for the communication though
Hi, the 868 MHz version has the advantage that it can work with devices that work with the XBee chip TI 868Mhz and besides also the strap to the heart there is no version for the eZ430 of 433 Mhz.
Do not know if it helps.
Greetings from Spain.