Sunday, July 06, 2008

Replacing the wires ...

...well, replacing most of the wires anyway. You can't replace the power wires unless they can make Tesla's work on wireless power very safe. But many of the other wires, like communication wires, are being replaced. Will this bring additional problems? Or will it be the ultimate solution? I don't know, but it's here to stay. Either way I know it will keep me employed. :-)

I've been working with others on a new home automation project called OpenRemote. One thing that's been made very clear is that wireless is a must. It's expensive to run cables and if a cable can be replaced by wireless technology then all the better, but it better be inexpensive.

Sometimes things are easy to do, you can replace 10Mbps Ethernet with WiFi (802.11b or g) or you can replace 100Mbps Ethernet with 802.11n (now, if they would only finalized the standard). To replace cables such as RS232 is a bit more difficult. Sending data at various speeds can be handled by WiFi and a terminal server but at an expense. Terminal servers are not cheap the lowest cost models are around $100 (US). Now, what if you need to toggle the control bits of an RS232 port for something like an IR dongle. Well this get a bit more complex. I am aware of a few ways of doing this but lowering the latency could be very important to doing this properly. Let say you need to turn on and off a bit (that's two commands) such as DTR or CTS really fast to generate the correct IR signal. It might take 50+ ms (about 100 Hz, remember on _|- and off -|_) to send each such command via a network at 9600 bps (64 bytes frames). In networking there can be a lot of overhead to send that one command. If such a command gets behind a large frame it could be delayed even more as you have to wait until that large frame gets done. This is not to say it can't be done it's just that it needs to be properly done.

Anyway, I've decided to look into this technology. I'm currently purchased four of the TI EZ430-RF25! 00 devel opment boards. It says it can do 200 kbps and I'm going to see if I can learn to communicate point (a master) to multi-point (multiple endpoints). This should be quite a challenge.


At 7/08/2008 12:54 AM, Anonymous Anonymous said...

Have you looked into eCoupled and Fulton Innovation's technology for your wireless power?

At 7/10/2008 10:19 PM, Anonymous Anonymous said...

Regarding wireless,
I have some automation experience.
And I'm not sure that replacing wires with batteries is progress.

I would rather have hardwired communications all over the place than a tangled mesh of communications that is suseptible to electrical interference) and relies on hundreds of battereis all of which need to be replaced.

If every appliance and light is hard wired for power, is it realy such a bother to have a few coms cables bringing my data back to a controller ?
My current opinion is that wireless has no place in any reliable automation system, and no future.
Perhaps Im wrong.
By the way, I make USB IO modules that will run on most operating systems, I can send you free units, but not if you insist on using wireless battery operated bits an pieces scattered all over the place.

At 7/10/2008 11:05 PM, Blogger Neil Cherry said...

Wireless power would obviate the need for batteries. Of course I question how it would work with people around.

Anon #1:

I haven't see eCoupled or Fulton Innovation's technology. I may look later.

Anon #2:

I have to agree with you, I prefer hard wire for most things but unless you are renovating or building new, adding new cables to an existing home is very difficult and expensive. Besides wireless provides you with that instant gratification that most people want (unless your neighborhood is saturated with traffic in the 2.4GHz range).

Oh, wireless != batteries in all instances. You can use wireless and have the device plugged in (though that would make a laptop less portable). It would be nice if we had a standard protocol for talking the power line (X10 doesn't cut it).

I'll be taking a look at the usb modules and I hope to be able to add them to my web pages, as soon as we get the URL straight. :-)


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