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Wireless current sensing

2009-08-11 20:17:39.579636+00 by Dan Lyke 10 comments

Yesterday I had a little spare time so I pulled out my RZRaven kit and attempted to muck with the firmware on it. It already has a command that's sendable from the USB stick to query the thermometer, so I figured I'd either use that ADC, or query another one on the device, and couple it to a Si85xx-EVB and build a little current measuring block.

Kind of a disaster, the default firmware doesn't compile to a size that fits on the device using AVR-GCC, when I trimmed out the features I didn't care about I was still having trouble getting the code to talk to the LCD and network controller, I tried downloading an eval copy of the IAR compiler, which I'd be okay with paying for, but it's one of those "we'll tell you how much it costs after we guess how much we can squeeze you for" products, and my simple attempts to program the device using their environment and their output binaries and my existing hardware didn't yield fruit.

So today I did just a moment of searching and ran across Tweet-A-Watt. I have one Kill-A-Watt that can be adapted to this, as I play with power monitoring in general I'm less and less convinced that there's much to be saved in my house, but it seems like this'd be a good place to start with wiring up the house with distributed sensors.

[ related topics: Hardware Hackery Software Engineering Embedded Devices Real Estate ]

comments in ascending chronological order (reverse):

#Comment Re: made: 2009-08-11 20:38:18.693797+00 by: meuon

Your home usage is probably guessable:

#Comment Re: made: 2009-08-11 22:27:33.774263+00 by: Dan Lyke

Soldering iron's only 25 watts, and that's an intermittent load. I'm guessing the 'scope draws more. Heating is gas, cooling is a window unit that I can just multiply the back label numbers by the number of hours per year we run it.

A lot of this is "oh, it'd be cool if" quickly gets replaced by "yeah, that's what I should have expected". It'd be cool if we could run the ceiling fans automatically, stuff like that, and this could be a step in that direction, but the more I look at just passive power monitoring the less I think it'll actually tell me anything.

#Comment Re: made: 2009-08-11 22:47:48.139036+00 by: meuon [edit history]

The big surprise to most people is 'dishwashers suck the juice' if you let them heat the water and heat up to dry dishes.

Time for a bike ride.. my second today :)

#Comment Re: made: 2009-08-12 00:08:51.310483+00 by: meuon

Finally looked at the hardware you linked to...Hmm...

#Comment Re: made: 2009-08-12 03:38:54.599407+00 by: Larry Burton

Here's some more hardware that might be of interest to you.

#Comment Re: made: 2009-08-12 06:13:07.258231+00 by: spc476

Why can't they make an intelligent circuit breaker box? Or just intelligent circuit breakers?

#Comment Re: made: 2009-08-12 13:46:40.348228+00 by: Larry Burton

They do.

#Comment Re: made: 2009-08-12 21:37:08.378579+00 by: spc476

Nice, if I had a substation I wanted to monitor, but I was thinking more in line of the home circuit breaker box.

#Comment Re: made: 2009-08-12 21:58:58.240549+00 by: Dan Lyke

Yeah, if Square D had current monitoring breakers in their HOM package I'd replace most in my box.

And if Leviton (or whomever, interop is easier inside the house) had currentonitoring plugs I'd be replacing 10 tomorrow.

#Comment Re: made: 2009-08-12 22:00:24.883314+00 by: meuon

spc476, They do, about $125+ retail per "breaker", and they don't fit in a normal breaker box, most are DIN rail mounted, and talk either Modbus or DNP or RS485 or.. or.. (add zigbee, lontalk, 6lowpan, etc.. etc.. as well)

I have 4 on a din rail next to my desk, that talk RS485 to a Zigbee-ish controller that will talk to a "Data Collector" via Zigbee. I have serial# 10001 of two of the devices, so I can't share much more than that. We'll be selling them soon though, and then I can.

When Americans start paying $1+ per kWh (Currently 10% of that) you'll see these in homes here. If the home wiring electrical inspector guys can handle the change of technology. They are showing up in commercial buildings, slowly. Mostly driven by the need to sub-meter tenants. The bad part is most commercial buildings wiring is a mess, and sometimes a single circuit feeds more than one tenant.