another Power Meter

[wolfgang]

Hi found today on web some interesting project to monitor multiple power outlets in a building and connect with xbee to PC. Would be great to replace the PC with iobridge. All parts are available as kit, so should be easy to assembly for everyone and all is done on low voltage side, as for the power side a Kill-o-watt is used.

Overview

http://www.ladyada.net/make/tweetawatt/index.html

The H/W part

http://www.ladyada.net/make/tweetawatt/solder.html

the S/W need to be changed to run on server...hint, hint......

http://www.ladyada.net/make/tweetawatt/database.html

some graphs

http://www.ladyada.net/make/tweetawatt/graph.html

some links

http://www.ladyada.net/make/tweetawatt/resc.html

basically all these links and more are from the left selction bar on the website (as reference is also iobridge power monitor shown 


//Wolfgang

[ohararp]

Wolgang you best bet would be to interpret the xbee data into a simple serial stream that you could send to the serial module of the iobridge.  Really this would be a pretty simpel project.  You'll need to study up on the XBEE API though.

[jason]

I was in the middle of prototyping a "power monitor" smart board until I got caught up in Maker Faire preperations.  If you can hang on for another month, we may have an ioBridge power monitor smart board that will do this sort of thing.

I have a Kill-A-Watt and thought it would be a simple hack to tie into the power reading functions.   It turns out that it's not simple at all.  The hack on ladyada.net basically ties into a signal corresponding to current through the device.  If you know anything about AC power calculation, measuring current alone can lead to very inaccurate power readings.  As an example, I have a small desk fan that uses about 25W.  However, because of the low power factor of the fan, calculating power based on current alone will give readings of about 14W.

I'm pointing this out for two reasons.

1) I was heavily criticized for ignoring power factor in my personal ioBridge power meter hack.  And even though I initially dismissed the comments as over zealous power monitoring purists, I now understand the need to use PF in calculations.

2) Although the Kill-A-Watt takes power factor into consideration and is reasonably accurate, the Tweet-A-Watt only uses current and is prone to the large errors.

Measuring electrical power is a much deeper subject than I ever expected.  Here are a few links in case you want to dig a little deeper yourself:

AC Power: http://en.wikipedia.org/wiki/AC_power

Power Factor: http://en.wikipedia.org/wiki/Power_factor

Power Factor and non-sinusoidal waveforms:  http://www.st.com/stonline/books/pdf/docs/4042.pdf

Another PF explanation: http://www1.eere.energy.gov/industry/bestpractices/pdfs/mc60405.pdf

[wolfgang]

Thanks for the info. Did not realize (did not proper read) that only current is send out. I know you need power factor to get true Wattage, VA its not very useful. Will wait for the board. I am still in the lab stage to try multiple things out with the iobridge. Just working to get my complete "Velcro Lab iobridge" working.
//Wolfgang

[iobridge]

The Tweet-a-Watt can still provide some useful "proportional power usage" and the power could be logged very easily with ioBridge and without the use of a dedicated PC. It's a worthwhile hack. I am sure the community would be interested.

[Outlet]

I was in the middle of prototyping a "power monitor" smart board until I got caught up in Maker Faire preperations.  If you can hang on for another month, we may have an ioBridge power monitor smart board that will do this sort of thing.

Any update with the status on this board?

Thanks!

[jason]

An ioBridge power monitor is still in the works.  However it isn't in the form of a smart board anymore.  There were too many limitation when trying to make it work in a smart board form factor.  Those limitations seriously limited it's potential accuracy and dynamic range.  We're working on a device that is specifically intended for power monitoring.  It's still a few months away from being ready. 

[Outlet]

Cool, thanks!

Do you have any suggestions for an inexpensive way to monitor the power status of a device (like an AC clamp that can connect to the iobridge?)..  I only need it to tell if a device is powered or not (it is a large power draw item).

Thanks in advance!

[jason]

The easiest way is to tie into an indicator light on the device (if it has one).

[Outlet]

The easiest way is to tie into an indicator light on the device (if it has one).

Okay.  I don't have a lot of experiences with electrical work like that (and the appliance appears to be sealed).  Is there a different way of doing it?

Thanks!

[texasclodhopper]

For an electronic novice, a non-invasive way to tie into an indicator light is with the light detector module.

You could easily remove the light detector from the board and physically move it so that it is exposed to the power indicator light. Make a little 'housing' around it to block the ambient light. Black tape will work for starters. (I've used black silicon sealant for this before, but it is permanent.)

Use the analog threshold controls at the server site, and you are good to go. When the power indicator goes on and off, you will be able to fire off an action to let you know.

The easiest way is to tie into an indicator light on the device (if it has one).

Okay.  I don't have a lot of experiences with electrical work like that (and the appliance appears to be sealed).  Is there a different way of doing it?

Thanks!

[Fodder1]

I found this device via the need/want for a power monitor. Has there been any movement on this?

CH

An ioBridge power monitor is still in the works.  However it isn't in the form of a smart board anymore.  There were too many limitation when trying to make it work in a smart board form factor.  Those limitations seriously limited it's potential accuracy and dynamic range.  We're working on a device that is specifically intended for power monitoring.  It's still a few months away from being ready. 

[jason]

We were pretty far along with this... then priorities shifted and we had to put it on the back burner.  In the mean-time, we're thinking about doing a "smart board" version that just measures current (and logs it of course).  It wouldn't quite be a full power meter, but it might get some people going with their home brew projects.

[Fodder1]

Hi Jason,

I love the muppets! bealer rules!!!

I am finding more and more things i can do with this little box of fun.

I would love to use this to monitor power for the house and single units. I could se me monitoring the following:

Total power usage
Plasma, Fishtank, servers, AirCon, the list goes on and on.

CH

[Tahoe]

Is it possible to integrate the brultech products with the iobridge? Can you inteface with zwave devices?

I have the new smarthome smartlinc device. It works fine. I even have a webcam running on it. But, the software isn't so hot.

I would like to use the brultech ECM-1240 with the iobridge to provide internet access and temp data.

Any thoughts?