Monitor house current Magazine article Info??

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cdenk
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Monitor house current Magazine article Info??

Post by cdenk » Fri Apr 09, 2010 2:03 pm

About 4 years ago, there was an article in either Nuts & Volts or Circuit Cellar magazine that showed how to measure the current (amps) on household electrical circuits. The method was to take say 6 wraps of #18 yellow wire around one circuit's hot wire at the circuit breaker. These pairs of wire were then routed to a PCB that had some circuits to prepare the signal for ADC conversion and then on to a Microprocessor, like a PIC.

IF someone can point me to the year/month of the issues, that would be appreciated. I believe the article spanned 2 months issues. Or if someone has the issues, and could scan the pages and E-mail them, that would be great. I go back about 3 years in magazines, some months ago, I sent the older (10 years) to a better home.

Our electric power cooperative will be going to smart metering shortly, and time of day rates will be phased in. I am hoping to be able to shift a good part of the heavy usage to the low rate times.

cdenk
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Looking for Circuit Cellar August, September 1996

Post by cdenk » Fri Apr 09, 2010 5:14 pm

Looking for copy of Circuit Cellar magazine article by Jeff Baachiochi, August, September 1996. OK to scan and E-mail. Thanks.

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MrAl
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Re: Monitor house current Magazine article Info??

Post by MrAl » Sat Apr 10, 2010 7:08 am

Hi there,


I dont have any info for exactly what you are looking for, but there are several ways to measure current in a wire and you might try different ideas to see what way you like best.

The first is using a current transformer, where the transformer is wired in series with the wire to be measured. The secondary then runs to your circuit where the voltage gets rectified and measured.

The second is the Hall Effect Device. These come in basically two types: the kind you make yourself and the kind you buy already made.
Obviously the ones you buy already made are easier to use, as you simply wire them in series with the line to be measured and the output runs to your circuit. The kind you make yourself involve buying a linear hall effect device and then mounting it close to the wire perhaps with a loop of steel to act as a field concentrator and the output of that device runs to your circuit.

Whatever way you choose, all you have to do to get it working and calibrated is to hook it up in series with a known load (such as a space heater or something like that) and note the reading you get and make adjustments as needed.

If you monitor several lines you can run them to a computer and analyze the power usage throughout the day and night for several days, then make a decision how to change the power usage routine.

Just to note, the hall effect sensors you purchase that are made for current measurement have to be electrically wired into the line to be measured, while the ones you make yourself only have to be physically placed so that the existing wire runs through the core. The current transformers sometimes require the line to be broken and wired in series, but with some of them you can just run the existing wire through the core one time to get it to work.
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Re: Monitor house current Magazine article Info??

Post by Robert Reed » Sat Apr 10, 2010 1:45 pm

"Six turns of yellow wire"- Hmmm, doesn't sound like much of a CT (current transformer).
Would take a lot of amplification to get a usable signal. There are CTs specifically designed for 60 Hz current monitoring and are commonly available. Mouser has them for $4-$6 each.
Cat.# 553-CST-1020 or Cat.# 553-CSE-187. the first one is a hollow core in which you pass the power lead thru. The second is break and insert style. One nice feature of the first one is that you can wrap multiple turns thru it to increase sensitivity. You can download the data sheets from their site for more info. Can be calibrated with a known load if desired.I have used both of these in the past with good results.
But the product called the "Kill-o-Watt" is king of the hill here. It is a plug in device into which the appliance is plugged into it. Reads volts,amps, VA, watts, but more importantly in your case, killowatt hours for a running log of actual power consumption. I got mine on E-Bay for $20. One downside though and that is its only good for 120VAC devices since those are the NEMA standard connections.

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jwax
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Re: Monitor house current Magazine article Info??

Post by jwax » Sun Apr 11, 2010 5:25 am

Would two "Kill-A-Watt" devices wired in series accurately log power consumed on a 220 VAC circuit? Hmm..

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Bob Scott
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Re: Monitor house current Magazine article Info??

Post by Bob Scott » Sun Apr 11, 2010 10:10 am

The Kill-A-Watt is made in Taiwan by "Prodigit" and marketed by "P3 International". They have models suitable for use on many voltages. See here for many capabilities:

http://en.wikipedia.org/wiki/Kill-A-Watt
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Re: Monitor house current Magazine article Info??

Post by stevech » Sun Apr 11, 2010 10:38 am

On the Homeseer.com forums, there are discussions among people that have whole-house power consumption devices with 24/7 computer interfaces. Mostly off the shelf products based on current sensing transformers clamped on to the mains wires in the breaker box.

cdenk
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Re: Monitor house current Magazine article Info??

Post by cdenk » Sun Apr 11, 2010 11:44 am

Thanks for the link to Homeseer.com. That will take a little studying to see if they have something that will do my job. I tend to DIY, and am able to design/build PCB's, have several PIC's and a PLC that manages a 3 fuel standby generator.

Another one is Smarthome.com. :)

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Re: Monitor house current Magazine article Info??

Post by SETEC_Astronomy » Sun Apr 11, 2010 6:04 pm

jwax wrote:Would two "Kill-A-Watt" devices wired in series accurately log power consumed on a 220 VAC circuit? Hmm..
That made me think of plugging a Kill-A-Watt into another to measure a Kill-A-Watt's current draw.

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Re: Monitor house current Magazine article Info??

Post by dacflyer » Mon Apr 12, 2010 4:50 am

heehe,, thats funny..


anyway , they do make a sort of hall effect sensor that just straps to the wire to measure current. i have to look up the number. and post it here later on,
i have 2 of them, but have not played with them yet. they are surface mount IC's mounted onto a tiny 3/4sq" bd, with a small connector. i hope to get time soon one day. was thinking to use them, one on each leg of the breaker box, and a led display on each one to show both sides of current draw. :P

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