Current logging

[seany]

I'm currently trying to figure out the best way to monitor current usage around my house. <p>What i have planned at the moment is to use some kind of serial ADC to poll some non contact current sensing coils around each circuit in my sub panel, and have that data logged into a computer to graph etc.<p>but I'm still looking for other ideas, and any model numbers that people would recommend for doing something like this.<p>Thanks for the help<p>Sean

[bodgy]

Sean,<p>There are a couple of ways to do this - you may want to look at the application notes on the Microchip site - for WattHour meters. Also look at Austriamicrosystems and their AS8118 IC and the Analog Devices AD7755.<p>Apart from the above ICs that convert RMS to DC plus have few extras up there sleeve, there are 3 main types of sensor - Current Transformer, Resistor and Hall Effect sensor.<p>Personally I prefer the Hall effect sensor especially those by LEM - I believe DigiKey stock them in the US - if not Farnell and RS do or direct from LEM in Switzerland themselves.<p>EPE magazine in the UK back in 1996 did a power meter project, also recently Silicon Chip magazine did something similar for a car ammeter, with a make yourself Hall Effect sensor. As this was designed for 30A circuits (DC) it would be a good basis for a design - just update the processor and perhaps use a different display.<p>Once you have converted the current into a DC voltage - then normal data logging techniques prevail. You could use an ADC chip or use a uP with built in ADC you actually won't need that high a resolution.<p>I'm interested in your project as although I ahve built EPE's meter, I am pondering designing one that not only show current in use, but also frequency/phase and voltage - basically a rehash of the Microchip design (the newer one they have two) The application note is AN220 - I was thinking of using an 18F part instead of the 16 part they use.<p>Colin

[haklesup]

The control board in a UPS does most of these things. Measure Frequency, Voltage of mains and output, Load usage and a few other parameters about the battery like temperature and DC voltage as well as charge/discharge current etc. and they already have a Serial or USB interface.<p>I can't remember where but some catalog had some as surplus. Not only that but the batteries in the UPS's don't last forever and end up getting scrapped occasionally. You may be able to adapt one of these boards to do the bulk of what you want.

[seany]

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by haklesup:
The control board in a UPS does most of these things. Measure Frequency, Voltage of mains and output, Load usage and a few other parameters about the battery like temperature and DC voltage as well as charge/discharge current etc. and they already have a Serial or USB interface.<p>I can't remember where but some catalog had some as surplus. Not only that but the batteries in the UPS's don't last forever and end up getting scrapped occasionally. You may be able to adapt one of these boards to do the bulk of what you want.<hr></blockquote><p>
Yes that would work, infact i have a spare semi dead ups floating around right now that i could take apart and examine, but i'm in the end going to need/want to monitor about 30-40 lines. so unless i found a surplus of just the boards for cheap... it just would be cost prohibative (sp?)<p>I fug up some anaglog devices ic that i'm going to mess with. will keep you guys posted if i come across anything intiresting.<p>
Sean