Re: Looking for ways to measure AC line voltage with a uP

On a sunny day (Fri, 24 Nov 2006 16:31:15 -0800) it happened John Larkin
<jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote in
<tk3fm2103181ilslpeabedc87ep492i5pu@xxxxxxx>:

On Fri, 24 Nov 2006 16:38:56 -0500, "DaveM"
<masondg4499@xxxxxxxxxxxxx> wrote:

"Donald" <Donald@xxxxxxxxxxxxxxxx> wrote in message
news:1pqdnVQTtYA4ofrYnZ2dnUVZ_qudnZ2d@xxxxxxxxxxxxxx
John Larkin wrote:

On Fri, 24 Nov 2006 10:55:59 -0700, Donald <Donald@xxxxxxxxxxxxxxxx>
wrote:



I would like to measure the AC line on a remote heater and water pump.

I can run a RS-485 to the site, but measuring the AC side is where I am
having to be creative.

My idea is to isolate the line measuring side from the uP.

What do you mean by "make accuracy expensive" ?

This is a one off project, for our hot tub. :-)

donald




How about a voltage stepdown transformer and a current transformer,
both running into a sound card?

Somebody must have done this by now; ask Google.

John


Good idea, if the site was closer. The RS-485 line is already 200Ft.

I have a uP already on-site measuring temperature.

Voltage and current are next.

donald


Not really such a good idea... The gain through a sound card is very
uncalibrated, and controlled by the volume slider in the sound mixer (assuming
Windows OS). The gain changes each time you adjust the volume of your favorite
CD track. So unpredictable as to be useless in this situation, unless you
provide (programmatically) some means of presetting the calibration.


Just set up the sound card gains and such when you use it. Heck, you
can do that in PowerBasic.

John

My PC is playing background music all day.... sound card 1 occupied.
For web video and TV soundcard 2 is used... different speaker (or headphone).
He may need that soundcard.
Soundcard 1 is also used for net2phone, skype etc. Or was it 2?
2 soundcards is not even enough.

.

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