Nice PIC project for someone..?

[vintage1]

What would be REALLY nice is for someone to make a true RMS power meter to go in series with a mains line cord to measure the true power consumption of domestic devices..both when running and on standby..

So take the V and I and sample about 250 times a cycle, mulitiply, sum integrate and smooth, and display in 1/10ths of a watt up to 3KW...

Oh and while you are at it, peak inrush current would be nice to know too :D

[mem]

How accurate do you need it? This device (http://www.amazon.com/P3-International-Kill-Electricity-Monitor/dp/B00009MDBU) costs $23 dollars and purports to measure true RMS

I am not sure if there is a 220/240 volt version, perhaps you could mod the 110v one :)

[vintage1]

There are 230v ones..but they aren't sensitive enough on low loads and they aren't that good at true RMS.

[AndyKunz]

Have you looked at Microchip's power line reference designs?

Whatever you come up with ought to handle 47-63Hz.

Andy

[Acetronics]

Vintage,

for simple devices 1% accuracy, see Conrad.fr part n° 12 21 81-75 ( Price: ....23.90 Euros !!!) catalog or ELV Germany catalog ( kits and semi-kits )

for precise measurements ... hand multimeters have done that since the "Silver shadow" made it's first miles !!!

you'll surely find from Farnell ...

Alain

[MatC]

Might need a fairly powerful PIC to do that nicely, would be beyond the midrange devices that I'm familiar with. You need 16bit maths for that accuracy, around what... 1000 samples/mains cycle? (You'd want it to handle SCR controlled devices after all). That's 50k operations per second, 5 mips at 20MHz, so around 100 pic-cycles/sample.
The highend devices would have no problem.

[lazy-b]

Guys, Saw an old Single Chip True-RMS to DC Voltage converter.......This is the same Chip use in True-RMS Digital Voltmeter........That chip is a little expensive.

[Acetronics]

Hi, Ellion

You were thinking to AD 536/636/736 ... ???

the last one is not so expensive ... :p

I've been using a pair of '636 to measure my Glow plugs parameters ... for at least 10 years !!!


Alain

[lazy-b]

Alain, Yes.....that chip look like more than 10 to 20 year old.......infact, When I am about to buy that chip, its not available anymore.

Plan to use the True-RMS to DC converter to monitor the average power going to Glow Plug......Finally, just use a simple Resistor/Capacitor network connect to cheap VU meter.

[Acetronics]

Plan to use the True-RMS to DC converter to monitor the average power going to Glow Plug......Finally, just use a simple Resistor/Capacitor network connect to cheap VU meter.

Hi, Ellion

:rolleyes: How do you do that if using a pair of 3 1/2 LCDs ...

Good question, I presume :D :D :D

a Pic and a "smart" table read ... :p

Alain

PS: for AD 736 see :
http://fr.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=9605061

AD 636

http://fr.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=405395

[lazy-b]

Alain, in the early days, have experimented lots of Glow Plug Igniter......I just use simple 555 Timer and Power Mosfet.

That AD736 is still available at RS-Component cost at P 780 (USD 16), I remember 20 years ago that cost about P 350......I am still looking for a Cheap Surplus DMM with True RMS Reading, if I can not get one maybe will just buy that chip.....Thanks for reminding that old old chip.

Here is our Latest Video its RC Submarine......have also Mirage 2000 electric Ducted fan........time to time I post our Video at www.rcphilippines.com

http://www1.rcphilippines.com/forum/index.php?topic=293.60

Ellion

[GeneSS]

Vintage
You also need to be able to measure power factor to calculate true power. Depending on the circuit that you are measuring, the voltage and current may not be in phase.

Gene