Sun 20 May 2007
Warning: This project deals with potentially dangerous voltages and should not be undertaken by those who are not properly trained in applicable safety practices.
This post describes the final design of my power meter as promised in a previous post. The basic ideas are the same: measure the current and voltage then multiply them and extract the DC offset for the average delivered power. The schematics and a bigger writeup are included in the PDF files below as well as a few results. It is not indicated in the schematics, but the power strip I chose has both surge protection as well as a re-settable fuse for further safety.
( power-meter.pdf ) ( power-meter-schematic.pdf )
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April 6th, 2008 at 8:47 pm
I´ve been trying to simulate your design but i can´t find the spice model pf the lct1062. I use Orcad9.2
April 6th, 2008 at 8:55 pm
Hi Diana,
It doesn’t look like Linear has a spice model for this chip and I don’t know off the top of my head if there is something comparable in the standard library. The chip is there to low-pass filter the multiplier output, so any low-pass filter will do. You can see if there is an available filter IC in your parts library or you can build an active filter system in your schematic, something like a 2nd or 4th order Sallen-Key (so your pass-band is unity gain). If you use a lower order filter and notice that you still have a ripple in your output voltage, you can lower the filter cutoff frequency. The trade-off is that the power-measurement circuit will be slower to respond to load changes. Hope this helps and let me know if you have any further questions.