Hey Jose, You could implement a very basic rectifier http://en.wikipedia.org/wiki/Rectifier#Single-phase_rectifiers to get an always-positive voltage
Alternatively, you could use something like the ADE7763 ( http://www.analog.com/en/analog-to-digital-converters/energy-measurement/ade7763/products/product.html), in combination with your step-down transformers to get all of the volts/amps/power/phase infor you're after. I would recommend this option. Regards, Andrew. On Friday, 1 November 2013 05:40:47 UTC+13, José Luis Redrejo wrote: > > > > El jueves, 31 de octubre de 2013 13:28:12 UTC+1, Dieter Wirz escribió: >> >> Really ouch. I you do it like this and connect your BB(B) to the lan, >> then all computers in your school are under tension (Brrrzzzz)! >> Therefore: NEVER USE A VOLTAGE DIVIDER WITH NET CURRENT, unless you >> really now what you do! >> You need to have a galvanic separation like a transformer or a diode. >> >> > I do, I do, maybe I didn't explain it . In my first message, the CONN_2 > connector is connected to a 220/9 AC Transformer, so, I'm using 9 V AC to > feed that circuit. > > > >> Have a look at this: >> >> http://www.instructables.com/id/Real-time-Web-Based-Household-Power-Usage-Monitor/?ALLSTEPS >> >> >> >> > Great, it's very similar to what I want to do. But, re-reading the > article I see he's using a power factor of 0.75 and a voltage value of 110 > V, to calculate Active Power. I want to measure these parameters to get the > real active /reactive power values, that's why I have the ADC_VAC line in > my circuit. That's exactly the line I don't know how to pass from > negative/positive values to only positive values lower than 1.8 v to feed > the BB ADC. > > > > >> >> On Wed, Oct 30, 2013 at 10:31 PM, Przemek Klosowski >> <[email protected]> wrote: >> > Ouch, and another ouch since you seem to live in a 220VAC country. You >> can't >> > just connect 220V to a voltage regulator---it has maximum allowed input >> > voltage around 35V---you'd exceed that by a factor of almost 10. >> > >> > You probably should either do some reading about line voltage >> electronics >> > and 220V power supplies (hint---what you propose could work if you used >> a >> > transformer to get 220V down to 12V or so). >> > >> > My suggestion to you would be to consider a low-cost commercial power >> meter >> > like Kill-A-Watt ($20 or so) then point a BBB with a webcam at its >> display, >> > and do >> > a little image processing to read out the power. People also cracked >> them >> > open and interfaced directly to their internal circuitry. >> > >> > >> > On Wed, Oct 30, 2013 at 2:57 PM, <[email protected]> wrote: >> >> >> >> I'd like to use my BeagleBone Black to build a small power efficiency >> >> station for my school. For that I plan to measure power consumption >> using a >> >> current transformer and a voltage transformer, feed the data into a >> small & >> >> fast database and show it through a web interface to the school staff. >> >> I see that 50 Hz are not a problem for BB ADCs, but I'm not sure at >> all >> >> using them is a good idea. >> >> Intially I planned to use the same voltage I must measure to power the >> BB. >> >> I'm starting from a circuit like the attached one (replacing the >> UA78M33 by >> >> a UA7805CKCT which provides up to 1.5 A output) >> >> >> >> Changing the R1/R2 divisor I can make the 220V signal lower , but I'd >> >> always get a signal with a negative side (-0.9V - +0.9V) in the best >> case. >> >> Same for the current transformer, after applying its output to a 100 >> ohms >> >> resistor. So, first, is it an awful idea to use BB for this purpose? >> If not, >> >> how can I avoid the negative part of the signal before feeding the BB >> ADCs? >> >> >> >> Thanks in advance >> >> >> >> -- >> >> For more options, visit http://beagleboard.org/discuss >> >> --- >> >> You received this message because you are subscribed to the Google >> Groups >> >> "BeagleBoard" group. >> >> To unsubscribe from this group and stop receiving emails from it, send >> an >> >> email to [email protected]. >> >> For more options, visit https://groups.google.com/groups/opt_out. >> > >> > >> > -- >> > For more options, visit http://beagleboard.org/discuss >> > --- >> > You received this message because you are subscribed to the Google >> Groups >> > "BeagleBoard" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> an >> > email to [email protected]. >> > For more options, visit https://groups.google.com/groups/opt_out. >> > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
