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] <javascript:>> 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] <javascript:>> > 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] <javascript:>. > >> 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] <javascript:>. > > 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.
