Homemade Power analyzer - Page 1
Forum section: electronics / projects

author: ViewPoint
author_rank: Newbie
timestamp: May 19, 2015, 03:09:31 pm
content: Hi guys,I am new here so be patientIn short, I am working on the student project with the task to make simple(but not to simple) Power analyzer (electronics and user interface) which will be capable of power measuring on the AC motors driven by Variable-Frequency drive.At first, Arduino + some shields looked as good way to start. But when I have done some research it was obvious that Arduino has to low sampling rate for good sampling of PWM signals from Var.F drive and making a solid user interface was also tricky thing to do.Back to the Google, I have found this board (Red Pitaya - there are other post on forum about it)http://www.elektor.com/red-pitaya-instrumentand according to the specification the HW (+ my additional electronics) side is more than capable of handling PWM supply signal. There are also examples of different instruments already implemented on it and they say that you can make your own user interface which is running on web browser so no additional SW is needed. (I am confused with that)My question is - What you think/suggest? Should i go with this board?Really long post, sorry :/Best

author: Marco
author_rank: Super Contributor
timestamp: May 19, 2015, 03:50:47 pm
content: Dunno, but the MyDAQ and the Analog Discovery boards might be interesting too (the former especially if you want to do it in labview).PS. none of these boards have much in the way of input protection ...

author: kripton2035
author_rank: Super Contributor
timestamp: May 19, 2015, 03:57:59 pm
content: a working example :http://www.electro-labs.com/diy-digital-ac-watt-meter/

author: dom0
author_rank: Super Contributor
timestamp: May 19, 2015, 04:54:00 pm
content: Quote from: kripton2035 on May 19, 2015, 03:57:59 pmI'd recommend some caution with the isolation interfaces between mains and the digital circuitry.For example, in the linked circuit they use an ACS712 current transducer IC, which is only rated for 180 Vpk if double isolation is required (which it is in this case, since DGND is not connected to PE!). From an engineering POV this is fine for 115 VAC, but not sufficient for 230 VAC operation. Connecting DGND to PE remedies this by lowering the required isolation to basic isolation, which is then fine with the ACS712 (rated to 350 Vpk for basic isolation).

author: dom0
author_rank: Super Contributor
timestamp: May 19, 2015, 04:58:43 pm
content: Oh and just by the way there are dedicated fully integrated chips for power meters available since a while, e.g. ADE7753. They contain all the necessary filtering and DSP functionality for the extracting the usual power parameters.

author: ViewPoint
author_rank: Newbie
timestamp: May 19, 2015, 07:48:09 pm
content: Hi,Thanks for replays.Marco ->MyDAQ and Analog Discovery are usable only with USB connection to the PC or laptop.LabView is not my first choice, but as i have look in to the details Red Pitaya also support LabView through SCPI commands and TCP connection.My goal was to make my own additional electronics which will handle high current/voltage side.http://redpitaya.com/make-your-app/#Exampleskripton2035 ->This board can be interesting but the integrated ADC (MCP3202 )is on my opinion to slow for PWM signal in Frequency Variable Drive. This PWM voltage signals are pwm modulated with switching frequencies from 5-10 kHz and slew rates in ns. Couple that with inductive load such is AC motors and you get current signals with substantial ripple.In order to calculate true rms, real and reactive power my sampling must be at least 1MS/s.(I think so)PS: They have also an LCR meterhttp://blog.redpitaya.com/?p=650http://blog.redpitaya.com/?cat=10dom->Of course, i am thinking about high frequency voltage and current transformers/toroids doisolate the mains._____So, in shortpower analyzer must be let’s say not to simple and little bit advanceadditional electronics is something what i must do (its student project)pow. analyzer must be standalone device - user interface is on device itself or non-connected pc/laptopThank you for your suggestion - i think that final blueprints are herebest