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  • Author Author: sftwrngnr
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Project power measurement

sftwrngnr

I've been thinking about how to measure the power usage of this project, since that is one of the design requirements, and I've decided that what I'm going to do is utilize a separate measurement and logging circuit so that the actual process of measuring the current draw isn't a parasitic draw.  The simplest solution I can come up with is to just have an arduino with a current and voltage measurement circuit attached to it log the data and report it upstream to the website separately.  As I read it, the parameters of the design challenge don't specify that the current draw must be included in the IOT data stream that is explicitly sent up, but do clearly state the requirement for the power measurement to be captured.  The way I see it, provided that I have a mechanism to send the power measurement datastream up to the site, I'm meeting the requirements of the design challenge.  Alternatively, I could have the SI Labs embedded processor pull the data from the Arduino periodically and transmit it to the other device en masse.

 

Any thoughts/Comments/Flogging?

  • in reply to RWReynolds

    Well, that makes me sad. Especially with the when powered via USB and debug mode, although I suppose I can use that to validate the measurements I'm getting from the external measurements.  Thank's for the heads up Rick!

  • John,

     

    One note on my suggesting the AEM be used for power monitoring. Apparently the AEM is only functional when the controller board is powered via USB and the power switch is in DBG mode. So if you switch to BATT mode you can't use it.

     

    From the EZ32 docs.

    "The Advanced Energy Monitor can only measure the current consumption of the EZR32 when the power selection switch is in the DBG

    position."

     

    Check out page 7 od the EZ32 users manual.

    https://www.silabs.com/Support%20Documents/TechnicalDocs/wstk6222_EZR32WG_915MHz_Wireless_Starter_Kit.pdf

  • in reply to sftwrngnr

    LOL! Great minds. Heck yeah... Over-engineering is fun when it's for fun.

     

    Very cool that you have your daughter working on this with you. image

  • in reply to sftwrngnr

    Gottcha John...

     

    Yeah, there is the issue of the sensor operating current but that should be pretty simple to know and account for in code. And I was thinking more along the lines of a single main power feed to the entire system and measuring total current at that point. Could just use an inductance style current transformer and a bit of circuitry I suppose. That should be totally non-invasive. As far as the energy usage on the MCU I'd definitely go with the built in AEM. it's available and seems relatively simple to read from code. That way you'd have total energy for total system efficiency and separate MCU energy to see how the power modes really work and how close to that 20na target we can get. image I hear ya on those ultra low power modes. Those numbers are crazy stuff.

     

    In SimplicityStudio there is an energy profiler function that will correlate your code, as in individual functions, to energy usage. That's wild! I really can't wait to play with the EZ32WG device and the dev software.

  • in reply to sftwrngnr

    I plan on having a separate power bus for the pumps and motors so as to avoid any unnecessary spikes on the device, so I have to measure that independently anyway, but given that the device has a way to measure power consumption on board, I may just eschew my paranoia and go with that for the device power consumption, and include the pump and motor bus draw as a separate data set.... or go totally OCD, measure both externally and use the internal as well. Why not over-engineer?! It's my time and my daughter needs the practice soldering!