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Power Monitor

Non-intrusive feedback loop for electrical systems.

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This project was created on 05/14/2014 and last updated 12 hours ago.

I designed these boards based on a schematic in the pdf by Christopher McNally on my github page.

This board monitors the temperature and humidity of a room with the DHT22, and uses the current transformers to monitor amperage going through the main lines.

Each datapoint for the current readings in the Xively screen shot is the Peak RMS for each reading.

I have been using this board at home to monitor the electrical consumption in the house, but the board also can sense ground faults, and be used to detect soil moisture levels.

See PDF on github page.

There are many aspects of this circuit that I have not verified yet, however it has been serving it's purpose so far.

The use for this board thus far was to monitor the temperature in my Aunt's basement because she had become sick last year and unable to live at home.  I could see that the heater was working by current draw  and that the temperature was above freezing.  The board has remained in use all winter and worked flawlessly. Additionally I could see when someone was in the house because of the lights being turned on and off (this proved useful at one time because it provided the exact time of an incident).

I just got the go ahead to put this board in a heat treatment/annealing furnace and start collecting data in an industrial setting.  What I am hoping to accomplish here is to be able to see when the heating coils or igniter begin to fail so that they can be replaced before causing down time or loss of product.  

As the project progresses I plan on monitoring voltage to provide true power readings, as well as other sensors and control boards as necessary.

What I hope to provide for home use is a box that can be installed by an electrician and monitor power consumption and provide feedback for automation systems.    

  • 1 × DHT22 Temperature and Humidity Sensor
  • 1 × LM358N Amplifier and Linear ICs / Operational Amplifiers
  • 2 × 3000:1 Current Transformer or 2000:1 Current Transformer
  • 1 × Arduino

Project logs
  • Ground Fault Test

    12 hours ago • 0 comments

    I hooked up the ground fault test box again, and took some measurements.  With a calculated ground fault of 0.09A I was getting an peak A rms reading on the arduino of 0.05A it was regular but not constant. 

    I was able to measure a calculated 0.1A ground fault with the meter and the arduino.  The arduino still  measured 0.05A but the meter measured 0.9A.  This wasn't a reliable measurement though.

    The detectable amperage is higher than the standard which is 0.06A at the highest, but I didn't set out to build a gfci and I am pleased with the results.  

    I did check the arduino at a measured 0.6A calculated load and measured 0.52 so I am happy that it was closer at this level.  I will continue to test the circuit and finish with three graphs, Calculated, Meter, and Arduino and compare the results, but I have to get a better dmm first.

  • Power Connector

    4 days ago • 0 comments

    This is probably old news for most people, but I just learned something today.

    On the DC power connector above the red wire is connected to the center pin and the black is connected to the casing contact.  When nothing is plugged in, the center connection that is not connected has continuity with the connection with the black wire.  

    When a power cable is inserted you lose continuity with the terminal that is not connected.  I believe that it is irrelevant now because I have revised my board but this was an issue with the way I layed out v2r0.  The chinese arduinos would work as is, but I was having some strange problems with the sparkfun arduinos. 

     It is a notable fail on my part because several weeks ago when I assembled the first board I had originally used the sparkfun arduino and ran into the strange problem and assumed that I had created a solder bridge somewhere  because I was lacking confidence in my smd soldering abilities.  I slavaged some parts and tossed the board aside.  

    The second build, the one in the main project picture, I used the chinese board because I did not want to risk damaging a $10 board when I had several $3 boards laying around.   

    Tonight I did some troubleshooting while building up a couple more boards and found the problem... I am almost always right to assume that if there is a problem it is because I did something wrong, but every now and then I need to take a closer look at the components.  I didn't know DC jacks had a switch inside. 

  • v1r4

    5 days ago • 0 comments

    Just got my first boards that I have done with a copper pour. I was dissapointed when I opened the package to see that they did not bevel the edges of the board.  I am not entirely sure that it wasn't the board house, but I think that it is because the way I created the polygon for the ground.  I'll post here for others to be mindful of it and so that I remember to come back to it when I find the solution.

View all 21 project logs


Jonathan Groff wrote 5 days ago null point

I wonder if you can pot these in urethane such that the sensors are not obscured, for ruggedization.

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jlbrian7 wrote 5 days ago null point

Conforma coat ...

and as far as that goes I thought if it ever came to it the board could be put in a watertight box and use amphenol or seacon connectors to mate with the electrical interfaces, but this would have to be a very specific situation.

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diysciborg wrote 15 days ago null point

A MASSIVE amount of work on power monitoring has been done at OpenEnergyMonitor. Check it out.

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jlbrian7 wrote 15 days ago null point

already seen that thanks

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Adam Fabio wrote a month ago null point

Looking good so far! Thanks for submitting your power monitor to The Hackaday Prize! Don't forget to upload some videos of the monitor doing it's thing - I really like the ground fault detection feature!

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jlbrian7 wrote a month ago null point

I should have a couple of video's up within the week. I have to build a box to induce a ground fault.

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arre_diels wrote 2 months ago null point

For an AC power monitor, you are missing a power-factor calculation, no? Just measuring the current will only do for resistive loads. (or am I missing the voltage measurement somewhere?)
Otherwise cool project though

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jlbrian7 wrote 2 months ago null point

the 150ohm resistor that ties the two lines together is the load

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jlbrian7 wrote 2 months ago null point

Sorry I misunderstood. You are correct I am not taking voltage measurements right now. So this only measures apparent power not true power.

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Jeff wrote 2 months ago null point

You could also list 'em on Tindie. Seems like the appropriate place for that kind of thing.

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jlbrian7 wrote 2 months ago null point

I will look into it.

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ucasano wrote 2 months ago null point

How do I reach the github page?

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perez.ernesto.j wrote 2 months ago 1 point

just let me know ebay link, ill gladly support by buying at least one of the shields

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jlbrian7 wrote 2 months ago null point

Will do. It should be up soon.

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