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Arduino Watts

Simple watt watt meter powered by Arduino.

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A simple solution to a simple problem. I want a watt meter for my computer. The bigger problem is that i did not want to pay for an expensive watt meter. What do? Build one from Arduino! The goals of this project are simple: Develop a circuit that can measure currents in real-time, both to cure a curiosity I have regarding how power-hungry my computer is, as well as estimate how much it impacts my utility bill. This will be my first dive into circuit design and development, so I'm hoping I dont kill myself or burn my house down.

Arduino Watts


An arduino based watt meter. Crazy, right? What would you do you use a microcontroller for in a watt meter? The answer would be nothing if you were to go buy one. But my answer is it is the brains behind your meter.


The concept came to me pretty much randomly one day at my desk-job. I was bored out of my mind when the thought came to me to make a watt meter. I dismissed it as a whatever project, not really thinking much about it at the time. Fast forward a couple months, and I revisited the idea and realized i could easily make this. So here we are, me making the meter a reality.

The circuit is actually pretty simple. You have the Pro Mini driving the display(this is the main reason why i needed a microcontroller, was to drive the LCD). Then you have an ACS712 passively measuring the current draw. The output is an analog signal sent to the Mini that will then process the input, run a quick calculation on it, and output the watts in real time. This design went thru a couple of different design revisions. The first one included an on-board voltage divider to also get the voltage. This was dropped because this would be tapped directly into my outlet, so it will be nearly constant at 120v. This value would just be a constant in the code. The current revision does not have a divider on board, and that is the design im moving forward with. The rest of this log will outline the layout of the circuit as well as possible future expansions. Come along for the ride!

  • 1 × ACS712-05b Hall-effect current sensing breakout board
  • 1 × Arduino Pro Mini 5v Microcontroller
  • 1 × OSEPP 16x2 LCD Panel For displaying watts in real-time.

  • Current Status, Future, and Revision 2

    Yaroslav Zhilin09/20/2016 at 14:44 0 comments

    This project was kind of on hold for the moment, but with all the sudden love from the community i think it deserves an update.

    I have not yet figured out power. I might devise a way to sip power from the 120v Main, so I dont have to have an extra power supply. Thinking i'll just use a 5v power supply, since it will be pretty easy to make that work.

    REVISION 2

    Revision 2 of Arduino Watts is a thought now. Revision 2 will be a very similar concept and design, but with a more logical layout and design of circuitry. I wasn't extremely happy with the final layout, it became messy quickly once i had to keep adding wires into there. I was still figuring out the LCD and Arduino mini interconnects at the time of the design. I will be uploading the wiring diagram for that here shortly, keep an eye out for that.

    I got a new motherboard for my computer, a pretty snazzy one at that. It has a built-in bluetooth antenna, so i'm thinking i may try to include bluetooth in this revision, or the next one for sure. Obviously i'd get it working with USB first, as a proof of concept. Then i'll implement bluetooth so i dont have *more* wires running around my pc area.

    More updates to come!

  • Powering the Arduino...

    Yaroslav Zhilin07/31/2016 at 18:01 3 comments

    One thing I have not decided on is powering the arduino. I have not gotten so far as to decide on or even figure out how to power it. A couple options would be to power it from the wall, by using a power 5v power supply and sticking it in a project box. Another option is some kind of battery, which woudlnt' make a whole lot of sense. The Third option is power it from USB and plug it into my computer. The only problem i have with that is it becomes dependant on having a USB power supply. I think I may opt for the power supply option, as i could fit one either in the project box or the outlet-in-a-box i have. Decisions, decisions!

  • Day 1-5

    Yaroslav Zhilin07/31/2016 at 17:56 0 comments

    Late to the project logs, so this has to be a combine effort!

    Starting placing and soldering components on the board.

    The general concept is Power is run on the surface, and data is run on the underside. Why i chose this is simply looks. The clean power runs look a lot nicer than the spaghetti mess that will become the underside. The only exception to this is for the ACS712 sensor; I had to solder on header pins through the breadboard, so i decided to run the power under the board for that. The header pins also raise the breakout board slightly, allowing me to run the 5v right under it. This works out for me since the 5v pin is the top most header. The resistors are there for contrast and brightness of the LCD and are the combination i think looks the best. I believe that they are 1k and 470.

    Initial testing after wiring in power only, before i put on(or even owned) the ACS712:

    Nothing too exciting there. I havent' even trimmed off excess wire at this stage yet.

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Discussions

k1hop wrote 09/18/2016 at 19:59 point

Good luck!  I'll be excited to see what kind of results you get.  I had once tried something very similar, but dropped the project in frustration when the WATTS shown by my device didn't make sense, and disagreed with those shown on a Kill-A-Watt unit (which did make sense).  Wasn't sure if it was my sampling, the RMS computation, watts vs. vars, or what.  Never found the source of the discrepancy, but it will be interesting to see what kind of results you get!

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K.C. Lee wrote 09/18/2016 at 20:03 point

Might want to look at this project: http://elm-chan.org/works/heco/report_e.html

for an AC Load Analyzer

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Yaroslav Zhilin wrote 09/19/2016 at 11:28 point

That's kind of where i was. The sampling was being calculated in a weird way. The code i was using was for low voltage (under 5v) so the amps to volts calculation was weird. That put a hold on the project till i can learn more about that. 

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Dustin wrote 08/02/2016 at 06:14 point

Looking good so far my man. LMK right away when you got this working and upload a video if you can. I think the next step would be to figure out what power costs you at the different times of day, month, year, etc, and incorporate real time cost into your meter. Maybe have something scrape the current pricing off the power company website, if they have that option. 

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