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Small OLED panel meter

DIY customizable 0.96'' display voltmeter, ammeter combo

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In 2017 I created this custom made panel meter from scratch.
https://hackaday.io/project/27794-build-your-own-panel-meter
Now I wanted to improve this design and thought of coming up with a new version that use the fancy 0.96'' OLED display. This design also has the merit of being smaller and nicer from many other points of view.

After I finished with this project, I begin to feel very nice about it and to really start to enjoy it. I believe it will serve me well in the future and I can only imagine that I am goin to incorporate it into different future creations. 

This time, for this project I decided to do something that might help many beginners out there. That is trying to explain how I created the schematic and my entire thought process that I put behind it. 

I managed to insert everything into a 3D printed case and the newly installed panel meter looks nicely on my power supply. 

The case *.stl files can be downloaded from here: 

https://cults3d.com/en/3d-model/various/case-files-for-the-small-oled-panel-meter-project

Pannel meter OLED version 2021.dch

schematic - to be opened with DipTrace

dch - 226.99 kB - 02/27/2021 at 15:26

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Pannel meter OLED version 2021.dip

Layout - To be opened with DipTrace

dip - 251.74 kB - 02/27/2021 at 15:26

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Pannel meter OLED Marius Taciuc Feb2021.zip

Complete set of gerber files which I used to order the actual PCBs

x-zip-compressed - 23.60 kB - 02/27/2021 at 15:26

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plain - 26.08 kB - 02/27/2021 at 15:26

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  • Warnings and precautions

    Marius Taciuc03/18/2021 at 17:54 0 comments

    This project could present some potential dangers if it is not handled properly. 

    - Short circuits or currents that are higher than 10A on the meter could damage the equipment and/ or generate domestic fires. 

    - Negative voltages on the measuring output of the meter are not allowed. The entire board and all the electronics in it are reverse polarity protected through the D101 diode, but negative voltages on the output might damage the shunt and other components. Please check the maximum ratings chart posted in this project. 

    - This device was designed for the purpose of learning and helping others learn about these things. Do not base industrial processes on it. Do not use this for military, aero-spatial medical or automotive applications. This device was not designed or tested for these purposes.  

    - Do not connect this device at the mains. Do not even begin to imagine trying to measure AC~ 110 -240V with it. It was not designed for this. Failing to comply with this might result in electrocution, death, injuries, shop equipment damage and/or fire. 

    - The designer of this device (AKA me) assumes no responsibility for any inconvenience that might result out of misusing this design. 

  • Inputs, outputs and maximum ratings

    Marius Taciuc03/17/2021 at 14:31 0 comments

    If you watch the video, you will understand that this meter has a jumper trace on the board and this allows it to be connected in two ways. If the jumper is present, the meter will be powered from the measured voltage. This automatically means that it will only measure voltages from 6V to 35V. If the user wants to disconnect the meter power from the measured power, that can be done by removing this link right here:

    You have to simply scrape off this trace or a length of 2mm out of it and interrupt its continuity. You can then solder an input power wire to the input terminal of the D101 diode on the other side of the board. This new wire will be the separate power input for the meter. In this way, the meter will measure voltages from 0 to 35V present on the J300 connector. 

    As for the maximum ratings this meter would be able to measure the followings:

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  • 1
    Ordering PCBs

    I ordered my PCBs from PCBway.com

    If you want to replicate this project, just send them the provided gerber files and they can send you the PCBs through mail anywhere in the world. I've been working with them for a long time now and they proved to be very reliable and trustworthy. 

  • 2
    How to calibrate

    Find this section in the firmware:

    It basically helps if your sw declared values of the components are matching the real values. So aside from the fact that I recommend using 1% components for the voltage divider and the OpAmp resistors, please take the most precise multimeter that you have laying around and measure the actual values of the components. 

    1) Measure and declare the proper value of R303. It must be 10K, but you can declare the actual value here.

    2) Measure and declare the real value of R302.

    3) Measure and declare the input voltage of the MCU. It should be around 3.3, but in reality you could find it to be 3.2 or 3.42. Write down the real value here.

    4) Measure and declare the R316 here. 

    5) Measure and declare the R317 here. 

    6) Finally compare the actual readings of your panel meter with a lab calibrated industrial multimeter. Write down the error. Then you can subtract the error here. Adjusting these constants will translate the measurements in the f(t) axis of the graph.  

  • 3
    How to flash it

    Like most of my MSP430 microcontroller projects, this one flashes in the same manner. Probably the most explicative sheet is the "added firmware" log inside the "Cookie Jar clock of passion" project. 

    https://hackaday.io/project/175830/logs

    I use the MSP430 LaunchPad as you can see in this link. For all of my projects I used IAR Embedded Workbench as the programming environment. 

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