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Episode 483: DIY Miniature Multimeter

 

Breadboarding is often the start of great projects but measuring on Breadboards is often not so great. The standard multimeter leads don't fit into breadboard holes and alligator clips are needed to connect to the circuit. There must be a better way! Clem designs a tiny Multimeter dedicated to be used with a breadboard! Easy to connect, battery powered and it even has a WI-FI so you can view the readings on your phone!

 

Get the PCB here: https://aisler.net/p/BKDRSPYV

Bill of Material:

Product Name Manufacturer Quantity Buy Kit
BAK Rechargeable Battery, 3.7 V, Lithium Polymer, 370 mAh, Connector BAK 1 Buy Now
MIDAS Graphic OLED, 96 x 16 Pixels, White on Black, 3V, I2C, 33mm x 10mm, -40 °C Midas 1 Buy Now
MCM Wire Kit, Jumper, Copper, 0.6 mm Diameter, 350 Piece MCM 1 Buy Now
FTDI Interface Analog Development Board LC234X, USB to UART Bridge FTDI 1 Buy Now
MICROCHIP Battery Charger for 1 Cell of Li-Ion, Li-Pol battery, 6V input, 4.2V / 500mA charge, SOT-23-5 Microchip 1 Buy Now
MICROCHIP Fixed LDO Voltage Regulator, 2.1V to 6V, 210mV Drop, 3.3V/500mA Out, SOT-223-3 Microchip 1 Buy Now
ESP32-S2-WROOM espressif 1 Buy Now
USB Connector, USB Type C, USB 3.1, Receptacle, 24 Ways, Surface Mount, Right Angle Molex 1 Buy Now
INA219 SOIC TI 1 Buy Now
0,1 Ohm current shunt resistor panasonic 1 Buy Now

 

Additional Parts:

 

Product Name
ESP32-S2-WROOM
Attachments:
MiniMultimeter_Resources.zip
element14 presents
DIY Miniature Multimeter

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Anonymous

  • Really impressive! I will spend some time with it when I have a moment to breathe :-)

     

    I would say use the ADC built into the INA219 instead of the less reliable CPU's builtin ADC.

    Other modes I'd add are slow scope, RMS volts/current/power.

  • in reply to aspork42

    Thakns for the feedback!

    Yes there are more usecases but I thought that is too abstract for the general viewer.
    I was thinking about tunring it into some sort of IOT sensor for machinery, that you can deploy on hard to reach points and use the data to predict maintanance/get notified if something goes wrong or just have an easier way to acess readings from there.

     

    the bom is  linked above, in the current version it costs about €40 to build a single one. (mostly down to the lipo and screen)

     

    I think its possible to manufacture these with some reeingineering (at scale , 5000ish pieces) at below €10 each. maybe even €5 if you take advantage of sleepmodes to put down battery requirements.

  • I love it!

    I see two different uses - "local" just as you have noted; and "Remote" where these are small enough to deploy out and about; perhaps around a larger machine like the power supply on a 3D printer.

    In the second use case, the screen could even be dropped off.

    Adding MQTT could also be useful and pretty simple in code. Then you can use all sorts of things like data logging into SQL and using Grafana to chart it out over time.

     

    What do you see as the BOM cost for these; as-built?

     

    ++Using an off-board ADC. Probably would get much more accuracy.

  • in reply to Azy

    thats why it has both

  • in reply to mayermakes

    Using an Android phone as an external screen would be brilliant, particularly for situations like remote measuring where you can't be near the DUT, but I wouldn't want to use a phone as the sole screen for the device. Sometimes I wanna grab a multimeter for a quick measurement, and having to also grab my phone, load the app and wait for that to load would be a real workflow breaker

  • in reply to airbornesurfer

    i never even tried paperclips,

  • in reply to DAB

    thanks, the screen is more intended to complete the mini multimeter apearance, its readable for me but I tend to use the wifi functionality more.

  • Finally! I can measure voltages on my breadboard components without having to use straightened paper clips as probes!

  • Nice build Clem.

     

    The screen is way too small for someone like me, but sending the data to your phone or computer makes up for that problem.

     

    DAB

  • in reply to kmikemoo

    well....

    as stated in the video that section gives me headachse, I tried multiple versions and that yielded the closest to the nomainal value of the resistor Imeasured, but my math could be totally wrong, I derived that section from some adc tutorial, and tried to adapt it.

    so if you have abetter understanding please feel free to improve the code.

    one thing I recently heard a lot is that the esps adc is not reliable so there might be another issue.

     

    on a future version I would likely outsource that to a dedicated adc chipp that feeds data back over i2C