The Ultimate Arduino Power Monitor

PowMeter was designed specifically to monitor power consumption of projects that use an Arduino Nano. Here’s what sets it apart:

Monitor both your Arduino’s power inputs.

Unlike normal USB power monitoring dongles, PowMeter can simultaneously monitor the power supplied to your Arduino both over USB and the Arduino’s VIN pin.

Display real-time power usage.

PowMeter has an onboard OLED screen for displaying real-time power usage over USB or VIN or both. This makes it a quick and noninvasive way to see what’s going on with your project.

Trigger events based on power usage.

PowMeter is versatile enough to serve as a power supervisor that lets your program know when the voltage and/or current are outside of nominal ranges you define.

Add unobtrusive power monitoring to any project.

PowMeter fits under the already very tiny Nano board, adding only ten grams of weight and 26 mm of length where the display peeks out. This makes PowMeter ideal for fitting into tight spaces.

Features & Specifications

• USB Power Monitoring
  • Range: 0–500 mA (constant), 0-24 V
  • Resolution: 0.025 mA, 10 mV
  • Accuracy: ±1% current, ±1% voltage
• VIN Power Monitoring
  • Range: 0–6 A (constant), max 8 A (spike), 0-24 V
  • Resolution: 0.25 mA, 10 mV
  • Accuracy: ±1% current, ±1% voltage
• OLED Display
  • Display voltage and current for USB and/or VIN
  • Room for three to four digits
  • Display available for use by your application
• I2C Interface
  • Configure shield
  • Query measurement values
• Open Source (to be released when shipping begins)
  • firmware
  • hardware
  • documentation
• Dimensions
  • Size: 69 mm x 18.2 mm x 18.5 mm
  • Weight: 10 grams
• Power
  • USB connector: mini Type-B
  • Current draw: ~10 mA

¹ To power the USB rail from an auxiliary power source.
² VIN monitoring can include auxiliary peripheral power consumption connected to the added VAUX pin.
³ To monitor VIN power source connected to the added VIN MON pin.

High side or low side measurement: when used as a Nano Shield, measurement is on the high side.

High resolution on the USB channel

By design, USB is a low power source. It is limited to 500 mA in regular Arduino applications. PowMeter uses a high performance current sense resistor of 100 mOhm in combination with the INA226 to get a resolution of only 0.025 mA on this channel. It could also be used to monitor any other power source up to 24 V with high resolution.

High current on the VIN channel

On the other hand, the VIN power source is normally used for power demanding applications. Often a 12 V source will power the peripherals (motors, etc.). On this channel a high performance, 10 mOhm current sense resistor allows measurement of currents up to 8 amps with a resolution of 0.25 mA.

PowMeter is designed for hobbyists, students, and professionals

• Developers working on projects that are weight sensitive, e.g., solar airplanes, will appreciate that PowMeter provides high resolution power consumption data while only weighing ten grams.
• STEM teachers often find that using multimeters in the classroom can be confusing and challenging for beginning students. PowMeter is a "plug and play" solution to their issue.
• Enthusiastic newcomers to the world of Arduino hardware development will appreciate how easy it is to use PowMeter.
• Developers who need to add compact, lightweight, accurate power monitoring to their project can incorporate PowMeter into their designs, freeing them from having to develop their own power monitoring circuits. Instead, they can focus on what makes their project unique and important.
• Hardware developers working on space-constrained projects will appreciate the small footprint of PowMeter, allowing them to add sophisticated power monitoring in just a small space. PowMeter's output options make it easy to incorporate it into existing designs.
• Arduino circuit designers can use PowMeter "on the fly" to get power consumption data from breadboarded prototypes.

Display

Four display layouts: both, only USB, only VIN and Alert. Power source voltage (in Volts) is displayed above current (in milliamperes).

Alerts displays the alert source ("USB V", "USB C", "VIN V", "VIN C") and the measured value that is outside the programmed boundaries.

Underneath picture shows the monitoring of both USB power and peripherals. USB voltage is 5.10 Volts and USB consumption is 4.11 mA. VIN MON is connected to a 12 V power source and the peripherals are connected to VAUX. They are drawing 1157 mA (and pulling down the voltage to 11.8 V).

Comparisons

¹120 ms, 250 ms, 500 ms, 1 s, 2 s, 4 s, 8 s

Program and Monitor Simultaneously

A special data cable is included in the package. It has:

• one regular USB mini B plug to power the PowMeter shield
• one data only USB mini B plug to program your Nano host board

This will allow you to program your board and monitor its power consumption at the same time. It can also serve anytime you would like to program an Arduino board but power it from a source other than USB.

Manufacturing Plan

PCBs will be high quality (2 oz copper), fabricated by one of the specialized Chinese companies everyone knows about.

Sourcing will be from major distributors like Digi-key and also other distributors I already ordered from for specific parts like the OLED I2C display module.

In the context of this prototyping project, depending on the number of backers I would either:

1. Assemble, program and inspect the boards myself.
2. Assemble partly with an assembly company and complete the programming and inspection myself.

There are a couple of options for assembly both in China, Spain and France.

Shipping & Fulfillment

Crowd Supply will handle all delivery except for the European Union. I will ship to all EU destinations. USA orders will be free of charge. All international (non-US) will be charged $7.

More details are provided on this useful page about ordering, paying, and shipping.

Risks & Challenges

Sourcing components might be problematic.

Lately I have seen a couple of retailers run out of INA stock. Also I got some fake, non-working parts. The issue seems to be resolved as of mid November 2018. This is a classic part so I don’t oversee a long lasting sourcing problem.

The 0.49" OLED I2C module might be difficult to get but there are a couple of retailers proposing it.

I also had problems with some Atmega chip, which were functional but mis-labelled. I will source this part only from a major distributor.

Since I am in France, proposing this shield on Crowd Supply (Portland USA) and sourcing from USA, China and possibly other countries there are shipping costs and delays that might impact the delivery. I focused on a relatively simple project at first for this reason and hope to deliver within a two month period.

Support & Documentation

You will be provided with a GitHub repository containing:

• The open source Arduino compatible firmware
• An Arduino "console" program to send commands from the Nano host board to the Shield
• Programming examples
• A complete user's manual

Example of a console program

If you have a question about ordering, paying, or shipping, please refer to The Crowd Supply Guide.