This solution uses a Dr. Wattson energy monitoring board to monitor a tool's power supply and power usage. The tool, or a component connected to the tool, provides a 3.3-5v digital signal indicating when the tool is active. You can configure the solution with upper and lower thresholds for voltage, current and power, and receive alerts when the monitor detects values out of range. The solution also senses vibration using the Notecard's built-in accelerometer, and this too can be used to generate alerts for over vibration.
The solution comprises hardware, firmware, Notehub environment variables and jsonata scripts.
To create a power monitor around the Dr. Wattson energy monitor board you will need:
Male-to-female grounded extension cable or suitable cables to wire an IEC or NEMA AC inlet and outlet to Dr. Wattson. 16 gauge is recommended as the minimum dimension. Please select a suitable wiring gauge for the maximum load required from the equipment being monitored.
Corded female NEMA socket for USB power, 18-gauge diameter minimum, such as a spliced male-to-female 18-gauge extension cable.
2 18-gauge color-coded insulated wires to power the Dr. Wattson board. (This can be taken from the extension cable used to build the USB power outlet.)
Soldering iron (to melt and bridge solder jumpers on the Dr. Wattson board for I2C address configuration)
Wire cutter and stripper
Spade connectors or solder
Crimper to crimp AC wires to spade connectors (if used)
Heat shrink tubing and a source of heat, such as a heat gun
The Dr. Wattson energy monitoring board monitors power by being looped into the mains AC wiring that powers the tool you want to monitor. Additionally, solder jumpers are configured to select the I2C address of the Dr. Wattson board.
The application firmware found under the firmware folder can be built using these development environments:
PlatformIO extension for Visual Studio Code
Arduino extension for Visual Studio Code
We recommend using one of the VS Code extensions, since they are easier to set up and use, and provide a comprehensive development experience. However, if you're familiar with the Arduino IDE, that can be used as well but requires a little more setup.
There is no special setup required for the project beyond what is normally required to configure a PlatformIO project in VSCode. This tutorial explains how to install and use the PlatformIO.
The PlatformIO project is located in the firmware folder, where you'll find platformio.ini that configures the project, including libraries required, location of the sources and compile-time definitions required.
The source code for the Arduino project is under firmware/notepower/ in this repository. We have included the correct configuration in .vscode/arduino.json which selects the Swan board as the build target and configures the required compiler options.
Before building the project, you will need to install the required libraries listed below.
Before compiling and uploading the sketch, be sure to install the STM32Duino board support package. The tutorial Using the Arduino IDE in the Swan documentation shows how to install support for Swan in Arduino IDE and how to compile and upload firmware.
You will also need to install the required libraries, and increase the serial receive buffer size, detailed below.
The Arduino framework by default provides a very small Serial input buffer, which means that if a developer wishes to use the serial port in a way that receives a large volume of data quickly, the data will be truncated and missed.
The workaround, which is required by this sketch, is to add a compiler flag that increases the serial buffer size.
Close the Arduino IDE if it is currently open.
Find the location of the platform.txt file for the board that you are building for. When building for Swan, which is an STM32 board supported by STM32Duino, this is located at
Create a file in that directory called platform.local.txt containing this line:
There are two ways to configure the ProductUID created in the Notehub setup above - either using the in-browser terminal to send a request to the Notecard, or by editing the firmware source code. For more details on what the ProductUID is and how it set it please see this guide.
The primary electrical connections are based around the Dr. Wattson monitoring board. The board's line input is plugged into your AC outlet and the tool is plugged into the board's AC load outlet. A USB power brick is also connected to the 18-guage USB power outlet that you added to the board.
During development and testing, you will typically power the Notecarrier and Swan via USB cables from your computer. When the application is deployed, you will use the USB power adapter plugged into monitor's USB power outlet.
To ensure the setup is working as expected, it's a good idea to test the application before deploying it in a real-world setting.
For testing, you will need a suitable tool to monitor and optionally measure the vibration of . We used a desk fan with off, low, medium and high settings that allows power consumption to be regulated with increasing vibration at higher speeds.
You configure the app using a number of environment variables. Configuration includes how often regular power monitoring events are sent, and the thresholds for anomalous vibration and electrical behavior that trigger an alert.
Alerts are sent when the current, voltage, power or vibration is outside the configured range or when a change greater than a given percent is detected.
These are the environment variables that you can configure according your use case:
heartbeat_mins: how many minutes between sending power notifications. The default is0 which means do not send regular power monitoring events, only send alerts. Sending a heartbeat event periodically provides regular monitoring of the source supply and equipment supply.
alert_under_voltage, alert_over_voltage: send an alert when the measured voltage is above or below the specified values in Volts. The default setting is 0 where no alerts are sent regardless of the measured voltage.
alert_change_voltage_percent: send an alert when the voltage changes by more than the given percent. The default value is 15, which sends an alert when a 15% or greater change is detected. Set to 0 to disable percentage change alerts.
alert_under_current_amps, alert_over_current_amps: send an alert when the measured current is above or below the specified values in Amps. The default setting is 0 where no alerts are sent regardless of the measured current.
alert_change_current_percent: send an alert when the measured current changes by more than the given percent. The default value is 15, which sends an alert when a 15% or greater change is detected. Set to 0 to disable percentage change alerts.
alert_under_power_watts, alert_over_power_watts: send an alert when the measured power is above or below the specified values in Watts. The default setting is 0 where no alerts are sent regardless of the measured power.
alert_change_power_percent: send an alert when the measured power changes by more than the given percent. The default value is 15, which sends an alert when a 15% or greater change is detected. Set to 0 to disable percentage change alerts.
These environment variables are set in Notehub, either per-device, per-fleet or per-project. For example, if you want all monitored equipment to send power monitoring events every 5 minutes, you would set heartbeat_mins to 5 at the project level in Notehub.
The Notecard accelerometer is used to sense vibration. Tool usage can be inferred from the measured vibration by setting environment variables that define the expected vibration characteristics. These variables define thresholds of vibration for when the tool is inactive and active. For details on how to determine the appropriate vibration thresholds, see Determining Vibration Thresholds below.
These environment variables define the vibration thresholds:
alert_off_vibration: the maximum vibration expected when the tool is inactive. Minimum value is 0, which is also the default. Must be less than or equal to alert_under_vibration.
alert_under_vibration: the minimum vibration expected when the tool is active. Must be equal or greater than alert_off_vibration and less than alert_over_vibration. The default value is 0.
alert_over_vibration: the maximum vibration expected when the tool is active. Must be greater than alert_under_vibration.
With these variables defined, the measured vibration is classified into into one these vibration categories:
none: when vibration is less than or equal to alert_off_vibration
low: when vibration is between alert_off_vibration and alert_under_vibration
normal: when vibration is between alert_under_vibration and alert_over_vibration
high: when vibration is greater than alert_over_vibration
The vibration property is added to power events with the values none, low, normal, high corresponding to the vibration categories above. The raw vibration value is also included, as vibration_raw: 123.45.
When alert_off_vibration, alert_under_vibration and alert_over_vibration are all undefined or 0, vibration is not sensed. Otherwise, vibration is sensed and vibration data is included with power monitoring events and alerts.
An alert is sent when the vibration is classified as low or high, which indicates vibration is outside of expected operating parameters. When a vibration alert is triggered, the alert property includes the word vibration, indicating the alert happened because of too little or too much vibration.
Four digital inputs act as activity sensors. Each Dr. Wattson instance is associated with a GPIO pin that indicates activity of the tool monitored by that instance:
instance 1: pin D10, 3.3v tolerant
instance 2: pin D11, 5v tolerant
instance 3: pin D12, 5v tolerant
instance 4: pin D13, 3.3v tolerant
In this solution, we configured our monitor with the I2C address 0x75 which corresponds to instance 2. This is why D11 was labelled as the activity line for the tool in the electrical schematic above. If your monitor board is configured to a different address, then use the corresponding pin as described above.
To monitor a given activity line, you set the environment variable inputX=true to enable sensing on that line, where X is the instance number. For example input2=true sets D11 as a GPIO input, and the logic level sensed on that pin is reported in monitoring events (from instance 2) via the active property.
In addition to monitoring the activity level of the tool with (inputX=true), you can configure the app to add additional behaviors that correlate the measured power with activity:
alert_power_activity_[1-4]=load: Correlates alerts for a given instance with the state of the instance's activity pin. With the load setting, the line power is checked against the activity state. When the pin is low, which indicates the tool is not active, line current and power are expected to be close to zero and voltage is expected to be within the over/under voltage configuration, since the load is continuously powered, but does not consume power when inactive. When the activity pin is high, line voltage, current and power are expected to be within the voltage, current and power ranges configured.
In this solution, the tool is monitored by instance 2, using the corresponding activity line (D11) to indicate when the tool is active, and so alert_power_activity_2=load is the setting used.
For a tool that is on continuously, the vibration configuration described above is sufficient to monitor vibration and send alerts for low or high vibration.
However, when monitoring a tool that is only active some of the time, it makes little sense to report a vibration alert due to low vibration when the tool is inactive. The alert_vibration_activity_line environment variable can be used to correlate the activity of the tool with the measured vibration:
alert_vibration_activity_line 1-4: indicates which activity line shows the activity of the tool. When this environment variable is defined, it correlates vibration alerts based on the activity of the tool and the vibration sensed:
When the tool is inactive, a vibration alert is sent when the vibration is not none.
When the tool is active, a vibration alert is sent when the vibration is not normal.
The alert is triggered on the instance specified in alert_vibration_activity_line. When alert_vibration_activity_line is 0 or undefined, the vibration data and alerts are present on all lines.
Vibration alerts are suppressed for the startup and shutdown period given for the corresponding line.
These variables describe how long it takes for the tool to startup or shutdown, or equivalently, for the electrical load and vibration to reach steady state. Power and vibration alerts related to activity are suppressed during the startup and shutdown period to avoid false alerts.
power_activity_startup_secs_[1-4]: the duration, in seconds, for how long it takes the power level to stabilize on becoming active. Alerts are suppressed for this period when a line goes from inactive to active. The default value is 0.
power_activity_shutdown_secs_[1-4]: the duration, in seconds, for how long it takes for the power level to stabilize on becoming inactive. Alerts are suppressed for this period when a line goes from active to inactive. The default value is 0.
The raw vibration measurement is used to determine the vibration level is derived from the movements of the accelerometer. The value is somewhat arbitrary and not calibrated, although it is consistent.
The simplest way to find out the values for the vibration variables is to measure the vibration reported when the tool is off and during normal use. Here's an outline of the process:
Start with none of the vibration environment variables defined, and the tool inactive.
Set heartbeat_mins to 1 to enable more frequent monitoring.
Enable vibration sensing by setting alert_under_vibration to 1.
With the tool still inactive, inspect the events in Notehub sent to power.qo, in particular the vibration_raw value.
Make a note of the highest reported vibration_raw value. This will serve as a guide for setting the alert_off_vibration variable.
Switch on the tool, and when fully started, continue monitoring the events for a number of minutes, using the tool in its normal modes of operation.
Make a note of the highest and lowest vibration_raw values reported. These will serve as a guide for setting the alert_under_vibration and alert_over_vibration variables.
Note: In order to accurately sense vibration, the Notecarrier must be secured to the tool and must be level with the ground. This is so the acceleration due to gravity can be accounted for when determining vibration from the accelerometer data.
Using the vibration values collected above, set the alert_off_vibration, alert_under_vibration and alert_over_vibration values. Again, with the tool inactive, and in normal use, inspect the vibration property to ensure it is none when the tool is not in use, and normal when it is in use.
Should you see any vibration measurements of low or high, then adjust the vibration thresholds accordingly. You may need to set power_activity_startup_secs_X and power_activity_shutdown_secs_X variables to avoid spurious low or high values as the tool is starting up or shutting down.
A power monitoring event is sent every heartbeat_mins minutes or when an alert is sent.
Events are sent to the notefile power.qo, and have this structure in the event body:
"instance": 1, // which of the connected Dr. Wattson monitors reported the event"current": 0.2846, // Line RMS current (A)"frequency": 59.8125, // Line AC frequency (Hz)"power": 7.9, // Line Power (Watts)"voltage": 118.6// Line RMS voltage (V)}
Regular monitoring events are not immediately synched to Notehub, but are sent once per hour, as given by the outbound property in the hub.set request. You can change this behavior by setting the preprocessor symbol SYNC_POWER_MONITORING_NOTES in app.h.
The event body also includes these named values:
reactivePower: The measured reactive power (in VAR).
apparentPower: The measured apparent power (in VA).
powerFactor: The power factor - active power divided by apparent power.
active: Set to True to indicate the corresponding instance pin is active.
When the device detects an alert condition, such as over or under voltage, current or power, or detects a change in these greater than the configured percentage, an alert event is sent immediately to Notehub. An alert event has the same properties as a power monitoring event, with the additional property alert that lists the comma-separated reasons for the alert. Depending upon the cause of the alert, you may see one or more of these values present:
undervoltage, overvoltage: the measured RMS voltage is not within the bounds set by the environment variables alert_under_voltage and alert_over_voltage.
voltage: the measured voltage changed by more than the percent specified in the environment variable alert_change_voltage_percent.
undercurrent, overcurrent: the measured RMS current is not within the bounds set by the environment variables alert_under_current_amps, alert_over_current_amps.
current: the measured current changed by more than the percent specified in the environment variable alert_change_current_percent.
underpower, overpower: the measured active power is not within the bounds set by the environment variables alert_under_power_watts and alert_over_power_watts.
power: the measured active power changed by more than the percent specified in the environment variable alert_change_power_percent.
Now that we have power monitoring events and alerts available, routing them from Notehub is our next step.
Notehub supports forwarding data to a wide range of API endpoints by using the Route feature. This can be used to forward your power monitoring data to external dashboards and alerts to a realtime notification service. Here, we will use Twilio SMS API to send a notification of an alert to a phone number.
Fill out the required fields for the Twilio SMS route, including "from" and "to" phone numbers, where "from" is your virtual Twilio number, and "to" is the number of the phone that receives the alerts. We will not be using placeholders for these numbers, but will use a placeholder for the message, so set the message field to [.body.customMessage].
Under "Notefiles", choose "Selected Notefiles", and check power.qo from "Include These Notefiles".
Under "Data", select "JSONata Expression" and copy and paste the contents of jsonata/route.jsonata into the text field "Insert your JSONata expression here".
Power alert from <serial-number> tool active: yes: overcurrent,power. 120V, 25A, 3000W. vib.: normal,123.
These are the parts of the message:
The first part of the message indicates which device the alert pertains to by its serial number, here <serial-number>.
The activity state comes next, indicating whether the tool is in use or not.
The alerts are next. Here, "overcurrent" and "power" alerts indicate that the measured current was higher than the alert_over_current_amps environment variable, and that power changed by more than alert_change_power_percent.
After that we have the power information, showing the measured voltage, current and power at the time of the alert.