Current Monitoring

DC Current Monitoring by the use of a ESP 32 Thing

Welcome to our BAE 305 Final Project

Built by: Daniel Barton, Juma Baryaa, Noah Cornett, Gina DeGraves, Cory Radcliff, and Julia Wallin

Background

For our initial project we were tasked with installing new transformers to create a power monitoring system for the Solar House. Unfortunately due to a tight budget, the architects could not allot us enough money to order the transformers or other parts we required. See the table below to find the estimated parts we intially needed along with the total cost. bae 305 - parts list pic Since the Solar House monitoring project was not going to work we had to switch focus. In order to keep with our intial focus of monitoring power, we decided to contact Dr. Colliver and ask about transformers to monitor power on a smaller scale. After several weeks of back and forth contact, we determined that this solution would take more time than we had availbile to us. So once again we decided to shift focus. Finally we decided the best move for the project was to focus on a much smaller scale. We chose to monitor power and current going through a DC circuit.

Summary

The purpose of our current monitoring system is to allow a user to insert any type of wire through the sensor and in return get a live current reading. This sytem is useful when wanting to measure current from DC circuit elements. Our simple design only consists of three parts. First, a current transducer that was used to measure current running through differnet elements. Next a Sparkfun Breadboard Power Supply Stick was used to power the sensor. Lastly, a ESP 32 Thing. This was programmed through Arduino to transform the current data onto a monitoring website.

Video

Click here to check out our video!

Materials

Sparkfun ESP 32 Thing
Breadboard
10K Ohm Resistor
HASS (50-600)-S Current Transducer
Various Male-Male Jumper Wires
Battery Pack
Sparkfun Breadboard Power Supply Stick 5V/3.3V
Micro-USB Cable
Arduino Programming Language

Assembly Procedures

First the Sparkfun Battery Pack was connected to the breadboard and the battery pack was connected. After that the current transducer needed to be connected to the breadboard. The spec sheet was located for our specific current transducer and from information provided on that, the correct wiring was determined. The Orange wire was connected to the 5V, the red wire was connected to the ground, and the brown wire(Vout) on the breadboard needed to be connected in series with a 10K Ohm resistor and the ground. The unconnected brown wire was our Vref. The Vref allows you to put your reference voltage anywhere and gives you that voltage. Normally Vref will be 2.5V.

After the current transducer and battery pack was connected, our last step was to get the sensor to send information to the ESP 32 Thing. To connect the ESP 32 Thing to the bread board it only required two additional wires. First we had to connect our wire from ground on the 32 Thing to the ground on the breadboard. After that we had to connect a wire from PIN 36 on the 32 Thing into series with the 10k Ohm resistor and the Vout(Brown wire). The complete setup can be seen in the image below.

After the circuit was setup we needed the ESP 32 Thing to trasmit data onto an online monitoring service. This was accomplished by trasmiting data to a website called ThingSpeak. The live monitoring website we created can be found here.

Schematics

The two images below represent shcematics of the HASS 300-S current transducer used in this project. These schematics where used to detmerine how to wire our sensor. sensor schematic

sensor info The image below shows in detail the ESP 32 Thing. From this we determined which PIN to wire the sensor up to. esp 32 thing schematic

Programming Code

The complete Arduino code for our project can be found here

The code section below reads the input coming from the sensor and calculates the current based on equations within the spec sheet of our specific transducer.

void loop() {
  // read the input on analog pin 0:
  int sensorValue = analogRead(36);
  Serial.print(sensorValue);
  Serial.print("\t");
  // Convert the analog reading 
  // On Uno,Mega,YunArduino:  0 - 1023 maps to 0 - 5 volts
  // On ESP8266:  0 - 1023 maps to 0 - 1 volts
  // On ESP32:  0 - 4095 maps to 0 - 1 volts, but will always return 0 as analogRead() has not been implemented yet
  // On MKR1000,Due: 0 - 4095 maps to 0 - 3.3 volts
  float voltage = sensorValue * ((VOLTAGE_MAX / VOLTAGE_MAXCOUNTS))+0.2;
  float current = (((voltage-2.5)* 300)/.625);
  Serial.print(voltage);
  Serial.print("V\t");
  Serial.println(current);  
  

Test Equipment

Coiled Wire and Motor

Test Procedures

To test the current and voltage monitor a coiled wire connected to a motor was wrapped through the current sensor five times.

Test Results

The results can be seen below. The average current was measured to be roughly 20 A and the voltage was roughly 2.5 V.

bae305 voltage graph 2

bae305 current graph

Discussion

Design Decisions

The circuit was designed very simply so that the current could be monitored from the sensor. Our wiring followed the schematics of the design file of the sensor. For the code, we made sure to be able to read both current and voltage so we could adhere to our project backlog.

Test Results Discussion

The test went to plan and everything worked. Both the current and voltage measured were the expected values.

References

The Current Transducer and spec sheet we used can be found here

The Sparkfun Breadboard can be found here and the Sparkfun ESP 32 Thing along with information and spec sheets can be found here

We monitored the current through the use of a MATLAB application called ThingSpeak. The libraries that we used in order to write the current monitoring code can be found here.