This is just a small project of mine designed to run on an ESP32. It will monitor the current flow over time and display a graph on its web interface.
Its preliminary purpose is to be used in electrolysis to count the number of electrons having passed through the medium. (Unit is Moles of Electrons)
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- This will have to be installed for successful compilation. (e.g. as ZIP in the Arduino IDE)
This software was tested on an ESP32-WROOM-32.
Required Modules:
- A current sensor based on the ACS712-chip. (Or similar)
- The sensor must be bidirectional and have its zero-point at half of VCC.
- A SPI SD-Card module such as the HW-125.
SPI Pinout of the ESP32:
| SPI PIN | ESP32 PIN |
|---|---|
| MOSI | GPIO 23 |
| MISO | GPIO 19 |
| SCK/CLK | GPIO 18 |
| CS/SS | GPIO 5 was used |
Note: In my experience the HW-125 has to be powered by 5V in order to properly work.
Current Sensor Pin: GPIO35
The contents of the SdCard folder have to be at the root directory of the inserted sdcard.
After flashing your ESP32 it should be ready.
Serial communication happens at 115200 baud.
Line terminator is just a newline character \n.
The first thing necessary is to setup wifi using the wifi command:
wifi <SSID> <Password>
(Also printable from the ESP32 using the command help)
| Command | Action |
|---|---|
| help | Displays this help |
| wifi <SSID> <pwd> | Sets WIFI SSID and password |
| printwifi | Display Wifi settings |
| wifistatus | Display Wifi status |
| setmes <interval> | Set Graph measurement interval (in seconds) |
| getmes | Display Graph measurement interval |
| setoff <voltage> | Set current sensor output offset |
| setmul <factor> | Set current sensor output coefficient |
| getcalib | Display current sensor calibration values (offset and coefficient) |
| startcalib1 <count> <aref> | Calibrate Offset (aref is applied current) |
| startcalib2 <count> <aref> | Calibrate Coefficient (aref is applied current) |
Use an external power supply which can be current limited. Supply a known amount of current through the current sensor.
Then use the startcalib commands to calibrate. Generally each of them only has to be performed once.
For example:
startcalib1 100 0
This will calibrate the offset when no current is applied. It will take record of 100 measurements and average them out. Afterwards a fitting offset will be calculated to bring the measured values closer the the real current that has been flowing (in this case 0).
startcalib2 100 5
This will find the correct multiplier so that the read value becomes the applied current (in this case 5 amps). Before the calibration has not finished do not change the applied current.
Start-Page
Graph of a run
