/fsk-energymeter

E-Formula electric energy meter for Formula Student Korea

Primary LanguageCOtherNOASSERTION

Formula Student Korea Electric Energy Meter

0. Features

  • Records the following values:
    • HV bus voltage
    • HV bus current
    • LV supply voltage
    • Ambient (CPU) temperature
    • Real-world time of each records
  • 100 Hz data sampling rate
  • Mounted as a USB Mass Storage device
  • Data visualizer available on most platforms

1. Specifications

MIN TYP MAX UNIT
Supply voltage1 6 28 V
Power consumption 0.25 0.5 W
HV bus voltage 0 600 V
HV bus voltage resolution 0.24 V
HV bus current -750 750 A
HV bus current resolution 0.64 A
Operational temperature -10 80 °C
IP rating IP 20
Startup time 570 600 ms
Record interval 10 15 ms
Possible data loss
on power brownout		 0 100 ms

1 When powered by USB, the device can startup with a minimum supply voltage of 4.5 V.

2. Connectors

LV HV
Model T4145415051-001 39291028
Image
Mate T4111402051-000 5557-02
Pinout 1: D-
2: D+
3: 5VOUT1
4: VIN
5: GND		 1: HV+
2: HV-

1 5VOUT is not used by the device. It outputs 5V and can drive current up to 800mA.

Wiring

Caution

Misconnection of the pins may cause permanent damage to the device.

Warning

When powered by USB, 5V rail of the USB must be connected to VIN, not 5VOUT.

3. Usage

There are 2 operation modes in the FSK-EEM device. When the FSK-EEM is in startup, it measures the LV supply voltage and decide the mode to run.

Record mode

If VIN >= 6V during startup, the device enters the record mode.

The device measure HV voltage, HV current, LV voltage and the CPU temperature every 10 ms.

Log files are created for every power cycles and synchronized every 100 ms.
During the file write, measurement may delayed up to 15 ms.

Important

The device performs a zero calibration of the HV voltage and current during the startup sequence.
Make sure that the HV voltage and current are at 0V and 0A until the the startup is complete.

USB mode

If VIN < 6V during startup, the device enters the USB mode.

When plugged in, the FSK-EEM USB Mass Storage will appear on the host PC.
It may took ~20 seconds to be mounted. See Troubleshootings for the details.

The recorded log files are stored in the drive like a standard USB memory stick.

Note

The drive is read-only. You cannot edit or delete the log files in the explorer.

Important

The timestamp part at the beginning of the log file's name is important to calculate the actual timestamp.
Do NOT edit the filename of the *.log file. JSON or CSV files are not affected.

FSK-EEM Viewer

Download the latest FSK-EEM Viewer from the Release or open the online viewer.

Open the record file in the FSK-EEM Viewer to visualize the data or export as a human-readable format.

Device Configuration

Click the Connect button and select the FSK-EEM device to connect.
The device's UID and the current time are displayed on successful connection.

  • Sync RTC button synchronizes the device clock with the host computer.
  • Delete button deletes the all log files stored in the device.
    Unplug and re-connect the device to see the change.

4. DIY

Hardware

Download the latest fsk-energymeter-pcb-<version>.zip from the Release.
The gerbers/ directory includes the gerber, BOM and CPL files for the JLCPCB PCBA(SMT) order.

Tip

Exclude through-hole components (connectors, debug pin header and the hall sensor) from the SMT assembly list. Purchase these parts from the global suppliers and solder it yourself for cheaper price and reduced setup fee.

Firmware

Download the latest fsk-energymeter-firmware-<version>.zip from the Release and upload the firmware-release.elf to the device with ST-Link.

5. Development

Firmware

Prerequisites

  1. Make sure following executables are in the $PATH.
    • arm-none-eabi-gcc
    • openocd
    • make
  1. Clone repository 
    git clone https://github.com/luftaquila/fsk-energymeter.git --recursive

Build and upload

cd fsk-energymeter/device/firmware
make program  # release build
make debug    # debug build

Viewer

Prerequisites

  1. Node.js >= v20
  2. Rust >= 1.81.0
  3. Clone the repository and install dependencies 
    git clone https://github.com/luftaquila/fsk-energymeter.git --recursive
cd fsk-energymeter/viewer/web
npm install
cd ../native
npm install

Build and run

  • Web

    cd fsk-energymeter/viewer/web
python -m http.server 80  # open http://localhost

  • Native

    cd fsk-energymeter/viewer/native
npm run tauri dev    # run
npm run tauri build  # build executables

6. Troubleshootings

1. FSK-EEM USB Mass Storage takes too long to be mounted on the host

The FSK-EEM uses the STM32F401, which implements a USB Full Speed PHY. It is decades-old technology with a maximum transfer speed of 12 Mbit/s. However, in the real world, the actual speed is around 4 Mbit/s or 0.5 MB/s.

When you plug the FSK-EEM device, the host(PC) will try to load the FAT table of the SDMMC into its memory. The size of the FAT32 FAT table is around 8 MB, so it took ~20 seconds for the FSK-EEM to be successfully mounted on the host computer. This is a hardware limitation in exchange of the lower cost.

The RTC sync or record delete functions will work immediately regardless of this limit.

2. Web Serial API not supported error on the FSK-EEM Viewer.

FSK-EEM Viewer's Device Configuration tab uses the Web Serial API to talk with the device, which has limited support across the platforms and browsers.

On MacOS, the native app uses the Safari for its WebView, which does not supports the API. The web version(URL or html file) of the FSK-EEM Viewer will work on the Chrome browser.

On Android and iOS, the API is not supported from the OS layer. Use the desktop version of the viewer to configure the device.

7. LICENSE

"THE BEERWARE LICENSE" (Revision 42):
LUFT-AQUILA wrote this project. As long as you retain this notice,
you can do whatever you want with this stuff. If we meet someday,
and you think this stuff is worth it, you can buy me a beer in return.