Making Your Own Crimpdeq

1. Required Materials

   • ESP32-C3-DevKit-RUST-1
     • Other ESP32 devices can be used, but you need to figure out how to charge the battery
   • Battery Holder
   • 18650 Battery
     • Other batteries might also work, as long as they can power the device
   • Crane Scale or Amazon alternative
     • Other crane-scales might also work
   • HX711

2. Disassemble the Crane Scale

   1. Desolder the battery connections.
   2. Desolder the four wires of the load cell (E-, S-, S+ and E+) from the PCB.
   3. Unscrew and remove the PCB along with the display.

3. Soldering Instructions

   1. Modify the HX711 Module:

      1. Update the sample rate: Most HX711 modules come with the RATE pin connected to GND, meaning that they sample at 10 Hz, if you want to sample at 80 Hz:
         1. Break the track of RATE pin.
         2. I did this by scratching the module with a knife.
         3. Verify with a multimeter that GND and the RATE pin are not connected anymore.
         • Make sure that you don't break the next connection.
         3. Solder the RATE to DVDD pin.
         4. Verify with a multimeter.
      2. Optimize the measurements for 3.3V: Most HX711 modules come with a setup for 5V, if you want to optimize the measurements for 3.3V:
         1. Connect, in parallel, a resistor between 20k and 27k to R1. R1 is the highlighted resistor in the image:
         • For more information, see this blogpost.
         • This step is not mandatory, but it improves the measurements.

   2. Connect the Crane Scale to the HX711:

      • Solder the 4 wires of the crane scale to the HX711. Usually the colors are:

      HX711 Pin	Load Cell Pin	Description
      E+	E+ (Red)	Excitation positive (to load cell)
      E-	E- (Black)	Excitation negative (to load cell)
      S+	S+ (Green)	Signal positive (from load cell)
      S-	S- (White)	Signal negative (from load cell)

      • Note that sometimes the S pins are referred as A.

   3. Connect the HX711 to the ESP32-C3-DevKit-RUST-1 devkit:

   HX711 Pin	ESP32-C3 Pin	Description
   VCC	3.3V	Power supply (3.3V)
   GND	GND	Ground
   DT (Data)	GPIO4	Data output from HX711
   SCK (Clock)	GPIO5	Clock signal for communication

   

   4. Verify all the connections with a multimeter.

4. Adapt the Scale Case:

   1. Create space for the USB connector.
      • I did this by placing the devkit, marking the space that I needed with a pen and then, heating a knife and melting the case.
   2. Install the battery holder:
      1. Glue, with some silicone, the battery holder, make sure to leave the lid for the original batteries of the scale open, as there is a hole for which you need to introduce the two wires of the battery holder.
      2. Solder the positive wire (red) of the battery holder to a switch/button, to turn on/off the device, then, solder the other pin of the button/switch to the B+ pin of ESP32-C3-DevKit-RUST-1.
      3. Solder the negative wire (black) of the battery holder to the B- pin of the ESP32-C3-DevKit-RUST-1.
   3. Close the case:
      1. Ensure all components are securely installed before closing the case.

5. Upload the firmware:

   1. Connect your device with a USB-C cable.

   2. Pull the crimpdeq repository:

      git clone https://github.com/crimpdeq/crimpdeq-firmware
      

      If you don't have git installed on your system, you can go to the green Code button and use the "Download ZIP" option.

   3. Upload the firmware to your device:

      1. Download the binary from the desired GitHub release.
      2. Open esp.huhn.me.
      3. Click Connect and select the serial port of your ESP board.
      4. Upload your .bin file(s).
      5. Click Program.

      See this blogpost for more details.

   4. Check if the calibration values work for your scale:

      1. Connect your device with ClimbHarder or Tindeq apps.
      2. Use the "Live View" option.
      3. Measure a known weight and verify that Crimpdeq measures the right value.
         1. If Crimpdeq calibration is off, see the Calibration chapter.