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Filament usage

About

grafana preview

This repo is about generic filament usage by the 3D printer:

  • read current filament weight via tensor beam attached to esp32
  • register esp32 in Home Assistant
  • Home Assistant exposes metrics in Prometheus format
  • metrics are scraped (fetched) by Prometheus instance
  • Grafana uses Prometheus as data source
  • Grafana dashboard uses some basic formulas to convert weight to meters of filament to be used

This allows to estimate how much filament is left and thus what to print without need for a filament change.

Known limitations

  • This can be done without Home Assistant - in that case you would just need to configure esp32 to expose prometheus metrics and then configure prometheus to scrape the device directly - do whatever you like.
  • I was not doing load cell calibration in esphome, I will do it in grafana dashboard

Hardware Bill of Materials

  • esp32 device such as nodemcu dev kit which as usb converter so you can attach it to the computer over USB

  • usb cable - depends on your hardware - so it may be USB-A to Micro-USB or USB-C to USB-C and so on...

  • power supply for esp32 - older phone charger over micro-usb or usb-c should be enough

  • load cell 5kg - notice that max weight is important and choose such load cell that it can sustain expected weight range, I suggest 5kg, otherwise anything more can be less precise or reaching lower read limit, and and anything less will reach the upper reading limits

  • load cell amplifier - with hx711 sensor

  • some metal/plastic/wooden planks + screws + washers

  • at least 4 dupont cables - between load cell amplifier and esp32

  • at least 2 example weights with precise values to calibrate the load cell, such as 0.5kg and 1kg - or a measuring cup from the kitchen that you can fill in with the water to reach given weight

  • soldering iron to connect load cell and gold pins to load cell amplifier

  • some device to run esphome dashboard / HomeAssistant / Prometheus / Grafana Raspberry Pi with at least 2GB of ram should be sufficient

Software Bill of Materials

  • WiFi network to attach esp32 device to it
  • existing HomeAssistant installation accessible over WiFi, I assume it already works

Hardware assembly

First I suggest to read here

  • create a 'weight setup', which means one plank attached to the bottom of the load cell, and the other plank is attached to the top of the load cell, all using generic nuts/bolts/washers

  • solder cables from load cell to load cell amplifier

  • solder gold pins to the load cell amplifier

  • attach dupont cables between load cell amplifier and esp32

Software

Esp32 device

  • install esphome on the device - I suggest via web-browser via USB cable

  • extend device config with hx711 params, below code fragment assumes that GPIO18 and GPIO19 are used to connect the device to esp32:

    sensor:
  - platform: hx711
    name: "HX711 Value"
    dout_pin: GPIO19
    clk_pin: GPIO18
    gain: 128
    update_interval: 10s

    You can see example config for the device here

  • in esphome dashboard find your device configuration and add the code above to the device, then flash esphome firmware, after a moment device should be back online

  • see if the tensor beam reacts to the changes - you just should be able to see raw values in esphome dashboard logs

  • import esp32 device to Home Assistant (usually you should get a notification about auto-discovery)

  • ensure tensor beam is not under load - write down the current raw value as LOAD_ZERO

  • place example known weight on the tensor beam, write down the raw value as LOAD_KNOWN, remove the weight, this will come in handy later on

HomeAssistant

  • prepare HomeAssistant to expose metrics - see here, in HomeAssistant you need just prometheus: line section in the config and restart HomeAssistant

Prometheus

  • configure Prometheus to scrape the metrics of the HomeAssistant - you may need to add basic auth via API key, below is example config fragment to use to copy/paste to Prometheus config:

      - authorization:
      credentials: redacted....put.your.own.credentials.here
    job_name: home-assistant
    metrics_path: /api/prometheus
    scrape_interval: 15s
    scrape_timeout: 10s
    static_configs:
    - targets:
      - home-assistant-host--or-ip-address:8123

    full details here,

  • check prometheus web ui if HomeAssitant target is healthy and thus it scrapes metrics correctly.

Grafana

Install dashboard

  • use Grafana and connect it to Prometheus as data source, ensure you can find hx711 metrics in the grafana - they should be under something like homeassistant_sensor_state{entity="sensor.esp32_devkit_v4_9e8360_hx711_value"}
  • add dashboard to the Grafana, it will be named Tensor Beam

Calculate load cell parameters

We can use y=ax+b equation to get the given weight from a load cell.

The y is the raw value which is reported by load cell. The x is the weight we place on the load cell.

We measured two weights before, and we know their values:

  • LOAD_ZERO when nothing was placed (x=0)
  • LOAD_KNOWN when we placed given known weight (for example 1kg)

we can calculate a and b - those will be needed below.

  • LOAD_ZERO = ax+b , but we assume x=0, thus b = LOAD_ZERO
  • LOAD_KNOWN = ax+b, and because we know b, we can write LOAD_KNOWN = ax + LOAD_ZERO, so, a = (LOAD_KNOWN - LOAD_ZERO)/x and because we know what weight we placed on the load cell we can replace it as x and will get the value of a

Now we have a and b values.

Configure dashboard values

  • go to the dashboard
  • click cog icon in top right fragment of the dashboard
  • on the left menu select Variables
  • edit Variable a and set it's Value to the a we calculated above, click Update
  • edit Variable b and set it's Value to the b we calculated above, click Update
  • do back and save the dashboard

Using dashboard on daily basis

  • Now when you are on the dashboard you can adjust parameters in the input fields on the top of the dashboard,
  • Adjust those to meet your needs such as spool size, filament diameter and density, on the right I've added some known example values for given spools.
  • Remember to change those values when you place a new spool.