Hey guys, I'm here to confess that I did it again... don't know actually if it is the new level of addiction but anyway here what I built as a my very first ESP32 project.

I never started any ESP32 project until today. The reason is that I never found a real use case that attracted me but the waiting is over and here we are with a really useful (😅) nappy counter. As usual, my sarcarsm is embedded in this content since any person can live without a nappy counter but no home-assistant-addicted guy can live without it once he/she knows he/she can do it.

How many of you have a little dinosaur under the roof and wondered how many nuppies your are gonna use in a day/week/year or when it was the last time you changed that dinousaur ?

Idea

The very first dummy (and simplest) idea was to add a wireless button (like any mqtt button)

to be clicked every time the little dinosaur change happen but it raised immediately 2 problems:

1. While changing any little dinosaur, it's literally impossible to remember to click also that smart button so ending with not so updated data.
2. Second and most importantly, it was so simple for an home-assistant-addicted guy 😆

Said that, I decided to move forward with the second idea instead which was to detect somehow the new nappy inside the bin automatically. Even if a computer vision approach could had been interesting, I didn't put the bar so high and decided to go with building a custom scale to weight the nappy bin and detect the weight change over the time; each weight variation would have mean a new nappy.

Ali Cart

As all the home assistant stories, even that one starts on Aliexpress app searching for the best discount to save at least a couple of cents.

I already had a breadboard and few cables so I just needed a load cell for the bin weight, the tft display to show the weight (not strictly necessary) and the esp32 as well.

Grand Total --> € 8,77

Execution

While the dinosour was sleeping I was able to take some waste wood that I had in my cellar, I know that at some point it could have been useful (wife is not usually with me on that).

For the basement I used a ticker panel compared to the top where the bin is then located for obvious reasons.

In order to put the load cell in the proper way, I had to add few shims within the base and the load cell itself.

I started using some bolts but it was not stable at all.

I had so to switch to a v2 version, more stable of course. I basically replaced the bolts with some alluminium scrap, always found in my cellar 😄

In that way the load cell was still working but the oscillation was near to zero, now.

In both cases I had to calibrate again the load cell sensor using a well known (e.g. a bottle of water of 1kg) weight.

EspHome at rescue!

Again, it was the first time for me on a ESPHome project so sorry if I'm not using all the smartest way but I found that procedure pretty easy and straightfrward.

Recipe

1. First, I connected just the esp32 to my laptop using usb-c port and have it connected through https://web.esphome.io/
2. Once connected I just
   1. Init/flash the ESPHome firmware in my esp32 board
   2. connect my esp32 to my local network (where even the HA system lives)
3. That's all from my laptop, from now on I did all the rest directly on my HA installation
4. Install ESPHome plugin and let him to autodiscover your device in your network

5. and from now on I just had to click on "EDIT" to customize the esphome behavior like below and install it. That's almost it.

esphome:
  name: esphome-web-68b440
  friendly_name: ESPHome Web 68b440 - load cell
  min_version: 2025.11.0
  name_add_mac_suffix: false

time:
  - platform: homeassistant
    id: homeassistant_time
    
esp32:
  variant: esp32
  framework:
    type: esp-idf

logger:

api:

ota:
  - platform: esphome

wifi:
  ssid: !secret wifi_ssid
  password: !secret wifi_password

captive_portal:

web_server:
  port: 80

spi:
  clk_pin: GPIO14
  mosi_pin: GPIO13
  interface: hardware

globals:
  - id: last_weight
    type: float
    restore_value: no
    initial_value: '0'

  - id: nappy_counter
    type: int
    restore_value: yes
    initial_value: '0'

  - id: last_nappy_timestamp
    type: long
    restore_value: yes
    initial_value: '0'
# HX711 sensor
sensor:
  - platform: hx711
    name: "Bin Weight"
    id: bin_weight
    dout_pin: GPIO19
    clk_pin: GPIO18
    gain: 128
    update_interval: 15s

    filters:
      - median:
          window_size: 7
          send_every: 3
      - calibrate_linear:
          - -618100 -> 0
          - -577500 -> 1000

    on_value:
      then:
        - lambda: |-
            float diff = x - id(last_weight);

            // threshold for new nappy (grams)
            if (diff > 30) {
              id(nappy_counter) += 1;
              id(last_nappy_timestamp) = id(homeassistant_time).now().timestamp;
            }

            id(last_weight) = x;

  - platform: template
    name: "Nappy Counter"
    id: nappy_counter_sensor
    lambda: |-
      return id(nappy_counter);
    update_interval: 10s

  - platform: template
    name: "Last Nappy Change"
    device_class: timestamp
    lambda: |-
      if (id(last_nappy_timestamp) == 0) return {};
      return id(last_nappy_timestamp);
    update_interval: 10s
    
font:
  - file: "gfonts://Roboto"
    id: font_large
    size: 40

display:
  - platform: st7735
    model: "INITR_BLACKTAB"
    cs_pin: GPIO15
    dc_pin: GPIO2
    reset_pin: GPIO4

    device_width: 128
    device_height: 160
    col_start: 0
    row_start: 0

    rotation: 90
    update_interval: 1s

    lambda: |-
      it.fill(Color(0,0,0));

      it.printf(10, 10, id(font_large), Color(0,255,0), "%.0f g", id(bin_weight).state);

      it.printf(10, 70, id(font_large), Color(255,255,255), "%d", id(nappy_counter));

6. Last but not least I had to make that device discovered like below

And finally I was able to create my newest useless dashboard 😅

Happy HA addiction.