Help with HX711 load cell

ESPHome
1

Hi, I have got a scale with a Load Cell that I am trying to integrate into esphome.

I have setup the load cell, but am unable to get any readings from it, instead I am just getting a static reading from the HX711, it does not change.

Wiring like this.

LOAD CELL | HX711
RED | E+
BLACK | E -
White | A-
GREEN | A +

[13:31:32][D][hx711:031]: 'HX711 Value': Got value -8388608
[13:31:32][D][sensor:094]: 'HX711 Value': Sending state -8388608.00000 kg with 3 decimals of accuracy

My full code.

esphome:
  name: weigh-test
  friendly_name: weigh-test

esp32:
  board: esp32dev
  framework:
    type: arduino

# Enable logging
logger:

# Enable Home Assistant API
api:
  encryption:
    key: ""

ota:
  - platform: esphome
    password: ""

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

  # Enable fallback hotspot (captive portal) in case wifi connection fails
  ap:
    ssid: "Weigh-Test Fallback Hotspot"
    password: ""

captive_portal:
    
sensor:
  - platform: hx711
    name: "HX711 Value"
    dout_pin: 12
    clk_pin: 13
    gain: 128
    unit_of_measurement: kg
    accuracy_decimals: 3
    update_interval: 5s
#    filters:
#      - calibrate_linear:
#        - -988.04303 -> 0

Any ideas what could be causing this?

Thanks

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2

Nothing pops up. Control your wiring.
Anyway, check the datasheet of your load cell, sometimes they use color coding differently from “standard”.
Also, generally don’t use Gpio12, it’s strapping pin and has internal pulldown.
And lastly, there’s no correct way of using that green module with 3.3V MCU. Supply voltage for excitation should be 5V, but giving that to VCC pin would/could damage Esp. There is module with separate VCC and VDD available.

image
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My green and purple modules worked with Esp32 (3.3V) though.

3

Sorry what?

4

That I don’t see any obvious error…

5

Oh right yea, I just changed to GPIOs 4 and 16 but same issue. The load cell is from this.

https://www.trademe.co.nz/a/marketplace/business-farming-industry/industrial/measuring-scales/listing/5148554077

6

It also has this board inside the unit.

I can’t seem to get any readings from the load cell even with a multimeter.

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7

If you have the wires disconnected, you should be able to measure the resistance between green and white, which should be around 300-1000 ohm. Resistance between black and red should be 10-20% higher than that between green/white.

8

I got this working last night by looking at a different diagram,

I wired it

Red >> HX711 A +
Black >> HX711 E -
White >> HX711 E+
Green >> HX711 A -

But, I am getting fluctuating values when there is no weight applied.

How am I supposed to get accurate readings with fluctuating values. Can I add some filters to try bring the noise down?

  [10:05:49][D][hx711:031]: 'HX711 Value': Got value 26006
  [10:05:49][D][sensor:094]: 'HX711 Value': Sending state 26006.00000 kg with 3 decimals of accuracy
  [10:05:54][D][hx711:031]: 'HX711 Value': Got value 25960
  [10:05:54][D][sensor:094]: 'HX711 Value': Sending state 25960.00000 kg with 3 decimals of accuracy
  [10:05:59][D][hx711:031]: 'HX711 Value': Got value 25965
  [10:05:59][D][sensor:094]: 'HX711 Value': Sending state 25965.00000 kg with 3 decimals of accuracy
  [10:06:04][D][hx711:031]: 'HX711 Value': Got value 25916
  [10:06:04][D][sensor:094]: 'HX711 Value': Sending state 25916.00000 kg with 3 decimals of accuracy
  [10:06:09][D][hx711:031]: 'HX711 Value': Got value 25985
  [10:06:09][D][sensor:094]: 'HX711 Value': Sending state 25985.00000 kg with 3 decimals of accuracy
9

There’ s 0.1% fluctuation on your shot.
I think you could be happy with that and yes you can use several filters to smooth the readings.