HX711

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mra2ko
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HX711

#1 Post by mra2ko » 08 May 2024, 10:46

Hi, anobody help me with HX711
I make one weight system for bee hive, is working... One load cell with 4 wire, HX711 and WemosD1 - working well.
My buddy want for others hives... I make it the same construction HW/SW version and etc...
But In first is raw value from HX711 WeightChanA: 975880.000 without load and in second is WeightChanA: 8428608.000 is a 10x more and maybe overlimit, why ?
Gain/offset and all around is the same. I change HX711 and D1 and still the same...

Any idea why is 10x more and overlimit ?

Thank

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Ath
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Re: HX711

#2 Post by Ath » 08 May 2024, 11:06

Have you checked your wiring? Don't make that too long, (triple)check the soldering/connections, the sensor-side is really low voltages, so quite sensitive to external influences.
/Ton (PayPal.me)

mra2ko
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Re: HX711

#3 Post by mra2ko » 08 May 2024, 11:22

Ath wrote: 08 May 2024, 11:06 Have you checked your wiring? Don't make that too long, (triple)check the soldering/connections, the sensor-side is really low voltages, so quite sensitive to external influences.
Yes, all is the same. If connect the new sensor to "old" unit with HX711+D1 work well. Problem is new HX711+D1. But i try 10pcs of hx711 and still overlimit

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Ath
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Re: HX711

#4 Post by Ath » 08 May 2024, 11:47

mra2ko wrote: 08 May 2024, 11:22 Problem is new HX711+D1. But i try 10pcs of hx711 and still overlimit
Ok, reduced to a hardware/board issue, that's unfortunate, but not much ESPEasy can do about that :?

Edit:
NB: You always have to calibrate the board and the sensor using real world weights, as there are analog parts involved, that imply a calibration.
/Ton (PayPal.me)

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Re: HX711

#5 Post by TD-er » 08 May 2024, 12:29

The HX711 does use extremely low voltage signals, so it is quite sensitive to noise.
Try eliminating any noise on the power.
e.g. add some 100 nF capacitor close to the power lines of the HX711.

Also make sure there is no strange current flowing so inspect the ground of the connection between the board and the ESP.

Maybe also check to see if there is dirt (or tiny solder balls) between the pins of the HX711.
Lately I have seen several boards bought via Ali which were not cleaned after production and those got lots of those really tiny solder balls still on the board.
Those are indication of old (expired) solder paste, so the solder joints may also be of poor quality.

mra2ko
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Re: HX711

#6 Post by mra2ko » 08 May 2024, 15:48

You mean calibrate from raw value to real units or something else ?
I just compare now raw value bettwen two identical constructions.


Ath wrote: 08 May 2024, 11:47
mra2ko wrote: 08 May 2024, 11:22 Problem is new HX711+D1. But i try 10pcs of hx711 and still overlimit
Ok, reduced to a hardware/board issue, that's unfortunate, but not much ESPEasy can do about that :?

Edit:
NB: You always have to calibrate the board and the sensor using real world weights, as there are analog parts involved, that imply a calibration.

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Ath
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Re: HX711

#7 Post by Ath » 08 May 2024, 17:09

mra2ko wrote: 08 May 2024, 15:48 You mean calibrate from raw value to real units or something else ?
I just compare now raw value bettwen two identical constructions.
Yes, as said, the analog voltages can be very low, so amplification has to be high to get measurable values with enough resolution, so calibration is required to match voltage x with 0 kg, and voltage y with 5 kg (or whatever the weight you expect to be applied max.), assuming that the scale is linear (but that's probably not entirely true).
/Ton (PayPal.me)

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Re: HX711

#8 Post by mra2ko » 08 May 2024, 18:25

Yes, but this is second step. I have problem with raw value before calibration. What is maximum raw value in input (number) and maximum INa voltaeg input ?


Ath wrote: 08 May 2024, 17:09
mra2ko wrote: 08 May 2024, 15:48 You mean calibrate from raw value to real units or something else ?
I just compare now raw value bettwen two identical constructions.
Yes, as said, the analog voltages can be very low, so amplification has to be high to get measurable values with enough resolution, so calibration is required to match voltage x with 0 kg, and voltage y with 5 kg (or whatever the weight you expect to be applied max.), assuming that the scale is linear (but that's probably not entirely true).

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Ath
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Re: HX711

#9 Post by Ath » 08 May 2024, 21:12

Well, the value read from the board is an int32 (32 bit integer), that can hold a max value between -2147483648 and +2147483647, so you're not yet close to that limit.
The value read from this sensor should be seen as a relative value, and as you have proven, is (mostly) related to the board, not so much to the connected load cell.
That explains why it is only really usable when calibrated, the raw value doesn't have an absolute meaning, only relative.

OT: When using the B channel, you'll see different raw values again, as it has a different (lower) resolution from the A channel... (but most users don't use the B channel).
/Ton (PayPal.me)

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Re: HX711

#10 Post by mra2ko » 13 May 2024, 19:42

Maximum voltage on input is 1.098V = 8428608.000 raw value in my HW... Not possible get more near int32... This is the main problem, input is on maximum limit. I test all about the RC filter and other, also power supply direct from baterry (no noise from PSU). I dont know, what is wrong, I am helpless :/

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Re: HX711

#11 Post by TD-er » 13 May 2024, 20:17

Are you 100% sure the pinout on the new boards is the same?
Can you test with 1 strain-loadcell to see if it is acting expected?
I have the feeling the pins might not be connected the same way to the HX711.

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Re: HX711

#12 Post by TD-er » 13 May 2024, 20:30

Just some other idea...
I have not yet seen fake chips of this one, but since every successful chip will appear as fake one if you wait long enough, it is a possibility.

Can you take a close-up of the chip and board of the working one and the not working one?
N.B. also any resistor values if possible/visible.

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Re: HX711

#13 Post by TD-er » 13 May 2024, 20:42

Also found this remark:
There are boards out there without a bottom ground plane, where E- is not connected to ground.
That can be corrected by soldering a wire between E- and gnd of the HX711.
Source: https://forum.arduino.cc/t/random-value ... /1072007/5

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