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Topic: HX711, long wire on which end? (Read 145 times) previous topic - next topic

palloquin

Hi there,

I'm planning something and would like your feedback.

In my (planned) setup I have:


[ arduino (or esp32) ]=========[ HX711 breakout board ]=========[ load cell ]


Between the arduino and the loadcell will be about 1m.

I'm guessing it's best to keep the HX711 board as close to the load cell as possible and have the wire to the arduino be a bit longer.

Do you agree?

Thank you!

MarkT

Long wires should ideally be shielded, you can add some capacitance across the outputs to kill RF pickup, 1nF ceramic ought to do for most purposes.

No, the connection between HX711 and Arduino has to be short, its high speed logic.  The sensor
connection is pretty low impedance and low bandwidth, so its actually going to cope better with
distance.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Wawa

Do you have a HX711 board with two power connections.
One for 5volt analogue and a one for 3.3volt digital.
If not, then you must modify the board for that.
Because the ESP shouldn't take 5volt logic, and the load cell part is unstable below ~4.6volt.
Leo..

palloquin

@mark, Thank you, I'll keep the two close together then and look at some shielded cable for the longer end. I have some cat6 STP lying around. I guess that should do.

@Wawa,  Thank you too! Yes, my HX711 board (sparkfun) has separate inputs. At the moment I have both hooked up to 3.3v and the tests don't (yet) show any instability...  Could that be depending on the type of load cell?

Wawa

Excitation voltage (E+) for the load cell goes through a 4.3volt regulator, controlled by the HX711.
That supply requires more than 4.6volt to do it's thing.

If you power that analogue part of the HX711 from 3.3volt, then you're powering the load cell with a potentially 'dirty' supply.
As a result, weight could fluctuate, depending on the variations of that 3.3volt supply.
Leo..

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