Using HX711 with Load Cell, but no weight measurement available

Other Hardware Sensors
1

Hello!

Thanks in advance for any help. I’m trying to put together a little project to measure weight with an Arduino, but I’m running into trouble.

Following various tutorials I’ve found online I think I’ve set things up properly. However, no matter what I do, the HX711 is never ready to provide a weight measurement.

First, I have one question that I can’t find an answer to that would really help me in debugging. If I disconnect the load cell and just leave the E+, E-, A+, A- open, should the hx711 provide a reading on the DOUT pin (switch to LOW)? Or will it always stay high? This would help me determine if the problem is with the hx711 setup or the load cell setup.

Ok, now for my setup. I have connected the DOUT and SCK pins to digital pins 2 and 3 on the arduino. I have connected the VCC pin to the 5v from the arduino, and the gnd pin to ground. I know I have the SCK pin connected properly because if I send the power on signal (keep SCK low), I can measure 4v across the E+ and E- pins. If I send the power off signal (SCK low followed by SCK high), the voltage drops to 0. However, no matter what I do, the DOUT pin is always high (indicating no reading available. I have been using the hx711 library that everyone online uses, but I’ve been doing direct digital write and reads to confirm the above behavior.

I think I have connected the E+, E-, A+, A- to the correct wires on the load cell. I have left the B+, B- disconnected.

If anyone has any ideas, I would really appreciate it.

Thank you!

2

If you have 4volt on E+, then you should have 2volt on A+ and A-

There should be almost 0volt between A+ and A-

Read the "how to post" sticky, so you know what/how to post the information we need.
A picture of the setup is the bare minimum.
Leo..

3

Leo,

Thank you for your help! I did the measurements you suggested, and I did see 2 volts between E+ and A+/A-. I was also able to measure a small voltage between A+ and A- ... this voltage varied as we put weight on the load cell .. so yeh!! The load cell works :slight_smile: ... But still no measurement from the hx711 ...

However, this convinced me that the issue was not the load cell, but rather the hx771. So I pulled out the spare hx711 that I had purchased, and I soldered the required connections on to that one. Once, I put that new one in it worked. So my problem was either that the original hx711 was a dud, or we damaged while soldering on the connectors, etc.

Going back to me first question, I tested the hx711 with no load cell connected, and it does in fact give measurements (all around 0). So in case any one else is searching the forums, the answer is you should always get a measurement back from the DOUT pin as long regardless as whether you have a load cell connected or not.

Thanks again!