I have one of the HX711 ADC devices that I want to use for a weighing application. I've fitted it to a breadboard and used demo firmware to poll the chip for readings. The behaviour is as follows: The ADC uses a PNP transistor to control the voltage that excites the bridge. The Base output from the ADC is right at VSUP, so no voltage goes to the bridge. enter image description here

Has anyone got success? failure? experience? with this device? I'm confused as to whether the communications from the MCU enable the base to move below VSUP allowing the bridge to be excited.

  • \$\begingroup\$ What values of R1 and R2 have you used? It looks like the chip is designed to adjust the voltage at BASE until the voltage read at VFB is equal to the "reference bypass" voltage - 1.25 V. \$\endgroup\$
    – LeoR
    Feb 16, 2015 at 13:02
  • 1
    \$\begingroup\$ It's one of the ebay boards, it looks like they assembled it. I had found some problems with my personal implementation (TX and RX weren't making contact in the breadboard) and the chip seems to require some communication before turning on the voltage adjuster. Now that it's working, the VFB is 1.25 as you mentioned. Thank you. \$\endgroup\$
    – frank b
    Feb 16, 2015 at 14:31

1 Answer 1


I had a problem with wiring (Tx and Rx not making contact), Note- the voltage adjuster doesn't seem to start until communications from the MCU have taken place.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.