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I have four strain gauges (50kg) with 5 wires each (red, black, white, green, yellow) and want too measure weight of a platform. I assume those should be hooked to hx711 load cell amplifier and esp32 MCU if possible.

I see two problems there:

  1. Strain gauge has recommended excitation voltage 10-15V which is not compatible to hx711 or esp32
  2. I assume I need to hook them to Wheatstone bridge, but single strain gauge is already a Wheatstone bridge. Can't figure out what should be the wiring scheme.

I purchased strain gauges in Aliexpress

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These loadcells already have a wheatstone bridge in it, you only need to wire it up correctly. According to the homepage the wiring is as follows: Red:power + Black:power - Green:signal + White: signal - Maybe the 5th wire isn't used or not important for you.

The exication voltage shouldn't be a problem. Just put the supply voltage of the HX711 to power+ and power-. The signal+ goes to in+ and signal- to in- of your HX711 module. According to its datasheet the HX711 has a serial protocol so you can wire it up ti the SDIO interface of your ESP32. This datasheet has an example C-driver in it.

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The answer to my question is:

  1. like Dennis Ernst wrote excitation voltage isn't a problem. Seem to work fine when powered from HX711

  2. You need to wire all 4 S type strain gauges in parallel and hook them to HX711.

No need for additional strain gauge power. Yellow wire in my case is strain gauge shield

Proved to be working.

IoT Industrial Scale article on Sparkfun site

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