Hi,
datasheet of HX711 says it goes to power down sleep when CLK pin is HIGH for more than 60us. It this mode it should consume < 1uA but I measured about 22uA by my DMM. I am using the "basic" module:
The 1 uA may be for the chip alone and the rest may be leakage through the external transistor. Just guessing.
I think it is a very good guess! Negligible leakage current into HX711's pin driving the transistor base is amplified by the transistor. When I get home I will try to add a small pull-up resistor to the base if it helps.
So I have tried it and it is wrong. When the chip is in power down mode by driving CLK pin HIGH, BASE pin is actively driven HIGH (as well as DOUT pin) turning off the transistor properly. I think the measured current is really consumed by the HX711 itself: when powered from my laptop's USB 5.2V the consumption is 22uA. With supply 5.0V it drops to 9uA. It is "0"uA with supply voltage 4V.
You could estimate the leakage current through the transistor by measuring the voltage at E+ and then doing the math. Or measure the current between E+ and your load cell, and then do the math to get voltage and then the additional current through the external voltage divider.
Also, not sure the test at 4v is meaningful, since most HX711 breakouts that I've seen are intended to be driven at 5v (even tho' the chip itself can go lower).
I have measured 450 nA after scale.power_down(); for the HX711 and a attached load cell, see Probleme beim power_down() des HX711 unter ArduinoCore für ESP32 - #6 by clemens - Low Power - Hiveeyes
