HX711 module VCC and no VDD

Projects General Guidance
1

Hi,

Circuit

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I am trying to build the above circuit powered by battery alone. Sparkfun HX711 is expensive and hence I am using Amazon HX711

HX711 module has Operating Voltage: 2.7V to 5VDC and Operating current: <10 mA

Sparkfun HX711 has VCC and VDD. VCC is the analog voltage to power the load cell. VDD is the digital supply voltage used to set the logic level. In many cases, you can just short VCC and VDD together. If your microcontroller uses 3.3V logic however, you'll want to connect VCC to 5V and VDD to 3.3V.

Amazon HX711 has only VCC and no VDD. Therefore, can I connect LoadCellHX711SF VCC to NodeMCU1 3V3 instead of connecting LoadCellHX711SF VDD to NodeMCU1 3V3?

Thanks and regards,
Rashmi

2

It looks like that Amazon unit is 5V only. You need to have at least 5V on the HX711 module's analog supply so that it can regulate to 4.2V to supply to the load cell.

3

I do not understand. Should I connect VCC to 5V battery and not connect it to nodemcu?

4

It would be better to use a module with the two supplies separated.

If you are stuck with this one then you need to convert the 5V output to 3.3V. The 3.3V input to the 5V module will probably work without conversion.

5

E+ and E- is the excitation voltage (power supply) for the load cell.
On the SparkFun board, VCC and VDD BOTH go to 5V.
HX711_Fritzing.JPG

HX711_Fritzing.JPG

6

JCA34F:
On the SparkFun board, VCC and VDD BOTH go to 5V.

Which is exactly what OP said - and this is indeed what you do when you use a 5V board. Not the NodeMCU which is a 3.3V board.

If you power your NodeMCU at 5V (USB) you can use the VU pin to supply 5V to the HX711 board.

A resistor divider (e.g. 4k7 + 10k) on the HX711 outputs brings down the level enough for the NodeMCU. The 3.3V level of the NodeMCUs outputs is indeed usually enough for a 5V input.