HX711 module VCC and no VDD

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Hi,

 

Circuit

 

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

 

Last Edited: Sat. Dec 7, 2019 - 07:28 PM
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Wrong Community, wrong Forum.  MAybe you should look at what Google has to offer in examples by simply typing HX711 in the search bar

 

I'll move this to general electronics.

 

Jim

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Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Welcome to the Forum.

 

Full disclosure: I've not used this chip.

 

I also can't see the "Circuit" you linked to. 

It would be easier if you embedded the circuit schematic into your post.

(Click on the "mountain range" icon, three to the left of the smilie face icon, to post a jpg image.)

 

The HX711 has THREE (+) power supply pins:

VSup      V supply, input to the on chip voltage regulator, 2.7 - 5.5 V

AVdd      Analog supply V+, 2.6 - 5.5 V

DVdd     Digital supply V+, 2.6 - 5.5 V

 

DVdd need to be the same voltage as the micro the chip is connected to.

If you are powering the micro at 3.3 V then connect DVdd to the same 3.3 V power supply V+ rail.

 

It would appear that the "Generic Amazon HX711" PCB uses only a single V+ pin.

So presumably on the PCB AVdd is directly connected to DVdd, the separate on-chip analog voltage regulator is actually not being used, and its Vsup is also connected to the AVdd and DVdd V+ rails.

The Vfb pin should be connected to Ground.

 

You should be able to follow the traces on your PCB and verify the above connections.

 

The benefit of this is that the connections are simple, there is a single V+ and a single Ground for the board.

 

The down side of that configuration  is that the analog circuitry is subjected to the electrical noise on the digital V+ and Digital Ground power rails.  Running the 24 bit ADCs on 5 V, (i.e. NOT the 3.3 V the micro is running at), might also improved the system's noise performance at small signal levels.  To see that difference one would need a very carefully designed PCB, power supply, and by-pass cap management.

 

So, bottom line, with the board you have, YES, you can connect the PCB's V+ to the same power supply as the micro, (3.3 V).

 

(I think that is what you were asking about.)

 

JC 

 

Edit: Typo

Last Edited: Sat. Dec 7, 2019 - 08:14 PM