3 wire Load cell - Increasing Sensitivity

Using Arduino Sensors
#1

Hey guys,

I just pulled two of these strain gauges from a bathroom scale, which look like this:

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So I used two of these to make a full bridge circuit using this wiring setup and connect it to HX711:

When i press one of the strain gauges, its shows me a positive increase in the load. But the major problem is I have to press the thing very hard to show me a change.

I want to measure very small stuff like in terms of grams. How do I increase the sensitivity of the sensor? Should I make a change in the software or any mistake in my hardware.

Thank you in advance :slight_smile:

#2

What led you to believe the gauges would read differently now than when they were in the bathroom scale? You can use a lever to multiply the force on the gauge.

Paul

#3

No. I actually wanted a small load sensor instead of the large 4 gauge setup to measure items in a bottle or a small jar.

So I wanted to place the items over the strain gauge and measure items.

Essentially I just wanted a small single point load sensor setup to weigh items.

That is why I pulled them out from the bathroom scale.

#4

cyberteen:
I want to measure very small stuff like in terms of grams.

Then you should use a load cell from a scale that is designed to weigh "very small stuff like in terms of grams." Such as one of these:http://www.awscales.com/portable-precision-scales-01-gram/229-amw-100-digital-pocket-scale

#5

or perhaps something like this might work for you:
Square Force-Sensitive Resistor (FSR) [Interlink 406] : ID 1075 : $8.95 : Adafruit Industries, Unique & fun DIY electronics and kits.

Or, look at load cell amplifiers.

Paul

#6

The load cells in diagram#2 are connected wrong.

E+ and E- from ONE cell has to be swapped.

So one outputs a positive going voltage, and the other one outputs a negative going voltage.
Leo..

#7

cyberteen:
I just pulled two of these strain gauges from a bathroom scale

…

I want to measure very small stuff like in terms of grams. How do I increase the sensitivity of the sensor?

You are asking to do eye surgery with a bulldozer.

You can’t. You need the sensor from a small kitchen scale, not a bathroom scale.

#8

Thanks for the replies guys! As pointed out, I was using a load cell with excess capacity to weigh smaller items.

I will also try out the lever setup.

Thanks again

#9