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Topic: Load cell issues (Read 2227 times) previous topic - next topic

Having Issues with my load cell. This is part of a bigger project but this bit I am stuck on. I am using a kmart cell ( tho I am sure that is not the issue) from a 0 to 5000g scale.// I say its not the issue because the Kmart cells seems to get the resolution it needs with less voltage and a very less amplifier.
When i output the voltage to the ADC on A0, the biggest spread I get is 14. For instance no load is 100, half a kg is 114. I am using a dedicated loadcell amplifier that puts out 4.73v for maximum input.//alsoconfident about my amplifier
Tried mapping the output but still cant get the resolution i need// I want to be at least gram accurate.
MY Question: Hardware issue eg my load cell?
                     Hardware issue eg the ADC on the arduinomega 2560?
                     Software issue eg I have very poor skills (i am basically reading analog input and converting to digital?
were do you think I am going wrong?


Do you have a multimeter to measure the voltages ?
You could measure the voltage at A0 and check if that matches what you are reading in your sketch.

We need to know a lot more.

Can you give a link to your load cell ?
How is it connected ? You could even upload a photo so we can see it.
Can you upload your sketch between code tag ? If you write a post, there are buttons above the input text field. The '#'-button is for the code tags.
Do you use USB to power your Arduino board ? That is okay for now.
Do you use the internal reference ?


How exactly have you connected the amplifier to the load cell and the Arduino? What load cell amplifier are you using?
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

I am at work and cant take a photo
the load cell is from honkong. A voltage regulator and amplifier.

It puts out o to 4.3v, 9 ma current
I am getting the full 4.3v at full excitation (hope thats a word)
I have the output in A0 and i am using the example sketch for reading and printing an analog value
i need to increase the "span" between 0 output and desired output

link to loadcell


Using nine volt battery and unaware of the significance of the internal reference


If the output of the loadcell amplifier is 0 to 4.3V, I assume it is working.
So you only need to read that in a sketch.
Did you also connect the GND of the amplifier to the GND of the Arduino ?

If the value of analogRead() is correct, you can use floating point math to calculate the weigth.
Code: [Select]

// example code, not tested.
float weigth;
int adc_value;

adc_value = analogRead(...);
weight = adc_value /1024 * 5.0 / 4.3 * 5.0;


I just did a simular project are work didnt use arduino but I will let you know what I had a hard time with is how to calibrate it for me I ended up doing it as follows

to zero
if zero button is pressed    zerocalibration = inputpin  //to zero have your scale fully assembled this will start you at 0

scaleoutput = (inputpin - zerocalibration)    //this will go in your loop

to calibrate I had a 1# weight for calibration and used this method
if calibration button is pushed      scaledivide = (scaleouput * 1)  //put the wieght on here

now to get your wieght
weight = scaleoutput / scaledivide

hope this helps and is understandable

Thanks for that
Scale all good now, just a matter of adjusting voltage to the bridge and the gain of the amp.
Next I want to tie the load cell output to the speed of the conveyor feeding it.


are you weighing a package going across a convoyer if so how fast are your packages going across on my project I had to be within .001 pounds (I think thats about .5 grams) accurate and weigh packages coming out of a machine at over 90 pieces per minute if this is what you are doing I can go into detail some of the things that helped me

I would be very interested in that if you would like to share it with me. What i have is edible nuts on a vibrating feed conveyor flowing into a scale/hopper. This drops at 100 grams into a machine making plastic tubes. A bag maker. I need to control the speed/feed ratio to dribble the last 5 grams.
I would have thought that after the initial calibration to zero, the scale would be linear for the rest of the day. I have some commercial equipment and thats my experience with that.
I also assume i will need some sort of PID compensation to get the last drops out
please contact me!


I am not quite picturing how your setup is where is the load cell in this is a bag produced and put on a platform that is being suspended by the load cell how many packages are you producing per minute

for my project in order to get a accurate result I had to average my package while it was on a 1ft square convoyer suspended by the loadcell I put a sensor on the end of the convoyer and while my package is seen by the sensor I took as many samples as I could and divided by how many samples I took

Hard to describe but i will have a go
An 18 inch long conveyor vibrates, transporting nuts, which drop of the end into a small hopper.
when the hopper has 100g in it
the conveyor stops;
then the hopper opens and the nuts fall out ( into a pipe that has a tube of plastic around it, sealed at the bottom. nuts go in, top gets sealed and cut, becoming the next bottom)
repeat 20 times a minute
I have this working, without a variable speed control for conveyor. The problem is the amount of nuts in free-fall when the conveyor stops makes the system very inaccurate.
i want to control the speed of conveyor proportional to the increase in weight, so the last 5 grams travel along very slowly, and i would like to adjust for average error from freefall. I would also like an over weight alarm for when three caramel macadamias stick together and fall over at the 99 grams weight, making the final bag 125 grams.


Hey Guys, Im working on a project measuring the force output form electric outboard motors.
I have the possibility to use an SLS410 load cell, an opamp op90 and an arduino uno.

Is there anyone who has made an code for that allready? Im not the best code writher so I would really appreciate the help!!

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