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From the minds at http://arduinotronics.blogspot.com/

Important Update!

Since so many people were having problems with the INA125P, we now have a new and improved version that uses the Hx711 24bit ADC amplifier module. http://arduinotronics.blogspot.com/2015/06/arduino-hx711-digital-scale.html


My goal was to create a programmable scale for weighing objects, parts counting, even directing product flow on a conveyor system.

I needed a load cell, a Arduino, and an amplifier.

Step 1: The Load Cell

On this load cell (from a Accuteck  W-8260-86W Postal Scale) the 4 wires coming from the load cell are:

Red: Excitation +
White: Signal +
Green: Signal -
Black: Excitation -

This matches the GSE / NCI / Sensotec wiring scheme.

http://www.controlweigh.com/loadcell_colors.htm
I disconnected the 4 wires from the control board in the scale, so they would be available for the next step.
<p>All the hacks on internet pertaining to load cell recommends use of an amplifier to get the signal readable by any microcontroller like Atmega (arduino). That's fair. But what I always wonder is how does the lcd work without an amplifier? How is that the scale is able to work without that amplifier??!! </p>
<p>I have made same circuit but I am getting a problem in amplifying the voltage. I have tried this with a 3 wired load sensor in which I am keeping 2 resistors on the breadboard and 2 wires (black and white) coming out of load sensor are connected to make a Wheatstone bridge and I am reading the value of voltage between red wire of load sensor and its other end in Wheatstone bridge. Now when I am applying force on load sensor then it's value are changing ( very minute change but still change I have to amplify that). Now my problem is I am able to amplify the value of the voltage but the change is so minute that it's amplification doesn't show up in comparison to the actual voltage. How should I go about it?</p>
<p>I have weight sensor(load cell) 4 wire sensor+hx711 amp,+arduino uno r3, test code what i found at net working fine.</p><p>but how i adding code weight limit alarm led ?</p><p>mean if value = X then ledpin output hight else low. i try many code but no working ?</p><p>full code need be if button1 high ledpin1 high.(run pump) then value == X limit then ledpin2 high else low(alarm stop pump). but i try many time write code and all style not working ,how thats must made ?????? </p>
<p>Hi, sir! I have a project about BMI Machine and I use the load cell as my sensor in weight. I just want to ask if how to call the output of the amplifier so I can manipulate it in the program, and use it in my actuator, which is the servo motor. Thank you so much for the response.</p>
<p>hello sir, I use the weight sensor for my final project. so, I want to ask you some question about weight sensor coding. can I use, the arduino coding in the microcontroller coding? its same or not? or in microcontroller have a other coding to make a programming? that,s all. thank you.</p>
The arduino is a microcontroller, based on the Atmel 328P. If you have a different microcontroller, you will have to modify the code and library appropriately.
Well, I posted all the code that make this project work, so you are free to change the code, but it does require some C programming savvy. I am available for custom programming. Cost would depend on the scope of the changes, but might be as little as $25
<p>Can a load cell be programmed to alert when something weighs less than it did when it was first placed on the sensor?</p>
yes, you can program it to alert on any decision code you write.
<p>Thanks for the quick response. Would there be any instructions that come with the product on how to do this or is it something that only a tech savvy person knows?</p>
<p>Wow, what great information. I am sure the info on your blog will help others,</p><p><a href="http://www.sensomaticloadcell.net/product-category/scale-load-cell/aluminum-small-load-cell/" rel="nofollow">http://www.sensomaticloadcell.net/product-category...</a></p>
<p>I got a Taylor scale (http://www.taylorusa.com/kitchen/food-scales/glass-digital-kitchen-scale.html) and can't seem to find the manufacturer, unless they are the manufacturer in which case they're not listed on the color charts you linked. The labels seem to be misaligned as well. Is there any other way to tell which are signal and excitations?</p>
assume red and black are power and ground, and white and green are signal, if scale reads funny, reverse white and green.
<p>Hello! Can you help me very urgent I need all the code for the operation of this scale var.l&uuml;tf hx711 I am using the Layout in this project? I'm sorry for bad english.</p>
code for the hx711 is at <a href="http://arduinotronics.blogspot.com/2015/06/arduino-hx711-digital-scale.html" rel="nofollow">http://arduinotronics.blogspot.com/2015/06/arduino-hx711-digital-scale.html</a>&nbsp;make sure you download and install the library.
<p>hey i want to know can i use AD620 amplifier instead of this one in the circuit??</p>
The code would be different.
<p>can you help me with the code i am using ad620 amplifier with pic18f452<br>and output after amplifier fluctuate's alot what should i do?<br>and i generate a formula from the practicle values of load (weights) and output voltage but it did not give write answer on proteus :(</p>
<p>There's no ad620, pic18f452 or proteus in this project. I regret that I cannot help you.</p>
im new to arduino.. wat basic launguage to prog arduino for all type of arduino project.? is there possible to create own library.? and wat language to be learn for library code....
arduino code and libraries are most commonly written in C/C++ it's easy to write a library, see <a href="http://arduinotronics.blogspot.com/2014/07/creating-super-simple-library.html" rel="nofollow">http://arduinotronics.blogspot.com/2014/07/creating-super-simple-library.html</a>
<p>Hi, We are creating a PoC with the load sensor attached to the shopping cart to weigh the weight of the items in the shopping cart. Can we use this kind of a scale fixed to the shopping cart. Do you see any issues?</p>
I don't see an issue. If the cart weight is included, subtract that out of your total before displaying.
<p>can this scale be applied to a travelling bag to show its weight?</p>
you can put anything you want on the scale, assuming you pick an appropriate load cell.
<p>This information is quite useful, I truly enjoyed.</p><p>http://www.sensomaticloadcell.net/product-category/double-ended-shear-beam-load-cell-2/</p>
<p>Hi,</p><p>What do you suggest for a good measure with the load cell ? How the load cell should be set respect to the table ? Can you show more picture of the hardware configuration ?</p>
just look inside a postal or bathroom scale, see how they are set up. I reused the existing case.
<p>I have a 100 kg single point shear beam load cell</p><p>Could anyone tell me which amplifier i should use ??</p>
if it's a 4 wire, use the HX711
<p>It's a 5 wire</p><p>Could we use the same for that too??</p>
<p>I've not seen a 5 wire. Do you have a make and model?</p>
<p>In a load cell with five wires, the extra wire is going to be the shield wire. It&rsquo;s usually yellow and connects to the ground terminal with the other wire.</p>
<p>Thank you very much for your valuable feedback.</p>
<p>Hi! I am quite new to arduino and loadcells. I am using a 10lbs (4.5kg) loadcell with arduino and the INA125. I connected it as shown however using a 1k ohm resistance and the amplification is too low and I cannot detect a change with the program. How do I determine the gain I need and thus the resistance required?</p><p>Thanks!</p>
You can get gain information from the data sheet, (6 ohm is a better fit) but I no longer recommend the INA125. The HX711 is much easier to use.
<p>Thanks for the help! I'll try a much lower resistance (after looking at the datasheet I see that 6 ohm would be a much better choice) and I will look into the HX711 as well for future projects! </p>
<p>sorry, data sheet url, http://www.ti.com/lit/ds/symlink/ina125.pdf</p>
<p>In sketches, I usually see the pin inputs. I do not see the pins that the code looks at. Am I missing something?</p>
right in the loop:<br><br>int analogValue = analogRead(0);
<p>hi, I am trying to build a arduino load cell which measures 100kgs. I found this guide very helpful. Can u please assist me in how much resistance and supply from arduino is needed to set the gain which can measure load upto 100kg.</p><p>regards!!</p>
<p>Has anybody gotten this to work with the code provided? I'v tried several times with identical equipment and the readings are garbage even after &quot;calibrating&quot;.</p>
I did. maybe you are having issues with your amplifier. I have a new amplifier coming that is designed for load cells, will be posting another instructable soon.
<p>We tried multiple INA125's and it did not make a difference. Three of them to be exact. The INA was amplifying but not nearly enough to make any sort of difference. We tested using highly precise desktop testing equipment and the when we put over 30lbs on the scale the difference with zero was about 0.000001mV. We were also using a very stable benchtop power supply. When we connect the load cell back to the original scale electronics it works great and is able to measure even 2 grams. </p><p>I honestly don't believe this tutorial works. Maybe if someone is successful and gets accurate results they can post and provide details of their code and setup. </p>
<p>hube268 and I figured out what the issue was and wish to share with everyone else what it was.</p><p>The scale we used had the E+ (red wire) and the E- (black wire) connections reversed on the PCB from the factory.</p><p>If you look carefully at the picture you'll see the E+ wire is directly coupled with the ground (black wire right next to it).</p><p>After discovering this, we switched the black and red wires on our breadboard and it worked as intended.</p>
<p>Awesome!</p>
<p>I got the code from <a href="http://christian.liljedahl.dk/guides/arduino-and-load-cell" rel="nofollow">http://christian.liljedahl.dk/guides/arduino-and-l...</a></p><p>It worked when I first built this project. </p>
<p>Hello Mr.<a href="http://ecx.images-amazon.com/images/I/41W9VpMz8EL._SX425_.jpg" rel="nofollow">sspence</a>, thanks for sharing your instructable helped me much to understand my scale schema. I bought this <a href="http://ecx.images-amazon.com/images/I/41W9VpMz8EL._SX425_.jpg" rel="nofollow">scale </a>with 4 load sensors (see the schema) could you please help me, which cables must be connected with the Arduino? </p>
<p>Hello, thanks for such well written instructions.</p><p>I'm getting analog readings all over the place. Any suggestion how I should go about troubleshooting it? I've calibrated as per directions but I'm not getting stable enough readings.<br>By the way, what should I expect the accuracy of the readings to be? Within 10 grams? I'm using a 7Kg max digital kitchen scale.</p>

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Bio: Professionally, I'm an IT Engineer (Executive Level) and Electronics Tech. I'm a Amateur Radio Operator (KK4HFJ). I lived off grid, with Solar (PV ... More »
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