High Precision Scale with Arduino

This is a very precise scale for any weight up to 1.5 kg!

Jul 10, 2018

47403 views

22 respects

Components and supplies

1

Arduino Nano R3

1

Standard LCD - 16x2 White on Blue

1

HX 711 scale module

Tools and machines

1

Saw

1

3D Printer (generic)

Apps and platforms

1

Arduino IDE

Project description

Code

The code

c_cpp

This code might be not the best written one, but please remember that this was one of my very first projects!

The code

c_cpp

This code might be not the best written one, but please remember that this was one of my very first projects!

Downloadable files

The connection of the HX711 module

The connection of the HX711 module

The connection of the HX711 module

The connection of the HX711 module

HX711 Library

HX711 Library

Documentation

The 3d model, altough it is just a prototype.

The 3d model, altough it is just a prototype.

The 3d model, altough it is just a prototype.

The 3d model, altough it is just a prototype.

Comments

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Anonymous user

2 years ago

Hi, what pins to connect the buttons?

eburman

2 years ago

According to the code it looks like the Tare button goes to pin 4, the Up button to pin 2 and the Down button to pin 3. The code doesn't make much sense to me. He assigns pins to the Up and Down buttons but I don't see where he uses them in the rest of the code. There are also other components like resistors and capacitors that are shown in the video. A schematic would have been extremely useful. You could try to follow the video to figure out how to wire it up but I find that it's difficult to follow especially since it's all in Russian language. I never did get around to building this project so I can't vouch for it. His instructions may be incomplete or misleading. Probably there are others who have designed similar projects. I'd look around for something that's more completely illustrated.

Anonymous user

2 years ago

This is cool!

Anonymous user

2 years ago

Interesting project. How much did the materials cost, and how long did it take to complete? As well, if the precision of the weight sensor could be increased, then this can become a viable alternative to a commercial analytical balance (+/- 0.0001 g or better).

mPelectronic

2 years ago

Thanks. The materials cost different depending on where you live. The wood costed me not more than 3€, I had to cut it to size. The building process shouldn't take longer than a day if you cut the wood and build the circuit on the same day. Increasing the precision is impossible, at least with this type of sensor. There are different versions of it: eg. 20kg, 5kg, 1kg. In this one I used the 1kg sensor, which is the most accurate. However, the chinese load cells are not always good quality and using them to build a commercial scale which requires high precision does not sound realistic. You can check out the video description, there is a parts list.

Anonymous user

2 years ago

Dear, Thanks for this interesting project. You did not share the schematics and wiring diagram to connect the LCD display. Is that normal? Best regards,

mPelectronic

2 years ago

Hi, thanks. I connected the display via I²C, so SDA to A4 and SCL to A5 on Arduino. There is a picture how to wire up the sensor. From the sketch you can see the pins for the buttons. Sorry, I don't have a proper schematic.

Anonymous user

2 years ago

Hi, I'm curious what "High Precision" means in that case. What is the Accuracy and the Repeatability in the range from 0 up to 1.5 kg?

mPelectronic

2 years ago

Hello. As you can see from the photo, it can measure up to one hundredth of a gram. There is no sense to go for more precision, because then there is no stable result. What do you mean with repeatability? If the result is the same after putting the object on and off the scale? Yes, it just depends how well you have calibrated it.

mPelectronic

2 years ago

Hello, thanks for the explanation. The scale is quite accurate, because I have compared it with a pharmaceutical scale and it did show the same result! However, it's just how well you calibrate it and how lucky you are, because the chinese load cells are not always the same quality. The repeatability is quite good as well, the maximum difference I could spot was 1-2g. I saw the design somewhere on project hub, now I understand that I could have done better. The weighting surface does not touch the walls, but using 2 load cells would be a good practise. All in all, thanks for your comment and advice!

paulgrimshaw

2 years ago

Precision and and accuracy are very different things. You may be displaying a value with precision 0.01g, but the value shown may only be accurate across the range to +/- 10% for example. Also repeatability is about how stable the measurement is. So for example if you measure in a cold room and then a warm room then how much does the measured value vary for the same weight? Also what happens to measurement over time - how much does the measurement drift away from the original if you repeat a measurement an hour later, or a few days later? A good test for basic accuracy would be to use some reference weights if you have any. So, for example, if you calibrate the scales with a 100g weight, then what readings do you get when weighing 1g, 10g and 1kg weights? What about when repeating (without recalibration) in a colder or hotter room, and/or some time later? One concern looking at the design is that the weighing surface appears to be touching the wooden sides. This could introduce a lot of inaccuracy over the range as a variable amount of weight will be supported by the sides rather than by the load cell. A way to improve this would be to use more than one load cell, making sure that the weighing surface is entirely supported by the load cells and adding up their values to get the total weight.

Anonymous user

2 years ago

Great project! I am new to Arduino overall but could you connect something to make the scale beep if past a certain threshold? For example to prevent overloading the scale or beep because you achieved a desirable weight for example?

Anonymous user

3 years ago

Hi, what pins to connect the buttons?

Anonymous user

2 years ago

According to the code it looks like the Tare button goes to pin 4, the Up button to pin 2 and the Down button to pin 3. The code doesn't make much sense to me. He assigns pins to the Up and Down buttons but I don't see where he uses them in the rest of the code. There are also other components like resistors and capacitors that are shown in the video. A schematic would have been extremely useful. You could try to follow the video to figure out how to wire it up but I find that it's difficult to follow especially since it's all in Russian language. I never did get around to building this project so I can't vouch for it. His instructions may be incomplete or misleading. Probably there are others who have designed similar projects. I'd look around for something that's more completely illustrated.

chaotix66

4 years ago

Great project! I am new to Arduino overall but could you connect something to make the scale beep if past a certain threshold? For example to prevent overloading the scale or beep because you achieved a desirable weight for example?

Anonymous user

6 years ago

Dear, Thanks for this interesting project. You did not share the schematics and wiring diagram to connect the LCD display. Is that normal? Best regards,

mPelectronic

2 years ago

Hi, thanks. I connected the display via I²C, so SDA to A4 and SCL to A5 on Arduino. There is a picture how to wire up the sensor. From the sketch you can see the pins for the buttons. Sorry, I don't have a proper schematic.

Anonymous user

7 years ago

Interesting project. How much did the materials cost, and how long did it take to complete? As well, if the precision of the weight sensor could be increased, then this can become a viable alternative to a commercial analytical balance (+/- 0.0001 g or better).

mPelectronic

2 years ago

Thanks. The materials cost different depending on where you live. The wood costed me not more than 3€, I had to cut it to size. The building process shouldn't take longer than a day if you cut the wood and build the circuit on the same day. Increasing the precision is impossible, at least with this type of sensor. There are different versions of it: eg. 20kg, 5kg, 1kg. In this one I used the 1kg sensor, which is the most accurate. However, the chinese load cells are not always good quality and using them to build a commercial scale which requires high precision does not sound realistic. You can check out the video description, there is a parts list.

eburman

7 years ago

I'm wondering where to get the HX711 library that you used. The ones that I've found so far don't compile with your code.

eburman

2 years ago

Thank you. The code compiles now. So, on to building the project!

mPelectronic

2 years ago

Hi, thanks for reminding! I've added the library so that you can download it. It changed its title somehow, but however...

mPelectronic

2 years ago

You are welcome! Make sure to check out the video, it might be a good help, although it is in Russian.

Anonymous user

7 years ago

Hi, I'm curious what "High Precision" means in that case. What is the Accuracy and the Repeatability in the range from 0 up to 1.5 kg?

paulgrimshaw

2 years ago

Precision and and accuracy are very different things. You may be displaying a value with precision 0.01g, but the value shown may only be accurate across the range to +/- 10% for example. Also repeatability is about how stable the measurement is. So for example if you measure in a cold room and then a warm room then how much does the measured value vary for the same weight? Also what happens to measurement over time - how much does the measurement drift away from the original if you repeat a measurement an hour later, or a few days later? A good test for basic accuracy would be to use some reference weights if you have any. So, for example, if you calibrate the scales with a 100g weight, then what readings do you get when weighing 1g, 10g and 1kg weights? What about when repeating (without recalibration) in a colder or hotter room, and/or some time later? One concern looking at the design is that the weighing surface appears to be touching the wooden sides. This could introduce a lot of inaccuracy over the range as a variable amount of weight will be supported by the sides rather than by the load cell. A way to improve this would be to use more than one load cell, making sure that the weighing surface is entirely supported by the load cells and adding up their values to get the total weight.

mPelectronic

2 years ago

Hello. As you can see from the photo, it can measure up to one hundredth of a gram. There is no sense to go for more precision, because then there is no stable result. What do you mean with repeatability? If the result is the same after putting the object on and off the scale? Yes, it just depends how well you have calibrated it.

mPelectronic

2 years ago

Hello, thanks for the explanation. The scale is quite accurate, because I have compared it with a pharmaceutical scale and it did show the same result! However, it's just how well you calibrate it and how lucky you are, because the chinese load cells are not always the same quality. The repeatability is quite good as well, the maximum difference I could spot was 1-2g. I saw the design somewhere on project hub, now I understand that I could have done better. The weighting surface does not touch the walls, but using 2 load cells would be a good practise. All in all, thanks for your comment and advice!

Anonymous user

7 years ago

This is cool!