Help: building scales which can link to led lights

[Neal9797]

Hello,

I am a designer working on a university project with a small understanding of technology building hence why I am turning to ask from you.

I want to create a product which is essentially a scales which measures weight and links to LED lights which will change from red to green at a range of weight. So for example a weight is under or over the inputted "green value" ranges then the LED lights will be red and when in the "green value" range it will be green.

I was thinking of using a arduino to create some kind of smart scales with a linked weight sensor but wanted input of how to make value ranges switch a colour of light.

If you have any reasonable solutions your suggestions are really appreciated and if you would like further clarification, let me know


cheers

 

[Les Jones]

Changing the colour of an LED from red to green is easy. All you have to do apply power to the tin for that colour led in the package. (Assuming a three pin LED.) What you will find more difficult is reading data from a keyboard, displaying data (The weight reading and the threashold value that you want change the LED colour and the data from the scale.) You will need to learn how to do all these things before you can start writting the code to run on the Arduino.

Les.

 

[ericgibbs]

I want to create a product which is essentially a scales which measures weight and links to LED lights which will change from red to green at a range of weight. So for example a weight is under or over the inputted "green value" ranges then the LED lights will be red and when in the "green value" range it will be green.

hi Neal,
The way I read your description suggests that the Green LED's will be Lit when ever the weight is below the 'range' and Red LED lit when over weight.

The Green's will be lit from Zero weight up to the range weight and the Red's will be lit above the range up to Full scale.!
IMO That's not going to be an accurate indication that a weight is in range.

Eric

 

[spec]

Hi Neal,

Can you tell us a bit more about your project?
(1) What weights are you planning on weighing?
(2) What accuracy do you need?
(3) what is you cost limit?
(4) Do you have the tools and experience to build and test electronic units?

If you go the microcontroller route the problem to solve is how to get the weight data into the microcontroller. Once that is achieved writing the code to set limits, display the results or pretty much anything else would be relatively straight-forward.

Here are the main options for getting the weight data:
(1) Buy some scales with a digital output, probably serial.
(2) Modify some standard scales which do not have a digital output to get a digital output.
(3) Build some scales from scratch.

(1) would be the simplest and quickest but scales with a digital output are liable to be expensive, but I do not know that for sure.

(2) Is an unknown quantity, but technically possible.

(3) Is not as radical as it might first seem. You can get strain gauges with a digital interface (or analog), so it would be a matter of building the mechanics, or perhaps adapting the mechanics from another scale.

spec

 

[spec]

Hi again Neal,

Option (2) in post #4 above may be possible with scales that have a LED display by connecting wires to the signals going to each seven-segment display (eight wires with decimal point for each digit).

A relatively simple bit of electronics could then connect the seven-segment data to a microcontroller.

From that point on it would be just be a matter of some simple programming.

An Arduino, or even a Raspberry Pi, would be good choices of microcontroller board.

spec

 

[tomizett]

I believe that Ben from the Applied Science YouTube channel has a video where he reverse engineers a cheap electronic balance to read the weight into a microcontroller. I don't have a link I'm afraid, but have a search on YouTube - I believe that it's part of his Cookie Making Machine project.

 

[Les Jones]

Hi tomizett,
I think this could be the link you had in mind.

It looks an interesting way for the OP to start his project.

Les.

 

[tomizett]

Nice one Les - that's the one. I often don't have time to look this stuff up if I'm posting form work, so thanks for finding it.
It's probably the cheapest, and fairly easy if the OP has the gear and a reasonable background knowledge.

 

[dr pepper]

Have a look at hx711 modules, 1/2 of the project already done for you, I used one recently.

 

[Les Jones]

Hi dr pepper,
Nice find. I notice that they can be bought on ebay together with the load cell. As the OP has not specified a weight range I don't know if any of the ebay load cells will be suitable.
Les.

 

[ericgibbs]

hi,
I have also used the HX711 from Amazon.
Nice and simple to program.
E

 

[dr pepper]

I had a scale displaying something on lcd within minutes, handy gizmo, I also tried it with an industrial loadcell, and that worked too.