I teach computer science at a high school, and I am helping the engineering class make something for football. Basically, it has 3 racks, each with a weight sensor, and a 6 pack of water bottles fits in each row. The goal is that there will be an indicator that will show how much water is left based on the weight.
Their idea was to wire 3 LEDs (green, yellow, and red) to each row and have them turn off as the water levels get lower (full is green, yellow is half, and red is near empty.) My concern was controlling 9 single LEDs off one Arduino.
My first thought was an LED strip on each row and it would light up more or less based on the weight. My second thought was one light per row and have it solid, blink, or off based on how much water is left.
I feel fine about the coding for this, but I am just unsure how to control that many lights on the hardware side.
So the project will consist of 3 scales with 3 LEDs per scale? Are the scales like load cells connected to amps like the HX711 load cell amp?
Why? That is easily done with an Uno or Nano unless you have other things that use pins.
You will need 9 pins for LEDs and 6 for the 3 load cell amps. That is 15 pins and an Uno or Nano has 18 pins (not counting Serial pins) available (the analog inputs are digital pins with analog input as a special function).
If you need more pins, an I2C IO expander or shift register can be used.
What are the LEDs? Do they take more than 20mA each?
Two full bottles could mask the weight of four empty bottles in a six-pack. An average weight would indicate all bottles were 1/3 full. I would weigh individual bottles.
You could address both of the first two by using the WS2812 (or similar) addressable LEDs - they let you control hundreds of LEDs with just a single data pin, and can be powered separately from the Arduino.