🔧Builder's Day

The build (one Saturday afternoon)

Parts you need (~$25 from Sunshine Hobbies or Amazon):

• 1× HX711 24-bit ADC breakout board
• 1× 5 kg load cell (four-wire half-bridge or full-bridge)
• 1× Arduino Uno or compatible
• 1× 16×2 character LCD (or OLED if you want to feel modern)
• A handful of jumper wires and a small breadboard

Wiring (about ten minutes):

The load cell has four wires. Red is excitation positive, black is excitation negative, white and green are the signal pair. Wire them to the HX711's E+, E-, A+, A- pins respectively. The HX711's data and clock pins go to two Arduino digital pins — D2 and D3 are common. Power the HX711 from the Arduino's 5V. Wire the LCD per its data sheet.

Code (the HX711 library does most of the work):

#include "HX711.h"
HX711 scale;
void setup() {
  scale.begin(D2, D3);     // data, clock
  scale.set_scale(420.0);  // calibrate this with a known weight
  scale.tare();            // zero out
}
void loop() {
  float grams = scale.get_units(10);  // average of 10 samples
  // ...write grams to LCD
  delay(200);
}

Calibration: Put a known weight (a 500g kettlebell, a 5 lb dumbbell) on the cell and tune the set_scale() value until the readout matches the known weight. That's it.

What you've actually built: A complete data acquisition chain from analog physical phenomenon (force) through transducer (load cell with strain gauges in Wheatstone configuration) through analog-to-digital conversion (HX711) to digital display (Arduino + LCD). Every test stand at Redstone is the same architecture — bigger sensors, more channels, faster sample rates, more sophisticated software, but the same chain.

If you have a kid old enough to follow along, this is the project that turns "Dad/Mom does mysterious work with rockets" into something they can see, touch, and measure. The first time they put their hand on the scale and watch the number change with how hard they press, the test engineering field has them.