Simple Arduino Sit-up Judge

Introduction: Simple Arduino Sit-up Judge

This simple Arduino setup and sketch will judge just how UP a sit-up needs to be to count. It will play one tone when you recline enough, and another when you sit up enough for a full crunch to count!

Ever get into an unnecessarily heated debate about someone else's crunches not counting? Me neither. But this gadget runs off a 9V battery and is light enough to hold to your chest or be placed in a chest pocket, and do the sit-up judging for you.


  • Arduino Uno
  • Tilt sensor (aka inclinometer)
  • Piezzo buzzer (passive buzzer)
  • 9V battery & barrel connector
  • M-F jumper wire

Step 1: Step 1: Wiring Up

The Arduino Uno can be powered by a 9V battery using a barrel power connector. Stick a cheap tilt sensor in the GND and Pin13 terminals, and wire the piezzo buzzer to the other GND and Pin6. The buzzer will only work if the negative (-ve) side is grounded.

Step 2: Step 2: Code

In the Arduino IDE, load this code and upload it to the Uno:

int inPin = 13;
int reading;
const int SpeakerPin = 6;
int lastsensorValue;

void setup() {
pinMode (inPin, INPUT);

void loop () {
reading = digitalRead(inPin);
if (reading == 1 && lastsensorValue == 0) {
tone(SpeakerPin, 1500, 300);
lastsensorValue = 1;
if (reading == 0 && lastsensorValue == 1) {
tone(SpeakerPin, 200, 300);
lastsensorValue = 0;
else {

Step 3: Step 3: Test & Enjoy

The buzzer will play one tone when you recline enough, and another tone when you sit up enough for a full crunch to count. Connecting the tilt sensor directly into the Uno headers leaves little room for the sensor to tilt away from the Uno board.

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    Tip 1 year ago

    it might help if you tell what each sound means when you do a sit-up