Now let's see how to turn off the NeoPixels one at a time during the count time. The basic idea is shown in the figure below.

Our timer starts at time zero (t=0) and counts for a total amount of time T (t=T). Since we have 10 NeoPixels on the Circuit Playground, we can break that time period up in to 10 equal slices. Each slice has a wait time of DT, which is equal to the total time T, divide by the number of NeoPixels, thus:

DT = T / 10

The idea now is to loop over each NeoPixel and wait this smaller amount of time DT. Once that time has elapsed, turn the NeoPixel off and move on to the next NeoPixel, etc.

Here's the previous code modified to do this:

// Circuit Playground Less Basic Timer
// Author: Carter Nelson
// MIT License (

#include <Adafruit_CircuitPlayground.h>

void setup() {
  // Initialize the Circuit Playground

void loop() {
  // Turn ON all the NeoPixels
  for (int p=0; p<10; p++) {
    CircuitPlayground.setPixelColor(p, 255, 255, 255);

  // Compute DT
  unsigned long DT = 5000/10;
  // Turn OFF the NeoPixels one at a time, waiting DT each time
  for (int p=0; p<10; p++) {
    CircuitPlayground.setPixelColor(p, 0, 0, 0);
  // Wait for button press to reset timer
  while (!CircuitPlayground.leftButton()   && 
         !CircuitPlayground.rightButton())  {
    // Do nothing, just waiting for a button press...

As you can see, the delay() command has been moved inside a loop. The loop runs 10 times, so the delay() command gets called 10 times. However, the total amount of time counted remains the same 5 seconds as before.

Next Step

Hourglasses typically don't have buttons that are pressed to reset them like our Circuit Playground code is doing. An hourglass is reset by simply flipping it over and letting the sand run through in the other direction. How can we simulate this action with the Circuit Playground? Well, maybe we can use the accelerometer. Let's give that a try.

This guide was first published on Dec 29, 2016. It was last updated on Mar 08, 2024.

This page (Less Basic Timer) was last updated on Dec 05, 2016.

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