Persistence of Vision LED staff

POV staff in action

This guide contains documentation for Persistence of Vision (POV) LED staff project, created by Alexander Kirillov <irobotics.store@gmail.com>.

This document describes version 4.1, which was released on May 10, 2023. An earlier version of this project was documented on Instructables web site. The version described here contains several improvements compared to the earlier one, see below.

For those wishing to reproduce this project, we are offering a kit of parts for sale through our Tindie store. However, all design files, software, BOM and more are published under open source license, so anyone can build their own version from scratch. You can find these files in the project GitHub repository: https://github.com/shurik179/povstaff

Overview

It is well known that even after a light has been turned off, human eye keeps “seeing” it for a fraction of second. This is known as Persistence of Vision, or POV, and it allows one to “paint” pictures by quickly moving a strip of LEDs, drawing one line of an image at a time in quick succession. If you search online (e.g. on Etsy), you can find quite a few toys based on this idea: pois, staffs, and more.

However, these are expensive: typical prices for a POV staff of decent resolution start at $500, and they use proprietary software, so there is no easy way to modify their behavior or add extra functionality. Thus, when looking for a birthday gift for a friend who enjoys painting with light, I decided to create my own open source version using readily available components.

My project builds upon the outstanding work of Phillip Burgess and Erin St Blaine from Adafruit; however, I made a few changes, upgrading the electronics.

Key Features

  • It is a two-sided staff, of total length 141 cm (55in); it is not collapsible. Each side of the staff has two 50cm/72 pixels LED strips, for the total of 288 LEDs. Thus, you can use it to show images with 72-px resolution.

  • Staff is powered by two 18650 Li-Ion batteries, which should be enough for at least 1 hr show, possibly as much as 2 hours, depending on intensity of your images. The batteries can be recharged via 5.5mm/2.1 barrel connector (or USB C cable, using included adapter); full charge time is about 5 hrs.

  • Images (in bitmap format) can be easily uploaded to the staff over WiFi. It has enough memory for about 50 images. The order in which images are shown is described in a separate plain text file, where you can put a list of images and durations. An image can be listed there several times, or none at all.

  • The staff contains an Inertial Motion Unit (IMU) which can be used to detect when the staff is in motion. The software uses it to adjust update frequency for images, so the images will not appear stretched or compressed regardless of how fast you are rotating it. You can also use it for controlling your show: e.g. stopping the staff vertically is used as a signal to move to the next image in the slideshow.

  • The software is based on Arduino IDE. It is available under an open source license and is easy to modify to suit your needs.

Differences from version 3

  • New MCU (ESP32-S3 QT Py)

  • Wireless uploading of images

  • Many changes to wiring

  • New 3d printed spacers and other components, printed in black resin.

  • Foam protectors at the ends of the staff, to protect the staff when dropped

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