You can build an IoT sensor for your 3D printer so you can be alerted if you’re out of filament. We think this is a great proof-of-concept that can help prevent failed prints. 

This project uses an IR Optical Sensor that can detect whenever an object passes by the sensor. The breakout is mounted to a 3D printed bracket right above the 3D printer. 

If nothing is detected, an LED buzzer alarm will be triggered letting you know your printer is out of filament.

An Adafruit QT Py ESP32-S2 reads the IR optical sensor and sends data to Adafruit IO whenever it detects missing filament.

The LED buzzer alarm is wired up to a Feather ESP32-S2 so it’s a separate device that can be in another room or workspace that’s away from the 3D printer.

This is great for CNC workshops and 3D printer farms that are in separate rooms away from operators.

This project uses Adafruit’s WipperSnapper, so there’s no code necessary -- making this really easy to set up and get going.

Just install the WipperSnapper firmware onto the Adafruit ESP32 dev board and add the Optical sensor from the Adafruit IO device page.


Close-up video of white finger triggering an optical reflective sensor breakout.
An optical reflective sensor is a composite electronic device with two elements - an IR LED and an IR photo-transistor. The IR LED blasts light, and when something bounces...
Angled shot of small square purple dev board.
What has your favorite Espressif WiFi microcontroller, comes with our favorite connector - the STEMMA QT, a chainable I2C port, and has...
Video of warning light glowing swirling LEDs.
THE REACTOR'S MELTING DOWN! GRAB THE FUEL CORE, JENNA, AND EVACUATE THE COMMAND CENTER! With this Rotating LED Warning Light with Adjustable Volume Buzzer Alarm,...
Angled shot of rectangular microcontroller.
What's Feather-shaped and has an ESP32-S2 WiFi module? What has a STEMMA QT connector for I2C devices? What has your favorite Espressif WiFi microcontroller and lots of Flash and...
Prototyping feather wing PCB with loose headers
A Feather board without ambition is a Feather board without FeatherWings!This is the FeatherWing Proto - a prototyping add-on for all Feather boards. Using our...
3 pack TIP120 Power Darlington Transistors
Transistors are powerful little electronic switches, and when our little NPN transistors aren't power enough for your project, we have been known to use these beefy TIP120...
Angled shot of black 2-pin 2.54mm terminal block.
After a long day out harvesting in the terminal block fields, we've returned with a veritable bounty of these very nice and compact 2.54mm/0.1" terminal blocks in a variety of...
Angled shot of 25 Through-Hole Resistors - 2.2K ohm 5% 1/4W.
ΩMG! You're not going to be able to resist these handy resistor packs! Well, axially, they do all of the resisting for you!This is a 25 Pack of 2.2K...
Angled shot of a Header Kit for Feather - 12-pin and 16-pin Female Header Set.
These two Female Headers alone are, well, lonely. But pair them with any of our 
Angled shot of STEMMA JST PH 3-Pin to Male Header Cable - 200mm.
This cable will let you turn a JST PH 3-pin cable port into 3 individual wires with high-quality 0.1" male header plugs on the end. We're carrying these to match up with our...
USB C to USB C cable. USB 3.1 gen 4 with E-Mark. 1 meter long
As technology changes and adapts, so does Adafruit! Rather than the regular USB A, this cable has USB C to USB C plugs!USB C is the latest...
2 x M2x8mm Screws
Filament Guide bar
3 x M2.5x5mm
TCRT (2) + FeatherWing Proto (1)
3 x M2x5mm
FeatherWing Proto (2) + Holder Mount (1)
2 x M2x12mm
2020 Bar screws

The diagram below provides a general visual reference for wiring of the components once you get to the Assembly page. This diagram was created using the software package Fritzing.

Adafruit Library for Fritzing

Adafruit uses the Adafruit's Fritzing parts library to create circuit diagrams for projects. You can download the library or just grab individual parts. Get the library and parts from GitHub - Adafruit Fritzing Parts.

The diagram for the driver circuit is shown above on a FeatherWing Proto board.
The red LED is a stand-in for the alarm.

The circuit uses pin D10 of the Feather through a resistor to the left leg of the transistor (base) in order to toggle when the transistor opens or closes the middle leg (collector), which allows the alarm circuit to go to ground via the right leg (emitter).

The middle leg connects to the any Ground pin.

The right leg connects to the USB pin.

FeatherWing Proto Socket headers

Solder Socket Headers on the FeatherWing Proto.

Feather Header Kit 

The Feather stacks on top of the FeatherWing Proto board with Pin Headers.

Ok - you've connected your board to WipperSnapper. Now what?

This page will give you a quick tour of Adafruit IO WipperSnapper and its core features.

WipperSnapper Device List

The Device List page provides a list of the devices you've connected to Adafruit IO WipperSnapper along with their connection status.

Think of it as a virtual inventory for your boards! 

You can visit this page at any time by navigating to

Wippersnapper Device Page

Clicking on a device from the Devices List page will bring you to its device page. This page is an interface to configure and interact with anything physically connected to your device.

You may think of it as the state of your device at any given time. 

When you register a device for the first time, this page will be empty, it's a clean slate!

WipperSnapper Components 

A "component" in WipperSnapper denotes anything which is physically connected to your hardware.

This can include sensors, buttons, LEDs, NeoPixels, displays, and more!

When you click New Component, your hardware will automatically connect to and configure the component using the settings you specified. No coding required! 

Additionally, a component also sets up a unique Adafruit IO feed to store the component's data stream on the web.

Do I need to set up my components every time I use WipperSnapper?

Nope! WipperSnapper remembers each component's configuration for each of your boards. The "state" of your board's configuration is saved to its device page.

When you re-connect a board to WipperSnapper, it will automatically re-configure every component listed on the Device Page. The most recent value stored on each component's feed will be sent to the device.

I do not see my the component I want to use listed in the component picker pop-up

We're actively working towards adding more components and component types to Adafruit Wippersnapper.

We also gladly take community contributions to Adafruit IO - You can add your own component by following this guide.

The WipperSnapper firmware and ecosystem are in BETA and are actively being developed to add functionality, more boards, more sensors, and fix bugs. We encourage you to try out WipperSnapper with the understanding that it is not final release software and is still in development. If you encounter any bugs, glitches, or difficulties during the beta period, or with this guide, please contact us via

What is WipperSnapper

WipperSnapper is a firmware designed to turn any WiFi-capable board into an Internet-of-Things device without programming a single line of code. WipperSnapper connects to Adafruit IO, a web platform designed (by Adafruit!) to display, respond, and interact with your project's data.

Simply load the WipperSnapper firmware onto your board, add credentials, and plug it into power. Your board will automatically register itself with your Adafruit IO account.

From there, you can add components to your board such as buttons, switches, potentiometers, sensors, and more! Components are dynamically added to hardware, so you can immediately start interacting, logging, and streaming the data your projects produce without writing code.

Sign up for

You will need an Adafruit IO account to use WipperSnapper on your board. If you do not already have one, head over to to create a free account.

Install USB Driver

Install CP2104 / CP2102N USB Driver

Many ESP32 boards have a USB-to-Serial converter that talks to the chip itself, and will need a driver on your computer's operating system. The driver is available for Mac, Windows, and Linux.

Install CH9102 / CH34X USB Driver

Newer ESP32 boards have a different USB-to-serial converter that talks to the chip itself, and will need a driver on your computer's operating system. The driver is available for Mac and Windows. It is already built into Linux.

If you would like more detail, check out the guide on installing these drivers.

Add a New Device to Adafruit IO

Log into your Adafruit IO account. Click the New Device button at the top of the page.

After clicking New Device, you should be on the board selector page. This page displays every board that is compatible with the WipperSnapper firmware.

In the board selector page's search bar, search for the QT Py ESP32 Pico. Once you've located the board you'd like to install WipperSnapper on, click the Choose Board button to bring you to the self-guided installation wizard.

Follow the step-by-step instructions on the page to install Wippersnapper on your device and connect it to Adafruit IO.

If the installation was successful, a popover should appear displaying that your board has successfully been detected by Adafruit IO.

Give your board a name and click "Continue to Device Page".

You should be brought to your board's device page.

Next, Visit this guide's WipperSnapper Essentials pages to learn how to interact with your board using Adafruit IO.

Feedback WipperSnapper is in beta and you can help improve it!

If you have  suggestions or general feedback about the installation process - visit, click "Contact Adafruit IO Support" and select "I have feedback or suggestions for the WipperSnapper Beta".


If you encountered an issue during installation, please try the steps below first.

If you're still unable to resolve the issue, or if your issue is not listed below, get in touch with us directly at Make sure to click  "Contact Adafruit IO Support" and select "There is an issue with WipperSnapper. Something is broken!"

I don't see my board on Adafruit IO, it is stuck connecting to WiFi

First, make sure that you selected the correct board on the board selector.

Next, please make sure that you entered your WiFi credentials properly, there are no spaces/special characters in either your network name (SSID) or password, and that you are connected to a 2.4GHz wireless network.

If you're still unable to connect your board to WiFi, please make a new post on the WipperSnapper technical support forum with the error you're experiencing, the LED colors which are blinking, and the board you're using.

I don't see my board on Adafruit IO, it is stuck "Registering with Adafruit IO"

Try hard-resetting your board by unplugging it from USB power and plugging it back in.

If the error is still occurring, please make a new post on the WipperSnapper technical support forum with information about what you're experiencing, the LED colors which are blinking (if applicable), and the board you're using.

"Uninstalling" WipperSnapper 

WipperSnapper firmware is an application that is loaded onto your board. There is nothing to "uninstall". However, you may want to "move" your board from running WipperSnapper to running Arduino or CircuitPython. You also may need to restore your board to the state it was shipped to you from the Adafruit factory. 

Moving from WipperSnapper to CircuitPython

Follow the steps on the Installing CircuitPython page to install CircuitPython on your board running WipperSnapper.

  • If you are unable to double-tap the RST button to enter the UF2 bootloader, follow the "Factory Resetting a WipperSnapper Board" instructions below.

Uploading this sketch will overwrite WipperSnapper. If you want to re-install WipperSnapper, follow the instructions at the top of this page.

Moving from WipperSnapper to Arduino

If you want to use your board with Arduino, you will use the Arduino IDE to load any sketch onto your board.

First, follow the page below to set up your Arduino IDE environment for use with your board.

Then, follow the page below to upload the "Arduino Blink" sketch to your board.

Uploading this sketch will overwrite WipperSnapper. If you want to re-install WipperSnapper, follow the instructions at the top of this page.

Factory Resetting a WipperSnapper Board

Sometimes, hardware gets into a state that requires it to be "restored" to the original state it shipped in. If you'd like to get your board back to its original factory state, follow the guide below.

Add Components

QT Py TCRT100 Component 

In the QT Py Device Click on the big + icon to add the TCTR100 component.

In the drop down set the Breakout Pin to A1.

Set the Return Interval to On Change.

Feather Warning Light Component 

In the Feather Device Click on the big + icon to add the Buzz 5v component.

In the drop down set the Buzzer 5V Pin to D10

Create New Action

Build the Actions to trigger the Warning Light

Filament Detected Action

Reactive Trigger Setup

  • Click on the Triggers block
  • Drag the Reactive block and snap it to the Trigger section in the Action block
  • In the Feed block select the TCRT1000 feed from the dropdown menu
  • Under the Operator section, select "<" from the dropdown menu.
  • In Values menu type 0


Action Setup

  • In the Values menu type 1
  • In the to section select Feather Buzzer 5V 

No Filament Detected Action

Create New Action

Build the Actions to trigger the Warning Light

  • Click the New Actions button.
  • Choose Yes, use Blockly!

Reactive Trigger Setup

  • Click on the Triggers block
  • Drag the Reactive block and snap it to the Trigger section in the Action block
  • In the Feed block select the TCRT1000 feed from the dropdown menu
  • Under the Operator section, select ">" from the dropdown menu.
  • In Values menu type 1

Action Setup

  • In the Values menu type 0
  • In the to section select Feather Buzzer 5V 

3D Printed Parts

STL files for 3D printing will need to be oriented for print using either FDM or SLS machines.

Parts were tested using with PLA filament.

Original design source files may be downloaded using the links below

Slice with Settings for PLA material 

The parts were sliced using CURA using the slice settings below.

  • PLA filament 200c extruder
  • 0.25 layer height
  • 10% gyroid infill
  • 60mm/s print speed
  • 60c heated bed

Solder QT Py

Use a STEMMA JST PH wire to the QT Py.

Solder the red wire to the 5v pin to the QT Py.
Solder the black wire to the gnd pin.
Solder the white wire to the A1 pin.

Plug the cable into the port on the TCRT1000 STEMMA.

Mount QT Py

Pass the QT Py through the printed holder, with the USB port close to the edge. Insert at an angle with the STEMMA port first, then apply slight pressure to the USB port to press fit into place.

Mount TCRT

Pass the TCRT board through the printed holder and align the screw holes to the QT Py holder.

Fasten TCRT

Use two M2.5x5mm screws to mount the TCRT board to the holder.

Fasten one M2x5mm screw to join both printed holders together.


2020 Mount

Use two M2x12mm screws to attach the 2020 mount.

Filament Guide

Use two M2x8mm screws to attach the filament guide.

USB power

Plug a USB cable to power, most printers have a USB port on the side. You can use a right angle adapter to connect.

Mount to 2020 frame

The bar part mounts to a 2020 extrusion frame. Place the filament over the grooves on the guide part to install. 

Build Warning Light Circuit

Follow the wiring on the Circuit Diagram page to build the driver for the warning light on a FeatherWing Proto board with socket Headers.

Mount to Warning Stand

Use M2x5mm screws to mount the FeatherWing Proto board to the standoffs on the stand part.

Mount Warning Light

Pass the wires on the warning light through the cutout on the stand print. Connect the Warning Light wires to the 2 pin terminal on the FeatherWing Proto board.

Align the screws on the warning light to the screw holes on the stand print. Use the included nuts to fasten the light to the stand.

Stack Feather to Proto board

Align and press the headers on the Feather to the FeatherWing Proto board. Use a USB C cable to power the Feather.

This guide was first published on Jul 02, 2024. It was last updated on Jul 03, 2024.