A Voice-Activation Conversion for Manual Paper Towel Dispensers

If the COVID-19 pandemic taught us anything, it was that we live in a dirty world. On any given day, a typical person faces exposure to bacteria and viruses at every turn. Even explicitly hygienic activities can, themselves, be dirty. Consider handwashing, which might force you to touch a faucet knob and then a paper towel dispenser after you’ve already scrubbed your mitts. Motion sensors attempt to address those issues, but they’re unreliable at the best of times. That’s why 3megabytesofhotram built “Say Loudly,” a voice-activated paper towel dispenser.

To avoid an unnecessary reinvention of the wheel, 3megabytesofhotram started with a manual paper towel dispenser made by Scott. That is the style with a crank on the side that wet-handed users turn to dispense a paper towel. It was important to use a model like that, because this conversion motorizes the dispensing mechanism and the crank provides a link for connecting the motor. It might have been even easier to start with a motion-activated dispenser that already had a motorized mechanism, but those are more expensive.

3megabytesofhotram needed their conversion to do two things: detect the proper voice command and rotate the dispensing mechanism.

To achieve that first goal, 3megabytesofhotram used a Raspberry Pi 4 Model B (2GB model) to run speech recognition software. Unfortunately, this project doesn’t yet have full documentation and 3megabytesofhotram doesn’t say what software they used. We don’t even know if that runs locally or if it goes through a cloud-based service. All we know is that the Raspberry Pi listens for voice command through a microphone connected via a MOSWAG USB adapter.

The dispensing mechanism is a bit more straightforward. A small geared DC motor, with an output shaft turning at just 10rpm, drives the previously manual crank. The Raspberry Pi controls that through a conventional H-bridge motor driver module. 3megabytesofhotram designed a few 3D-printed adapter parts, like pulleys, to connect the motor to the crank mechanism with a 10mm toothed timing belt.

You won’t be able to perform this conversion yourself until 3megabytesofhotram fleshes out the project documentation, but it is still cool to see in action.

And if you’ve read this far without catching it, you should know that this was inspired by a silly prank. That original prank was to put a sticker on a regular paper towel dispenser that says “Voice activated. Say loudly, ‘Dispense towel.’” So, this is something of a double-reverse-prank, as this actually does require voice activation.