Maker Laszlo Bardos has turned to an Arduino Nano to power a smart yet surprisingly entirely-network-free reminder checklist system for the wall by his front door.
"The list of items to remember are printed on a transparency with red/green LEDs controlled by a [Maxim Integrated] MAX2719 serving as the back lights," Bardos explains of the guts of the build. "Each LED is in its own compartment in a 3D-printed box to prevent the light from illuminating other list items."
"I also used a piece of a LED diffuser that I salvaged from an old TV. If I want to change lists without printing a new list, I can also write on the Plexiglass sheet with a wet-erase or dry-erase marker."
Where most reminder projects lean into the Internet of Things (IoT), relying on centralized databases and API calls to pull down data and update completed tasks, this build is significantly less connected: The physical list lights up automatically, and items are "ticked off" by pressing a physical button.
"Of note: This is the first project that I used a lithium ion battery that I scavenged from a vape that I found by the side of the road," Bardos adds. "The battery is controlled by a TP4056 lithium battery charging board to keep things safe."
"Interestingly enough, I had trouble with a boost converter that was supposed to bring the voltage up to 5V, but I found that the circuit worked just fine without it so the whole thing is running on 4.1 V. I'm curious how it will behave as the battery depletes. I might have to go back in and add a boost converter."