Track Those Leftovers With This Little Timer

May 1, 2022 by Jenny List 28 Comments

We’ve all at some point in our lives opened the fridge door and immediately wished we hadn’t. A miasma of stench envelops us as we discover that last Saturday’s leftovers have been forgotten, and have gone off. If only we had some way to keep track of such things, to avoid such a stench-laden moment. Step forward [ThinkLearnDo], with a little timer designed for exactly that purpose.

The operation is simple enough, press the button and place the unit on top of the container with the leftovers in it. If you haven’t eaten the leftovers within a week, the LED will start blinking. The blink is a subtle reminder to deal with the old food before it becomes a problem.

Onboard is a Holtek HT68F001 microcontroller with a coin cell for power, not much else is needed. The Holtek is an unusual choice, one of several brands of super-inexpensive Chinese microcontrollers we see less commonly than ATmegas and STM32s. This is exactly the place where such a minimal computer fits perfectly: a way to add a little bit of smarts to a very cheap item with minimal strain on the BoM.

If these chips interest you, a while back we covered a run-down of the different families including the Holtek and the famous 3-cent Padauk chips.

64×16 LED MQTT Laundry Display

October 11, 2016 by Rich Hawkes 2 Comments

When you have an MQTT broker receiving messages, you want to be able to see them. [Xose Pérez] already had a system set up that sent him notifications, but he had a pair of 32×16 LED matrices, so he decided to make a big, bright sign to let him know when he got an important message sent to the broker.

[Xose Pérez] had already built a laundry monitor which was sending messages to an MQTT broker so he wouldn’t forget his laundry sitting in the washing machine. To communicate with the broker, he used an ESP-12. He had already ported an Arduino library for the Holtek HT1362C display drivers used by the matrices to work with his driver board.

He wanted to try out SMD soldering so he built a custom PCB to hold the ESP-12, power supply, passive components, and a connector and he describes his methods and results. Instead of hardcoded messages, he wanted the system to be configurable and display messages coming in, not only from his laundry system, but also from other sensors. A web interface, built with jQuery and WebSockets, running on the ESP-12 allows the user to subscribe to a topic on the broker and show a customized name and value on the display when a payload is available.

All-in-all, [Xose Pérez] has posted a great tutorial in which he goes over the hardware he built, the libraries he used, SMD soldering, how he made the enclosure, and even his choice in IDE (PlatformIO). He also posted the software, board designs and enclosure models software and hardware on bitbucket. The end result is a great looking LED matrix that displays not only his laundry’s status, but also anything else he wants to from his MQTT broker.

If you want to try your hand with MQTT, the ESP8266 is a wonderful device for sensor nodes, and any Linux box (like the Raspberry Pi) makes an easy broker. Check out [Elliot Williams’] Minimal MQTT series and you will be up and running in no time.