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Arduino bin reminder This simple project came about when one person in our street put out the wrong coloured bin. This created confusion in the street as most people copied what bin the earlier neighbour had put out, including yours truly. I decided to check the council website for the bin timetable. After wasting about half an hour, I found that the council, in its wisdom, had put the 2024 calendar up and deleted the 2023 timetable before the end of the year! I remembered Silicon Chip published a bin reminder project some years ago (January 2013; siliconchip. au/Article/1315). While it is an excellent design with many great features, I wanted something very simple with no buttons for anyone to fiddle with. The circuit presented here is straightforward, using little more than a real-time clock module and an Arduino Uno. All of the programming is done in the sketch code rather than using buttons. I have commented the sketch so it is easy to set your bin colour LEDs and their timing. If, when the Arduino is powered up, it detects that the real-time clock module does not have a valid date and time, it sets them to the date and time that the sketch was compiled and uploaded, which should be just a few seconds earlier. That slight time difference will be inconsequential to the device’s job. The sketch changes the display over at 1:30am every Sunday morning, to tell the user what the bin colours are for the week. When the circuit boots up, the LEDs for the current week will be displayed. The reminder will then change to your setting for the alternate week the following Sunday morning. The Sunday after that, the LEDs will swap back again. This cycle continues while power is applied. The unit must be kept powered up continuously (do not press the Arduino reset once programmed). As shown in the circuit diagram, I achieved that with a trickle-charged 9V NiMH battery. The software sketch for this project can be downloaded from: siliconchip.au/Shop/6/352 Geoff Coppa, Toormina, NSW. ($80) flows through LED2 (red). The 5V supply rail is chosen carefully because it needs to be sufficient to light the LEDs but not so high that it could cause reverse breakdown in the transistor or LEDs, which could cause both an erroneous result and possibly damage the transistor. The fourth section of the chip (IC1d) is not used, so its inputs are tied to the 0V rail. Raj K. Gorkhali, Hetauda, Nepal ($50). siliconchip.com.au Australia's electronics magazine June 2024  97