It Keeps on Going and… Arduino Edition

How long can you keep an Arduino circuit running on three AA batteries? With careful design, [educ8s] built a temperature sensor that lasts well over a year on a single charge of three 2250 mAH rechargeable cells (or, at least, should last that long).

Like most long-life designs, this temperature sensor spends most of its time sleeping. The design uses a DS18B20 temperature sensor and a Nokia 5110 LCD display. It also uses a photoresistor to shut off the LCD display in the dark for further power savings.

During sleep, the device only draws 260 microamps with the display on and 70 microamps with the display off. Every two minutes, the processor wakes up and reads the temperature, drawing about 12 milliamps for a very short time.

Along with the code, [educ8s] has a spreadsheet that computes the battery life based on the different measured parameters and the battery vendor’s claimed self discharge rate.

Of course, with a bigger battery pack, you could get even more service from a charge. If you need a refresher on battery selection, we covered that not long ago. Or you can check out a ridiculously complete battery comparison site if you want to improve your battery selection.

Continue reading “It Keeps on Going and… Arduino Edition”

Environmental monitoring

[Daniel Klien] sent me his thermd environmental monitoring project. It’s written in perl, but the cool part is the sheer number of supported devices. It’s pretty rare when a single developer is given test hardware so he can add support for it.

Sure, this isn’t a hardware hack, but temperature logging is one of those irritating problems of hardware hacking. I’ve got loads of uses for it – coffee roasting, house management, battery charging, monitoring for my EV motorcycle project.