Thursday, March 5, 2009

Data Logging Circuit - 2.5 Mbytes

This is a small and simple remote data logger I designed a few years ago. Originally it connected to a GPS unit, and recorded the GPS position, but I've since expanded it to have more memory, a temperature sensor (DS1820), and more general purpose to record voltages and other data as I need it. The design is based on any PIC similar to the PIC16F648 controller, and has up to five AT45DB041 SPI non-volatile memory devices which each have 500kbytes of storage. Just a few years ago 2.5Mbytes of storage was a big deal ;-)

I've used these for remote temperature monitoring, and other low-power data logging. It takes data every 5 seconds, and records it to memory - then when it detects a PC serial port, it dumps out the data so it can be imported to Excel.

The memory requires 3.3V, so it has a simple surfacemount regulator. Nice and simple. Email me if you want the PIC code to try it out. Now-a-days it is easy and inexpensive to simply have a FAT file system chip on the board and a flashdrive to record all the data. Memory is so cheap now, its great.

I've resurrected the design to do a summer experiment with the kids - our plan was to launch a GPS unit in a weather balloon and track it. The 2nd GPS unit is to be launched in a float bouy out into the ocean at the mouth of the Columbia River. Problem is recovery. So... now the plan is to use two GPS enabled cellphones - i415 I got for $10 on ebay! These bad boys track real-time via cellphone towers, so if we don't recover the units, oh well - we still got our data. And the price is right. More on this project in a later podcast this summer - stay tuned!
Like all of our software and electronic projects, we are after data rather than making a product. We usually build our own to keep them under $20 per project, so we can so as many projects as possible. Feel free to email if you have questions or want details on this data logger.

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