We have built a versatile and reliable data logger for only $15. The circuit is very easy to put together and a reliable device, which would be a great addition to any school's Science Department or for home use. The data logger uses a PICAXE-08 chip which is very cheap and very easy to program using free software. The program can run on virtually any PC so it is ideal for beginners or those that are interested in electronics. We have successfully tested many sensors and carried out field tests. We are very happy because it is much cheaper than the 'professional' sensors and data loggers that sell for about $300. We plan to use a PICAXE-18 chip in our next version of the data logger.

Materials

Results and Discussion

The PICAXE-08 chip is very cheap and very easy to program using free software. It doesn't require soldering if you use a wish board to plug the chip into. The PICAXE-08 can be connected to LDR's, infrared detectors, microphones and thermistors to act as light, sound and heat sensors, etc. We carried out a trial to test the data logger and its programme.

The graph shows it is effective at recording a change in temperature over many hours. Once recorded, even with no power, the PICAXE is said to be able to remember the information it recorded for a minimum of forty years! When first switched on, the PICAXE-08 sends any prior stored data as pin 0 serial data via the standard programming serial lead. When using the Programming Editor software, press F8 to view and copy this data. We use notepad to Save as ".csv" data then Microsoft Excel to plot graphs. The PICAXE circuit can be left out side in a container (plastic box, Milo tin or sealed plastic bag) and it still works.

Conclusions

This simple inexpensive and reliable device would be a great addition to any engineer's equipment and any schools science department. Our data logger is versatile because you use more then one type of sensor and use it in many places indoors or outdoors. It costs about $15 compared to $300 for the commercial version. The PICAXE-18 will be able to run about 4 or 5 different sensors all at once. It will also be better than the PICAXE-08 because you do not need lots of other PICAXE chips and it has more data storage space.