We really need advices in making a DAQ with SD card used as a storage device..what are the considerations in doing it? what components are we going to use in the system..and how are we going to handle the programming of the microcontroller especially in the data storage part..we are going to use it in our project "Earthquake Monitoring System"..we really need your help guys!! its really urgent... thank you very mucH!

 

You have a lot of work to do.

The sensors you decide to use wil have some output. This may have to be rescaled or offset to be an input to your A to D converter.

The A to D must have a range and the right number of bits to give sensible conversions. 8 bits will be much too coarse, but even 12 bits may not be enough. Possibly there is some seismological data standard to suggest the selection of A to D hardware.

Here is a link - http://www.sdcard.org/home - that will let you get all the information you will need to use SD card storage for your project.

In the middle, of course, is the microprocessor. It will have to take in the data from the A to D converter (if you find you need more than 10 bits, this will be an external device). It may also convert the raw data into engineering units. And it will have to store the data onto the SD card. Possibly, you will wish to have the uC time stamp the readings, and use some form of memory management so it does not accidentally overwrite previously stored readings. There may also be an international standard that would be preferable to format your readings into.

I would suggest that the choice of components is yours, driven by the requirements of the overall system.

 

Find a nice A/D converter that meets your specifications with an SPI/I2C interface. Read it into a microcontroller, then have the microcontroller act/control a realtime clock, timestamp the data, then store it into SD.

Usually microcontrollers have libraries for this. You need to pick the resolution and sampling rate sensibly, since it dictates the bandwidth and storage capacity requirements.

I know that the PSoC has integrated SPI and SD card controllers. Also, most modern microcontrollers have libraries to control SD or USB mass storage devices.

Steve