View Full Version : Architecture for data logging/robotics project

03-01-2007, 06:23 AM
Greetings! Joined this board in hope of getting advice on how to tackle a data logging/robotics job.
The job involves acquiring a bunch of data samples and transmitting them to Excel for analysis and long-term storage.

The data consists of pressure measurements generating by pushing a sensor against a Thing To Be Tested.
The test cycle lasts about 1 second. I need 512 8-bit samples per cycle, so the time available to take and store each sample is about 2 mS.
There are 128 Things To Be Tested, with a delay of about 1 second between test cycles.
So I either need to be able to store 512 x 128 = 64K of data for batch transmission to Excel at a later time,
or I need to send the 512 bytes acquired during each cycle to Excel during the 1-second interval before the next cycle begins.

I would like to accomplish this with stock components, but don't see how I can achieve the required sampling speed and data capacity without custom hardware.
How would you approach this job? If special hardware is required, what would it be?
Thanks for your thoughts.

J Alsina

Brian Carpenter
03-01-2007, 07:08 AM
www.sddatalogger.com log it and view it in excel


It's Only A Stupid Question If You Have Not Googled It First!!

03-01-2007, 09:08 AM
It could probably be done with the SD Data Logger, but it won't be easy.
The logger works at 19,200 baud (which is 1920 character per second or about 0.5mSec).
Then there is the time to receive the ack from the logger, and the time to write the data.

The saving grace would be the 16K of SRAM on the data logger.
The data can be taken and stored in the SRAM, then during the 1 second pause, pull it from SRAM and write it to the data card.
It would take at least .267 seconds to read it from SRAM, then again that time to write it back to be stored, plus time to write the data. It would be pretty close.

The big advantage would be that you can just pull the SD card and plug it into your PC and open the file in Excel.


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Post Edited (Bean (Hitt Consulting)) : 3/1/2007 6:42:30 PM GMT

03-02-2007, 01:33 AM
Is the sensor such that it can be connected to the computer for storage or does the storage have to be offline?

- Stephen