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Topic: A more prceise real-time clock for arduino (Read 1 time) previous topic - next topic

aliirmak

Hi,

I am looking for a more precise rtc then DS1307 for data logging. Since I am planning to sample the data at around 1000 Hz, I need something that counts mili and/or microseconds.

I was thinking also there may be also synchronization problem  between how arduino samples the data and matches it with the rtc. but first things first...

Any suggestions for the part?

Btw, why do people want to buy ds1307 while arduino has an internal clock? Does that mean arduino is not accurate enough?




fm

Use the internal clock, the millis function returns just that, millis since board powered up. Careful, since this rolls over every 49 days more or less.

People use a RTC to read a calendar date and to keep a clock. If you intend to stamp the time every milli your application is going to be spending most of it's time reading the ds1307.
   

robtillaart


Another option is to investigate into the DS1390 or DS1394  -     http://datasheets.maxim-ic.com/en/ds/DS1390-DS1394.pdf  -

it has 1/100 second precision 
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

wildbill

Bearing in mind that the Arduino has very little RAM, what are you going to do with your data? Serial is questionable, it blocks on transmit and will eat into the time you have to sample. Push it to an SD card?

aliirmak

#4
Sep 18, 2011, 05:40 pm Last Edit: Sep 18, 2011, 05:53 pm by aliirmak Reason: 1
Thanks for responses.

i was planning to use serial to push the data to my computer but if it that doesn't work, than i am going to use sd card or xbee protocol. maybe it is a better idea to have an external ram or go for a more advanced board such as mega.

i wonder if uno32 board is going to solve the bottleneck at ram for me...

robtillaart


If you go for the MEGA there is a nice RAM board to be found here - http://ruggedcircuits.com/html/megaram.html -
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

aliirmak

I am planning to sample free vibration data of a dynamic system for 30 seconds or so by sampling it with 1000 Hz. I am planning to store the data in my computer.
I don't need to get time stamp data if a very precise and accurate time clock is present.
The goal is getting power spectrum of the data.
So it may be counted as a cheap dynamic signal acquisition and on-line data processing on host-computer.

I bought a MCP3202 but i am very hesitant about i may need a very good clock.

Not worried about AA filters for now. In fact, the sensors have a built-infilter rolling off at 50 Hz.

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