8-Channel Analogue Data Logger by John Becker
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Everyday Practical Electronics/ ETI  August & September 1999

Using the new PIC 16F877 microcontroller opens up new possibilities
for versatile analogue data capture.

This article is a 'mini tutorial' on the use of 16F87x as well as
describing a versatile and compact piece of test equipment.

* Use the file datalog_v2.zip which contains the latest version of software
* uploaded 2nd Nov 99.

DATA LOGGER SPECIFICATIONS 

• Up to 8 channels of analogue data input, 10-bit conversion
• Up to 8 channels of serial data storage and retrieval using
  onboard serial memory (up to 2 megabits)
• Analogue sampling rates selectable from 0.5 seconds to 62 seconds
  (one-second increments from first second upwards)
• Sample rate adjustable up or down using two switches
• External clock option selectable in place of internal sampling clock
  (allowing sample taking to be triggered by external source)
• Maximum sampling count limit switch-selectable from 255 bytes to 16K bytes
  (subject to memory chips actually used), stepped in powers of two.
• Continuous "no-limit" option
• Automatic cessation of sampling when count limit reached
  (no over-writing through count roll-over to zero unless required)
• Choice of non-volatile serial memory chip size from 32K bits to 256K bits/ channel
  (2 megabits maximum in total)
• 10-bit ADC sampling resolution
• Sampled data value stored as two bytes
• Automatic non-volatile storage of current sampling count value when
  current data logging session ended
• Automatic non-volatile storage of Rate and Memory factors
• L.C.D. display of elapsed time for current sampling session
• L.C.D. display of current count value


• Prototype has run under DOS and Wins 3.1/95, on 20MHz '386 to 120MHz Pentium
  (Win '98 compatibility untested)
• Analogue signal input range OV to +5V

PLEASE READ DLOGREAD.TXT for important late-breaking news from the author.


The latest version of the software is available from
ftp://ftp.epemag.wimborne.co.uk/pub/PICS/datalog

Please refer to the EPE web site for details of ordering back issues, subscriptions etc.
http://www.epemag.wimborne.co.uk

Last updated 2nd November 99