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Reccomendations for cheap data-logger?

Discussion in 'Hobby Electronics' started by Rod Out Back, Mar 26, 2006.

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  1. Rod Out Back

    Rod Out Back Guest

    Folks,

    Looking for a cheap data-logger for recording DC volts(0-40) on a
    remote site. I'm not looking for anything fancy, but I'd prefer a
    reasonable memory and USB port. Weatherproof would be nice, but not
    essential.

    I'd prefer ready-to-go models, but would consider something that
    requires (minimal) work to set up.

    Any ideas appreciated.


    Cheers,

    Rod.....Out Back
     
  2. Rob

    Rob Guest

    Hi Rod - whats cheap?
    Do you want self powered or is external pwr available?

    A "Tiny talk" logger in a 35mm film canister used to be a couple of hundred
    $. You could stick a divider on the front end.

    Check out Hastings data loggers (Oz)



    rob
     
  3. Rod Out Back

    Rod Out Back Guest

    Rob,

    Many thanks; I'll have a look at them in detail tomorrow. However,
    the few of the tinytalk units that measure voltage seem to only go to
    25v max.

    I'll probably need the unit to be self-powered, as the power available
    at the remote site will be variable at best.

    As far as cheap is concerned, I dont want to spend more than
    $300-$400Au apiece. Dont know if this is going to get me what I want,
    but I would like to think I can find something that suits.

    Thanks again,


    Cheers,

    Rod.....Out Back
     
  4. Rob

    Rob Guest

    Rod - you can extend the voltage input range with a couple of resistors.
    Making up a 2:1 divider from two equal value resistors (try 10k+10k? 0.4W)
    will double the input voltage range of the logger. So a 25V max input logger
    would work well. Range would become 0-->50V. Depending on how smart the
    logger is, you may be able to configure it to the new range, if not just
    double the values of the data logged after after you download it.
    rob
     
  5. Rod Out Back

    Rod Out Back Guest

    Rob,

    Yes; that'd work (only need a max of 40vDC, so 50V would be great).
    Easy to double the results to get real voltage(if the logger cant be
    configured). I might ring Hastings to see what the tinytalk loggers
    are worth.

    How do I connect the resistors to achieve this? (assume a simple sort
    of lad here in electronics...).

    Many thanks.


    Cheers,

    Rod.....Out Back
     
  6. Mike

    Mike Guest

    Whats the required sample rate, ie How many readings per sec or minute ?

    And

    How many samples or what period do you want it to record ?

    And

    Do you need a trigger input,
    ie. Only start logging if input voltage is between a certain range
    or exceeds a certain value ?

    And it might also be of interest to know how long the device
    will be in the field before its re-acquired, though these days
    that is not as much an issue as it can power down and retain
    in non-volatile memory etc.

    What are the environmental conditions, will it be in the sun
    in the middle of the day or subject to moisture, splashed etc ?

    --
    Regards
    Mike
    * GMC/VL Commodore, Calais VL Turbo FuseRail that wont warp or melt !
    * High grade milspec ignition driver electronics now in development
    * Twin Tyres to suit most sedans, trikes and motorcycle sidecars
    http://niche.iinet.net.au
     
  7. Rob

    Rob Guest




    Rod, hopefully you can make out my sketch below.



    0-50V in >------------
    |
    |
    [ ]
    [ ] 10k
    [ ]
    |
    |-----------> 0-25V to logger input
    | |
    [ ] |
    [ ] 10k |
    [ ] ---
    | --- 0.1uF ceramic cap.
    | |
    | |
    Ground >-------------------------> to logger 0V / Ground



    The resistors are in series, because they are equal in value half of the
    voltage placed across the two resistors will appear across each resistor. ie
    for 12V input you will get 6V across each resistor.
    For 40V you will get 20V out.

    A 0.1uF capacitor across the lower resistor may help if you find you are
    getting noisy readings.

    Not sure what odds and ends you have to build from - you could build it on a
    3 wide bit of terminal strip, some strip board or even solder the resistors
    together and then tack on the input, output and ground wires then heatshrink
    it to prevent shorts etc.

    Be careful - I assume the 40V may be from batteries / solar supply or
    something - fit a low value fuse close to the voltage source just to be
    sure, better to replace a fuse than replace wiring / fight the fire or
    whatever......

    At 50V you will have 25V on each resistor ==> 62mW power dissipated in each
    R. So 1/4W / 400mW or whatever metal film resistors will be ok. Try to get
    1% tolerance parts. Without knowing more about the source you are connecting
    to or the logger input etc, I'd guess you'd get within a
    one or two hundred odd millivolts of the true voltage value. If you want
    better accuracy the easiest thing to do would be to measure the input and
    the output with you multimeter and work out a correction factor that you can
    apply to the logged data.

    rob

    PS - All care but no responsibility taken!!
     
  8. Alex Gibson

    Alex Gibson Guest

    If you are prepared to break out the soldering iron , can program an avr
    and have time.

    avr butterfly + carrier board

    http://www.siwawi.arubi.uni-kl.de/avr_projects/bf_logger/index.html
    http://www.siwawi.arubi.uni-kl.de/avr_projects/bf_logger/robolog/index.html

    avr butterfly carrier board
    http://www.ecrostech.com/Products/Butterfly/Intro.htm0

    avr butterfly code package for avr gcc
    http://www.siwawi.arubi.uni-kl.de/avr_projects/#bf_app

    swr meter using avr butterfly
    http://www.qsl.net/kd1jv/digiswr.HTM

    avr butterfly mp3
    http://butterflymp3.sourceforge.net/


    Or futurlec.com pic compact flash board
    http://futurlec.com/CompBoard.shtml

    Would need to program the board


    Alex
     
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