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Thermocouple to PC interface, redux

Discussion in 'Electronic Design' started by [email protected], Sep 6, 2006.

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  1. Guest

    I want to take my Type K thermocouple, interface to some sort of device
    (call it Black Box A) and have Black Box A interface (by serial port is
    fine) to a PC, to record temperature data (T between 20 C and 100 C)
    from an experiment. Even better if it can log data from two
    thermocouples simultaneously, but for now one is fine.

    To the flame throwers out there: my background is in chemical
    engineering, not electrical engineering.

    I'd thought an ATTiny11-6PC ($0.53 from Mouser!) would do the trick.
    Was planning on using the on-board analog comparator to provide the A/D
    conversion, as mentioned here:

    http://atmel.com/dyn/resources/prod_documents/DOC0942.PDF

    And I know I'll need a high-voltage programmer, something like this:

    http://www.geocities.com/westfw/electronics/attiny11-prog-notes.html

    However, when looking for schematics to cobble this all together (to
    build the "motherboard", so to speak), I come up blank.

    Any suggestions?

    Maybe I'm barking up the wrong tree... do I simply need an ADC without
    a microcontroller to send the data serially to a PC?

    Thanks,

    Michael
     
  2. Phil Hobbs

    Phil Hobbs Guest

    Wiring up a uP is pretty simple if you've done it once. Is this a
    temperature measurement project or a uP learning project? If it's
    temperature measurement, you can buy serial interface or USB analog I/O
    modules all over the place.

    Cheers,

    Phil Hobbs
     
  3. Guest


    Yeah, it's a learning project.

    So, am I on the right track with the ATTiny11? Just looking for a
    schematic... no I don't need an LCD display on the Black Box... a
    40-pin AT90S--- just seems like immense overkill for something simple
    like this...

    Michael
     
  4. What will you use for a cold junction? I'd buy a DMM with a type K input and
    a serial connection - the price will be a fraction of the time investment.
     
  5. linnix

    linnix Guest

    Tiny 11 does not have a UART, which you need to talk to a PC.

    Yes, if you plug in a board on the PC. Or you can use a serially
    connected board with A2D.
     
  6. Take a controller with ADC such as the Tiny26 and an NTC.

    Rene
     
  7. Donald

    Donald Guest

    Some ideas here:

    http://ww1.microchip.com/downloads/en/AppNotes/00844a.pdf
     
  8. Rich Grise

    Rich Grise Guest

    ....

    What's your budget? If you just want to get the job done, then
    check this out:
    http://www.omega.com/ppt/pptsc.asp?ref=HH66R&Nav=m02

    Or browse their whole website. (just truncate the link.)

    I don't work for them, I just remembered "Omega" and checked
    for one. As it happens, it's rather a pleasant website to visit,
    as well. :) (no flash, no java, no geopoops, etc. :) )

    Have Fun!
    Rich
     
  9. Rich Grise

    Rich Grise Guest

    Then, just pull stuff out of your hat and see what works! That's
    what "learning" means. ;-)

    Have Fun!
    Rich
     
  10. Guest

    I just might give that a shot. Thanks. I'd actually bought my
    non-RS-232 handheld thermocouple display from them for about $100, a
    decade ago. Came in really handy.

    Part of the fun is also in learning something new. Which I did,
    today... use a MAX232 or equivalent to interface to the serial port...
    hmm...

    Fry's in Sacramento sells a breadboard (with wires) for about $6.25,
    last time I checked last week. Don't have exact specs, but looking at
    a ruler, it's probably about 7 or 8 inches by 3 inches, or so. Know
    anyone who can beat that price? ;-) Else I'll have to drive out there
    next time I'm in the area (kinda far from East Sac, where I am).

    To my surprise, the Fry's does NOT carry any PICs or Atmel chips. Not
    even any PIC/Atmel books, or even a copy of Circuit Cellar magazine.
    Shame. But they have plenty of floppy disk controller chips, and even
    a few Z-80s for sale.

    Michael
     
  11. Steve

    Steve Guest

    $100 USB 24 bit multi-channel with enough resolution and low noise to
    directly digitize the low mV signals from themocouples, LabVIEW and
    ..NET drivers

    http://www.emant.com/318004.page
     
  12. Guest


    Thanks for that.

    After some research, I think I'll stick with this one:
    http://www.circuitcellar.com/library/print/0503/moyer154/7.htm

    It has a MAX232 for the RS-232, and an LM35 for ambient temperature
    reference (if I understand the drawing correctly).

    I won't need the 44780 LCD, and I probably won't need the 74HCT4052
    multiplexer (or is it a necessary part of the design?)

    The idea was to use it to monitor a solar cooker ( that I *still*
    haven't built yet (!!) ) in the backyard. Will probably connect the
    temperature acquisition device to an old laptop I have lying around.

    Thanks,

    Michael
     
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