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Re: Method of producing a ramp voltage over a period of a day or days with display

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  • rtstofer
    ... Whether you datalog or not, you are still faced with driving the 2 axis. If the y-axis is still analog (data digitized), all you have to do is scale the
    Message 1 of 39 , Jul 3, 2011
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      --- In Electronics_101@yahoogroups.com, "g8voq" <hobby_electronics@...> wrote:

      > On the Arduino site someone started a thread "Open Source Data Logger Project Using the Arduino?" I think this led to this product:
      >
      > http://www.sparkfun.com/products/9530
      >
      > So, buy one of these and log the data. If I did that, somehow the logged data would have to lead to the control of the plotter in both X and Y directions.
      >
      > I know. most people would just have the PC show the plot on the monitor screen and print off that :c)
      >

      Whether you datalog or not, you are still faced with driving the 2 axis. If the y-axis is still analog (data digitized), all you have to do is scale the value to fill the axis. If you log the data, you can digitally scale the values.

      But you still need to get to analog voltages so the DAC that has been mentioned several times is still the main part of the project.

      Here is a datasheet for a single or dual channel DAC with a LOAD signal to synchronize the channels. It uses SPI for communications to a uC so it will easily interface with any uC.

      http://ww1.microchip.com/downloads/en/devicedoc/21897a.pdf

      Here's a single channel 16 bit version that doesn't allow synchronization. It might be useful if the y-axis input is still an analog voltage.

      http://datasheets.maxim-ic.com/en/ds/MAX5541.pdf

      No doubt there are other DACs that will provide more resolution an better control.

      You might still have to scale the DAC output to provide sufficient voltage swing for the length of the x-axis.

      I can't imagine how you are going to get long term stability of the voltages.

      If you need to get involved with analog voltage scaling, read Chapter 4 of "Op Amps For Everyone". Google for it.

      Richard
    • g8voq
      Just in case anyone is interested, I joined the Arduino Forum, because I think I ought to be using a microprocessor. http://arduino.cc/forum/ See topic
      Message 39 of 39 , Oct 13, 2011
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        Just in case anyone is interested, I joined the Arduino Forum, because I think I ought to be using a microprocessor.

        http://arduino.cc/forum/

        See topic entitled "Generating a ramp voltage with a repitition rate of 24 hours or more". Rich
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