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• Added the component list (Read this if you want to replace some of them)!

  a_baumgartner • 02/19/2020 at 10:47 • 0 comments

  I've added the components of the bill of materials (BOM) to the project.

  These components are what I have used to build this, of course you can change most of them to other values. 

  When using other operational amplifiers, be aware to choose components that are suited for this usage and that the pinout and the functionality might is different. 

  The following specs should be handled with care:

  • Replacing the opamp of the precision current sink:
    
    • You need opamps with very low offset voltage .
    • Input common mode range has to include GND (as it is single supply).
    • A shutdown functionality which results in a high impedance output of the opamp is recommended (to ensure a safe deactivated state of the load).
    • You will have to think about stability. (The LTC1152 features a compensation input which can be used to reduce the open loop gain to maintain stable with capacitive loads of the opamp such as MOSFETs.)
    • Supply voltage should include more than 8V (as this is the supply voltage of the precision current sink).
  • Replacing the opamp of the measurement filter stage:
    • Again very low offset voltage.
    • Input common mode range should include GND.
      • Its nice if the amplifier is completely rail to rail input and output.
    • Low bias currents are a must have due to the pretty high impudent voltage sensing.
    • Maybe the feedback network of the Sallen-Key lowpass filter has to be changed (Hint: I've used the filter wizard from Analog Devices to find good values).

  Other things that can be changed:

  • You can also use any micro controller that features SPI and 3 GPIOs to use the load (such as ARDUINO :) ).
  • By changing the shunt resistor (and maybe the reverse polarity protection MOSFET) you can scale  your current range to a higher or lower value.
  • By changing the voltage divider of the voltage measurement, this range is also adaptable.
  • You can use MOSFETs or bipolar transistors (preferably in darlington circuit) as the main power sink.

  Enough for now,

  if you have any questions about the project or want to know something specific, feel free to ask :)!

• Added all necessary project files for building the load!

  a_baumgartner • 02/17/2020 at 14:35 • 0 comments

  Hello there!

  Again some good news:

  You can find all needed files for the software part including workspace of the microcontroller program (code composer studio from TI) and the Visual studio project to run/adapt the GUI on your PC.

  Also the schematics and the PCB of the hardware is uploaded!

  Very important:

  All files of the project (including hard- and software) are published with the GPLV3 If you are unsure about your permissions, check https://www.gnu.org/licenses/gpl-3.0.html.

  (If you find any mistakes in the licensing of this project, please tell me. I will try to correct this.)

  After grading is completed, also the written part of this thesis will be uploaded to this project page.

• Main work is done!

  a_baumgartner • 01/30/2020 at 21:01 • 0 comments

  Good news: Work seems to be nearly finished, I have added some features and specs of the project!

  More to come soon.

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