SNVAA20 July   2021 DRV8833 , DRV8833 , LMR33630 , LMR33630

 

  1.   Trademarks
  2. 1Introduction
  3. 2Motorized Resistive Load Architecture
    1. 2.1 Controller Board
    2. 2.2 Resistor Plate
  4. 3Motorized Resistive Load Design
    1. 3.1 Controller Board Design
      1. 3.1.1 Power Management
      2. 3.1.2 Power Converter Selection
      3. 3.1.3 Interface and ADC Selection
    2. 3.2 Resistor Plate Design
      1. 3.2.1 Motor and Motor Driver Selection
      2. 3.2.2 Resistor Track
      3. 3.2.3 Mechanical Arm Assembly
      4. 3.2.4 Feedback Control
  5. 4Thermal Considerations
  6. 5Performance and Results
  7. 6Summary
  8. 7Appendix
    1. 7.1 Controller Board Main Schematic
    2. 7.2 Controller Board Sub-Schematics
    3. 7.3 Resistor Plate Schematics
    4. 7.4 Python Code

6 Summary

A motorized resistive load is an effective and convenient means of loading different systems and voltage rails. The resistive load track enables feedback control while maintaining a load that can operate at voltages as low as zero volts, making it suitable for testing voltage rails, even as they ramp up or down. Resistive loads are also preferred for stability testing, such as generating a bode plot for a control loop of the power converter. This resistive load offers the functionality of an automated rheostat in a convenient and relatively compact form.

Additional modifications can also be introduced to meet specialized applications. For example, active cooling can be introduced to potentially increase the current rating of the apparatus, or the code and controller module can be modified to suit a controller other than the Raspberry Pi or allow for automation and automated testing. Additionally, the feedback scheme can be modified to sense the voltage over the first sense resistor, which will be proportional to the current drawn by the load, rather than use an external voltage reference with a variable resistive divider. Calibration routines can also be programmed to maintain accuracy and account for changes in resistance over time as the apparatus wears with use.