Anchor

From Hackstrich
Revision as of 13:54, 20 September 2011 by SarahEmm (talk | contribs) (Updating status with yesterday's work.)

Anchor will be an electronic current/voltage sink, for testing/characterizing power supplies and other similar tasks.

TODO

  • Add a sound outputting device for alerts when the unit shuts down or other similar situations.

Status

  • 2011-09-19: Completed rev. 1 schematic, started working on board layout and got about 80% completed, remaining to complete are the USB port, one of the two expansion slots, and GND.
  • 2011-09-18: Worked on schematic, completed the two ADC sections and the DAC section for measurement and load driving.
  • Pre-September 2011: Put together majority of desired specs and started putting BOM together, put together UI part of the schematic.

Specs/Brainstorming

  • Desired features/specs:
    • Constant current and constant voltage options
      • Maybe constant power too?
    • Ramp-up/down automatically and track outputs
    • Pulse load to test transient response
    • 5A/100V maximums
      • 500W dissipation in a FET is a bit nuts, so it won't be 5A *at* 100V
      • 100W continuous, 500W pulse might be reasonable? Would be nice anyway.
    • Some kind of computer interface for more complicated tests/more detailed data analysis
      • USB would be easy to implement
      • RS232 would be even easier to implement
      • Ethernet could be cool, but that seems overkill here
      • GPIB would be the traditional choice for test gear, but I've never done any work with it
    • Add-on module system for adding extra monitoring channels for things that might be expensive to implement or not commonly used
      • Temperature monitoring (a couple channels worth) would be good, as you often want to monitor chips/pass elements/etc. while load testing supplies
        • Everything to do with thermocouples is expensive, so making this an add-on module would be good
    • Direct connection to mains, as power bricks are annoying in hackerspaces where gear is moved around a lot
  • PIC24FJ256DA210 will be used as it has all the graphics/LCD drive/acceleration built in to enable a nice colour TFT display
    • Inputs
      • Digital
        • Load On/Off
        • Event trigger switch
        • CC/CV mode?
        • 3 for UI quadrature encoder
        • 2 for touchscreen
      • MCU-integrated 10-bit ADC
        • Heatsink temperature
        • 2 for touchscreen
    • Outputs
      • Digital
        • CC/CV mode relay (if required)
        • Scope trigger output
        • Load disconnect relay
        • 3x SPI /SS outputs
    • Communication Busses
      • I2C
        • AR1020 I2C resistive touchscreen controller (will try to eliminate it and do it in the PIC for revision 2)
      • SPI
        • 2x LTC2450 SPI 16-bit ADC for current and voltage measurement
        • 1x MCP4921 12-bit DAC for driving the MOSFET
  • Want a graphical LCD for the output/UI, and the PIC chosen will drive a nice TFT
    • WQVGA is a nice size, can get a menu/buttons on the side and still have room for the info display
    • The Newhaven NHD-43-480272MF-ATXI-T-1 from Mouser seems the best option for size/touch/resolution