Anchor

From Hackstrich
Revision as of 16:26, 21 October 2011 by SarahEmm (talk | contribs) (Adding a photo!)

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

Status

  • 2011-10-20: Mostly assembled first Anchor logic board, except for DAC (wrong pkg), vADC (missed ordering), and heat sink (will add later once low-power tests are done). TFT is arriving tomorrow evening. Have put a request in with Eric to order the missing parts in his next order (mid-next week).
  • 2011-10-18: Received Anchor logic board PCBs.
  • 2011-10-15: Fixed most of the known issues with the rev. 1 PSU board.
  • 2011-10-13: Built first Anchor PSU board, works as designed, putting out 3.3v! There are a couple very minor issues which have been noted here.
  • 2011-10-12: Parts for Anchor PSU and logic board have been received.
  • 2011-10-09: Anchor PSU PCB received, order placed for all PSU and logic board parts.
  • 2011-09-22: Tagged as rev. 1 and sent to Laen for PCB manufacturing. Parts still need to be ordered.
  • 2011-09-21: Added speaker and completed the rest of the routing. Added silkscreen to all connectors/test points/button/etc. One final check tomorrow, then will be sent to Laen.
  • 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
        • Implemented on rev. 1
      • RS232 would be even easier to implement
        • Implemented on rev. 1
      • Ethernet could be cool, but that seems overkill here
        • The LXI standard seems useful for this, could be implemented on an expansion card
      • GPIB would be the traditional choice for test gear, but I've never done any work with it
        • Could be implemented on an expansion card later if there is any need
    • 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

Revision 1 Issues

PSU

  • Fixed on rev. 2 - Fuse holder pins are bigger than holes
  • IEC connector ground tab would interfere with caps if anything was connected to it
  • Fixed on rev. 2 - Up on power switch is off, down is on
  • Fixed on rev. 2 - Plastic on output connector covers URL
  • Added on rev. 2 - No power LED on the board

Logic Board

  • Silkscreen for U7 and U8 is on wrong layer so not on PCBs
  • Silkscreen missing on SW1
  • No test points for backlight voltage
  • Fixed on BOM - R10, R11 missing from BOM
  • Fixed on BOM - One ADC missing from BOM qty-wise
  • Fixed on BOM to SOIC8 version - U8 (output DAC) footprint is SOIC8, chip is MSOP
  • No LEDs for power or status included
  • K1 silkscreen doesn't match part, so relay overlaps Q2
  • SW1 is facing inwards instead of out the front panel!
  • SW1 is missing silkscreen
  • SW2 is comedically tiny
  • Second copy of 'rev. 1' text under LCD connector
  • C21 footprint is bigger than actual part

Photos

Anchor PSU + mostly-complete logic board

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