Avalanche photo diode (APD)

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Avalanche photo diode (APD) power supply unit (PSU)

APD Description

A small circuit board that uses a 90 VDC input to generate a user controllable 60 to 80 VDC regulated output with setting and regulation to 0.03 V with 2 uAmp typical load. To protect the APD load, under any condition, the maximum current must be limited to 20 uAmp.

APD Design constraints

  • physical: none. Expected size is a few inches by a few inches (XY) and no particular limits on the Z axis either.
    • Include some sort of mounting scheme for standoffs or something for use on the lab bench.
    • larger leaded, old fashioned, low density components are preferred where possible to easy lab testing and customization. Avoid small surface mount parts where possible.
    • Circuit board layers: 2 (for minimal cost and simple assembly and rework).
  • input power connector: none.
    • input PSU will be something like the CircuitSpecialist.com CS12001X for users in the US with 120VAC @ 60 Hz.
    • International users, with different VAC such as 240 VAC @ 50 Hz, will need to find their own external PSU.
  • output power connector: none.
  • Control
    • Strictly manual.
    • No computer control, eg I2C or GPIB, of any type required.
    • No on off switch. Output disabled by turning off the external PSU or disconnecting the input wires.
  • Monitor
    • Strictly manual.
    • Must include test points for external test equipment, such as multimeter or oscilloscope, to probe the board.
    • input voltage and current monitoring: none. these will be checked manually.
    • output voltage and current monitoring: none; these will be checked manually.
  • storage temperature range: none.
  • operating temperature range: none. But expect 0 to 45 degC is a useful starting point.
  • altitude: none. But expect 0 to 10,000 ft is a useful starting point.
  • electrical efficiency: none.
  • vibration: none.
  • radiation: none.

APD inputs

  • 2 wires 18 to 30 AWG
    • wire 1: VDC nominally 5 VDC or more above the required max output VDC.
      • Maximum VDC input : 100 VDC
      • Maximum VAC input : 0 VAC
    • wire 2: VDC return aka ground

APD outputs

  • 2 wires 18 to 30 AWG
    • wire 1: manually set VDC for the APD load. Nominally 60 to 80 VDC ?
      • Maximum output current : 20 uAmp.
      • Please note: this board has lots of capacitors. It can take 35 seconds or more from when the input power is removed until the output is completely 0 Volts and 0 Amps.
    • wire 2: VDC return aka ground
    • the input and output grounds are identical. There is only this 1 ground. There are no separate chassis, signal, safety, ... grounds.
    • The 4 mounting holes are directly connected to the 1 ground.

APD Design Files

  • Block Diagram
    • TBD

APD photographs

Blank Circuit Board

Assembled Circuit Board

Reworked Circuit Board

  • what rework ?

APD Test Results

APD Chassis / Enclosure

APD Contributors

  • Dan Werthimer
  • Rick Raffanti
  • Calvin Cheng
  • Matt Dexter

APD Schedule

Here's a somewhat randomly selected dates of possible significance.

  • 2013feb26 Initial schematic design review. Thanks Rick.
  • 2013marxx Start of search for student to finish the schematics and place and route the circuit board
  • 2013aug30 Schematic capture and PCB place and route assigned to RAL staff.
  • 2013sep10 final review of schematics and PCB
  • 2013sep12 PCB fabrication order placed. 50 boards in total.
  • 2013sep13 Bill of materials (BOM) complete; components ordering
  • 2013oct08 S/N 001 assembly (stuff and solder) started (not all parts have arrived yet)
  • 2013oct18 S/N 001 lab testing - all the basic operations except max output current.
  • 2013oct25 S/N 001 lab testing - verify max output current isn't too large.
  • 2013novxx S/N 002 and S/N 003 are fully assembled and ready to be tested. S/N 004..050 are still blank PCBs
  • 2013dec04 find analog over temperature switch as a fail safe for load.
  • 2013dec05 S/N 001 sent to U Toronto for first use with an APD
  • 2013dec19 The combination of APD S/N 001 and the 200uAPD has been successfully tested in the lab.
  • 2013dec21 Wiki page created
  • 2014jan23 S/N 002 and S/N 003: have passed low level initial testing and are ready for the next level of testing/use.