Continuity Tester

I want to build a continuity tester that's fast, tiny, and can attach to a board I'm reversing so I don't need full multimeter when reversing boards away from a desk. The hardware files for this can be found on GitHub at sarahemm/continuity_tester.

Status

• 2018-01-11: Received PCBs and parts, started assembling.
• 2017-12-13: Completed PCB design, sent to OSH Park for manufacturing.
• 2017-12-11: Started putting idea together after spending lots of hours reversing for the DMS project. BOM and schematic done, PCB layout in progress.

Features

• Fast, latching to catch quick pulses as probe is dragged along multiple pins.
• Visual/audio switchable options
• Lasts a long time on a CR2032 or similar
• Clips or magnets to a board I'm working on to save having another thing to put somewhere.

Rev001 Issues

• Holes for jacks are way too small (addressed in ECO A)
• Footprint for trimmers fits, but is way way oversized
• LED footprints are backwards (anode/cathode swapped, addressed in ECO B)
• Beeper/LEDs respond "analogly" due to the capacitor on the TRIGGER line
  • Need to add a Schmitt trigger or something similar to make this sound/look nicer
• Current draw idle is a bit higher than I'd like, should try to optimize this further
• Duty cycle control isn't really useful, should reevaluate need for it in Rev002

Rev001 ECOs =

• A - Trim legs on both jacks slightly to enable them to fit through the holes.
• B - Mount LEDs upside down to work around the reversed footprint.

Current Draw

• Rev001 w/ ECO A+B
  • Idle - 465uA
  • Beeper - 1.5mA
  • LEDs - 3mA