2017-11-12 EMF 2018 Collaboration Meeting

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Where / when: Nottinghack, studio; 2017-11-12 (Sun), 09:45 ish

Attendees: Ian D, Daniel S, Mouse.


Multi-Sessor Board

Ian has made a multi-sensor board with five IR sensors, and AND gate + indicator LED. We tested this and it worked fine (except maybe one of the sensors was a bit iffy.

We hooked this up to the Uno running Daniel's code, the H-bridge and a big fat relay. It worked, but sometimes reset the Uno. We used a proper bench supply and re-wired it so the power was connected directly to the relay rather than routed through the Uno's Vin pin, and the resetting stopped.

The relay was used to switch a large mains load (air compressor pump) without indicent.

Brief discussion of serial protocol

  • MODBUS? Uses polling. With lots of devices this might end up increasing latency
  • Custom, simpler - no polling might mean collisions, but really, we don't care if a hit doesn't register now and then...

Component review for sensor board

  • Pro Mini
  • Relay (+ possible transistor driver for it) + diode for spike protection
  • IR sensor board
    • AND gate package
    • space for 4 IR sensors
    • jumper to select single sensor or multi-sensor+AND gates
  • Max485 + 2 x connectors for daisy chaining

We discussed connectors for the RS495 network - RJ11 vs. RJ45:

  • RJ11 cables have tigher turn radius and we have piles of them at the space; however wiring of these cables seems very variable - some have just two conductors and so on
  • RJ45 worse turn radius, and chance to plug them into an ethernet socket and fry it... but cabling is more concistent and also very cheap and availabale

Probably going with RJ45 + cheap CAT5 cable.

KiCAD example

As a precursor to sitting down and designing the actual sensor board, Ian showed us a very basic way through doing a KiCAD project.

Next Steps

  • Daniel will set up a form for discussion / async design messages
  • Ian looks like he's going to design the board
  • Mouse is gonna fart about with KiCAD and try to be useful for next time

Next Meeting