A project log for Appliance Timer

Rugged & simple timer to control everything from room lighting to air conditioners.

Brian CornellBrian Cornell 07/16/2018 at 01:510 Comments

Timer needs a reboot.  I love the simplicity of the gesture interface but as the feature set has grown it has become a pain in the ass.  It's easy to lose your place and what & how much you can communicate is limited.  It's also a hassle to setup if it's plugged in under a table or something.  For me it's really important to keep the box clean - no buttons, switches, dials, etc.  That means some sort of remote control.

Right now the plan is to use Bluetooth, probably Microchip's RN4678 and data exchange over the GATT profile talking to a smartphone appl.  This will make configuration a snap, along with changing them during operation.  New features can also be added.  To accommodate this and keep the same PCB / case footprint several things need to happen.

  1. Reevaluate the logic supply's capacity.  The mechanical relay requires 40mA.  The controller & SSR require up to 20mA.  That only leaves 40mA for Bluetooth with no headroom.  A slightly larger supply will likely be required but must be condensed to a smaller footprint than the existing one.
  2. The continuity sense circuit's PCB footprint must be condensed.  Possible & necessary to make room for Bluetooth module.
  3. Review MCU capability against Bluetooth requirements and additional features.

In parallel enough work should be done on the smartphone appl to ensure that protocol overhead and its impact on the MCU are accounted for before the hardware design is frozen.

I'll probably start with #s 1 & 2 and some rework on the PCB but not sure when that will happen.