How to set up a outlet that turns itself off after set interval (how to get hot water without getting into hot water...)

[hartzell]

Note: I also posted this over on r/HomeKit.

---

I have a recirculating pump on my hot water heater (basement) that lets me avoid wasting water while I wait for the shower (top floor) to get hot. I want to run for a bit every morning and evening (e.g. via automations) and I also want to be able to poke it (e.g. a button on my phone's widget page) at other times and have it run for 5 minutes and then shut itself off (so that I don't forget).

I spent a while trying to get close to this behavior using the Home app and the Home+ app, looking at automations, scenes, shortcuts on the hub, and shortcuts on the phone. Shortcuts on the phone _almost_ worked by if the phone went to sleep the pump was never shut off.

I ended up solving it using the RavenCore v2 (aka HomeKit Architect Assistant) firmware on an Athom US plug v2; RavenCore v2 allows me to define multiple HomeKit services on a single device. I defined:

• an "outlet" that switched on and off normally and could be switched via a double-press of the button; and
• an "outlet" that switched on and off normally but had an associated timer (via the "inching" configuration) that turned it off after a set interval and could be switched via a single-press of the button.

The Home app sees two accessories ("outlets"), I added time based automations to the first "outlet" and defined a shortcut in the Shortcut app that turns on the second "outlet".

Problem solved. I thought I'd share a how-to here on the chance that it might be helpful for other folks.

The Home Architect Assistant wiki is excellent and has everything that you need to install and configure the firmware. My Athom plug was running Tasmota (they sell them preflashed) so I was able to use Tasmota's firmware upgrade page to install HAA's tasmota2haa.bin.gz firmware. That provides an access point (HAA-XXXXXX) that you can use to provide your wifi info and it then proceeds to download and install the main firmware. It takes ~5 minutes to install and boot each of those firmwares, patience is a virtue. I found it useful to have a ping running in a terminal window so that I could watch it reboot itself.

The other useful tidbit might be my MEPLHAA script (configuration). It's set up for the Athom plug, similar plugs probably just need to adjust the GPIOs. It

• defines GPIO 12 and 13 as binary outputs
• defines GPIO 5 as a binary input with button behavior,
• declares that there is an LED on GPIO 13
• sets up an 8-second press of the button on GPIO 5 to reboot the plug in setup mode
• adds two "outlet" services that are very similar
  • when they're switched off they set GPIO 12 to 0
  • when they're switched on they set GPIO 12 to 1
  • when one is turned on it uses a service message (m) to set the state of the other to off (switching on the timer overrides the fact that it was already switched on, switching on the "normal" outlet overrides the fact that there was a timer running)
  • configures a the button for each service (single press for timed outlet, double press for normal outlet)
  • BUT/AND the timed outlet sets an "inching" value (i) of 360 seconds so that it will switch itself off 6 minutes after being switched on.

Here's the corresponding JSON (I compactificate it to a single line with jq -c before pasting it into the config box, which HAA recommends to "save memory").

{
  "c": {
    "io": [
      [
        [
          12,
          13
        ],
        2
      ],
      [
        [
          5
        ],
        6
      ]
    ],
    "l": 13,
    "b": [
      [
        5,
        5
      ]
    ]
  },
  "a": [
    {
      "t": 2,
      "0": {
        "r": [
          [
            12
          ]
        ]
      },
      "1": {
        "r": [
          [
            12,
            1
          ]
        ],
        "m": [
          [
            2,
            2
          ]
        ]
      },
      "b": [
        [
          5,
          2
        ]
      ]
    },
    {
      "t": 2,
      "i": 360,
      "0": {
        "r": [
          [
            12
          ]
        ]
      },
      "1": {
        "r": [
          [
            12,
            1
          ]
        ],
        "m": [
          [
            1,
            2
          ]
        ]
      },
      "b": [
        [
          5,
          1
        ]
      ]
    }
  ]
}