hvac_pid

# HVAC PID

*Disclaimer: This library was implemented with the supervised help of AI.*

HVAC PID is a general-purpose Elixir PID controller for discrete control
loops. It supports direct and reverse action, independent P, I, and D
terms, bounded output with anti-windup, a hold deadzone, and smooth
transitions between manual and automatic control. The caller supplies each
sample, its elapsed time, and the actuator interface.

## Installation

Add `hvac_pid` to your dependencies in `mix.exs`:

```elixir
def deps do
  [
    {:hvac_pid, "~> 0.1.0"}
  ]
end
```

The published docs will be at <https://hexdocs.pm/hvac_pid>.

## Quick start

```elixir
{:ok, pid} = HvacPid.Controller.new(out_min: 0, out_max: 100, kp: 8, tn: 20)
{:ok, pid} = HvacPid.Controller.set_mode(pid, :automatic)
{:ok, command, pid} = HvacPid.Controller.step(pid, 21.0, 19.0, 0.25)
```

Here the measurement is 2 units below the setpoint, so the default
`:direct` action gives a first command of 16. Use `direction: :reverse`
when increasing the command lowers the measured value. Pass the returned
`pid` to the next call. The `HvacPid.Controller` module docs explain the
control law and how to handle retuning, pauses, and actuator overrides.

## Development

Run `mix test --cover` for the unit tests, simulated heating and cooling
loops, and the 95% coverage gate. Use `mix deps.get` and `mix docs` to build
the module documentation locally.

Licensed under [Apache-2.0](https://www.apache.org/licenses/LICENSE-2.0).