ramp-thermostat

A Node-RED contrib-node that emulates a programmable thermostat.

Wikipedia Source: A programmable thermostat is a thermostat which is designed to adjust the temperature according to a series of programmed settings that take effect at different times of the day. Programmable thermostats may also be called clock thermostats.

The ramp-thermostat controls an actuator depending on the current input temperature and the target temperature (setpoint). The target temperature is defined by a profile for a day period (00:00-23:59). A weekly or holiday setting can be achieved using several profiles.

Configuration

The target temperature is defined by a profile that provides the value depending on the current time 00:00-23:59. The profile consists of several points whose connections build a sequence of lines. The switching moment can be optimized by defining a gradient line like a ramp.

A profile has at least 2 points and must start at 00:00 and end at 23:59.

The hysteresis is used to prevent osciliation. The [+] value is added to the target and the [-] (absolute) value is subtracted from the target. Within this neutral zone no action accurs.

Usage

This node expects a numeric msg.payload containing the current temperature (number). The msg.topic should be set to setCurrent. It will calculate the target temperature depending on msg.payload at the current time and output 3 values:

• state (boolean)
• current temperature (number)
• target temperature (number)

The state (true/false) is used to control an actuator. The current and target temperature outputs can be wired e.g. into an ui_chart node.

Runtime settings

setTarget

msg.topic: setTarget
msg.payload: nn.n (number)

The target will be valid until a new target or a profile is set again or until node-red is restarted.

setHysteresisPlus

msg.topic: setHysteresisPlus
msg.payload: nn.n (number)

The Hydteresis will be valid until a new hysteresis is set again or until node-red is restated.

setHysteresisMinus

msg.topic: setHysteresisMinus
msg.payload: nn.n (number)

The Hydteresis will be valid until a new hysteresis is set again or until node-red is restated.

getProfile

msg.topic: getProfile
msg.payload: profile-name

The profile object is sent to the output 3:

msg.topic: getProfile
msg.payload: {
  "name": "profile-name",
  "points": [{
    "00:00": 18
  }, {
    "04:00": 18
  }, {
    "08:00": 20.5
  }, {
    "12:00": 20.5
  }, {
    "12:00": 19
  }, {
    "12:30": 19
  }, {
    "13:30": 20.5
  }, {
    "19:00": 20.5
  }, {
    "19:00": 18
  }, {
    "23:59": 18
  }]
}

setProfile

msg.topic: setProfile
msg.payload: profile-name

The profile-name is one of the existing profiles that are configured in the ramp-thermostat node.

You can even define an input profile (JSON object) with more than 10 points:

msg.topic: setProfile
msg.payload: {
    "name": "dining room",
    "points": [
        {"00:00": 18},
        {"03:00": 18},
        {"06:00": 18.5},
        {"08:00": 20},
        {"10:00": 20},
        {"11:00": 20.5},
        {"12:30": 20.5},
        {"12:30": 19.5},
        {"15:00": 19.5},
        {"17:00": 20.5},
        {"19:00": 20.5},
        {"19:00": 20},
        {"21:30": 20},
        {"21:30": 18},
        {"23:59": 18}
    ]
}

Examples

The profile is defined using 6 points:

"time" : temp

"00:00": 18.0
"03:00": 18.0
"06:00": 20.0
"19:00": 20.0
"20:00": 18.0
"23:59": 18.0