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AN36: IP Thermostat with a Web interface

Poseidon can be used for monitoring over an IP network, or as a thermostat or hygrostat. Application Note 36 describes the available local / remote thermostat function options and the Poseidon unit setup.

Any Poseidon unit with relay outputs can be used as a thermostat:

Poseidon 3468

Poseidon 3268

Poseidon 4002


When a local condition is used to control an output, the Poseidon unit works as a thermostat or hygrostat. The input can be a temperature sensor (thermostat), humidity sensor (hygrostat), or even a contact. The output switching threshold does not depend on the sensor's "SafeRange". Therefore, the Poseidon can, for example, turn on additional cooling at 30°C and send an e-mail alert at 35°C.

Simple thermostat

The heating is switched on if the temperature is too low, a fan is switched on if the temperature is too high. Works even without a network connection.

thermostat, heating, fan and Poseidon IP control unit connected to the internet

  • If TEMP < 5°C then HEATER = ON
  • If TEMP > 35°C then FAN = ON
  • Hysteresis = 1°C to prevent output oscillation near 5°C and 35°C

Setting up this configuration

  • (1) Select the output control mode, either locally or via the WEB or M2M interface.
  • (2) Output closes if the reading is greater than / equal to / less than the specified value.
  • (3) Value to compare against.
  • (4) Select the sensor that should control the output. Each output can be controlled by a different sensor.

Remote alerts and alarms

Poseidon works as a thermostat but still retains the e-mailing and SNMP Trap functionality. A frequently requested feature – alerting an operator to excessive temperature with a pop-up message – can be implemented with the free version of the PD Trigger application.

thermometer, hygrometer, and an alarm displayed as a pop-up window in a central SW


Networked thermostat

The thermostat function can work over an IP network, too. With Box-2-Box mode and SNMP Traps, an input sensor can be interconnected with an output of another device. Only a Damocles unit can receive SNMP traps.

  • (1) Thermostat within a single device.
  • (2) A thermometer at a Poseidon unit, named "Something #01", sends a SNMP Trap to the Damocles unit whenever its reading is outside of the Safe Range. The alarm value is copied to "output #01".
  • (3) A contact at a Poseidon unit, named "Something #02", sends a SNMP Trap to the Damocles unit whenever its input state changes. The alarm value is copied to "output #02".

IP thermostat over a network: Ethernet / Internet connection between a temperature sensor and an output.

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