PhilHornby
Senior Member
The Dimplex Opti-myst range of Electric Stoves, such as this Oakhurst model, are a combination of a Fan Heater and a device that uses water vapour to simulate smoke & flames. The smoke simulation is very realistic, but the in-built 'thermostat' that controls the Fan Heater, is somewhat less impressive. It is effectively little more than a variable power setting, with a lot of hysteresis and needs frequent adjustment. The heater cannot be controlled by switching its Mains input, as it enters a Standby mode when first powered up, which prevents an off-the-shelf Remote Thermostat being used.
However, the heater is supplied with an IR Remote Control, that can be used to control it (after a fashion!). The Remote Control uses NEC codes and has three buttons :-
The strange IR implementation means that the commands should only be sent by an external temperature sensing device when a change of state is detected. They cannot sensibly be repeated at intervals, to counter them being missed or obstructed. In the case of the 'OFF' commands, such a strategy would be likely to shorten the life of the bulbs and the 'smoke' generator. Also, the heater emits a series of loud beeps to indicate which mode it is in, which could quickly become annoying, if repeated frequently.
A variety of temperature-sensing devices could be used, but for maximum "W.A.F.", I modified a commercial 'Horstmann' wall-mounted thermostat (which cost £2.50 in a sale bin!). The normally voltage-free Relay contacts were rewired internally, to provide either 3V or 0V depending on the State of the thermostat. The thermostat's 3V supply proved sufficient to drive the Picaxe 08M2, which simply senses the state of the relay and sends the appropriate IR commands when a change of state occurs.
The circuit was built on a Rev Ed. 08M2 prototyping board, which was cut down slightly to fit inside the thermostat case. The IR section (LED, transistor and two resistors), was sourced from an old IR Remote Control. When power is first applied to the heater, it needs to be manually set to a state that matches the controlling thermostat.
Modified commercial thermostat. (needs some Red film over the LED to complete it) Schematic =>
Code follows in next post.
However, the heater is supplied with an IR Remote Control, that can be used to control it (after a fashion!). The Remote Control uses NEC codes and has three buttons :-
- 'Flame-only' - Switches on just the Flame effect, if pressed when the heater is in Standby mode. No effect if pressed in 'Heat' mode.
- 'Standby' - switches off the Fan Heater and the Flame effect.
- 'Heat' - will switch from Standby or Flame-only to Flame AND heat. Subsequent presses toggle between 1KW and 2KW heat settings.
The strange IR implementation means that the commands should only be sent by an external temperature sensing device when a change of state is detected. They cannot sensibly be repeated at intervals, to counter them being missed or obstructed. In the case of the 'OFF' commands, such a strategy would be likely to shorten the life of the bulbs and the 'smoke' generator. Also, the heater emits a series of loud beeps to indicate which mode it is in, which could quickly become annoying, if repeated frequently.
A variety of temperature-sensing devices could be used, but for maximum "W.A.F.", I modified a commercial 'Horstmann' wall-mounted thermostat (which cost £2.50 in a sale bin!). The normally voltage-free Relay contacts were rewired internally, to provide either 3V or 0V depending on the State of the thermostat. The thermostat's 3V supply proved sufficient to drive the Picaxe 08M2, which simply senses the state of the relay and sends the appropriate IR commands when a change of state occurs.
The circuit was built on a Rev Ed. 08M2 prototyping board, which was cut down slightly to fit inside the thermostat case. The IR section (LED, transistor and two resistors), was sourced from an old IR Remote Control. When power is first applied to the heater, it needs to be manually set to a state that matches the controlling thermostat.
Modified commercial thermostat. (needs some Red film over the LED to complete it) Schematic =>
Code follows in next post.
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