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AutoVent 2 with optional PC control
The AutoVent 2 can control the roof and side vents on most types of greenhouse including gull-wing, saw-tooth and side vented The venting algorithm will try to control both temperature AND relative humidity. If heating is available then this too will be used to try to control humidity in addition to temperature. The roof venting uses an intelligent algorithm to adjust the nudge size taking into account present roof position, size of error, rate of error change, differential temperature (inside – outside) and wind effect. The variable speed exhaust operates at a small (user settable) differential above the normal set point so that if the normal setpoint is not achieved the exhaust fans come on to assist. Heating Air heating can be by either proportional control or ON/OFF control. Proportional control is normally used in conjunction with a boiler heating water pipes. This provides a very gentle heat and the heating pipes can be positioned either under the grow beds or between the rows of plants. In this way less heat need be supplied as compared with general warm-air heating. Water pipe heating is gentle, economical and avoids sudden drying of the air. The heating is used to control both the temperature and the relative humidity. Fogging Fogging may be used to assist with cooling or to increase humidity in dry weather. Two outputs are used; one that comes on constantly while fogging is called for and another that pulses on for short periods to inject puffs of fog. This function may also be used to operate low pressure misting in propagation houses where it may be controlled by a short period solar integrator. By adding a low cost output expansion module the fogging can be increased to 4 zones. Stirring fans A single stage of stirring is provided. This is normally set to come on whenever the vents are closed, when humidity is excessive or when fogging. Shading Shading is available only in houses having less than two side wall vents. (Output S2 is used). It operates to maintain the light level below a user set maximum. If the maximum light level is exceeded it will start to close immediately but once closed requires the light to remain below the setpoint for at least the time specified by the user. Purging In the event of very high humidity, the controller can be programmed to go into a purging mode. In this mode it increases the heating temperature by a few degrees (user set) to try to dry the air. Eventually the humidity will creep up again due to plant transpiration and the controller will nudge open the vents (or if no vents it will switch on an exhaust fan) for a few seconds (user set) to exhaust the warm humid air. Then the vents will close and the heater will again warm and dry the fresh air. This purging cycle will continue until the humidity is brought under control. CO2 (Option) CO2 is measured and injected providing 1) there is sufficient light, 2) the vents are closed or 3) the vents are below a set limit. The user may specify any desired level of CO2 from 0 to 2000ppm and the system will try to provide this when the above conditions are satisfied. Lighting (Option) By adding an output expansion module up to 3 banks of lights can be added. Each bank can be used for any of the three functions :-
Supplemental A 52 week schedule may be entered from the PC (keyboard or from disk) which specifies the minimum day length and/or the minimum daily integrated solar PPFD for each week of the year. The system automatically adjusts these factors at midnight every Sunday night; thus the system can simulate the day-length and total daily photosysnthetic effect of changing seasons. PC interface The optional PC interface allows the settings to be viewed and set from the user-friendly Compugrow software. It also facilitates the collection of measured data and events from the controller for logging to the hard drive whence it may be displayed graphically for ease of interpretation. The computer interface also allows for alarms to sound at the PC (via the PC sound card) or even be auto-dialled out to a telephone or pager (via the PC MODEM). If remote access software is installed (eg PCAnywhere) the PC and hence the controller may be accessed from anywhere in the world (password protected of-course) |
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