In smaller sized greenhouses, a manual program opened and closed by hand could be installed. These work easiest when the screen material is backed by a track system.
Start time – when each morning will the display system start operation
Stop period – when in the afternoon will the screen system stop operation
Light level – at what light strength will the screen become activated either to open up or close
Maximum/minimum temperature – what are the limits of temperature desired
Maximum/minimum humidity – What exactly are the limitations of humidity desired
Gap positions – this units the percent open or close placement under different circumstances such as in early stages a winter morning to rack drive for greenhouse china reduce thermal shock or during the summer to provide better shading. The gap methods and speed of movement can be controlled in some systems.
Time delay – under changeable climate this avoids frequent opening and closing
Wind speed – To reduce warmth loss, the screen can be closed early under high wind speed conditions
Snow detection – this can open the display and turn on the heat when it begins to snow.
The typical system uses nylon monofilament or stainless steel cables to support the screen materials. The screen material can either rest on top of the network of cables or become suspended by hooks from the cables. A gearmotor powers a drum or rack and pinion that movements the leading edge of the screen material. Control is either with a manual switch or electronic controller.
Based on the above, the grower is required to enter the following parameters into the controller:
A weather station is required to provide outdoor light level, temperature, humidity, wind and rain or snow conditions.