In smaller greenhouses, a manual program opened and closed yourself could be installed. These work easiest when the screen material is backed by a monitor system.
Start time – when each morning will the screen system start operation
Stop period – when in the afternoon will the display screen system stop operation
Light level – at what light strength will the screen be activated either to open or close
Maximum/minimum temperature – what are the limits of temperature desired
Maximum/minimum humidity – What are the limits of humidity desired
Gap positions – this units the percent open or close position under different circumstances such as in early stages a winter morning to reduce thermal shock or during the summer to supply better shading. The gap steps and speed of motion can be controlled in a few systems.
Time delay – below changeable weather conditions this avoids frequent opening and closing
Wind speed – To lessen high temperature loss, the screen could be closed early under high wind speed conditions
Snow detection – this can open the screen and turn on the heat when it starts 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 moves the leading edge of the screen material. Control is definitely either with a manual switch or rack drive for greenhouse china electronic controller.
Based on the above, 
the grower must 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.