In smaller greenhouses, a manual system opened and closed by hand could possibly be installed. These work simplest when the screen materials is backed by a monitor system.
Start time – when in the morning will the display system start operation
Stop time – when in the afternoon will the display system stop operation
Light level – in what light strength will the screen become activated either to open 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 position under different conditions such as early on a winter morning to lessen thermal shock or through the summer to provide better shading. The gap measures and speed of motion can be controlled in a few systems.
Time delay – under changeable weather conditions this avoids frequent opening and closing
Wind speed – To reduce temperature loss, the screen could be closed early below high wind speed conditions
Snow detection – this can open the screen and turn on the heat when it begins to snow.
The standard system uses nylon monofilament or stainless steel cables to support the screen material. The screen material can either rest on top of the network of cables or end up being 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 can be either with a manual switch or electronic controller.
Based on the above, the grower must enter the following parameters into the controller:
A weather station is required to provide rack drive for greenhouse china outdoor light level, temperature, humidity, 
wind and rain or snow conditions.