Well, I realised that I have two problems...

The first, the motor which has to raise the skin is not so strong as I want. Then, I thought two ways to solve the problem:

- Change the motor to another stronger (but I hasn't that and it supposes more energy to do the motor works).

- Change the system to raise the skin (like little pulleys or something like that over the greenhouse)

I accept recommendations !

The second problem is that, for the first video (that has been removed and I think I have to do it again...) I did the connections with a protoboard only, not soldered. Now, of course, I want to make it in a PCB, but I have not those materials (sheet, acids, all that) and, because of this, I will take more time for doing it while I get all necessary things. 

I'm sorry for the delay, I have not even started with the degree and I'm not very experienced making machines. 

Thanks for reading !